# 3.70s vs 3.90s worth it?



## Skippy597 (Dec 11, 2017)

Hey guys so I jumping the gun a little but I'm planning out my build and buying parts and hopefully will have time to start assembly this fall. Here's where I'm at 1966 lemans, still acquiring the engine but so far 400 with forged flat tops, ported edelbrock round port heads (way more head than I need but I got a good deal on them used) cr is right at 10:1, offy 5499 (here comes the hate but I'm determined to run this), dual 750s, and strongly leaning towards the lunati 30510511 solid flat tappet cam, muncie m20 and for sure will be getting a gear vendors but might be a bit after it's driving. 

So the idea of the build for me is retro street machine but I do plan on driving it a lot. I am putting a quick performance 9" in and not sure on the gears. It's a toss up between 3.70 or 3.90s, it will be running a 275/60r15 tire. I really want to run solid 12s with the car and I know the 3.90s will put that cam in its happier place at the end of track but how bad is it living with 3.90 gears? Also the ideal 10:1 first gear final drive is pretty close when choosing 3.90s. 

Anyways interested in what you guys think. 
Thanks


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## armyadarkness (Dec 7, 2020)

No one's going to hate 1500 cfms on an engine that prefers half that, but if youre determined to use dual 750's, maybe bump the cubes up to 500.

Im a bit confused about your original question. Seems like your determined to build a hard-core race car but that you're insisting on using street car stuff for mild street manners?

Dual 750's on a 400 is going to eliminate all streetability and get you about 7 MPG, at a time when gas is $5 a gallon. So you're definitely hitting your race-car goal there.

But when you worry about 3.90's, and talk about a gear vendors, then you now sound like you want a street cruiser and plan on racking up some miles!

I have a strict policy that I don't give anyone advice theyre not asking for, but in this case, Im making an exception.

Build your 400 into a 428, put dual 500's on it, 373 gears. Sell the Muncie, forget the gear vendors, and put a Tremec in it for the same money. Youll then have a wicked fast track car, with great streetability.

If you insist on sticking with your original idea, then yes, 456's in the rear and get a 55 gallon gas tank.


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## 67ventwindow (Mar 3, 2020)

Using Spicer's calculator. Spicer Engine RPM Calculator it looks like you can do 65 at 3k with the Muncie and that tire size. Once you get the gear vendors in it will be a great for long drives. 

Any particular reason for using Quick Performance? I will need a new rear end in the next couple years like to hear a different view point.


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## Skippy597 (Dec 11, 2017)

I don't feel like you were trying to be too helpful but I think the dual 750s kinda blinded ya to the rest of the build. Dual 750s does not equal 1500 cfm and even the old offy manuals state that if your engine liked a single 750 before then your going to need 2 750s to equal the performance. Also have talked with guys who specifically set up dual quads and that's been the general concensus for what I should run, but if I hate it I'll pull them off and put some 625s on. Also forgot to mention these are carters not holleys. 

As far as the rest of the build it's not too hot, the cam is definitely on the hotter side but should be streetable (still might decide to step down a little to the crower 60310), the whole setup is being put together with used parts for cheap so some fancier parts that don't seem like they belong is because they were cheap. 

Really going for the old school street machine look and feel, using vintage speed parts where I can. But it's going to be driven. 

I have thought about the TKX but ultimately I have a rebuilt m20 and I think gear vendors are really cool and is cheaper to setup than doing the whole swap.


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## Skippy597 (Dec 11, 2017)

67ventwindow said:


> Using Spicer's calculator. Spicer Engine RPM Calculator it looks like you can do 65 at 3k with the Muncie and that tire size. Once you get the gear vendors in it will be a great for long drives.
> 
> Any particular reason for using Quick Performance? I will need a new rear end in the next couple years like to hear a different view point.


Thanks, I'm leaning towards the 3.90s and if they're terrible ill step down. 

Quick performance seems to offer the best deal of a complete 9" outfitted how I want and I've heard a lot of good things about them. I currently have a rebuilt 10 bolt with posi and 3.23 gears but that's not going to work with my build.


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## Skippy597 (Dec 11, 2017)

Was just curious of the general thought if stepping from 3.70s to 3.90s is worth it or if I can get enough performance with the 3.70s?


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## armyadarkness (Dec 7, 2020)

Skippy597 said:


> I don't feel like you were trying to be too helpful but I think the dual 750s kinda blinded ya to the rest of the build. Dual 750s does not equal 1500 cfm and even the old offy manuals state that if your engine liked a single 750 before then your going to need 2 750s to equal the performance. Also have talked with guys who specifically set up dual quads and that's been the general concensus for what I should run, but if I hate it I'll pull them off and put some 625s on. Also forgot to mention these are carters not holleys.
> 
> As far as the rest of the build it's not too hot, the cam is definitely on the hotter side but should be streetable (still might decide to step down a little to the crower 60310), the whole setup is being put together with used parts for cheap so some fancier parts that don't seem like they belong is because they were cheap.
> 
> ...


I can assure you that I was trying to be helpful. If I was going to insult anyone, I wouldnt do it here. If your question was merely subjective material, which I disagreed with, then I wouldnt have commented at all... but you described building a track car and you were looking to tame it and add weight. I was merely trying to clarify how that would work against you.

That being said, Butler performance outright refused to sell me the cam I wanted, because they said it was too big for a worked 400. I also run Carter carbs and I use an 800. That being said, this is why I dont give advice on incomplete/ subjective content. Like you, I disagreed with their advice... but disagreeing with Butler on a Pontiac forum is rarely a good idea... so guess what cam I got?

As for the Tremec, it's a drop in swap for a Muncie and it costs the same as a muncie and it costs the same as a gear vendors... just so you know.


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## Skippy597 (Dec 11, 2017)

armyadarkness said:


> I can assure you that I was trying to be helpful. If I was going to insult anyone, I wouldnt do it here.
> 
> That being said, Butler performance outright refused to sell me the cam I wanted, because they said it was too big for a worked 400. I also run Carter carbs and I use an 800. That being said, this is why I dont give advice on incomplete/ subjective content.
> 
> As for the Tremec, it's a drop in swap for a Muncie and it costs the same as a muncie and it costs the same as a gear vendors... just so you know.


My apologies, maybe I read the previous post with a wrong tone of voice. 

The tkx swap quote I have received was $5000 which isnt too terrible but a fair amount more than the 3000 for the gear vendors. I figured since I already have a professionally rebuilt m20 that I may as well just slap it in and then as funds allow I'll add the gear vendors. But everything is subject to change, heck my car is on jack stands right now. The idea behind the 3.90s is to make the cam happier, but I also figured that guys back in the day would daily drive they're street rods so why can't I. And it's really only gonna be for special occasions and I feel the steeper gear would make it funner in those instances, if this was my true daily I would just keep the 3.23 rear I have and go with a smaller hydraulic cam.


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## armyadarkness (Dec 7, 2020)

Skippy597 said:


> My apologies, maybe I read the previous post with a wrong tone of voice.


Meh... Im a sarcastic ass, so dont sweat it. But yeah, I spend the majority of my life on this forum trying to help people keep their cars running... and learning along the way.

Yes a TKX swap is $5000, but the Trans itself is only $2800. In my experience, that is nearly the same cost as a rebuilt Muncie. So you ould likely sell the Muncie and break even!

You would then use all of your Muncie parts with it, except for a different clutch disc. Same bell housing, flywheel, pressure plate, zbar linkage.... And the gear Vendors is another $2500, so by my math, you could kill two birds with one stone.


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## armyadarkness (Dec 7, 2020)

Skippy597 said:


> The idea behind the 3.90s is to make the cam happier,


If you had an auto, Id agree fully.


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## Baaad65 (Aug 29, 2019)

What kind of horsepower are you aiming for? If it's close to 500 do you really want to run the M20 if your racing it...sounds like a bad idea IMO.


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## armyadarkness (Dec 7, 2020)

Skippy597 said:


> guys back in the day would daily drive they're street rods so why can't I. And it's really only gonna be for special occasions and I feel the steeper gear would make it funner in those instances, if this was my true daily I would just keep the 3.23 rear I have and go with a smaller hydraulic cam.


I have a numbers matching, 2nd owner, survivor 67 GTO, and I've put 2000 miles on it in the last month. I also have a loaded 2022 Z71 Silverado, so lord knows I dont have to drive the GTO.


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## Skippy597 (Dec 11, 2017)

armyadarkness said:


> If you had an auto, Id agree fully.


Well the car is an auto but I'm installing the 4 speed. The frame has been powdercoated and I don't have the tab for the z bar so I am planning a hydraulic clutch setup. So maybe the tkx is the better way to go but since I already have the Muncie I figured I can get that in for under $1000 vs spending an additional $3000 right off the bat. So maybe I should plan ok doing the tkx swap instead of the gear vendors but still start with the Muncie as it will speed up the process of getting my car on the road.


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## Skippy597 (Dec 11, 2017)

Baaad65 said:


> What kind of horsepower are you aiming for? If it's close to 500 do you really want to run the M20 if your racing it...sounds like a bad idea IMO.


Really shooting for the 450 mark, I feel like that's doable or at least close to it.


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## armyadarkness (Dec 7, 2020)

Well, here's the absolute largest cam that Butler would sell me, for a 30 over 400 with 10.5 compression, headers, 800cfm carb, and ported 670 heads. They said there was no point in flowing any more air and fuel into an engine that didnt have the volume to accept it. That's why I was worried about your dual big carb idea. And... my cam is bigger than most of the other guys here, whom have much larger engines.

Great parts only work in the right combo, which is why you couldnt simply put a 4bbl on a 2bbl car, and get the same performance. Like I said, not trying to crush your dream, just trying to help you hit your target. 

Ive considered dual quads on my car, but I would use 400-500's.


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## armyadarkness (Dec 7, 2020)

I hope you guys appreciate the sacrifices I make to be here. Ive been seeing this ad, 24/7, for six months.


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## Baaad65 (Aug 29, 2019)

Skippy597 said:


> Really shooting for the 450 mark, I feel like that's doable or at least close to it.


Shouldn't be that hard with the right recipe, mine dynoed at 472 with iron heads, 9.36 compression, stock intake and 800 quad. Now I have an Edelbrock Performer RPM, 1.65 rockers and a Quickfuel 850 dp so I'm hoping I should be close to 500hp. But it is a 461


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## Jared (Apr 19, 2013)

I'll start out by saying I think the tunnel ram with dual quads will look killer sticking out of the hood (no hood?). A pair of velocity stacks to boot would be epic! The two 750 CFM carbs and an extremely aggressive cam profile feeding a moderately built 400 is a little bit of a concern especially since you seem to want to highway drive it. Personally, I'd spec out a milder cam and use the smaller carbs that Amy recommends and go with the 3.90 gears, skip the gear vender. You're probably going to need to keep the RPMs on the higher side to make the tunnel ram work. Again, this will look killer. I think you can and should build this but maybe not so close to the ragged edge.

Side note. I'm running a 461 with ported iron heads, larger exhaust valves, 9.5-1 compression, a Torquer II intake, and shorty headers with a 4 speed and 3.23 rear gears. Right now I have an 800 CFM Edelbrock on it and it doesn't seem to want any more. I doubt fuel mileage is part of your equation but I may be getting 8 MPG with mine on a really good day.

You may want to touch base with PJ. I think he is in the process of building something similar but on a 455.


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## Jared (Apr 19, 2013)

BTW. I'm not hating on your ideas. There are aspects of my setup that are frowned upon on here as well.


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## O52 (Jan 27, 2019)

armyadarkness said:


> I hope you guys appreciate the sacrifices I make to be here. Ive been seeing this ad, 24/7, for six months.


What ads? I don't see no stinking ads.


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## Baaad65 (Aug 29, 2019)

O52 said:


> What ads? I don't see no stinking ads.


That's what I was thinking, no ads here.


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## armyadarkness (Dec 7, 2020)

O52 said:


> What ads? I don't see no stinking ads.


In the upper right hand corner of the GTO forum I always have some disgusting toenail fungus advertisement


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## 67ventwindow (Mar 3, 2020)

armyadarkness said:


> In the upper right hand corner of the GTO forum I always have some disgusting toenail fungus advertisement


 And as soon as you mention it it shows up on mine, I quess I wll; pay the money not to see your toes,


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## Skippy597 (Dec 11, 2017)

Jared said:


> I'll start out by saying I think the tunnel ram with dual quads will look killer sticking out of the hood (no hood?). A pair of velocity stacks to boot would be epic! The two 750 CFM carbs and an extremely aggressive cam profile feeding a moderately built 400 is a little bit of a concern especially since you seem to want to highway drive it. Personally, I'd spec out a milder cam and use the smaller carbs that Amy recommends and go with the 3.90 gears, skip the gear vender. You're probably going to need to keep the RPMs on the higher side to make the tunnel ram work. Again, this will look killer. I think you can and should build this but maybe not so close to the ragged edge.
> 
> Side note. I'm running a 461 with ported iron heads, larger exhaust valves, 9.5-1 compression, a Torquer II intake, and shorty headers with a 4 speed and 3.23 rear gears. Right now I have an 800 CFM Edelbrock on it and it doesn't seem to want any more. I doubt fuel mileage is part of your equation but I may be getting 8 MPG with mine on a really good day.
> 
> You may want to touch base with PJ. I think he is in the process of building something similar but on a 455.


Thanks Jared, 
I'm happy someone gets the idea I'm going for. I could be wrong (usually am) but while the cam listed is on the bigger side but I don't think it's on the ragged edge. It's a solid flat tappet so I'll lash it at .025 which tames it quite a bit, but I don't think it will be terrible. There lots of guys running the crower 60310 lashed at .020 with no issues but are on the lower side of 400 and I would like to stand just a nudge higher.


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> In the upper right hand corner of the GTO forum I always have some disgusting toenail fungus advertisement


Not on any of my devices, guess you're the lucky one 😉


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## Baaad65 (Aug 29, 2019)

Skippy597 said:


> Thanks Jared,
> I'm happy someone gets the idea I'm going for. I could be wrong (usually am) but while the cam listed is on the bigger side but I don't think it's on the ragged edge. It's a solid flat tappet so I'll lash it at .025 which tames it quite a bit, but I don't think it will be terrible. There lots of guys running the crower 60310 lashed at .020 with no issues but are on the lower side of 400 and I would like to stand just a nudge higher.


We all got it and I have thought dual quads under the hood would be cool I think army was trying to help you have a car you could drive on the street and not be disappointed after all the time and money you're going to spend, that's all.


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## PontiacJim (Dec 29, 2012)

Skippy597 said:


> Hey guys so I jumping the gun a little but I'm planning out my build and buying parts and hopefully will have time to start assembly this fall. Here's where I'm at 1966 lemans, still acquiring the engine but so far 400 with forged flat tops, ported edelbrock round port heads (way more head than I need but I got a good deal on them used) cr is right at 10:1, offy 5499 (here comes the hate but I'm determined to run this), dual 750s, and strongly leaning towards the lunati 30510511 solid flat tappet cam, muncie m20 and for sure will be getting a gear vendors but might be a bit after it's driving.
> 
> So the idea of the build for me is retro street machine but I do plan on driving it a lot. I am putting a quick performance 9" in and not sure on the gears. It's a toss up between 3.70 or 3.90s, it will be running a 275/60r15 tire. I really want to run solid 12s with the car and I know the 3.90s will put that cam in its happier place at the end of track but how bad is it living with 3.90 gears? Also the ideal 10:1 first gear final drive is pretty close when choosing 3.90s.
> 
> ...


OK, my thoughts. Some part mismatching, but my opinion.

Since you plan to go with the Gear vendors OD at some point, I would go with 3.90's. I Have the Quick Performance 9" and went with 3.90's and the TKO-600 with a .64 OD. The OD is key and what you want to match your rear gearing to. You want to use one of the many online gear/tire/RPM/MPH calculators and input your OD gear to get somewhere around 2,300 - 2,500 RPM's at 70 MPH. You might go a little lower on engine RPM, BUT, with what you are building, you are going to have a high RPM engine and anything lower might be bogging the engine down. The beauty of a 9" is that if your select a wrong gear, you can easily purchase a complete gear set-up and simply swap it in - one reason I got the 9".

I would figure on a 6,000 - 6,500 RPM engine for all out running.

The Offy 5499 is a low rise intake. The 750 Eddy's or old AFB's will work fine. You are correct that select a carb that would work for a single 4-Bbl and get 2 of them. The 750 might be a touch big, BUT, the vacuum secondaries only open as much as needed and correctly jetted and your power valve springs matched to your engine's vacuum, you should be OK.

However, the ports are the standard D-port shape and you are using Eddy heads with RAIV port size. A slight mismatch, but not killer. You may have to do a little port matching just to make sure the bottom of the ports are a match. If the intake ports is smaller and will "fit" into the Eddy port without any mismatch where a "lip" is created and the air flow from the intake hits it, then you are good. You don't want any kind of step at the head side as this will create turbulence. So get the correct intake gaskets for the heads and lay it up against the intake to see how they match.

The Offy being a "low profile" may not be what you want as it may drop off early when your engine has more RPM's in mind. I personally would add a 2" 4-hole spacer that will create a little more air/fuel velocity and raise your RPM band. You can certainly try with out, then try a 1" or 2" spacer.

The Eddy heads will flow around 280 CFM's. With this amount of CFM's, they may cause the engine to be a little lazy on the bottom end, but really work hard at mid & upper RPM's - its all about air flow and port velocity. But, the smaller intake runners may aid port velocity as well as be the same reason the engine will quit pulling because the heads want more and the intake is your restriction. Still worth giving it a try.

10.1 compression is OK with aluminum heads.

The Crower 60310 solid is indeed a mid-high RPM cam in a 400. Same cam I am using in my 455 build - larger cubes will make it a little milder. But, I plan on using 1.65 ratio rockers which will add more lift. The Eddy heads can use more lift, but depends on your valve springs. I have iron heads flowing 235 CFM's @ .550" lift and want to maximize my head flow.

You will want forged piston/forged rods - everything balanced. Butler Pro-flow 60 PSI oil pump and hardened pump drive to replace the factory piece. As a minimum, a 1973 type oil pan with baffle.

You will want a good ignition system and tailor the timing/curve to your engine. *Rev limiter is a must.*


Just some thoughts.


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## Skippy597 (Dec 11, 2017)

PontiacJim said:


> OK, my thoughts. Some part mismatching, but my opinion.
> 
> Since you plan to go with the Gear vendors OD at some point, I would go with 3.90's. I Have the Quick Performance 9" and went with 3.90's and the TKO-600 with a .64 OD. The OD is key and what you want to match your rear gearing to. You want to use one of the many online gear/tire/RPM/MPH calculators and input your OD gear to get somewhere around 2,300 - 2,500 RPM's at 70 MPH. You might go a little lower on engine RPM, BUT, with what you are building, you are going to have a high RPM engine and anything lower might be bogging the engine down. The beauty of a 9" is that if your select a wrong gear, you can easily purchase a complete gear set-up and simply swap it in - one reason I got the 9".
> 
> ...


Thank you so much! This is really good and useful info. I do plan on port matching the intake as I was worried about that as well, also will be using 1" 4 hole spacers and might adjust as necessary. The engine is built by a member of the py forum who used it in his tractor pulling dragster and revved it out to 7k. It has forged pistons and rods and is internally balanced. I am certainly planning on the butler pro 60 PSI pump as well. It may not be the best planned engine but it's got some really good parts that I acquired for really cheap. All said I won't have much more than 5k in the engine, heads and all. If it doesn't work then I will learn and can adapt. 

So I will plan on the 3.89 gear set and like you said if its terrible it's easy to change. But I think it will keep the engine in its happy place. 

As for the cam I do plan on advancing it 4 degrees to help the lower end a bit.


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## lust4speed (Jul 5, 2019)

One of the engine combinations I ran years back was the Offy with two 650's, Edelbrock 305 CFM heads, Dougs Headers, and a HR288XR-10 cam with Harland Sharp 1.65 rockers. I would race the car every now and then when the club would have a strip day. Someone offered me an amount I didn't want to refuse for the manifold and carbs. Replaced the setup with an RPM manifold and an Edelbrock AVS 800 carb. Next time out at the track the car ran two tenths quicker with the single 4-barrel. Even with the manifold being port matched and the carbs jetted on the dyno, the combination made maximum horsepower at 5,165 RPM with power dropping off after that. Those dog-leg runners are just not that efficient. Two positives: Killer looks and fuel mileage was excellent returning 15.8 MPG on several long freeway trips to shows out of area.

Price of the Gear Vendors has skyrocketed, and equals the bare cost of the TKX trans. The remainder of the swap cost is going to be the same for the TKX or Muncie, and the Muncie is only rated about 450 foot pounds compared to 600 for the Tremec. You might get tired of repairing/replacing Muncie parts. The lackluster .78 overdrive of the Gear Vendors isn't much of an overdrive ratio.

Also I would recommend running the cam straight up at Comp's 108° intake centerline. Your problem isn't going to be lack of torque but tire smoke with either rear gear. Cam companies spend a bunch of time to maximize their cams and usually the smart money will stay with their recommendation.


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## Jared (Apr 19, 2013)

armyadarkness said:


> In the upper right hand corner of the GTO forum I always have some disgusting toenail fungus advertisement


They paid the $40 for premium and don't see the adds. Mine is still for Christian day schools.


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## Jared (Apr 19, 2013)

Skippy597 said:


> Thank you so much! This is really good and useful info. I do plan on port matching the intake as I was worried about that as well, also will be using 1" 4 hole spacers and might adjust as necessary. The engine is built by a member of the py forum who used it in his tractor pulling dragster and revved it out to 7k. It has forged pistons and rods and is internally balanced. I am certainly planning on the butler pro 60 PSI pump as well. It may not be the best planned engine but it's got some really good parts that I acquired for really cheap. All said I won't have much more than 5k in the engine, heads and all. If it doesn't work then I will learn and can adapt.
> 
> So I will plan on the 3.89 gear set and like you said if its terrible it's easy to change. But I think it will keep the engine in its happy place.
> 
> As for the cam I do plan on advancing it 4 degrees to help the lower end a bit.


For that cost in, you have to do this. I think if you talk yourself out of it, there will always be the what if question about this. Most builds skyrocket past $10K easily and don't have the wow factor yours will. Worst case is you use the parts that don't work for you and probably break even going in a different direction. 

I'll admit I tossed around dual quads on mine. What held me back is wanting to keep my car extremely stock looking. Mine is so plain that it barely gets a look until I start it up. Having to cut the hood would affect that look.


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## armyadarkness (Dec 7, 2020)

Baaad65 said:


> That's what I was thinking, no ads here.


Really?


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## michaelfind (Dec 14, 2018)

O52 said:


> What ads? I don't see no stinking ads.


I think that means that Army is not a "premium member" so he gets to look at toenail fungus ads.


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## 67ventwindow (Mar 3, 2020)

michaelfind said:


> I think that means that Army is not a "premium member" so he gets to look at toenail fungus ads.


 Do you mean to say those arnt Amy's toes? Nothing that a die grinder can't fix. Little garage pedicure. Tin snips work in a pinch.


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## lust4speed (Jul 5, 2019)

No gross adds on my screen and I'm just a registered member.

Also have to correct my previous post, and I blame it on the toenails. Looked at Army's posted cam card and thought it was the one in question. I'll stick to saying that the cam manufacturer's recommendations are derived from their research and usually can't be bettered. The few times I tried advancing/retarding the cam with dyno testing I've only lost power in parts of the RPM band. There's an optimal place for cam events and unless the manufacturer screwed up designing the cam you won't see improvements. Reducing bottom end torque also kills efficiency and one of those results would be a decrease in gas mileage since you usually cruise in the lower part of the torque curve.


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## Skippy597 (Dec 11, 2017)

Here are the 2 cams I am looking at, both are solid flat tappet cams. 

Crower 60310 INT/EXH - Dur @ .050” Lift: 240°/248° RR: 1.5/1.5 Gross Lift: .477”/.501” LSA: 112° RPM: 2800 to 6000 Redline: 6500

Lunati 30510511 - Duration @ .050 (Int/Exh): 243/251 ; Gross Valve Lift (Int/Exh): .518/.530 ; LSA/ICL: 110/104 ; Valve Lash (Int/Exh): .022/.024 ; RPM Range: 2500-6500


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## PontiacJim (Dec 29, 2012)

Skippy597 said:


> Here are the 2 cams I am looking at, both are solid flat tappet cams.
> 
> Crower 60310 INT/EXH - Dur @ .050” Lift: 240°/248° RR: 1.5/1.5 Gross Lift: .477”/.501” LSA: 112° RPM: 2800 to 6000 Redline: 6500
> 
> Lunati 30510511 - Duration @ .050 (Int/Exh): 243/251 ; Gross Valve Lift (Int/Exh): .518/.530 ; LSA/ICL: 110/104 ; Valve Lash (Int/Exh): .022/.024 ; RPM Range: 2500-6500


Lunati 30510511 - very similar to the VooDoo 704 hydraulic cam which has a power band of 2K-6K. Many seem to like the 704 cam. Certainly better lift numbers.

The 110 LSA will also build a little more cylinder pressure on the lower RPM's which can create an issue with detonation. If you have power brakes, most likely engine vacuum will be reduced. I am not a fan of the 110 LSA unless in a low compression build. I read that Lunati can grind the cam at 112LSA for no extra charge, but you would have to confirm that.

The 110LSA will typically have a narrower, but "explosive," power band in the mid-range and when it find's it peak, will drop off power very quickly. I had an XE274 Comp Cams in an 8.2 compression 400 engine. Great cam, plenty of pep, but it quit at around 5,500 - 5,600 RPM's. It would spin higher, but no power gain at all.

The 112LSA will have a broader power band and better engine vacuum.

Give it a try. The thing about a flat tappet cam/lifters is that they are not killer priced and if you are not happy, you can always go with something else. Sometimes you just have to "wing-it."


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## Skippy597 (Dec 11, 2017)

PontiacJim said:


> Lunati 30510511 - very similar to the VooDoo 704 hydraulic cam which has a power band of 2K-6K. Many seem to like the 704 cam. Certainly better lift numbers.
> 
> The 110 LSA will also build a little more cylinder pressure on the lower RPM's which can create an issue with detonation. If you have power brakes, most likely engine vacuum will be reduced. I am not a fan of the 110 LSA unless in a low compression build. I read that Lunati can grind the cam at 112LSA for no extra charge, but you would have to confirm that.
> 
> ...


Right on, so would you recommend the lunati cam if I can get it ground on a 112?


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## ylwgto (Oct 27, 2009)

Jared said:


> I'll start out by saying I think the tunnel ram with dual quads will look killer sticking out of the hood


Completely agree...go for it!

You inspired me to search the interweb for Pontiac tunnel rams and I saw this video (crappy quality but great exhaust sound). Looks badass.


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## PontiacJim (Dec 29, 2012)

Skippy597 said:


> Right on, so would you recommend the lunati cam if I can get it ground on a 112?



Ya, I think I might go for it. But, I am in the camp that bigger is better and bigger isn't always better. I am using 2 800CFM AVS2 carbs on my tunnel ram which most will say is too big. OK, I get it. But I can also do some adjusting if need be to include altering the amount the secondaries open and kill some of the CFM's. If not, then I will go with smaller carbs and say "lesson learned, don't go with too big of a carb on your tunnel ram." LOL With a 4-speed I feel you can adjust for going a little over the top because you have a clutch and don't have to worry so much about matching stall speeds to the cam/engine. It may have some poor manners at your lower RPM's, but you usually don't stay there long and gears can put you where you want to go so it is more tolerable. Gas mileage is going to suck, but you don't build one of these cars for gas mileage.


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## Eric Animal (Oct 28, 2007)

Skippy597 said:


> Was just curious of the general thought if stepping from 3.70s to 3.90s is worth it or if I can get enough performance with the 3.70s?


With the proper cam and motor set-up 3.70 should be enough.....BUT everything should "match and work well together....3.70 rear gears are a bit stikk for the street....use an OD transmission.....


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