# 400 stroker



## Droach6498 (Nov 1, 2020)

Im rebuilding my 67 400 block, have to bore it to .060 over so I decided to add a bit of hp make it a stroker. The supplier says I need a 850 cfm carb. should be running around 500hp any thoughts about the carb? has 4.25 stroke, 1.65 rockers aluminum heads 325cfm 85cc.


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## PontiacJim (Dec 29, 2012)

850 should be about right with the big cubes and CFM's. Aweful lot of CFM's, make sure you select a good cam so you don't lose port velocity and have a "soggy" engine on the lower RPM's and the engine only wakes up from mid-range and on up.

Make sure the rest of your drivetrain can handle that kind of HP and the TQ should be even more.


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## Baaad65 (Aug 29, 2019)

I have the same setup but not as much head flow, this what I went with from a guy that only does custom carbs.


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## Baaad65 (Aug 29, 2019)

Just have to keep giving it some pedal until it warms up a bit so it will idle because of there's no choke, but then it's lights out.


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## Droach6498 (Nov 1, 2020)

PontiacJim said:


> 850 should be about right with the big cubes and CFM's. Aweful lot of CFM's, make sure you select a good cam so you don't lose port velocity and have a "soggy" engine on the lower RPM's and the engine only wakes up from mid-range and on up.
> 
> Make sure the rest of your drivetrain can handle that kind of HP and the TQ should be even more.


thats what Im freakin about he had a 550hp+ set of parts sending me with a 950hp carb they,re racing carbs I told him to tone it down to 500 max thats Jeff Kauffman. i want to street and street strip but I have a max , these look interesting


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## BearGFR (Aug 25, 2008)

Droach6498 said:


> thats what Im freakin about he had a 550hp+ set of parts sending me with a 950hp carb they,re racing carbs I told him to tone it down to 500 max thats Jeff Kauffman. i want to street and street strip but I have a max , these look interesting


The way to 'tone it down' is to keep your right big toe out of the carburetor  Carb CFM ratings are evaluated at wide open throttle and at a specific amount of manifold vacuum (very low, but still not zero). 
Restricting air flow is what throttle blades do. That's their one and only job. Doesn't matter if you 'go crazy' and put a 1050 Dominator on it, if you drive it 'sedately', the engine will never see that much flow. 
The only time a carb can be "too big" is if the engine underneath it isn't capable of pulling enough air through it at a high enough velocity to make it function correctly.

Bear


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## Atarchus (Aug 4, 2020)

I have a 112LSA, 230 @ .050 hydraulic roller in my 461. I made peak hp at 5200rpm and still have VERY solid torque down low. I think if I did it all over again, I might go one step bigger at 236 @ .050, I think that would be a really nice balance of low end torque and high end power. But, I'm still happy with my cam selection and it idles happily at 675rpm with about 13 pounds of vacuum. Just giving you some info to think about because I know I spent a LOT of time reading about different cams and watching youtube videos lol.


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## Baaad65 (Aug 29, 2019)

I've seen some blogs mentioning Kaufman using big carbs too but they're a good outfit and think they know what they're talking about even though they're more race oriented, someone a while back described an engine as a big air pump so the more air you can get through it with the right supporting cast the better and you can always down jet the carb to make it seem smaller if you're parts aren't up for it. I started with a 780 Street avenger vacuum secondary on my 461 and it just felt choked plus the vac secondary was a bad idea with a stick that's why I'm not the smartest one around but thanks to these experts on this site I'm learning, so listen to them they know what they're talking about.


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## BearGFR (Aug 25, 2008)

Baaad65 said:


> ... you can always down jet the carb to make it seem smaller if you're parts aren't up for it...


No no no no no no! Trying that is a sure way to ruin your engine by running it way too lean, which makes it much more likely to get into detonation - or worse.

A carburetor doesn't "know" anything except for how much air is flowing through it and creating a vacuum depression because of the venturis. This vacuum depression is what pushes fuel through the metering jets, which have to be sized in the correct ratio to that volume of air in order to provide the correct air/fuel mixture. 
It doesn't know how 'big' the engine is, or how many cylinders it has, or anything else except for air flow volume/velocity, and it feeds fuel in proportion to how much air is passing through it. The only variables that affect jetting are air density/oxygen content, and in some cases air distribution through the intake manifold (when cylinders fire adjacent to each other, one can tend to 'steal' fuel from the other and make it tend to run lean.) That's what 'stagger jetting' is all about - using different size jets on each of the two primarys or secondaries to try to 'even out' the mixtures that each cylinder sees. It assumes that cylinders will tend to be fed from the carburetor bore that's closest.

That's why most of the time you can buy a carburetor from a quality vendor, take it out of the box, and put it on your engine and it will be right - no matter what kind of engine you're putting it on. Jet size is determined mostly by air density (oxygen content) - not engine size. You'll tend to need smaller jets at higher altitude and/or hotter air temps because there's less oxygen in the air. The reverse is true for lower altitudes/colder air. That's why at the track serious racers are always concerned about the current density altitude and air 'moisture grains'. That determines how much oxygen is available in the air.

Bear


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## Baaad65 (Aug 29, 2019)

Great information and that's why I should not be giving advice when I know just enough to be dangerous, I was just thinking he shouldn't be afraid of a 950 carb with his head flow numbers but like I said he needs the components to support it, of course it's going to have huge jets and didn't mean he should run it so lean that is does damage I guess you would have to dial it in with an AFR meter that's all. I'll sit down and be quiet now


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## BearGFR (Aug 25, 2008)

If you've got access to the Motor Trend channel, there's a great series out there on it: "Engine Masters". They do all kinds of back to back dyno testing/myth busting on that show and it's very enlightening/informative. There used to be a few episodes out on Youtube but I don't know if they're still there. 
One of the episodes showed that there's pretty much no such thing as a carb that's "too big".

Bear


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## michaelfind (Dec 14, 2018)

I am running two 600cfm edelbrocks on my 467 stroker and it's not too much. Bear is correct, the motor will only draw what it pulls through the carbs no matter how big or how many. I can very calmly cruise down the neighborhood streets without much noise, then really let it scream out on tracks or open roads. The big right toe control is crucial.


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## Baaad65 (Aug 29, 2019)

Droach I would give Steve that's the guy I bought my carb from his number is encrypted in his description I know it's Ebay but he has a 100% rating and good prices, this is all he does and sounds like he knows his stuff, I told him my setup and recommended something. I bolted it on and haven't touched anything but the idle screw and it's been perfect, also I went directly through PayPal and he didn't charge me shipping...he's not the most friendly guy but I don't want to live with him I just want a good carb from him.


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## Baaad65 (Aug 29, 2019)

Also forgot to mention I'm running a 1/2" poly carb spacer it keeps the carb and fuel cooler and maybe helps equal air/fuel distribution a little bit since I have a divided plenum...good luck👍


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## PontiacJim (Dec 29, 2012)

Droach6498 said:


> thats what Im freakin about he had a 550hp+ set of parts sending me with a 950hp carb they,re racing carbs I told him to tone it down to 500 max thats Jeff Kauffman. i want to street and street strip but I have a max , these look interesting


To get 325 CFM's, I believe they are going to port the heads - if I am correct the "stock" flow on those KRE heads is 280 CFM which is plenty.

Keep in mind, 325 CFM's *WON'T* be using a stock cast iron intake to go with it. So now you will have to upgrade - most likely a single plane type to match head flow and to accept a square bore type carb. No sense in having heads that will flow 325 when your intake only flows 230 CFM's - it becomes a choke point.

You will most likely need a roller cam in the .550-600" lift and 280-290 duration on an 112 LSA. Make sure you get the lifter brace so you don't take any chances of busting out a lifter bore. Some engines can experience core shift and if by chance you have thin walls on a lifter bore, it can crack/bust. The brace adds insurance no matter if someone says you do not need it - get it, period.

I would not recommend 1.65 roller rockers, I would go 1.5 for an "easier" lift/drop of the valves. Make sure you get stainless steel if going full roller, not aluminum of any kind - just ask *BearGFR* about his experience.

As pointed out, to utilize the full potential of your big build, you want good airflow from the carb. Can you put a smaller carb on? Sure, you can put a 2-Bbl on it, but don't expect to go past 3,000 RPM's because the 2 Bbl will not supply enough air to feed the engine, nor will it perform well when you mash the gas.

The 850 - 900 would be good for a big flowing engine. Trying to go smaller on jetting will hurt performance as it would run lean, probably run the engine hot, detonate, and lack the performance out of the carb/engine.

Throw mileage out the window with a car/engine that size. The only way will be to "feather" the gas pedal like an egg is under it and even then, mileage may suck. On the PY forum, there was a member who said he had 600HP, an automatic, engine in perfect tune, and can get 20 MPG. Well, I say BS, but he said he used a GPS to confirm his miles driven and he used 2.5 gallons for a 50 mile section of road. What he most likely did not include is that he started at the top of one of those Canadian mountains and put it in neutral all the way to the bottom as he coasted down at an idle. So there is one example of 600HP and 20 MPG.

Just make sure parts are matched and you will have a fun ride.


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## Droach6498 (Nov 1, 2020)

Baaad65 said:


> Just have to keep giving it some pedal until it warms up a bit so it will idle because of there's no choke, but then it's lights out.
> View attachment 142967


is this recent I dont see it on ebay


Atarchus said:


> I have a 112LSA, 230 @ .050 hydraulic roller in my 461. I made peak hp at 5200rpm and still have VERY solid torque down low. I think if I did it all over again, I might go one step bigger at 236 @ .050, I think that would be a really nice balance of low end torque and high end power. But, I'm still happy with my cam selection and it idles happily at 675rpm with about 13 pounds of vacuum. Just giving you some info to think about because I know I spent a LOT of time reading about different cams and watching youtube videos lol.


thats what Ima doin YT, books, magazines etc. I think Im going to go with this guy who sells custom made carbs to your specs. Combo of Holley & QFT reasonable at $559 for 850 thats not what sells me though its his knowledge me telling him what I have and what I want to do he puts it together to that


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## Droach6498 (Nov 1, 2020)

Baaad65 said:


> Just have to keep giving it some pedal until it warms up a bit so it will idle because of there's no choke, but then it's lights out.
> View attachment 142967


thanks his price has gone up a bit but I really like the fact he specs it all out foryou as Im sure Iwould have it all f***ed up


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## Baaad65 (Aug 29, 2019)

So did you find him?


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## Baaad65 (Aug 29, 2019)

So PJ you just recommended not using 1.65 aluminum rockers is that because of high lift he would need, reason I asked is I just changed out my rockers to the 1.65 Scorpion Race rockers so my lift went from .520 to. 570 with full roller, now you have me worried but I checked with Butler and he said it would be fine but recommended the endurance rockers which are lighter and better for higher rpms which I wasn't hitting so I went with the beefier model. Also called Scorpion and they were fine with it too, I have 7K3 heads with screw in studs and elongated push rod holes.


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## Droach6498 (Nov 1, 2020)

PontiacJim said:


> To get 325 CFM's, I believe they are going to port the heads - if I am correct the "stock" flow on those KRE heads is 280 CFM which is plenty.
> 
> Keep in mind, 325 CFM's *WON'T* be using a stock cast iron intake to go with it. So now you will have to upgrade - most likely a single plane type to match head flow and to accept a square bore type carb. No sense in having heads that will flow 325 when your intake only flows 230 CFM's - it becomes a choke point.
> 
> ...


I see the lifter brace where does it go?



Baaad65 said:


> So did you find him?


I did looks like a very good carb 1 and he fine tunes it to your specs which really is a seller to me. I dont need it for a few months but when Im ready I will begetting it from him, I dont want it sitting around for a coulw months or so waiting for parts.
Did you get one from him?


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## PontiacJim (Dec 29, 2012)

Baaad65 said:


> So PJ you just recommended not using 1.65 aluminum rockers is that because of high lift he would need, reason I asked is I just changed out my rockers to the 1.65 Scorpion Race rockers so my lift went from .520 to. 570 with full roller, now you have me worried but I checked with Butler and he said it would be fine but recommended the endurance rockers which are lighter and better for higher rpms which I wasn't hitting so I went with the beefier model. Also called Scorpion and they were fine with it too, I have 7K3 heads with screw in studs and elongated push rod holes.


Read the first couple of posts in this thread, and maybe Bear will comment and give you what he thinks of aluminum roller rockers:









(re)Building my engine - finally


FINALLY - in the process of rebuilding my engine. This time, I'll be using Crower stainless rockers and Crower mechanical roller lifters (with their High Pressure Pin Oiling Option). I'm also stepping it up a little :grin2: This cam delivers 15 degrees more duration and 0.020 more lift than...




www.gtoforum.com





*Read this PY post beginning with Post #26:*





__





Melling 1.65 stamped rockers for street use. - Page 2 - PY Online Forums - Bringing the Pontiac Hobby Together


Page 2- Melling 1.65 stamped rockers for street use. Pontiac - Street



forums.maxperformanceinc.com


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## Baaad65 (Aug 29, 2019)

Yes the 850 QFT in the picture.


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## coyote595 (Dec 4, 2019)

OK, I must know what happened to Bear's aluminum rockers! Let's hear it!


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## Baaad65 (Aug 29, 2019)

Ok PJ I went back and read Bears whole engine build thread, he mentions one broken rocker which can happen to anything that moves from humans to clocks. What brand was it he never stated, I think I did my due diligent in researching if 1.65 rockers were going to be ok, first internet searches, then called and talked to a tech at Butler who had my motor build and head build sheet which was marked up for using 1.65 as they used 7/16 screw in studs, elongated push rod holes, tested the spring pressures at [email protected] .573 lift. ( Scorpion Race rockers are good for 950lbs) So he had no problems with me using the Scorpion endurance rockers that they sell. Next I called and talked to a tech at Scorpion and he said I would be good to go only that I didn't need the endurance line as those are for 7000 rpm and up because they are lighter so I went with the race version which are beefier. I would hope all these people wouldn't lie to me and Scorpion seems to be one of the best out there, and there were cheaper versions like PRW and Summit but something like this that if it breaks people get hurt I didn't cheap, my electric fans yes because if they quit nobody gets hurt, the motor won't see 6000 rpm and I guess I'll hope for the best since I sold my 1.5 PRW rockers two weeks ago. Just trying to squeeze every horse out of this thing with an easy and relatively cheap upgrade like we all want to do. And again thanks for all your input and knowledge, I'm really learning a lot


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## PontiacJim (Dec 29, 2012)

Baaad65 said:


> Ok PJ I went back and read Bears whole engine build thread, he mentions one broken rocker which can happen to anything that moves from humans to clocks. What brand was it he never stated, I think I did my due diligent in researching if 1.65 rockers were going to be ok, first internet searches, then called and talked to a tech at Butler who had my motor build and head build sheet which was marked up for using 1.65 as they used 7/16 screw in studs, elongated push rod holes, tested the spring pressures at [email protected] .573 lift. ( Scorpion Race rockers are good for 950lbs) So he had no problems with me using the Scorpion endurance rockers that they sell. Next I called and talked to a tech at Scorpion and he said I would be good to go only that I didn't need the endurance line as those are for 7000 rpm and up because they are lighter so I went with the race version which are beefier. I would hope all these people wouldn't lie to me and Scorpion seems to be one of the best out there, and there were cheaper versions like PRW and Summit but something like this that if it breaks people get hurt I didn't cheap, my electric fans yes because if they quit nobody gets hurt, the motor won't see 6000 rpm and I guess I'll hope for the best since I sold my 1.5 PRW rockers two weeks ago. Just trying to squeeze every horse out of this thing with an easy and relatively cheap upgrade like we all want to do. And again thanks for all your input and knowledge, I'm really learning a lot



OK, got a PM from *BearGFR* on the rocker arms. Here is what he said,

"Yeah, I had 1.65 Scorpions in my 461 and was running a mild to moderate solid roller at the time. The engine had been together about 5 years at that point. One of them came apart. The bearings went away which let the rocker flop around, so it beat the crap out of it, the valve stem, the retainer, and put shrapnel all through the motor.

I run Crower stainless full rollers now, and they're 1.5's, but the cam I'm running now makes more lift and duration with the 1.5's than the previous one I had did with 1.65's."

So there is a personal experience and it caused an engine rebuild. Luckily it did not take out the engine or a cylinder. I know there are always those who will say they are the best to use and no issues. But, when I read an honest experience of a part failure and you can read in Bear's engine rebuild that he does check things as he assembles, I have to listen and re-consider if I want to take a chance on a specific part. Some guys will never have an issue, some guys have lots of money to do rebuilds at will - I don't have good luck and my budget can't afford to keep throwing engines at my car, so I select parts on the side of caution and pass up others even when they are a "deal" that suits my wallet much better.


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## Baaad65 (Aug 29, 2019)

That was unfortunate bad luck I guess and if I saw a bunch of bad stories on those rockers I would never use them and that's why I didn't use the prw aluminum or Summit copycats. I fix things every day that break even brand new stuff it just happens, I have an MSD dist with a broken reluctor paddle does that mean MSD distributors are junk and no one should use them, I don't think so...I'm just hoping Bear had a bad rocker that was a one in a million and it doesn't happen to me 👍


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## coyote595 (Dec 4, 2019)

I never had a catastrophic alum rocker failure, but I did have an observation that made me prefer steel rocker rockers over aluminum. Years ago in my Firebird, I built up a 406. The valve train with RA4 heads consisted of a Crane solid flat tappet cam (245/256 duration @ .050 .483/.506 lift), Crower solid lifters, RA4 pushrods, Crane 1.5 alum roller needle bearing rockers, Isky machined keepers, Crane dual springs, titanium valve spring retainers and RA4 valves. Ran this engine very frequently up to 6500 RPM for 8 years and 40K miles. What finally killed it was the tranny deciding not to do the 2-3 shift during a race against a 5.0 nitrous Mustang. It over-revved, and after that, I heard a rod knock. Still beat the Ford! Upon disassembly, aside from the spun rod bearing, the roller rockers had wear of the aluminum body where the end of the roller tip thrusts against the body. The aluminum wore such that the roller tips had a lot of end play. Didn't fail, but I wonder how much longer they would have lasted. This is why I was so curious to hear Bear's experience with them.


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## qwkvet (Oct 28, 2014)

Droach6498 said:


> Im rebuilding my 67 400 block, have to bore it to .060 over so I decided to add a bit of hp make it a stroker. The supplier says I need a 850 cfm carb. should be running around 500hp any thoughts about the carb? has 4.25 stroke, 1.65 rockers aluminum heads 325cfm 85cc.


Talk to the guys at Pro Systems 727-490-5717. I have a 400 stroked to 461, Butler cnc ported aluminum heads etc. It pulled 572 hp and 604 tq on a 96 degree day with a limited rpm run. Pro System built the carb to exactly what i had in my motor and what i wanted out of it. I have this motor in my 65 GTO in front of a tremec 6-speed and it will run without a cough, sputter, dead smooth at 1200 rpm and will pull to 6500 in a heartbeat. They did small orifice large venturi, or vice versa, im no carb expert lol but it has been flawless for 3 years. I got the low rpm driveability i wanted with all the top end power the heads and .650 lift cam can make. I believe they said its 800cfm but performs like a bigger carb wide open but gives me that low rpm smoothness i wanted.


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## Baaad65 (Aug 29, 2019)

Sounds like a great setup, loved to see it


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