# Motor and Tranny Rebuild



## Jim (Oct 30, 2008)

All right, I have kicked this around for a while and have finally decided to take this approach on rebuilding my motor and transmission, I think..
Parameters: 1967 GTO with 400. This is a budget build on a street machine only, so dependability, pump gas, etc, are all essential.

Tranny: I will stay with the original 4 speed and have it gone thru. I thought about a different transmission but like the original and think it would be the best bet for the money. (I am running 3.42's in the rear)

Motor: I want to be pushing about 500 HP or better. I have the 670 heads and will have them redone. I know the motor has an Erson Cam and the heads have had some work as I noticed they had anodized rockers. I will have the motor gone thru with new pistons, cam, lifters..........I presently have both an Edelbrock Torker II and a performer series intake. I would like to reuse one of these. I would probably go with a Holley double pumper.
I am also going to put on the Ram Air III Exhaust manifold. I have 2 1/2 flowmaster exhaust presently.

Any comments, ideas, do's or dont's.

I appreciate all reasonable input (and some not) 

Thanks

Jim:cheers


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## Rukee (Feb 8, 2007)

What compression ratio is going to allow you to hit 500hp with pump gas?
I'd think to hit those #s with a 400 block you'd have to run compression high enough to warrant race gas only.


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## Jim (Oct 30, 2008)

Rukee said:


> What compression ratio is going to allow you to hit 500hp with pump gas?
> I'd think to hit those #s with a 400 block you'd have to run compression high enough to warrant race gas only.


Good question. I don't know enough about this stuff to answer that. Maybe I am asking for to much? Talking with some motorheads they seemed to think that I should be able to get 1 1/2 Hp per Cubic inch without to much problem using pump gas. I don't know. Share your thoughts.....


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## jetstang (Nov 5, 2008)

I'm with Rukee, 500 HP on pump gas with a 400 is pretty hopefull. You can get 500 ft lbs of torque easier. To get there you will need a camshaft that won't be streetable. Check out some of the pontiac engine builder sites, they make huge power on pump gas. I think you are looking at a Tomahawk intake and aluminum heads to get there. Build a 400 HP 400 and throw a 100 shot of NOS on it, that way it would still be streetable.


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## 66tempestGT (Nov 28, 2009)

just a sidenote, not much to "go through" in a four speed if it works good now and doesnt leak.


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## allpawl66 (May 9, 2008)

I have a 400 that has over 500 horse that runs on 87 octane pump gas , forged stroker , roller cam , Kauffman alum. heads . Contact Spotts performance in Pa. All he builds is Pontiac engines , nothing else . Dyno info:

* Out of the box heads make 552 tq and 500 HP on a 463 CID engine with a std hyd camshaft
* 85cc 325cfm set on a 535 CID pump gas makes 675 HP @ 5800 rpm's with hyd roller on 12inches of vac @ 800 rpm's
* Out of the box set on a 461 CID make 531 HP @ 5600 rpm's on pump gas & hyd roller
* 74cc race gas roller cam 487 CID makes 695 HP @ 6400 rpm's with single Dominator carb
* 325 cfm - 74 cc heads on 463 cid run 9.62 @ 137 in 3250 lb 65' GTO


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## Rukee (Feb 8, 2007)

^Those heads sound awesome!!


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## jetstang (Nov 5, 2008)

allpawl66 said:


> I have a 400 that has over 500 horse that runs on 87 octane pump gas , forged stroker , roller cam , Kauffman alum. heads . Contact Spotts performance in Pa. All he builds is Pontiac engines , nothing else .


Nice stuff, but he was asking about a budget build 400, keeping the old intake. Now, Roller cam and aluminum heads is not a budget build, unless you have deep pockets.


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## geeteeohguy (Feb 2, 2008)

I don't think there's any such thing as a 500HP Pontiac budget build. Especially on pump gas. My recommendation would be dished pistons, a nice cam, and stock intake. Dependable, fun, usable. As stated by the folks above, it takes a lot of $$$ and knowledge to squeeze that kind of power from a relatively stock 400. It takes expensive aftermarket parts, too. Also, the 670 is a great performance head, but one of THE worst heads to use when trying to run pump gas unless you have dished pistons. The closed chamber design makes them The King of Ping. I know this from personal experience!!!!


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## allpawl66 (May 9, 2008)

You are right it is expensive , dished pistons , good rod bolts , balance bottom end , good cam dialed in, roller if possible , thick head gaskets and port the 670s. should be in the 400 hp. range .


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## Thumpin455 (Feb 17, 2010)

You could open the chambers a bit, but you wont gain much. A stock bore 455 with 670 heads comes in around 11:1 with zero deck, and a 400 would need to lose timing and run a cam that bleeds pressure down low to survive. I buck the system a bit so I would just run it on E85 with a 467 stroker kit, but not everyone wants to do that and actually I am doing exactly that. 

To get 500hp or close to it, on pump gas, a stroker with dished pistons would be in order. Have the heads street ported to at least [email protected] .500, and open up some RAIII manifolds, and rework the intake a bit to flow better in the plenum. A cam with around 235/238 on the intake with a 108 to 110 LSA would get you close and still be sorta streetable if you have a big enough dish to keep it out of inaudible detonation. 

The 455 that had my 670s on it made 540hp/570tq running 11.3:1 with headers and a TorkerII/850 and a UD 288/296 on 108 hyd cam. You could get pretty close to 500 with stock intake and worked manifolds with the right cam. Doing it with a 400 will require more airflow, more compression, and more cam. You wont like driving it around on the street with a 400 like that, but the 455/467 will rock your socks off, and probably break the 4 speed. The 455 in my car broke both a M20 and a B&W ST10 so yours wont be long for this world if you build a 500hp engine for it.


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