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I'm just now creating a plan of attack for a 70 GTO 4 speed. It will be a few years before its on the road, but I want to have a game plan so I know what route to go.

Currently the car has a 400 and a Muncie that is going to get a total rebuild basically from the ground up. It's been neglected for years and most parts will need to be replaced or rebuilt. The silver lining is it can all be done the way I want as it needs to be redone anyways.

I've already decided a number of things. The car will be a street cruiser and reliability and driveability are major focus points.

FiTech fuel EFI "carb" setup
Hydraulic roller cam
3.23 (or similar) highway friendly gearset (no OD)

The car currently has a non original 400 and best I can tell, with its #62 heads will not run 92 octane unleaded. I'm going to attempt to get it started in the next few days, but it hasn't run in 20 years. I'd like to keep the 400 short block and freshen it up. Since I would need new heads and hardened valve seats, I'd probably go aluminum heads, like the Kauffman ones.

I'm just not sure what to expect performance wise from that setup, refreshed 400, aluminum heads, medium sized roller cam, EFI and 3.23 gears. I want it to be a fun street bruiser that could knock off mid 12's and look good punishing some 295 radials, which I don't think is asking much. If the 400 isn't any good anymore, I'd probably get a rebuilt 400 (or 455) but stay with iron heads at a more realistic 9-9.5 cr.
 

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you got a good plan here...depending on your elevation you should run 12s easily...you can also run 12s in a dead nuts reliable cruiser with a different, and much cheaper, combo...a 455 with stock heads, intake manifold, a mild performance hydraulic flat tappet cam and q-jet would also do it....if you put a little steeper gears in it, with or without an over drive trans, a 400 would also perform about as well with a factory iron setup or maybe a performer rpm manifold and headers. good luck with your goals....best...john
 

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Consistent mid 12 sec performance on the street in a 3800-4000 lb A-body with rock hard 295-50's with 3.23 (or 3.08) gearing behind a 406-412 as motivation is not going to be a piece of cake. To take advantage of the higher flowing heads, and matched cam, a 400 is going to want more gear.

With such a goal and set of parameters, would reconsider just throwing a very expensive topend, i.e.; heads, HR, and what amounts to a throttle body at a "400". Going to need much more torque at a lower rpm with as high of gearing as a 3.23. Since you have the 400 block,and imagine it it not something of high value like a factory 4 bolt RA app block, this is one of the few times, I'd urge using the current 400 block and going with an aftermarket 3" main 4.25 stroke crank, matched forged rods, and modern forged pistons. Top the resulting 461+ off with well thought out 80-85 cc alum head and matching cam combination. With the extra cubes, will also have room to grow, if your performance goals increase.
 

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"...I want it to be a fun street bruiser that could knock off mid 12's and look good punishing some 295 radials..."


The easiest way to meet your goal is with a long stroke engine. As long as your block's casting number does not end with 557, it can be used for the stroker build. Butler sells balanced cast crank stroker assemblies for about $1600-$1700 shipped.

Butler Performance - Pontiac Engine & Rotating Assembly Combinations - Featuring Eagle Pontiac Kits

There are crank, piston, and rod upgrades available at extra cost.

OR, you may come out better buying a stroker shortblock, or complete crate longblock, from one of the Pontiac engine builders. One of the the cheapest good quality shortblocks I know of is from Len Williams. He can also build 'em with any upgrades you want, in both short and long block.

455 Short Block

455 Long Block

Sandoval has the shortblocks for about the same price.

pontiac crate engines

6x-8 heads will work, are cheaper, and likely won't need new seats, like the early heads will. Also won't need dish pistons, with the 6x heads. But, since you are considering alum heads & a roller cam, I assume you have enuff $$ for a nice engine build, and don't care about having any of the "correct" numbered parts, so I'd go with 85cc KRE alum D-port heads, & a small hyd roller cam, with some decent alum roller rockers.

Kauffman Racing Equipment

Kauffman Racing Equipment

Butler Performance - Pontiac Camshafts

Harland Sharp Original Roller Rockers S6001 - Free Shipping on Orders Over $99 at Summit Racing

Scorpion Endurance Series Rocker Arms 3052 - Free Shipping on Orders Over $99 at Summit Racing

If you wanna save a few hundred bucks, most any of the 041 grind HFT cams, with Rhoads lifters, will produce the power you want. There are also lots of other HFT cams that will work. But if you don't use Rhoads lifters, most recommend only the Hylift-Johnson 951R lifters. The Rhoads are modified Hylift-Johnsons.

Paul Knippen is a Pontiac engine builder who sells the Hylift-Johnsons.

https://www.facebook.com/PaulKnippensMuscleMotors/

Two of the most popular versions of the 041 grind are the Crower 60919, and the Melling SPC-8. The Melling is cheaper. I used several of these in some of our bracket cars.

Engine Camshaft Stock Melling SPC 8 Fits 68 70 Pontiac Firebird 6 6L V8 | eBay

Rhoads Original Hydraulic Flat Tappet Lifters 9518 - Free Shipping on Orders Over $99 at Summit Racing

I'm a carb guy. I know absolutely nothing about a fuel injection deal for a Pontiac, so I won't say any more about it. We always ran 750 Q-jets on our 12 sec bracket engines. :smile3:

PS: Keep in mind that when you increase the hp/torque that much, the stock 8.2" rear end may not be up to the task, if you get any traction. I'd consider upgrading to a 12-bolt rear, or at least an 8.5" 10-bolt. We ran stock 12-bolts and never broke any part of one, running down into the high 11's, with big slicks--TH400/455/3.55-4.11 gears. But, a new, complete 12-bolt is about $3000 or more. :surprise:

http://www.moserengineering.com/complete-rear-end-assemblies/muscle-pak-rear-ends/12-bolt-musclepak.html

http://www.ebay.com/itm/12-BOLT-CHEVELLE-POSI-REAREND-GTO-442-A-BODY-/281922184339

http://www.ebay.com/itm/CHEVELLE-CUSTOM-BUILT-CHEVY-12-BOLT-REAR-END-EL-CAMINO-A-BODY-GS-OLDS-AXLE-DIFF-/262191884074?hash=item3d0bdaa72a:g:S4IAAOxye3BRr9~-&vxp=mtr

Pinion head may be able to fix you up with something a little cheaper. ?
 

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I just purchased a 70 Judge with a stock RAIII 400. I'm going to be adding the FITech EFI system next month. I'll let you know the results.
 

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Discussion Starter #6
Great information guys. I just wasn't sure what to expect as I've done much more with LS cars, this is my first old school build.

The only way I was going to justify aluminum heads is if I was keeping the 400 that's in there now, but upon further inspection, it's looking like I would just get a new long block - and I was in fact looking at Len Williams like posted! 455 long block with aluminum heads is not in the budget. The good news is that with a 455 and the wide ratio m20 that's in there, I should be able to do a 3.08 gear set and with a 27" rear tire it should be a decent highway cruiser and still have plenty of grunt.

If the car ran high 12's or even bottom 13's I would be just fine with that, but I don't want to be any slower than that. Our elevation is 900, so that's not an issue. I'm also not great with a manual so I know that I wouldn't be in the 12's with it, but it gives me an idea of what to expect.

I've also confirmed that it does still have a 10 bolt 8.2 and I'm trying to find a 8.5 or a 12 bolt, but not having much luck. I'd like to find someone that sells rebuilt ones ready to install as I'll be too busy with this whole build to try and learn settings up rear ends.

Appreciate you guys giving detailed responses - I'm trying to sponge up as much info as possible. I had a modified 2005 GTO, Trailblazer SS and now have a cam/ supercharged G8 GT, but I feel like I'm starting from scratch with this beast.
 

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Discussion Starter #7
I just purchased a 70 Judge with a stock RAIII 400. I'm going to be adding the FITech EFI system next month. I'll let you know the results.
I'd really be interested to hear about it! I was looking at the GO EFI or meanstreet. I'm not sure if there are any differences besides 600hp or 800hp.


I've read nothing but good things. I'm getting a bit ahead of myself as the engine comes next year, this year is all tear down, some floor pan patching and everything under the car.
 
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