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Discussion Starter · #1 ·
Surprise its a Pontiac 400! But I posted this on the pontiac board and got zip for help.

What I've got:
68 GTO convertible; m-21 with 3.90 gears & posi. I'm going to take the block up to be machined Friday and was hoping to get some suggestions on parts.

This car will not be raced, it will be strictly a cruiser but I do want it to be quicker than stock.

here is what I know I am going with:
new 5140 rods
Factory intake & Q-jet
Stock crank
Stock #16 casting heads; (2.11/1.77 int/exh valves; 72 cc chambers, screw-in studs)

Do I need HV or HP oil pump?
What pistons would let me run pump gas? Would flat tops be OK? I don't think I need forged for this build but am open to suggestions.
What cam would run strong on the pump gas compression and get the most out of the 4-speed and 3.90 gears? I will upgrade springs if necessary.
 

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Get a 455 crank modified to fit. You could buy some cheap-junk Chinese crank--but I'm not recommending that.

Lotsa stroke, nice small main bearings. Best of both Pontiac worlds.

With the extra torque, you could drop the rear gear a bit for improved fuel economy.
 

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Discussion Starter · #3 ·
I thought about that but then wouldn't that make my weenie 8.2 cry and want to snap like a twig? Or since I have the beefier posi carrier do you think it would be OK?
 

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Discussion Starter · #5 ·
Nope, not going to run headers on this poncho.
 

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I think with flat tops with those heads will put you at around 10.2 compression ,i would limit camshaft duration too [email protected] and around .500 lift (hyd falt tappet). run some 29inch tires and you should be good. your ten bolt will last a long time as long as you dont dump the clutch @4500 with slicks.
 

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If not running headers I would run Ram Air Manifolds then.:thumbsup: Just put them on mine. Really helped in the upper rpm range. With a 400 and decent compression at least 9:1 then run a good size cam, in mine I think I have a [email protected] A 280 magnum comp cam would do nicely. I have a Qjet that Cliff helped me rebuild and that helped alot too. I have 3.23 gears with my 4 speed and it all works great, with 3.90's you will definately launch.:eek: Also a MSD with a 6k rpm limit is nice piece of mind on an expensive motor.
 

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Discussion Starter · #8 ·
Cool, good info - I must've been blackballed on the pontiac for admitting I owned a chevy!

I don't have any manifolds at all for it so the ram air manifolds would be a nice, stealthy upgrade.

I have been looking for some dished pistons but not having much luck so far.

Here's the cam I've been looking at:

Lunati Voodoo 60903
* Advertised Duration (Int/Exh): 268/276
* Duration @ .050 (Int/Exh): 227/233
* Gross Valve Lift (Int/Exh): .489/.504
* LSA/ICL: 110/106
* RPM Range: 1600-5800
 

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Get a real good porting job done on the heads, that seems to wake up that engine. Coworker did the stroker thing on his poncho and was impressed with cubes that were added. After he got the heads done he really had a smile on his face. He swears they added more power then the cubes.
 

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Make sure the person that bores and hones your block does it with a deck plate and knows how to use it. Shop around. Don't go to someone just because they are close to the house.
 

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Do you have this book by Jim Hand?

Amazon.com: How to Build Max Performance Pontiac V8s (S-A Design): Jim Hand: Books (not a for sale ad, just a link)

If not, add it to the book shelf it's a good read.

In the back there are a bunch of engine build examples, of all sizes, from different builders. For the 400's they say dished piston will give about 9.3 to 1 compression, with flat tops about 10.2 to 1 like someone said earlier. The cam choices were all over the place from 221/229 (int./exh. at .050) to 231/239, with lifts in the range of .480 to .525. A bunch of brands were mentioned also, like Comp, Crower, Ultradyne, and good old Pontiac Ram Air IV (stock specs). They all claimed expected performance in the high 12's to low 13's with a good set up.

The cam you're looking at fits right in with all the examples. With your 4-speed and rear gears, You could probably go a little big on the cam and get away with it no problem.

He really didn't cover oil pumps too much. Just said that for moderate engines they want moderate pressure like 55 - 60 psi, and for high revving engines (race only I guess) they need a stronger pump like 80 psi.

For your enjoyment, DynoSim came up with 379 HP @ 5500 and 436 TQ @ 3500. This was with 9.5 to 1 compression, flow numbers for #16 heads with medium port work (whatever that entails), the VooDoo cam you list, and H.P. manifolds w/mufflers. I know you said you weren't going to run headers, but with small tube headers w/mufflers it jumped to 423 HP @ 5500 and 467 TQ @ 4000.
 

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Discussion Starter · #13 ·
Yep I do have that book! It is a great read.

436 TQ sounds like fun!! :D
 

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i have a buddy that i help build pontiacs. for a street/strip we feel the 400 is the best. the 455 pontiac has a main bearing journal that is too large, also it gets real expensive when buy you custom pistons so you can have a long enough rod it. 455 stroker kits are ok, but they are expensive. the stock crank is nodular material and can take a lot of abuse. the stock rods are cast and are junk!!! 5140 rods are ok, but why not 4340??? srp makes a nice flat top. they are lighter than the old trw. the trw had 4 valve reliefs. the srp has 2. the compression will be around 10.25 to 1 with those heads and srp pistons.with a pontiac this can cuase problems with pump gas. you can get by with 92 unleaded, but you had better get rid of the sharp edges in the combustion chamber. the heads you have are a d port exhaust correct??? the ram air 4 manifolds are a round port and dont line up very nicely. this brings up head choices. the kre aka kauffman heads are the way to fly!!!! they use the more common d port exhaust, this makes the header choice cheaper and easier. yes i said headers, a pontiac cant breathe without them!!! the kre heads will outflow a fully ported ram air 4 head. they are also aluminum. have you priced what it costs for pontiac valves??? ferrea's are not cheap!!!! you could end up with a lot of money in those old cast iron ones!!!! the kre will make more power than any stock head period!!!!! kre even has a crower cam matched to the heads. my favorite crower dealer sells us the cam/lifters for under $200!!!!. you need to find a copy of the HO RACING PONTIAC BOOK. this was written in part by ken croice. you will need the factory HO style oil pump. the factory SD is not the way to go. if you can get ahold of ken croice he will sell you the dissy gear that goes with the HO pump also. the stock gear doesnt like the HO pump. the milidon pan is the best. the stock windage tray is junk, it need lots of holes drilled in it to work. the deck surface on a pontiac does not require a torque plate. we have tried it with and without, and always produces the same rusults. the deck is plenty thick on the pontiac. i hope this helps.:D the HO PONTIAC RACING BOOK has diagrams for porting stock style heads also. http://www.krepower.com/
 

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Discussion Starter · #15 ·
I appreciate the input!

I dropped off the block yesterday, and gave him the crank to get it checked and cut/polished. He said he'd be in touch with me on tuesday or so after he cleaned and magged it. Nice guy.

After he saw the crank he said "its wounded!" It did have a lot of old scuzzy oil on it but I don't think it was that bad.
 

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I FORGOT TO ADD-MAKE DAMN SURE THE MACHINIST CHECKS THE FIT BETWEEN THE SNOUT AND THE BALANCER!!!! the balancer is not a press fit and is often damaged!!!! ALSO MAKE SURE THE MACHINIST KNOWS THAT THE RIGHT SIDE OF THE BLOCK SITS FOWARD ON A PONTIAC. THE CHEVYS HAVE THE LEFT SIDE MORE FOWARD. THIS HINT WILL GET THE ROD/PISTON LOCATION CORRECT. ***** MAKE SURE THE MACHINIST DOES NOT DISTURB THE DOWELL PINS ON THE MAIN WEBS OR YOU WILL LOSE YOUR MAIN ALIGNMENT!!!!






I appreciate the input!

I dropped off the block yesterday, and gave him the crank to get it checked and cut/polished. He said he'd be in touch with me on tuesday or so after he cleaned and magged it. Nice guy.

After he saw the crank he said "its wounded!" It did have a lot of old scuzzy oil on it but I don't think it was that bad.
 

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Discussion Starter · #19 ·
I've already bought the jim hand book. Its a great read and I got way more help than I ever could've imagined from this board; in fact 300% more than I got from the pontiac website. I posted this message over there 1 day before I posted it here and I got all of 2 replies; only one of which was even close to helpful.
 
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