[TransAm 474]

Hi everyone, we are getting ready to build yet another Pontiac 400, this time it is a 1979 PWH W72 400 out of a Trans Am. We have ordered a bunch of parts for it already this morning, that we already knew that we are going to need, but I haven't ordered the Camshaft just yet, but I will at some point today, figured I would chime in here first and let you all critique the plan I'm thinking before I do so. I've did a ton of research here, and we have settled on the Lunati VooDoo 262/268 219/227 112° 10510702 camshaft. We haven't used a Lunati VooDoo as of yet, and the way people here seem to love them, we want to give one a try. We even thought about the "703", but I dont think this engine will have quite enough compression for it, so we are leaning more towards the "702". We are gonna try and do everything we can to get it up at 9-1 compression or maybe a little more if possible. I know it is difficult to get good compression out of a 400 with 6X4 heads, but this build has to remain numbers matching, so we will just have to maximize what we have to work with. Here is the build I'm thinking

1979 PWH 400 .030" over
Zero Decked
Stock crank
Stock Rods w ARP Bolts(atleast at this time)
Icon Flat Top Piston
Melling M54DS pump
Stock (non ported) 6X4 heads, 7/16" Studs and Polylocks, Milled .030"(maybe that will get them down to around 86cc chamber?)(I'm going to cc the heads, but dont have engine apart yet)
Felpro 1016 .039" head gasket
Quench .039"
Goal is for 9.0 to 9.2-1compression
Lunati VooDoo 702 Camshaft
262/268 Advertised Duration
219/227@.050
.468"/.489" lift
112° Lobe Seperation
Thinking of Installing it at 106° I.C. according to the advice of Harold Brookshire and Paul Carter
Crower Camsaver lifters
Crower 68404 Valve Springs
Cloyes 3512X9 billet timing set
Stock 1.5 rockers
Stock Cast Iron intake
Qjet Recalibrated with Cliff Ruggles parts
Recurved HEI distributor
1 3/4" headers, dual 2.5" exhaust
Super T10 4-Speed Manual transmission
3.23 rear gears

This is 100% street car on pump gas in an original 1979 Trans Am. What do you'll think about this combination? Sound like a good plan?

Thanks

[steve25]

With the piston speed of a 400 and like a 9 to 1 comp with 6X heads I would be looking to bring up my exh flow numbers so as to get a tad better exh to intake ratio by other means then the duel pattern Cam if I could as this will hell you to make higher cranking compression numbers.

Stock 6X heads at .500” lift flow 206 cfm @28” on the intake side and 145 cfm @28” out the lesser flowing center exh ports for a 69% exh to intake ratio and for a as mentioned limited compression motor it would a good thing to get that ratio up to 75%,
Stock D port big exh valve heads flow 158 cfm @28” @ .500”lift just for reference.

The headers will add another 3% to the stock exh numbers above about .400” lift.

Since your fighting for closer to 9.5 compression you can get two pluses at the same time by stepping up to a 1.77” exh valve which installed with even a half way decent 3 angle valve job pick up 15 cfm in low and mid lift flow along with making the chamber a tad smaller to pick up the compression a little.

A mill of .030” will knock out 5 CCs of volume .
Do those pistons have 4 valve notches, or only 2?

[TransAm 474]

Originally Posted by steve25

A mill of .030” will knock out 5 CCs of volume .
Do those pistons have 4 valve notches, or only 2?

Thank Steve! Pistons have just 2 reliefs, 4.5 cc.

[ta man]

I'd suggest opening up the pushrods for future possible use of 1.65 rockers..I forget what the 68404's will handle at stock installed height..but I think its a .540 lift or something close like that.
I like this build..these smog low compression engines make great power with more compression and wise cam choices.
As with most threads..this will quickly snowball into a million dollar suggested build very quickly within a few pages.

[Skip Fix]

I agree with opening up for 11.65s. My 6x-8s on the stock 78 motor handled them no rubbing, the 6x-4s in the 81 car did -and I did not check before assemble so I was screwed there. They also hit way down -the Spotts tool gets you clearance down there.

My 6x-4s were 93 before I smoothed off the chamber edges, measured the same after a 0.050 mill.

If you ad larger valves like 1.77s you almost get too much exhaust flow. A 1.72 might balance it out some over the 1.66s. If you go with the "normal D port" valve length 5.09 you get a little better IH for springs, what I used in mine.

My 78 stock deck stock heads and TRW ran OK with a Cam Dynamics 228/228 ,then a comp XE 262. I thiknk your Voodoo should be a good choice.

[steve25]

Good point TA man about the escalating cost !

Maybe with post / builds like this the OP can for instance say that his Dollar limit on the motor is 4K and then no one responding back can reply which a suggestion that will cost more then let’s say 500 bucks which can be decided upon by the OP.

[Jay S]

I think you have a good plan. FWIW, I do not think the lower compression is a good reason to go with the 702 over the 703. The 703 will make more power with the same low compression, especially with the headers, 702 is mainly a hp trade off for drivability and a smoother, broader powerband. I do not think you would see any gains with 1.65s on either cam with stock heads. They go turbulent before .5” lift, both cams are already close to that with 1.5s. But if you think that might be a future direction now is the time.

[steve25]

I would add to your parts list a heavy duty oil pump drive shaft.
I recall on my 78 TA I had even though I drove the car year round to and from work daily I opened up the rear of the shaker and picked up a nice chunk of power due to the high pressure air at the base of the Windshield above 60 mph.
If you do , or will do this mod be sure to tell Cliff when you send the Carb out to him, because as I recall I had to modify either my secondary metering rods or the rod hanger to get things right fuel mixture wise .

[TransAm 474]

Originally Posted by Jay S

I think you have a good plan. FWIW, I do not think the lower compression is a good reason to go with the 702 over the 703. The 703 will make more power with the same low compression, especially with the headers, 702 is mainly a hp trade off for drivability and a smoother, broader powerband. I do not think you would see any gains with 1.65s on either cam with stock heads. They go turbulent before .5” lift, both cams are already close to that with 1.5s. But if you think that might be a future direction now is the time.

Thanks Jay, I think I am still leaning towards the 702 for this build, it is just a fun street daily driver that will never be raced, and the 702 should retain the best low end power and drivability I would think. I've listened to the 703 in 400's on YouTube, and while I love the sound, they sound pretty rowdy, and most of those application usually have 9.7 to 10-1 compression. We dont mind some thump at idle, just not enough to hurt low end. The 702 looks pretty mild for a 400 really, but I would think it would still have a little sound? If we were building a higher compression 400, we would definitely go with the 703 no doubt.

[BDH79TA]

FWIW, when I asked these same questions for my 428 build years ago, it absolutely got into the million dollar build advice. While I've got a little more engine to start with, my build is very much the same that you're planning.

428 .030 over, 6X-4 with .030 off the heads, .015 off the block deck, KB pistons, etc. In the end I should be right around 9.25 to 1. The cam choice drove me nuts. I didn't want to give up too much low end but I did want a noticable idle. The two rarely coincide. After some coaxing from others and consideration I went with the VooDoo 703.

I rebuilt the carb myself, but with Cliff R parts and advice. I went with an MSD ready to run distributor for tunability. In current form, this is mated to a TH350 with a 3.08 rear in my 79 T/A. It's a respectable cam and performs very well. With careful tuning I'm really glad I chose the 703.

I just got it up and running last fall and don't have any numbers to share, but from a driver stand point it worked out nicely. I am in the middle of converting to a 4 speed for the fun factor but had no real driving issues mated to the TH350.

Good luck with your build. I feel your pain when it comes to cam choice and driveability.

[Jay S]

The 703 is really a 9.0-9.5 compression cam, even in a 400. IRC Lunati even says that in there description, they actually have that right. 702 and the 703 pretty much want the same compression range. Running either for lower compression just give them more advance, which I believe 106 was already mentioned for the 702, should be good there. 702 is 267/273 @ .006 tappet, more seat timing than advertised. Should say that on the card.

[TransAm 474]

I appreciate everyone's help on this! The build plans have now changed for this engine, and will now be a 467 with a Butler Performance stroker Rotating Kit. Please see the new thread here and let me know what you think...

https://forums.maxperformanceinc.com...d.php?t=849029