hey guys i know this has probably been asked 100 time before but could you please humor me? i own a 1978 trans-am that i am fixing up for just a cruiser/ hot rod and was wondering if anyone has actually dyno test a stock 6.6 engine? i have gotten alot of mixed answers on this question. some say the advertised hp from the factory is correct and others say the factory derated the engine for insurance reasons. I think i read somewhere that my t/a pumps out about 230 hp maybe less. and if any of you know of any good engine building books i have the one written by jim hand witch is great but was looking for more. any help would greatly be appreciated.  

If your TA has the original engine, it is either the 180hp 400 or the 220hp W72 400, sorry I don't recall the codes for each, but your local Pontiac dealer can tell you from your VIN number. Don't know of any better books than Jim Hand's.  

Yeah, I looked up the codes.  Coded WC if bolted to a four speed and X7 if needing an automatic for the 1978 TA.  Sorry, I have no good answers for your question, GTO.  

hey barney and dave thanks for replying to my thread unfortunatly i do have the no frills 180 hp ta. kinda starting to wonder if it would even be worth rebuilding the 400 or just swapping out motor and trans with a 350 chevy i think i could get alot more hp for the buck with the chevy motor. i have always owned chevys but have been wanting a ta since i was 15. what do you guys think chevy swap or stay with the pontiac motor?  

PLEASE DON"T DO IT!!!! Seriously, the only difference between your 180hp and the 220hp is the heads and camshaft, the heads are identical except for the combustion chamber size (regular 6X heads give a compression ratio of 7.7:1, the 6X-4 heads are 8.5:1). The exhaust system is different too from the converter back, your car would have had a single pipe and crossflow muffler with dual tailpipes, the W72 220hp had a "Y" pipe and two resonators behind the cat and two full length tailpipes. A good rebuild with a .030 bore and new pistons, rebuilt heads- milled to increase the comp ratio and a mild modern cam, will increase the power greatly. Don't forget the exhaust system, my formula has 2.25" duals with turbo mufflers, using the full length stock tailpipes, hooked up to the stock manifolds. It is a nice fitting system made by a local shop and it is quiet (not stock quiet though!) and I don't worry about headers leaking and dragging. Another area to look at is the rear gears, many of these cars had 2.41, 2.56, 2.73 gears which won't be quick off the line with any engine short of a 500 ft. lb. 455. Try 3.08 or 3.42, the bottom end will improve greatly and the highway rpm and manners will still be good. Also consider a mild (2000-2500 rpm) stall speed torque converter- unless you have the 4-spd! Keep the stock intake and 4 barrel carb- with a good rebuild the Q-jet will work great. If you go this route the appearance and value of your car will only increase instead of the usual "hack-job" that most Chevy swaps end up. Not that some guys can't do a good swap, just that most don't bother doing it right. Hop I helped you.
Steve  

hey steve thanks for the reply and the answer to my next question . you just single handedly convienced me to keep the 400. i have been searching for along time now on a mild to moderate build for the 400 and this was my last stop before i started the engine swap. i live in va. and here,... there is only two types of guys ford or chevy so trying to find info on a pontiac build is slim to none around here every speed shop i went to wanted to sell me a set of edelbrock heads and then go from there. they would be great but 1700 for a set really started to put a bad taste in my mouth. anyway i think i read a thread you wrote awhile back that was entitled 6x vs 5c. was wondering how that build was going and what kind of hp are you expecting to get with that build?  what i am shooting for is somewhere between 350 and 400 hp but without spending 1700 on a set of heads........does it sound possible?  

To be honest my own 400 is on the back burner for awhile, I'm currently running a 75 350 pontiac with the 5C heads, stock 4bbl carb and intake with stock exhaust manifolds and a mild Crane cam. I just got it in the car in August and I'm still running 2.73:1 gears behind a TH400 trans, so it's no barn burner! It is really strong from 2500rpm-up. This winter I'm swapping in a 3.42posi when I replace my sagged out rear springs. Lots has been written about the 6X heads(5C's are virtually identical)flowing just as well as the earlier D-port heads, the drawback is their low compression ratio, however if you work with a good machinist and have the block deck shaved to get the pistons as close to zero deck height as possible and mill the heads, you should be able to get 9:1 which will work better with todays low octane gas than the older heads which have 10.5 or 11:1 compression. I agree on the price for Edelbrock heads, I'm sure you can live without them and still get 350hp easy. Call Comp Cams or Crane for a cam recommendation, they will need lots of info, but they will get you the best cam for your combo. Unless you want to modify your shaker hood or use an adapter kit, you can't really use any aluminum intakes except the Performer, which isn't much better than the stock piece. Check out the tech articles on this site to see what fits, there is a whole article on intakes, plus two onn the stock smog intake and how good it really is. The important thing to remember is that a 78 400 isn't really any different under the heads than a 69/70 400, yes the castings have changed a bit and are lighter, but the bore, stroke and pistons are virtually the same. Swap on a set of early heads and a 068 or 744 cam and ram air exhaust manifolds with good, true dual exhaust, and you have a 78 RA3 ! Your Chevy and Ford buddies won't believe it! Is your car an auto or 4spd?  

Mine is a automatic. i plan on installing a shift kit and about 2500 stall when all is said and done. when i was at the machine shop i asked them if i had the block decked and heads shaved if it would raise my comp. and they said not enough to make a difference and then tried to sell me a set of heads. that i think is what discouraged me from building the 400. what book can i buy that will give me all the info that i would need on the motor?  

Try Jim Hand's book, you can see it at this website, along with Cliff Ruggles book on Q-jet carbs. My buddy, who has a PHS documented 69 RA3 Judge ragtop, 69 GTO hardtop (428, 4spd-3.91 gears), 66 389 tripower GTO and 79 Formula with 400/4spd 3.42 combo, swears by Jim's book and all his cars run hard. He believes that if your going to drive a Pontiac, especially a GTO, it better work right, so you don't spoil the good name!
If you can find a 75 350 w/5C heads or a 76 350 w/6X heads they have smaller combustion chambers than the 400 and will give you the 9:1 cr after milling and they already have hardened seats for use with unleaded gas. Sorry I should have mentioned that earlier, that's my plan for my 400, is to use the heads from my 350.

http://www.pontiacstreetperformance.com/