# Question on a 76 400ci



## X~Nightstalker (Mar 28, 2009)

So I found a block out of a 76 grand prix..havnt bought it yet but its the best I have found so far. 

My concerns are with the power available from the 76 one compared to a pre-71 block.



geeteeohguy said:


> Use a later 400 as stated above (more common, timing cover is available, etc.) The only real difference in early to late HP figures is due to vompression ratio and camshafts, and compression ration is controlled solely by the cylinder heads. So, you can get a common, mid '70's 400, and use better heads, and have a good runner. Be careful about compression, though. You want to run 87cc heads or larger with stock pistons. All heads earlier than '71 except for the 455 heads have 64-72cc heads, and result in 10.5-11.0:1 compression, which is unworkable on today's gas.


I already plan on replacing pistons and the usual stuff on a rebuild.

Now in understanding the above I need to get different heads if I want any serious power? Other then Edelbrock, does anyone else build new heads? 

1000 a piece is pretty steep....im sure I could find it a little cheaper, but not by much. As mentioned I should get 87cc, there are also 72cc heads...He said with stock pistons as in I should use stock if I plan on using pump gas? If I get better aftermarket ones can I use the 72cc heads?



A lot of questions in this one...lol 
I have yet to venture into rebuilding engines much, so I am a bit of a novice in that department. Thanks for all the input!!!!!!!!:cheers

**EDIT** Just got info that it the engine code is 500557 Which would make it one of these-
YS F-body 75 400 185 Turbo 350 L-78 S 1x4 500557 2
YS F-body 76 400 185 Turbo 350 L-78 Z 1x4 500557 2


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## Petey D (Feb 14, 2009)

The 76 400 is a smog motor, it has lower compression than earlier models, and probably makes around 200hp give or take. 

There are a lot of different head manufacturers out there, all varying in price, a few examples are Trick Flow, Brodix, Canton, Dart... the list goes on, but I'd expect to pay about 1k for a good set. I picked up a set of Dart heads (87s) for $700 Cdn used.

Which heads you use depends on which cam and intake you plan to use. There are a lot of different combos out there that will work well together, and even more that won't. 

Hopefully the other guys will be able to give you some examples of good combos to use, If we were talking about Fords I'd know a bunch of them, but I'm still learning about Ponchos, I'm still looking for the right cam to go with my dart heads and RPM intake.

Hope this helps at least a bit. Good luck.


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## Koppster (Jul 27, 2008)

First off, I defer to experts for corrections; however,... :cheers

If you're going to rebuild it, a 400 block is a 400 block...it will be what you create.

I have a 76 400 bottom end (block) in my 64. It was bored .60 over and the pistons were replaced as was the oil pump. Not certain on the compression ratio, but certain they are not stock.

The top end (heads, cam, valve train, intake, carb, etc.) are all Edelbrock.

The car runs very (did I say very?) strong; although, I don't know how many ponys as I have not dyno'd it. If I had to guess, I would estimate between 350 and 400 hps given the top end set up.

Rick


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## X~Nightstalker (Mar 28, 2009)

Thanks guys. At least I know I have some options. The Edelbrock heads are just so damn expensive.
I got the word from the shop that is going to build my engine...he said that he could get about 320-370HP from the 76 block. Its looking like I will find out later if I should get different heads or not. Now its just time to outbid some people for the engine!


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## geeteeohguy (Feb 2, 2008)

Check the pontiac sights on the web and get ahold of a cylinder head chart. You'll find the listings of all of the stock, cast iron heads and their cc's. There are several heads that would fill your bill, all for waaaay less money. Some of the early '70's 350 heads are good, like the 7k3, I think. You want around 85--100 cc's. 85-90 is best. If you use dished pistons, you can use any high perf '70 or earlier 68-72cc head with great results. Some good pre-'70 ones are #12's (I have a set for sale), #670's, #16's, and on and on.


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## Too Many Projects (Nov 15, 2008)

Like geeteeohguy says, I would be looking at stock heads. My concern would be the valve size. Smog heads tend to have smaller valves, which limits breathing and cam choices a little. The pistons can be matched to any size combustion chamber to achieve the desired compression ratio. Be aware that it STILL costs a considerable amount of coin to convert pre-hardened seat heads to live very long on unleaded fuel, so the optimum choice would be a decent head that has hardened seats already or a set of older heads that have been converted. Building an engine from scratch can be fun and frustrating at the same time so do the research, take your time finding the right combination and put it together the way you want it.:cheers

Here's a good chart to compare heads by number, valve size and combustion chamber size. I'm not sure what year Pontiac went to hardened seats but this will get you started.
Pontiac Power


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## Jstreet (Mar 9, 2009)

I have a 400 block out of a 75 T/A with #16, 1968 heads, Holley 3310, Edelbrock P4B Intake and Hookers. The car runs very strong. Not sure the horsepower but it will smoke 'em in third gear on the stock Muncie M20.


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## X~Nightstalker (Mar 28, 2009)

Awesome guys! For this one I am having a friend of the family taking care of the whole rebuild...I am stationed in Hawaii and want the engine ready for install when I get transferred to the National Guard in May. If I get the block I am aiming for, I was told I could get about 370HP....which is about what I was wanting. That was with the stock heads....Ill add an update when I have it set in motion. 

Thanks again:cheers


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## Jstreet (Mar 9, 2009)

Post your head codes, cam/internals and the top-end carb/intake youplan on using and I'm sure you'll get some good feedback. Stock heads from a 76 may not be the ticket.


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## X~Nightstalker (Mar 28, 2009)

I got the 76 block on Ebay for $350. It was running strong when the guy pulled it out. It comes with everything from the carb to the oil pan. He is also including a TH400 and the DS with the deal. I think I lucked out on this one. Not too bad for a whole set up. 


Now its on to accessories for after the rebuild...


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## Jstreet (Mar 9, 2009)

Don't trust the whole "running strong" thing. Sounds like you got a deal with the tranny too, but Id still be weary of problems after the install. (especially on the tranny side) Automatics almost never work right after a rebuild or don't last very long in my experience. Better to go with a new unit IMHO. Date/code everything and see what you have. Post the codes.You'll be glad you did.


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## X~Nightstalker (Mar 28, 2009)

Im gonna save the trans for later use. The engine is going to go through a full rebuild. 
I do hear what you are saying about the "running strong". Who knows, people use anything to sell a product. Im just hoping for no major damage or repairs.


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