# 400 tear down



## Goat noob (Apr 16, 2021)

Hey!
I just picked up a Pontiac 400 from a 71 GTO that is eventually going into my 68 goat that powered by a 557 cast engine. I’m currently in the process of disassembling the engine and nothing seems to have any excessive wear. Cam, lifters, heads… everything came off with ease. I am told thr engine spun a bearing and has been on an engine stand for a few years since. I plan to remove the crank tonight and further examine it for any damage. Is my best bet to leave it up to the discretion of my local machine shop to tell me to reuse parts from the car or should I just start buying new parts once the block is In the hands of the machinist? I have #16 heads and #96 heads for the car. Looking for suggestions on what should go on it. I can’t afford to build a race motor but I’d like to have around 400hp when it’s all said and done.


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## PontiacJim (Dec 29, 2012)

Goat noob said:


> Hey!
> I just picked up a Pontiac 400 from a 71 GTO that is eventually going into my 68 goat that powered by a 557 cast engine. I’m currently in the process of disassembling the engine and nothing seems to have any excessive wear. Cam, lifters, heads… everything came off with ease. I am told thr engine spun a bearing and has been on an engine stand for a few years since. I plan to remove the crank tonight and further examine it for any damage. Is my best bet to leave it up to the discretion of my local machine shop to tell me to reuse parts from the car or should I just start buying new parts once the block is In the hands of the machinist? I have #16 heads and #96 heads for the car. Looking for suggestions on what should go on it. I can’t afford to build a race motor but I’d like to have around 400hp when it’s all said and done.


First step is the machine shop for hot tanking, magnafluxing for cracks, and then evaluating the block & crank. He will tell you what bore size he can go with and how much the crank will need turning. Then you can order parts accordingly.

For a street engine with cast iron heads, shoot for a 9.0-9.3 compression ratio.

To be honest, your best bang for the buck will be a Butler stroker kit that will include a new crank. It will also include forged rods, bearings, pistons/pins, and balancing - all of which you are going to need anyway. You will have more cubic inches to offset the lowered compression and add more Torque. You will want to CC your heads to know what piston dish is needed to drop compression.

Now you can save money by sticking more with stock parts if budget is important. You can have the casr rods rebuilt and use the better ARP rod bolts, but with the age of these engines, it is insurance to at least purchase an inexpensive aftermarket forged I-beam connecting rod like the factory piece. Stronger and you won't have to worry about over revving and breaking a cast rod.

You can get cheaper replacement pistons if needed, and I have rebuilt engines using the old pistons and honing the cylinders, but more than likely you may need the block to be bored and new pistons. So you have options based on price - but you still need to know the CC's of the head chamber to match piston domes/valve reliefs to get to a good pump gas compression unless you are planning to use high octane gas or an additive.

So those are the first key points I would suggest. Bunch more, but that is for starters. Check out the reading section for book suggestions and there are a couple books recommended on engine building that you should familiarize yourself with so you can know what your machinist/engine builder is talking about.

Price wise to rebuild an engine, maybe $4,000 - $4,500 on the low side if you rebuild the heads, and on up from there depending on parts selected.


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## Goat noob (Apr 16, 2021)

PontiacJim said:


> First step is the machine shop for hot tanking, magnafluxing for cracks, and then evaluating the block & crank. He will tell you what bore size he can go with and how much the crank will need turning. Then you can order parts accordingly.
> 
> For a street engine with cast iron heads, shoot for a 9.0-9.3 compression ratio.
> 
> ...


Awesome! Thank you for the info. My #16 heads are 72cc and the #96 is 96cc according to a few Google searches. I can’t justify buying new heads when I have 2 pair sitting in the garage. All signs point to stroker kit whenever I read up on increasing performance. I’ll keep you posted as things start to move.


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## PontiacJim (Dec 29, 2012)

Goat noob said:


> Awesome! Thank you for the info. My #16 heads are 72cc and the #96 is 96cc according to a few Google searches. I can’t justify buying new heads when I have 2 pair sitting in the garage. All signs point to stroker kit whenever I read up on increasing performance. I’ll keep you posted as things start to move.


My 455 build I am doing uses the 7K3 heads which are also 96 CC's, but I did a little blending in the chambers and they cc'd to 98. Many Pontiac heads will be a few CC's over what the factory states them to be, but CC'ing one of the chambers AFTER you do the heads/valve job will provide an exact number that can then be used along with bore, deck height, gasket thickness to determine how many CC's you will need to get out of the tops of the pistons by either larger valve reliefs or a dished piston.

So if the engine block checks out, I would suggest doing your heads so that you can get an accurate CC number from one of the chambers and go from there.

This is the compression ratio calculator many of us use. It may not be 100% accurate if assembling a NASA rocket engine, but it will be close enough in accuracy for a street build. You can see the items you will want to know the numbers for in determining the compression ratio.



Compression Ratio Calculator - Wallace Racing


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## Atarchus (Aug 4, 2020)

I sourced a 461ci stroker kit from Butler, runs great! I also went for the forged crank, figured go big or go home. In hindsight, I probably wouldn't do the forged crankshaft again. It's definitely overkill for my build and I'm never going to use nitrous in my convertible lol


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## Goat noob (Apr 16, 2021)

Update:
The motor is at the machine shop and he is going to dip and magnaflux it. I have the option to save some $ and just have the crank cut for $150. I know I’ll be leaving performance on the table if I don’t go the stroker route. I’m looking at butler performance to source my parts for whatever direction I choose to go in with this build, unless you all have another vendor you like. I know you can’t just go anywhere for Pontiac parts like Chevy or Ford. If I keep it budget friendly I would just research what cam would pair well with my heads (either #16 or 96) and have a pair of those heads really worked. I haven’t found anyone here in northeastern Pennsylvania so far that is comfortable porting heads. This is my first rodeo tangling with a machinist so any insight is appreciated.


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## Atarchus (Aug 4, 2020)

If you decide to order from Butler, make sure you call to order, it will likely save you some money


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## Goat noob (Apr 16, 2021)

PontiacJim said:


> My 455 build I am doing uses the 7K3 heads which are also 96 CC's, but I did a little blending in the chambers and they cc'd to 98. Many Pontiac heads will be a few CC's over what the factory states them to be, but CC'ing one of the chambers AFTER you do the heads/valve job will provide an exact number that can then be used along with bore, deck height, gasket thickness to determine how many CC's you will need to get out of the tops of the pistons by either larger valve reliefs or a dished piston.
> 
> So if the engine block checks out, I would suggest doing your heads so that you can get an accurate CC number from one of the chambers and go from there.
> 
> ...


Using the compression ratio calculator with what I know, my compression came to 11.58. I see a lot of numbers thrown around on forums and people I’ve talked to about what you can get away with on 93 octane and the numbers are pretty inconsistent. If 11.58 is too high (I’m sure it is) what type of piston would you recommend to lower that compression?


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## Lemans guy (Oct 14, 2014)

As Atarchus said, call Butler, they will help you also pick out the correct dished pistons to get your compression right.


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## Lemans guy (Oct 14, 2014)

Butler ports heads if you want that done. I live not far from them MSD have been there a number of times. Very professional crew, quality work and parts.


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## Lemans guy (Oct 14, 2014)

MSD is typo…


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## Goat noob (Apr 16, 2021)

Lemans guy said:


> Butler ports heads if you want that done. I live not far from them MSD have been there a number of times. Very professional crew, quality work and parts.


I’ve only read amazing things about them. I’ll have to give them a call and get some insight. Thank you!


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## PontiacJim (Dec 29, 2012)

Goat noob said:


> Using the compression ratio calculator with what I know, my compression came to 11.58. I see a lot of numbers thrown around on forums and people I’ve talked to about what you can get away with on 93 octane and the numbers are pretty inconsistent. If 11.58 is too high (I’m sure it is) what type of piston would you recommend to lower that compression?


You had to have done some wrong calculations! LOL Pontiac uses flat tops in most all engines and then the combustion chambers are what dictate the compression. The 1968 400 with #16 (big valve heads) would only have around 10.5 compression (maybe even a tad bit less but are advertised at 10.75). The 1971 400 with #96 heads would only have 8.2 compression.

So your options are to use a dished piston or one with larger valve reliefs to drop compression with the #16 heads OR use the #96 heads(96 cc's) and bring compression up by "zero decking" (which i figured to be about 3.2 cc's ), mill the heads .030" (.005 = 1 cc, so another 6 cc's), then use a .027" Cometic head gasket versus Felpro .041". Use a piston with only 2 eyebrow valve reliefs vs 4, so this will make pistons "left" & "right" and 4 reliefs are 6.6 cc's and I used 1/2 or 3.3 cc's. So with all that, I calculated 9.36 compression which is perfect for pump gas. Without the zero deck and 3.2 cc's, you still get 9.09 compression. If using the 4 eyebrow pistons and 6.6 cc's, the compression drops further to 8.84 compression. Use the Felpro head gaskets at .041", compression is now 8.61 compression.

So you can see how raising compression can be done with the larger chamber #96 heads - none of those compression ratio's are bad for a street engine and pump gas when selecting a matching cam and top end.

On the other hand, the #16 heads appear to need a piston having around a 14 cc dish or combined valve reliefs. The pistons would be the cleanest and simpler choice, but either head when matched to the other components will work - the key is selecting the parts and matching any machine work.

I would opt for the #16 heads because they would be easiest as long as they test to be good and can be rebuilt without issue.

400 HP will also be dependent on compression ratio, cam selection, and the RPM range you see the engine spinning.


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## Goat noob (Apr 16, 2021)

Lol I figured I was doing something wrong with the calculator. I’ll dig the #16’s from my dads basement and have the machinist take a look at them. I don’t even have a RPM tach in the car. He said he’ll have an update on the condition of the block and crank in the next week or so. I’ll keep you all updated. I appreciate all the info!


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## Goat noob (Apr 16, 2021)

Hey all,
Update:
The block is bored .30 over .20 on the rods and .10 on the mains. Crank is cut and in my garage standing up in a garbage bag to keep dirt and dust away. I should have the rest of the engine on my stand in a few weeks. The #16 heads are with the machinist now and will be redone if they check out. I am going to assemble this engine in my garage this winter. Does anyone have experience with Ames?









Stage 3 Performance Master Rebuild Kit for 1967-1979 Pontiac 400 Engines


Kit Includes -Sealed Power 4 valve relief flat top pistons (press fit pin)-Hastings moly piston rings set-Sealed Power engine gasket set -Melling oil pump-Engine Pro main & rod bearing set-Durabond camshaft bearing set-Engine Pro timing chain set-Melling freeze plug kit-Engine Pro stage 3...




www.amsracing.net





the link above is substantially cheaper than a build kit from butler. I am keeping price in mind in case I rebuild this engine and it grenades shortly after installation. Does anyone have any insight?
Thanks.


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## PontiacJim (Dec 29, 2012)

Goat noob said:


> Hey all,
> Update:
> The block is bored .30 over .20 on the rods and .10 on the mains. Crank is cut and in my garage standing up in a garbage bag to keep dirt and dust away. I should have the rest of the engine on my stand in a few weeks. The #16 heads are with the machinist now and will be redone if they check out. I am going to assemble this engine in my garage this winter. Does anyone have experience with Ames?
> 
> ...


As good as any since Ames offers it. Are you keeping the stock rods? Magnafluxed, ARP rod bolts, resized? You are going to balance the engine right?

You may be using octane booster with the high compression, so don't be surprised.


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## Goat noob (Apr 16, 2021)

Keeping the stock rods. He said one had to be reconditioned. I have all the bolts that came off the engine, is it foolish to reuse them? I’ll have to research balancing the engine. I was hoping that kit wouldn’t push me over the edge of operating on 93. Should I look into different pistons? What kind of questions would you ask my builder based on the information I put forward. This is my first rodeo, you saw how bad I botched the CR calculator a few weeks back ha.


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