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Need help[ on engine rebuilt- 1970 GTO


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Hi, I have a numbers matching 400 in my 1970 GTO. Doing a restoration on the car so we pulled the engine to go thru. The shop says it has been bored 30 over and 8.5 pistons installed in the last rebuild, don't know the cam. He said by the bearing numbers it looked like it was rebuilt around 2001 or so. He says it is showing some wear.



My question is what would be recommended rebuilt if I just want to get back to stock or a little more, run on pump gas, idle and start nice but be able to light them up once in a while? It's an A/C and Auto Car.



Thanks so much for your help




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I assume that the 8.5 pistons are the compression ratio? For a pump friendly you can keep those or even bump up to 9.0 maybe 9.3. Check out Butler Perfomance for the parts I would probably stick to a cam that has less then .480 lift on both the intake and exhaust for a smooth idle with a little more grunt. If you can save the rotating assembly then you can save a tone of money. Also look at gasket matching the intake and exhaust for a few more ponies.



Are you going to do the rebuild or is your machine shop?


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A machine shop will be doing it, yes the pistons are 8.5 to 1. The cam I think is 3/4 lift, what the previous owner thinks.



By rotating assembly, you mean the crank ?


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A machine shop will be doing it, yes the pistons are 8.5 to 1. The cam I think is 3/4 lift, what the previous owner thinks.

By rotating assembly, you mean the crank ?

If replacing your crank/rod bearings, they can go 30 as well. Assuming the crank was milled before on the last rebuild it's already been turned down at least 10. Personal opinion... anything more than 20 replace. I've found the thicker the bearings, the easier they will spin. They only have to move 1/8 in, to block the oil port to that journal. = $$$$ Bring this up to your machine shop. If they know YOU KNOW, they will be more likely to give you honest information/advise on your build. Another personal preference is Michigan Clevite bearings.....The ONLY bearings I will use.

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There is a Pontiac only auto wrecker but I cannot remember the name. It will probably come to me later.


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Interesting situation we have here bundy. I agree with everything notallthere and JUSTA6 states. I am a fan of Clevite bearings as well. They are in my .30-over 455 (462) in my '72 Lemans. I run about 9.5 to 1 on premium pump gas. Also ARP bolts/studs inside, I use stock bolts only where they show externally (i.e. some head bolts are external along with the exhaust and intake manifold bolts)



You have a numbers matching '70 GTO. So I will assume that you wish to keep it that way. Now you will have to search the internet, swaps, large Pontiac meets, etc. to track down a set of #13 heads. You are in luck (to some extent) that Pontiac used the #13 on both the GTO and the Grand Prix, so there should be more of them out there. Still I think you will have a difficult time find a set (I hope not but I am trying to be real here too). It won't be impossible, it will just take time and don't expect them to be inexpensive. The guys who are selling them know these heads are for Goats and Judges. Be prepared to buy the set of heads, not just one, when you find them, unless they are only selling - then ask why they are only selling one.



Rotating assembly refers to all the moving parts of the engine - crank, pistons, rods, cam, and valvetrain.



For a cam selection, the Pontiac stock cam profiles were pretty good. Malcom "Mac" McKellar was a cam guru at Pontiac back in the day. So his so called "grinds" are very good right out of the box. A McKellar #10 profile might the best choice. A know a lot of Pontiac guys that swear by that cam profile. All else fails ask your machine shop for an RV cam profile. The key is you want to be able to generate enough vacuum to run all your stock accessories. I would definitely run a hydraulic over solid lifter cam. I think Crane has a version of the McKellar profile in both hydraulic and solid lifter versions.



Here are list of salvage yard you can try to contact for your #13 head - but obviously there is no guarantee they will have it.



Desert Valley Auto Parts


Frank's Pontiac Parts


East West Auto Parts Inc


Indiana Pontiacs.com


CTC Auto Ranch




I suggest going to the Trans Am Nationals in Dayton OH and the Pontiac Nationals in Norwalk OH in August, the GTOAA or POCI conventions in July. They have the largest Pontiac parts swaps meets. Also, eBay, craiglist, etc. whatever works.


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Thank you all for your help, I have located some # 13 heads, on guy will split them at $250 per or I can get a set delivered to my door for $325. Thought I would go with the single unless some one else needs just one. We keep everyone posted on the project.


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Thank you all for your help, I have located some # 13 heads, on guy will split them at $250 per or I can get a set delivered to my door for $325. Thought I would go with the single unless some one else needs just one. We keep everyone posted on the project.

For that price I would take both of them and shelf one of them.

:agreed:

Congratulations on finding a set, the hard part is over with. I agree with notallthere and Ghost, write the check and buy the set of heads. For one thing, they are probably a matched set. So their casting dates are the same. That is something judges will look at it if you are going for a concurs style restoration on your car. You split the set, that might raise some eyebrows. Once you have this set, then you can see if the old can be repaired or go about find another single head with a casting date exactly or closely matching yours (at that point you can be fussy and take your time).

Take these new heads to your machine shop and get assurance they that have hardened seats and valve guides installed. Without knowing what these heads were used for, it is money well spent to insure these heads can stand up to today's unleaded fuel. Don't assume that they are prepped properly before, let the machine shop do their magic. A three angle valve job and some gasket matching and port/polishing will definitely let these heads breath a whole lot better for not a lot of money.

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Getting a head for my Farmall costs like $300-350 bucks and they were the same for the C113 and C123 which was used for YEARS. So there are many out there ontop of aftermarket manufacture. Tractors to cars, I'd say getting a pair of matching heads for that price is a goddamn steal!


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Getting a head for my Farmall costs like $300-350 bucks and they were the same for the C113 and C123 which was used for YEARS. So there are many out there ontop of aftermarket manufacture. Tractors to cars, I'd say getting a pair of matching heads for that price is a goddamn steal!

Agreed. A friend of mine has purchased a set of ultra rate Ram Air V heads. He is in the process of building a correct Ram Air V motor for his '69 Judge or '69 Trans Am. I know what he paid for the set of heads, it well exceeds the cost of my entire engine rebuild. I hate to think what the entire motor will eventually cost him to get the correct intake, block, etc.

Oh I forgot to mention - be sure to go with the new Viton rear main seals from B-O-P Engineering and don't go with the stock rope seal rear main. Rope seals are what the factory used and over time they begin to leak. The new BOP rear main seal is a lot more expensive but well worth it.

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