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post #1 of 8 (permalink) Old 08-03-2015, 03:49 PM Thread Starter
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Need advice

Hi folks, newish member. I posted in the introduction section. I have a 65 gto that has original engine. About 25 yrs. ago I brought the heads in to a local guy to have them worked on. Then life started and the car has sat without heads for 25 yrs. When I bought the car the engine had been rebuilt in 1978. It has about 10,000 miles on it. Pistons are .030 over. The cylinder walls are oxidized but not pitted rusty. Two of the pistons are slightly pitted. Should I have someone go through the engine and if I do should I consider having different pistons installed to lower compression so as to run on pump gas. I do have 110 octane gas in town that I can get at a local station. For how long that will be available I do not know. I do not know how much I will be driving the car when it is done.The car will be a driver nothing will be restored to show room quality. Do not have the time or money. It is still in relatively good shape. Another thing to consider is that I have a 1966 389 that I took from a 66 Bonneville that is completely intact and ran great 20 yrs ago when I took it out of the 62 Catalina station wagon that at the time was my wifes everyday car. Could turn that into a stroker. Money is an object. Appreciate advice.
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post #2 of 8 (permalink) Old 08-04-2015, 07:08 PM
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Kinda tough to tell without seeing it, but 25 years is a long time to be sitting open like that unless you took some precautions to protect it like keeping the cylinder walls coated with oil. If you can take a green scotch-brite pad and get them back to clean and shiny, and still see the hone marks, then it might be worth a try.

Compression is another matter. For a street driven car unless you have a source and are prepared to spend the money for the fuel it needs, I'd hesitate to run it without a piston change to drop compression down to 9.3:1 or so. Doing that means the motor has to come apart anyway so there's your chance to clean up the cylinder walls. If you're going that far, consider carefully about replacing the factory rods with some good forged ones. I like stroker motors, having built one for my car but they're not a budget-friendly option.

What do you want to do with the car when it's done?


Springtown, TEXAS
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post #3 of 8 (permalink) Old 08-05-2015, 10:39 AM
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Where are you located? Your engine needs to come apart for cleaning and inspection, any way you look at it. While there, better connecting rods and dished pistons are the way to go. You're looking at $<300 for the rods and about $550 for some Ross pistons in any dish you want. Rebuilding a Pontiac engine is not a cheap thing, but being that it is a 1965 GTO with it's original engine, it is an excellent investment. You will have a nice running old goat that has some real value if you need to sell it (because it now runs!). My vote is to stick with the original engine and do the rods and pistons. And to get a PONTIAC oriented machine shop to do the work.
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post #4 of 8 (permalink) Old 08-05-2015, 12:07 PM
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And to get a PONTIAC oriented machine shop to do the work.

This is easier said than done especially out here on the west coast.
If it is the original parts matching engine you don't want just any mook doing the work and the guys that are reputable are backed up for months.
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post #5 of 8 (permalink) Old 08-05-2015, 05:19 PM Thread Starter
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Thanks for the reply's. I am at a bit of a stand still not having enough technical knowledge to make a decision on the direction I should take. Bear and geeteeoguy you both mentioned new rods and pistons and I guess I was thinking along those lines. I know I need to go through the engine so that seems like logical good sound advice. I live in Wisconsin and the pontiac guy (who still has my heads after 25 yrs) is no longer doing work. So I need to find someone else. Please bear with my simple questions as I pick your brains. I can help myself well enough with the mechanical end of things but I have little technical knowledge as to what I should be doing. Question: if the compression is lowered to accommodate practicality do I not lose horse power in the process.
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post #6 of 8 (permalink) Old 08-05-2015, 06:07 PM
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"Question: if the compression is lowered to accommodate practicality do I not lose horse power in the process."

Yes, and no. If all you did was lower the compression then yes you would lose some HP. Now the question would be did you lose the HP due to the lowered compression or a camshaft grind that no longer suits the lowered compression?

That said, the engine built with the lowered compression and "correct" camshaft will not lose HP, but you then benefit by being able to use pump gas anywhere you travel.

The key to getting good HP will be having the "squish" area (the space between the top of your piston and the head) somewhere in the .040" -.045" clearance depending on type of piston/connecting rod material used. Some will "zero deck" the block, but I am not a fan of cutting the block down .020" and then being able to use the .040" head gasket to get your clearance. I'd rather not cut my block if only to square/resurface it a minimal amount. Cut it .020" and if you rebuild it again later and it needs to be cut, you may have a problem.

On my 455 build I went with a Cometic .027" gasket with my pistons .020" down in the hole. Gets me a .047" squish, but forged pistons/rods are going to expand and I plan on a small shot of nitrous (which generates more heat) so the .047" should be right where I want to be.

Cometic gaskets are not cheap at $100 each whereas you can zero deck your block and use an inexpensive (and good) Felpro head gasket, but I just rather not cut a block if not necessary.

Next big decision is the camshaft specs and grind. The compression will ultimately determine your Lobe Separation Angle(LSA), 110, 112, 114. Of course many other factors come into play, but this selection is key. This has been covered before here on the forums. Get a feel for some of the engine&camshaft questions/replies. Lot of info to absorb and then do your own research or inquiry.

If you need a machine shop in Wisconsin, contact "Grumpy" on his facebook page. Check out the '64 Lemans 326CI he recently assembled. He can give you the name of the shop that assembled his engine. He can also be contacted through our forums as his member name is Grumpy. Use my name and tell him I recommended you contact him about your engine. Begin there and see what you come up with. Then hit us with questions.
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post #7 of 8 (permalink) Old 08-05-2015, 08:47 PM
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"...about $550 for some Ross pistons in any dish.."

Please post a link to where you can buy 389 Pontiac dish Ross pistons/pins/shipping for $550. I haven't seen any Ross prices anywhere near that. Thanks.

Anyhow, if the OP wants to use a 389 block and crank, he can use the '66 engine he mentioned, and keep the original for future sale or resto. If the block will accept an overbore to 4.120, I'd do that and run std bore 400 SP L2262F forged pistons, with some of the LG5-6625I RPM 5140 forged rods. Then I'd run some 6x-4 heads, with a small Voodoo cam.


This would be a very pump gas friendly engine. Also, the heads have screw-in studs and 2.11 intake valves. I'd run a Performer intake and a Q-jet.

"... I have a 1966 389... Could turn that into a stroker..."

The stroker gets my vote. I'd go with a Butler balanced stroker assembly and 6x-8 heads. You can usually find some 6x cores for about the price of having screw-in studs installed in the 389 heads. But, just the assembly is about $2000. So, a crate engine from Len Williams will probably be cheaper than having a stroker built with a 389 block.

He has a 400 pump gas crate for less than $4000, and a 455 with forged rods and pistons, for $4500 + shipping. Don't have a clue what the max budget is for this engine build. These are just some options.

400 Long Block

455 Long Block
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post #8 of 8 (permalink) Old 08-06-2015, 03:23 PM Thread Starter
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thanks pontiacjim and oldschool for info. I was hoping for responses like this. A lot to think about. I was going to ask some questions about strokers but I think going that route is not possible with my budget. Plus I love my wife and I see nothing but pain in the future spending that kind of money. We shall see, not ruling anything out yet. I am just getting into this again after many years and have a lot to learn . I guess I like the idea of using the original engine. I am going to be 60 next yr. and just want to enjoy the car before I cant. I will be having lots more questions along the way. Thanks thanks.
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