[RonBurgundy]

I'm considering having my 389 bored .60 over to try and get as much performance out of it as possible. Some friends say it should be fine, others say I may have overheating issues. None of them are Pontiac guys. Should I be concerned about this?

[slowbird]

Originally Posted by RonBurgundy

I'm considering having my 389 bored .60 over to try and get as much performance out of it as possible. Some friends say it should be fine, others say I may have overheating issues. None of them are Pontiac guys. Should I be concerned about this?

No. We ran a 60 over 389 for years and years, no issues.

[Blued and Painted]

Does it need to be bored?
If induction and exhaust remain the same, then the power gain will be minimal.

[gtofreek]

If it will clean at .030" I would just do that. Taking a standard block straight out to .060" is a waste, unless it's a race only engine, and you need to squeek every last ounce of power out of it to make a class. Otherwise, in a street engine, you will never notice the difference between .030" and .060". You'll just using up a block that is getting harder, and harder to find every year.

If it's already .030", you could try .040" or going .060" shouldn't be a problem. I have taken quite a few 389's out .090" and they are still running just fine to this day. The main concern would be porosity erosion from, the inside out to the cylinder wall. I have bored some other engines that were fine where they were, and after boring them a fair amount over, have uncovered pin holes that would leak. One was a 330 Hemi. Tried to take it out .125" to make a 354[as per customers request], and every cylinder had pin holes down near the bottom afterwards. Never encountered that yet with a Pontiac, but that doesn't mean it can't happen. Probably not at .060" though. After all, you are only making the cylinder .015" thinner, all the way around, then it would be at .030".

[moontower69]

The current 389 in my 65 Goat is 60 over and never had any issues at all with overheating in last 5 years.

But I wouldn't go more than that, when I bought my Goat it had a .090 over 389 (seller lied to me and said it was 60 over, you know who you are J Tollerico) and that motor was a disaster and had overheating issues.

[RonBurgundy]

The pistons I'm looking at using are a 4.120 bore which I believe equates to just under a 60 over bore for my 389. I don't believe my engine needs a 60 over, but I'd like to get as much performance as possible out of it.

[gtofreek]

Will the valve reliefs in those pistons work with your heads? If so, there shouldn't be a problem going .057" over.

[RonBurgundy]

Originally Posted by gtofreek

Will the valve reliefs in those pistons work with your heads? If so, there shouldn't be a problem going .057" over.

I believe so. I'm using the original 76 casting heads. The pistons are flat top Wisecos.

Thanks

[gtofreek]

For those heads, the valve reliefs need to be really close to center of the piston. If they are out about half way to the outside of the piston, you may have issue with piston to valve clearance depending on the cam you run. Were those pistons designed for a 389? If not, Butler sell some nice forged pistons for the 389 that are a pretty nice piece at a good price.

[RonBurgundy]

[QUOTE=gtofreek;5709315]For those heads, the valve reliefs need to be really close to center of the piston. If they are out about half way to the outside of the piston, you may have issue with piston to valve clearance depending on the cam you run. Were those pistons designed for a 389? If not, Butler sell some nice forged pistons for the 389 that are a pretty nice piece at a good price.[/QUOTE

Not sure. They're new old stock. Here's the link to them.
http://m.ebay.com/itm/152454054573

[GRX]

Should be fine. Have bored more than one 389 .088 over to use 30 over 400 slugs which provide more options. Sonic test adds peace of mind.

[b-man]

Never bore your block any more than needed for bore cleanup, thick cylinder walls are more stable and seal up better. Better ring seal equals more power. I remember reading about the 455 SD being campaigned by H-O Racing, the +.060 block lost measurable power over the previous +.030 block in Super Stock racing. I know you're not building an engine for class racing, but food for thought anyway.

Just because others have had success boring their 389 blocks +.060 or +.090 is no guarantee that yours will have integrity at one of those sizes. A friend of mine who recently put together a 421 for me has written here about a '66 389 block that had such thin cylinder walls at just +.030 that the block couldn't be used. It was the worst block he'd ever encountered.

For another measly 5 or 6 cubic inches it's just not worth it to bore your block +.060 if it will clean up at +.030 or +.040.

By the way, the pistons in that eBay link are not correct for what you're trying to do, no matter whether you're using early 20-degree heads ('66 and earlier) or 14-degree ('67-up). Single intake valve relief, who knows what they might be good for.

[Will]

Originally Posted by b-man

Never bore your block any more than needed for bore cleanup, ...

For another measly 5 or 6 cubic inches it's just not worth it to bore your block +.060 if it will clean up at +.030 or +.040.

By the way, the pistons in that eBay link are not correct for what you're trying to do, no matter whether you're using early 20-degree heads ('66 and earlier) or 14-degree ('67-up). Single intake valve relief, who knows what they might be good for.

Couldn't agree more. You will never notice the difference 6 or fewer cubes will make.

AND those pistons - they are NOT Pontiac pistons. I dunno what they're for, maybe a Chevy with the Pontiac NASCAR heads? Pin diameter is wrong, pin height is wrong, valve reliefs are wrong.

[geeteeohguy]

Originally Posted by Will

Couldn't agree more. You will never notice the difference 6 or fewer cubes will make.

AND those pistons - they are NOT Pontiac pistons. I dunno what they're for, maybe a Chevy with the Pontiac NASCAR heads? Pin diameter is wrong, pin height is wrong, valve reliefs are wrong.

X3 or 4 on this. Boring out any more than necessary to clean it up is a bad plan.

[gtofreek]

[QUOTE=RonBurgundy;5709320]

Originally Posted by gtofreek

For those heads, the valve reliefs need to be really close to center of the piston. If they are out about half way to the outside of the piston, you may have issue with piston to valve clearance depending on the cam you run. Were those pistons designed for a 389? If not, Butler sell some nice forged pistons for the 389 that are a pretty nice piece at a good price.[/QUOTE

Not sure. They're new old stock. Here's the link to them.
http://m.ebay.com/itm/152454054573

You don't want to buy those. They are for a Pontiac headed SB Chevy, NASCAR type engine. That won't work in a Pontiac engine. That compression height is about right for a Pontiac 4" stroke crank, but it is also correct for a SB Chevy 350 crank, with a 5.7" rod. They also do not have valve reliefs for the exhaust. Oversized BB Chevy piston pin also. They are just all wrong.

[RonBurgundy]

Thanks everyone for the input I appreciate it.

[Tom Vaught]

Originally Posted by slowbird

No. We ran a 60 over 389 for years and years, no issues.

SAME HERE. Put 400 pistons in a 389, a better camshaft, later model ported #16 heads, HSD intake, 850 cfm carb, point distributor.

Once I had the carb dialed in the thing ran great. 11.55 at 117 with the 400 engine and a 9" tire.

Tom V.

I did put a higher fin count radiator (from Superior Radiator in Mt Clemens Michigan) in the car and ran good gas in the car.

[hurryinhoosier62]

Originally Posted by b-man

Never bore your block any more than needed for bore cleanup, thick cylinder walls are more stable and seal up better. Better ring seal equals more power. I remember reading about the 455 SD being campaigned by H-O Racing, the +.060 block lost measurable power over the previous +.030 block in Super Stock racing. I know you're not building an engine for class racing, but food for thought anyway.

Just because others have had success boring their 389 blocks +.060 or +.090 is no guarantee that yours will have integrity at one of those sizes. A friend of mine who recently put together a 421 for me has written here about a '66 389 block that had such thin cylinder walls at just +.030 that the block couldn't be used. It was the worst block he'd ever encountered.

For another measly 5 or 6 cubic inches it's just not worth it to bore your block +.060 if it will clean up at +.030 or +.040.

By the way, the pistons in that eBay link are not correct for what you're trying to do, no matter whether you're using early 20-degree heads ('66 and earlier) or 14-degree ('67-up). Single intake valve relief, who knows what they might be good for.

X 2, Bart. I know of two late model 389s (both cast in early 1966) that had excessively thin cylinder walls. One was in my uncle's '66 Tempest (special order). The other was in a deceased friend's '66 GTO. The one in my uncle's Tempest actually failed in service. The one in my friend's GTO was found during ultrasonic testing. The worst of the cylinder walls was only .060 thick. Personally, I will not take a bore +.060 unless the block has been ultrasonically tested. You can do it IF the cylinder walls are thick enough, but why do it IF you have other options?

[Jerry H.]

Originally Posted by hurryinhoosier62

X 2, Bart. I know of two late model 389s (both cast in early 1966) that had excessively thin cylinder walls. One was in my uncle's '66 Tempest (special order). The other was in a deceased friend's '66 GTO. The one in my uncle's Tempest actually failed in service. The one in my friend's GTO was found during ultrasonic testing. The worst of the cylinder walls was only .060 thick. Personally, I will not take a bore +.060 unless the block has been ultrasonically tested. You can do it IF the cylinder walls are thick enough, but why do it IF you have other options?

Your uncle had a 66 Tempest that came from the factory with a 389? If so, I would sure like to see the PHS on that one.

[ichabod]

I have had my 1965 389 bored to 60 over. It is a original match in a 65 GTO tripwr 77 heads. This car also has matching trans and rear end dealer instaled 4:33 gear. The car has run warm 200 dgrees in the summer. I dont drive this car any distance due to the gearing. A lot of the heat I believe is due to the atypical gearing. I totally agree with if not necessary don't do it.