Shortbed70

Ok first off I have a 09 5.3 shortblock I’m building into a bracket race engine. I have a set of 862 heads with pac springs. I’m wanting to get my compression up as much as possible without having to buy $1000 pistons. The motor is carbed and I haven’t picked a cam yet. How much can be removed from the head deck safely? I know every .005 is supposed to be a 1cc reduction but I’ve also heard of people saying the 862/706 heads were not 61.5 as stated.

G Atsma

According to the Summit guide on LS engines, they are indeed 61cc. You can bank on that.

64post

iTrader: (5)

862s? They’re not all 61.cc, they are sometimes 64cc, check them before use. The Ca. Edition of that head had more volume in the chamber for NOX reduction purposes, I was told.

G Atsma

You were told wrong. ALL 862 & 707 heads have 61cc chambers. There were no Calif. versions. They might have used larger chamber 6.0 truck heads.

LLLosingit

iTrader: (4)

Don't be so sure, There have been a few people claiming they had 862's that measured higher than 61.5 and couple that had them clean up surfaced and still ended up larger than 61.5 . I've never bothered to measure them myself but if four or five people say they measured higher I tend to believe it might be true, Why would they lie about it?

64post

iTrader: (5)

Oh yeah you again Mr Kia ( know it all) Mr 9000 posts about nothing really. I’m sure everyone is wrong but you.What the hell have you ever built and completed , Mr Kia? That you know every detail about every subject on this site.? Nobody can speak from experience or have different take without you correcting them.

G Atsma

You can take your comments and blow them out your ***.
I got my figures from the Summit LS website.
OK, head chambers might vary a cc or two due to production variances, but there are not variations of head types as they are casting numbers. Different spec, different casting number. Any changes to a casting would have to be machined in a side operation, and that is not happening.
I KNOW what I know, and apparently it's a LOT more than you. Don't like it, go cry to your Mommy.
BTW, the count is now over 10k posts if that matters to you. It doesn't to me. Just a number...

64post

iTrader: (5)

10, 000 comments of nothing based on experience, I can see that, just shallow Capt Obvious stuff. Let’s see your completed builds that you have so much experience to correct everyone.......

G Atsma

I don't owe you a thing. Go blow a goat.

1FastBrick

iTrader: (16)

There was no California Version of heads. How do they know where it's going to end up when they produce it?

Yes, There were early trucks that were 49 state federal emissions vehicles and Some that where 50 state legal When sold new. But the difference was added Air Injection on 50 state legal.

Air injection only works on Start up to help the cats light off faster.

Look at the combustion chamber design on an 862/706 Head Vs. a 243/799 Head. There is no way the 862/706 heads are 65cc in stock form. Yes, there is variances in casting and machining process So it's possible one set is near 61CC and another set is 62cc

I would venture to guess those claiming 64-65 CC are not using accurate equipment to measure the chamber size.

G Atsma

Thank you, 1FastBrick! I would say some guys get me pulling my hair out, but there's nothing left to pull…. lol

1FastBrick

iTrader: (16)

You don't need it anyway. It just slows you down. Ask a swimmer...

G Atsma

TOO TRUE!!! LOL You seem to have intimate knowledge of this? Have a good one, man!

LLLosingit

iTrader: (4)

Not sure it was this site or not but the reason for the post back then was because a builder was wanting to let other people know to check them because his shop had a set that had one head 65cc and the other was 61cc on the same engine that was brought in by a customer, Of course there were doubters until a couple other people posted they had the same over sized chamber heads. 3-4cc is small amount and it could have been a first run batch or a change over mistake. Either way I tend to believe them because as I said earlier why would they lie about it? It wouldn't be the first time people have found variances in parts coming from parts manufacturers.
Some of you may not know this but all the big manufacturers rely on associate companies to supply them finished parts, They don't make everything themselves and much of the R&D work is done by these much smaller companies.

1FastBrick

iTrader: (16)

I know of a video online where a guy claims they are 65 cc but he is not using accurate equipment.

Do you have a link to the thread with actual proof?

LLLosingit

iTrader: (4)

I looked for it but it was quite a while ago and I'm not even sure if it was on tech or another site. I was trying to remember the name of the shop that made the post but have no idea who it was. And I'm not sure what you call accurate equipment, Most medical equipment very accurate and the store bought stuff is usually accurate. They wouldn't want to be found liable for people overdosing lol
Link to video?

1FastBrick

iTrader: (16)

To me, A burette is accurate.

A syringing for feeding worm medicine for a horse is not as accurate especially when you have to refill it to make a measurement...

64post

iTrader: (5)

You seem to be shooting from the hip Mr Brick, do u have anything factual that says ALL 862s are 61ccs? And you’re certain that the people that cc’d them and claimed they were bigger than 61 we’re doing it wrong?

madmann26

It’s common knowledge that the 862s are all sand cast heads, which could explain the variances in the chamber size.

However, ALL GM documentation says that 706 AND 862 heads have a combustion chamber size of 61.15cc.

Anyone other than GM that reports anything different is looking for Internet fame.

1FastBrick

iTrader: (16)

I never said they were all exactly 61 CC.

But can you Prove a California specific 862 casting???