Getting 502 heads back this week - Team Camaro Tech
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post #1 of 4 (permalink) Old Jan 4th, 17, 10:15 AM Thread Starter
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Dave
 
Join Date: Jul 2005
Location: Virginia/Mass
Posts: 2,990
Getting 502 heads back this week

Some of you know I have a 8.0L 489ci block bored .020. (4.30" x 4.25") ~494ci now. 10.2" deck. I'm putting a set of 502ci 12562934 heads on it that were milled down to 108ccs that are coming back this week. I'm going with a Lunati 20010723 Gen VI cam even though Lunati recommended a Mk IV with the same specs for some reason. (241/249 @.050" .625/.625)
What I'm trying to find out is mainly about the quench area and head gaskets. I have flat pistons with a piston to deck distance of .010". It was decked .010". I want to bump the compression as much as I can without causing problems. Initially I was going to use metal shim gaskets that are .018" squished, but I only found them for Mk IV and that also got me thinking about the quench area and the piston to head clearance. I think I'm going to be stuck with at least .027" thick gaskets for a total of .037" quench.
My questions:

1st I haven't been able to measure the Piston to Valve clearance yet. Do you think I have anything to be concerned with? I'm hoping I don't have to grind valve reliefs, but I'm prepared if I have too.

2nd What do you think about .037" for the quench? Too close? This would give me 9.65:1 compression. .037" gaskets plus the .010" piston to deck would give me 9.48:1.

3rd and most important to me right now... I know the difference between Mk IV and Gen VI BBC head gaskets is that Mk IV has two coolant holes on each end and Gen VI only has one. I feel like I'm extremely limited on Gen VI head gaskets and everything I want is available in Mk IV. It's a heck of a lot cheaper too. Is the extra coolant passage that big of a deal on a street motor?

Mk IV on the left, Gen VI on the right:




'69 SS396 X66 L34 08D M21 BS
460ci Gen VI 9.75:1 AED 950 carb
241/249 @ .050" .625/.625 110 LSA

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post #2 of 4 (permalink) Old Jan 4th, 17, 11:09 AM
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Chet
 
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Re: Getting 502 heads back this week

10% power increase for every FULL point of compression increase. What you are talking about won't be felt by you at all. Assuming 500 HP a full point would be 50 HP, you're talking about .17 increase in compression...5-10 HP. Not enough to worry about and complicate things. iGo with the best quench and don't worry about the compression
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post #3 of 4 (permalink) Old Jan 4th, 17, 12:20 PM Thread Starter
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Dave
 
Join Date: Jul 2005
Location: Virginia/Mass
Posts: 2,990
Re: Getting 502 heads back this week

Quote:
Originally Posted by onefiness View Post
10% power increase for every FULL point of compression increase. What you are talking about won't be felt by you at all. Assuming 500 HP a full point would be 50 HP, you're talking about .17 increase in compression...5-10 HP. Not enough to worry about and complicate things. iGo with the best quench and don't worry about the compression
Fair enough. Makes sense. I guess I was just trying to hard to get it closer to 10.0:1.
Now to figure out which gaskets. I'm going to wait to place the heads on to see where the piston to valve clearance ends up first.

Thanks.

'69 SS396 X66 L34 08D M21 BS
460ci Gen VI 9.75:1 AED 950 carb
241/249 @ .050" .625/.625 110 LSA

Semper Fi!

"The galleries are full of critics. They play no ball, they fight no fights. They make no mistakes because they attempt nothing."
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post #4 of 4 (permalink) Old Jan 4th, 17, 07:37 PM
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Morgan
 
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Re: Getting 502 heads back this week

My guess is you will be fine for ptv clearance
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