Hi guys. I'm looking for some advice on selecting head gaskets. I got my L-98 block back from the machinist bored .040" over and just finished putting the short block together. Checking piston to deck height, here's what I've measured; (+) = out of the hole, (-) is below deck.
CYL #1 = +.002, #3 +.005, #5 -.001, #7 -.004" / #2 -.004, #4 .000, #6 -.005, #8 -.002. Pistons are SRP forged flat tops with 2-valve reliefs, -5cc. The rotating assembly was balanced, with 6" rods and 3.75" stroke crank. Compression calculator shows 11.03:1. The cam is a Comp Cams HR 112.0 +4, DUR @ .050 is: INT 236, EXH 242; lift is .579/.585. Valve timing is: @ .050 INT open = 10 BTDC, close is 46 ABDC // EXH @.050 is 57 BBDC; INT is 5 ATDC.

Running AFR 1095 Competition Eliminator heads, untouched. Static compression with a .039" gasket comes out to 11.03:1 and Dynamic compression is at the ragged edge of 9.06:1. I have 92 octane fuel available at best and this is a naturally aspirated motor with a Holley Stealth Ram intake. Am I good to move forward with the .039" head gaskets or should I get a different gasket to lose compression? This is a project/weekend warrior, not a daily driver. A4 with a Vigilante 3600 stall and 3.73 gears.

I think I'm good but looking for a second opinion. CYL #1 and 3 have me concerned... This is my 3rd motor I've rebuilt, so I'm not an expert by any means...
Thanks!

 

recheck your measuring

stretched rods?
were they resized?

.005 is soooo small, but id double check your measurements to be certain.
Then, ask your machine shop who did the work for you

 

You probably don't want to hear this but get the decks resurfaced.

 

Yes, you're right. I'm definitely not interested in disassembly and resurfacing. Can I not fix this with gaskets? How about pulling piston #1 and #3 to have them machined down? If I resurface, I'd think all of the pistons would be sticking out of the hole...right? I'm not in a rush; I've got time to figure it out and do it right.
Thanks for the input.
~Tim

 

This is my old 383 in my sig. I got stationed in Japan and the car sat in the Pacific Northwest for approx. 6-years. When I returned and got it running again, the rings wouldn't seal. Teardown showed it needed a .010" overbore to clean up corrosion in the cylinder walls. Crank was polished, not sure if the rods were resized, they shouldn't have been since I already had ARP studs... I'll re-measure in a bit, but I checked it twice before posting. I was hoping this would have been an easy fix.
Thanks again!
~Tim

 

That's the difference between building an engine and assembling an engine. To make sure its perfect, the engine will probably be assembled and disassembled 3-4 times to make sure everything is right.

And no. If the deck surface isn't perfect, just using a new head gasket is a minor fix with no guarantee it won't blow out. Its a coin flip. Spend the money now or spend it when it blows and causes more damage.

Do not modify pistons. It will throw the balance weight off. Even a few grams will make a big difference especially at high rpms.

 

picture of engine?
deck surface?
pistons?

 

Yes, I was thinking I need to share pics as well. Here's multiple measurements of piston #3. Every spot I measure is different. All rings installed, couldn't really see any piston rock by pressing down on one side or the other. The first time I measured it I just slid the indicator from deck to piston and wrote down the measurement. I used .010 for zero deck height. Don't blast me too bad here; the last time I built an engine was in 2006. I'm sure I'm reading it wrong cause I now see it's different everywhere. I probably should just stick with center of the piston eh? Sorry for being a noob with critical measurements, but thanks for the help!

 

Just went to the school of Youtube. Looks like I need to re-measure everything. The machinist I used is solid; he's been in the business for 20+ years. My engine building experience...not so much! LOL! I'll remeasure all of them tomorrow at center of piston!
Thanks for your patience and bearing with me as I learn!

 

Ok, I'll take spears if you got 'em! I remeasured everything tonight at center of piston and I'm GTG! Here's what I came up with.
CYL1 = .000, CYL 3 = .000, CYL 5 = -.003, CYL 7 = -.003, CYL 2 = -.001, CYL 4 = -.001, CYL 6 = -.003, CYL 8 = -.003. I'm moving forward with a .039 gasket. Thanks for the insight fellas! I'll post up progress as I move forward...
~Tim

 

If you care to measure yet again and wish to avoid any error when sliding the dial bridge from the deck to the piston, just use the dial to determine TDC and then a bridge micrometer to measure depth, The that margin for error is eliminated.
Just my two cents. If you have the time as you say, that's something easily revisited.