What to do about compression?

[BARRACUDA1968]

I pulled my motor this spring to fix the cometics leaking oil. I'm going back through my calculations to make sure I get the right head gasket thickness.

I do not want to go back to cometics. I don't want to risk them not sealing again. I'm tired of wrenching. I'm considering the Felpro 9441pt which I used for the calculations below. My heads have been CC'd

This is the Summit calculator. Before I go any farther I wanted any and all opinions with the felpro 9441's. I'm going to push my car in to the 10's. The tune I had in the car was at 23 psi before I pulled the motor. It ran strong and zero KR. Just leaked a lot of oil. Will I regret using these felpro's long term or should I consider another route? I want the motor to stay in the car for a while.

I've been advised to start with a new block due to this one being line bored too much and running a .-010 chain and short deck height. If so now's the time and I can have a new block prepped correctly for cometics. I hate to spend the money but I'm tired of failures too. I found an engine builder close by who has TQ plates and has done several motors for other members. He seemed like a good guy and said he uses cometics and never has had a problem. To be honest I'm on the fence on what to do. My gut says do a new short block. My wallet is wanting a break from this car.

If I'm doing this right my compression would be right in line.

Bore: (diameter) 3.830
Stroke: 3.625
Cylinder Head Volume: 49
Effective Dome Volume:
Use (-) for Dome and (+) for Dish. +27
Deck Clearance: .007
Compressed Gasket Thickness: .063
Number of Cylinders: 6
Compression Ratio : 8.67 : 1
Total Displacement (in.3) : 250.58
Total Displacement cc's : 4107.87

 

[Mr.Spool]

There is nothing wrong with a cometic head gasket I've had very good luck with them but things do need to be done right nevertheless you should be able to run a Fel-Pro gasket without any issues as well.I understand you have had alot of issues with the car and agree you should make keeping the car together a priority.

 

[BARRACUDA1968]

I use cometics on my Cuda and have never had an issue. We installed them dry on that motor.

Can't really say it was the block or head surface because oil seeped through each layer almost like the head was loose. They sealed the water ports though. Wierd

 

[forcefed3.8's]

The leaking oil is a chance you take with the cometics. Sometimes they seal, sometimes they dont. It isnt a sign of the gasket failing. The waterports are embossed, the oil drainback holes are not. I have started using a small amount of sealant on the oil drain back, a small smear on each side of the gasket. I stopped using the copper spray.
I have used felpro 9441s into the high 9s, not sure how that much cylinder pressure is working them, but so far so good. That engine is coming apart this spring.

 

[earlbrown]

I can make you a set of pistons that account for your lower deck that will put the compression where ever you want it with whatever head gasket you want to run.

Not sure if that's cost effective with your build, but I know my slugs would let you solve your problem and keep you from having to start over with machining on a used block.

If you want to play with the calcs, pick the easiest to seal head gasket you like, then use 22CCs for my inverted domes. You'll find you can now go higher than was previously possible and/or run a nice thick gasket that's not a $100 Cometic.

 

[robzombie]

To answer your question,you can use the felpro gasket without any issues if KR is held in check.
They will take you in the tens for years and be trouble free. Like forcefed has done as well as many others they hold up in the nines without issue but I'm sure he has no KR issues.

I've run them at 26/28 lbs. of boost for three years before I had other issues that took them out.

I was going to run the cometics on my stroker but after reading all the horror stories of leaks I decided to stay with the felpro gasket as they are pretty forgiving and trouble free.

I like you want to drive my car and not fight leaks or have to put sealer in my system to fix a problem that shouldn't exist in the first place.

 

[TurboBuRick]

Cometic's are the most durable though they can be a pita to seal up. I put them on dry and have pretty good luck. Recently i've started to run a bead of right stuff along the seam on the front and back of the engine. There is no way anything is getting by that.

Rick

 

[robzombie]

Cometic's are the most durable though they can be a pita to seal up. I put them on dry and have pretty good luck. Recently i've started to run a bead of right stuff along the seam on the front and back of the engine. There is no way anything is getting by that.

Rick

I thought about doing the same thing. When I bought my motor either the owner or WEBER had liberally smeared the entire gasket with high temp orange RTV.
He said that was the way it came from Weber, but I find it hard to believe that a builder would put the motor together like that. I guess it's possible as I found other issues that shouldn't have been been done by any reputable builder.

My other concerns were that putting any rtv, copper spay or whatever the latest trick to seal them was that it not only alters compression ratio, if put on only around water or oil ports it would cause uneven clamping force.

The only way I would use them is dry and have both surfaces prepped for them. I also know that the chances of having to use some kind of sealer [tabs] would be over 80% from what I've read of the problems people have had with them.

People may like them and have no issues with them and that's fine for them, but the stories of problems with leaks far out ways the success stories and is the reason I stick with the 9441 gaskets.

I look at it from a different perspective.

If you run cometics they are less forgiving under detonation because they won't blow unless it's something major and will continue to seal [compression] not oil or water for a longer period of time [false sense of security] allowing more damage to happen to the RTA, such as wiped out bearings, bent rods or worse.

With steel shim or 9441 gaskets you will have to replace them and find the problem or it will happen again but chances are the RTA will be fine because the gasket blows instead of raising the screw up thresh hold to where you could do more damage.

There are motors out there running over 30lbs. and in the nines with no issues on 9441 gaskets.

The moral of all this is that if you have a safe tune and stay on top of it the 9441 gasket is the best choice for a trouble and leak free motor from my experience and what I've read.

 

[TT/Ameasap]

Just try the Felpro's. You will not be totally satisfied until you try another gasket. There is no reason to put the cometics back on the car and chance more leaks.
I would keep compression low on an alky car, but bumping the compression will help spool that turbo faster.

 

[robzombie]

Just try the Felpro's. You will not be totally satisfied until you try another gasket. There is no reason to put the cometics back on the car and chance more leaks.
I would keep compression low on an alky car, but bumping the compression will help spool that turbo faster.

He and I have a real close combo and I have no trouble spooling my turbo.

In fact on the street I have to be careful not to floor it as the boost comes up fast and the tires spin even faster, pun intended.

Getting to third gear is the challenge and when done right the car is a beast.

 

[TT/Ameasap]

He and I have a real close combo and I have no trouble spooling my turbo.

In fact on the street I have to be careful not to floor it as the boost comes up fast and the tires spin even faster, pun intended.

Getting to third gear is the challenge and when done right the car is a beast.

He has a little bit of lag off the line. I have been in his car a couple times now.... He has a few options to get rid of it, but thats up to Brett. I'll let him tell you about his ride in mine...lol

 

[Mr.Spool]

I found an engine builder close by who has TQ plates and has done several motors for other members. He seemed like a good guy and said he uses cometics and never has had a problem.

if the guy will stand by it and knows what he is doing then there is nothing wrong with a statement like that or you can just throw a set of felpros on your motor and call it a day.see how the car runs and it might turn out your only getting unlucky with the cometics or hand the motor off and let someone who has had success with the cometics put it together for you.

 

[forcefed3.8's]

I have success with cometics as far a sealing compression. Leaking oil, i have a 50% success rate. I have learned to live with it. It is the nature of the beast. I wouldnt call a slight oil seep a failure of the gasket. This is a turbo car, they blow oil out of every place possible.

 

[BARRACUDA1968]

I could have lived with a small leak but mine was pretty bad toward the end.

If I was tracking the car or short cruises once in a while I may have lived with it but I live in a small town and I drive this car 300 miles a day sometimes so it get's messy and stinky with that type of oil leak.

I need to get off my a$$ and get the motor put back together. I've managed to get one head cleaned up so far, that's it.

I've misplaced my motivation.

 

[robzombie]

I could have lived with a small leak but mine was pretty bad toward the end.

If I was tracking the car or short cruises once in a while I may have lived with it but I live in a small town and I drive this car 300 miles a day sometimes so it get's messy and stinky with that type of oil leak.

I need to get off my a$$ and get the motor put back together. I've managed to get one head cleaned up so far, that's it.

I've misplaced my motivation.

Very easy to do with these cars when it's one thing after another.