Help , 0 compression in #5
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
I'm sorry to hear that the cause was air injection...are you sure? the gasket tear lines up where the wound is on the piston? I really did not believe that an air leak could have caused that much of a hot spot...if anything I thought that it would be a dead hole with the A/F Ratio so far outta whack that it couldn't fire at all. The cost of an education...
We're not going to discuss my education tuition over the years...
I gotta hand it to ya, you;re sure staying positive and objective ! I'd have been in the padded cell again if this had happened to me
years ago,
I recall a new paint job...that sexy deep blue that came on the Impala SS many yrs ago and a few vettes. GS colors I think..anyway,
Less than 1 week later I parked up under the back end of a Pick-up truck with a drop down ball hitch...went about 3/4 of the way up the hood. Like a chain saw had run up the hood...
I was in therapy for months.....
I'm glad that you;re coping better ! Few things hurt worse than your Corvette being injured..
Let us/me know how we can help.
We're not going to discuss my education tuition over the years...
I gotta hand it to ya, you;re sure staying positive and objective ! I'd have been in the padded cell again if this had happened to me
years ago,
I recall a new paint job...that sexy deep blue that came on the Impala SS many yrs ago and a few vettes. GS colors I think..anyway,
Less than 1 week later I parked up under the back end of a Pick-up truck with a drop down ball hitch...went about 3/4 of the way up the hood. Like a chain saw had run up the hood...
I was in therapy for months.....
I'm glad that you;re coping better ! Few things hurt worse than your Corvette being injured..
Let us/me know how we can help.
Last edited by leesvet; Dec 5, 2012 at 03:31 PM.
Thread Starter
Pro
Joined: Dec 1999
Posts: 673
Likes: 0
From: Venetia,Pa,USA
I've had the pan on and off. Indeed the pan can be removed and replaced without pulling the engine.
I'm in the process of reassembling the engine. The piston/rings/rodbearing have been replaced on the bad cylinder. There was a really small rub mark on the wall. If it has a compression within 10% of 180 PSI I'll be thrilled. If not I'm done. 53 years of working on cars I no longer enjoy it. Remember this was a new short block. The AFR heads have been checked by a engine builder. On new years day I'll replace the intake manifold. I'm also buying new injectors just in case. The only defect I found was a torn intake gasket on #5 piston runner. The bad cylinder. Then within a couple of days I'll replace the super ram. Within a month I should know the results.
As you can see it takes effort due to lack of desire for me to work on the car. If it works out I'll race another year if not I'll sell or part out the car.
Thanks again for all comments and after everything is up and running I'll post the results.
I'm in the process of reassembling the engine. The piston/rings/rodbearing have been replaced on the bad cylinder. There was a really small rub mark on the wall. If it has a compression within 10% of 180 PSI I'll be thrilled. If not I'm done. 53 years of working on cars I no longer enjoy it. Remember this was a new short block. The AFR heads have been checked by a engine builder. On new years day I'll replace the intake manifold. I'm also buying new injectors just in case. The only defect I found was a torn intake gasket on #5 piston runner. The bad cylinder. Then within a couple of days I'll replace the super ram. Within a month I should know the results.
As you can see it takes effort due to lack of desire for me to work on the car. If it works out I'll race another year if not I'll sell or part out the car.
Thanks again for all comments and after everything is up and running I'll post the results.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
I think I read you have a SuperRam manifold. If you do, I'll give you a tip that has worked for me. Because my manifold and runners have been extrude honed, I need to trim the standard runner manifolds to fit my larger runners. When that is done, I use a small amount of Ultrablue silicone on the manifold side of the runner gaskets. On the runner side, I use a small amount of white lithium grease. I then assemble the runners and plenum. Doing this will allow the runner gaskets to be used over and over, in my case dozens of times. The white grease helps keep the gasket from sticking and seals any possible vacuum leaks. Good luck.
Thread Starter
Pro
Joined: Dec 1999
Posts: 673
Likes: 0
From: Venetia,Pa,USA
Engine is back together. Replaced the melted #5 piston with new piston and rings. Started engine yesterday and sounds and runs great.
A compression check of all cylinders resulted in 195PSI +/- 4PSI. While I had the heads off I had them checked out and 0.010" machined off. The previous compressions were 182 PSI with a estimated compression of 9.5 : 1. What compression would I expect with the listed cylinder pressures?? Racing the car previously I used 93 octane pump gas. I expect I'll need to mix some 100 octane with the pump gas??? Yes / no???
Again THANKS FOR ALL INFO
I want to thank you guys for convincing me that indeed the race oil pan would indeed come off without removing engine from car. It is easier than I would have believed.
A compression check of all cylinders resulted in 195PSI +/- 4PSI. While I had the heads off I had them checked out and 0.010" machined off. The previous compressions were 182 PSI with a estimated compression of 9.5 : 1. What compression would I expect with the listed cylinder pressures?? Racing the car previously I used 93 octane pump gas. I expect I'll need to mix some 100 octane with the pump gas??? Yes / no???
Again THANKS FOR ALL INFO
I want to thank you guys for convincing me that indeed the race oil pan would indeed come off without removing engine from car. It is easier than I would have believed.
Racer
Joined: Aug 2010
Posts: 297
Likes: 9
From: Holiday Shores IL
...
A compression check of all cylinders resulted in 195PSI +/- 4PSI. While I had the heads off I had them checked out and 0.010" machined off. The previous compressions were 182 PSI with a estimated compression of 9.5 : 1. What compression would I expect with the listed cylinder pressures?? ....
A compression check of all cylinders resulted in 195PSI +/- 4PSI. While I had the heads off I had them checked out and 0.010" machined off. The previous compressions were 182 PSI with a estimated compression of 9.5 : 1. What compression would I expect with the listed cylinder pressures?? ....
Too many variables such as valve timing and overlap.
The time to calculate compression ratio is while the heads are off.
It involves taking precise measurements. They include:
Volume of the cylinder head chamber with the valves in place.
Volume of any depressions or protrusions in the piston.
Distance from top of piston(flat portion) to block deck at TDC and at BDC.
Cylinder bore diameter.
Gasket thickness. (Depending on how accurate you want to be, you would measure the bore diameter of the gasket too)
Basically you calculate the volume of the cylinder at BDC and at TDC then divide the two.
Shaving .01 off the cylinder heads will not greatly change your compression ratio. I don't know what the general measurements are for your engine, but I would guess an increase of maybe 0.1. (1/10)
If you are concerned about leaning out, get a wide band a/f gauge setup. This will let you know if the engine is not tuned properly.
Better yet, if you don't want the hassle, take you car to a good place that does dyno tuning and them tweak the computer for whatever fuel you want to run.
I'm glad it's all back together and that you didn't walk away from it.
Have fun.
Race Director
Joined: Sep 2003
Posts: 16,838
Likes: 341
From: Database Error Indiana
.010 only took about 3 cc from the chambers, I think. AFR or their we site could tell you how many cc per .010 milled. Thats not going to be a huge compression increase. You should not need race gas.
Dont you love the fact that you could do this without removing the motor ?
Dont you love the fact that you could do this without removing the motor ?
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