Stroker update -- Need advice

parts were here waiting for me when I got home tonight! I'm beat. I'll start looking into it tomorrow.

Thanks!

Matthew
 
I've got the valve cover off...very clearly on exhaust valve #1 the seal has lifted from it's seat and is floating on the valve stem. intake seal looks OK..#2 seals look OK too which has me worried...

Anyways... I've set #1 piston to tdc and hooked up my air compressor to the cylinder using the compression tester hose with the valve core removed. The air just leaks out of the cylinder (can definitely hear it) and my compressor can't make enough air to keep it compressed. all marks are lined up properly and I can see the piston top thru the spark plug hole. I'm going to try a known good piston (#3) to see if I'm doing something wrong or if my compressor just isn't up to the task. Any ideas? I can't believe I've bought all the tooling to do this..practiced spring removal on my spare head and am going to get stuck bringing it some place to get this done...

Matthew
 
Using same process on Piston #3 I was able to keep the cylinder compressed to the point where the compressor could keep up with the leak and keep a steady 100psi in the cylinder -- the tank volume was even increasing. I tried #1 again with the same result (rapid leaking).

For giggles I ran a quick compression check on #1 and #3 while cold -- 4 cranks with throttle body wide open...

#3 showed 120... #1 showed 90.

Sigh...what next?

Matthew
 
5-90 said:
What next? Wet compression test.

By the way - when I've used an air holder, I've found it useful to load the cylinder a little before TDC, then turn it the rest of the way up to add a little pressure.

5-90
Click to expand...

at what rate should air leak from the cylinders? on #1 there was a steady loud hiss and corresponding drop of pressure. #3 was much quieter but still a steady hiss. Out of the three times I tried it on #1 it pushed the piston back down the cylinder twice (In my readings I have seen it mentioned that this can be expected). On the two times I tested #3 it pushed the piston back down once -- but it didn't matter...while the compressor constantly ran it could keep the PSI above 100 on #3. I have the warm compression #'s posted above...I know that cold tests don't mean a whole lot. It's interesting to me though that I could have performed the process on a 'known good' cylinder vs a 'problem' cylinder with my compressor. I don't remember what it's output is at 90 psi...but it's not a whole lot.

Sorry if I sound discouraged...but I was so close--and yet so far...

Matthew
 
Got a leakdown gage? Typically, 90% or higher pressure retention is acceptable, 95% or better is good, 98-99% is excellent. "Needs checking" is 80-90%, and "Needs service soon" is 80% or less. Again, this is using a "leakdown" gage rather than a "compression" gage - what you're checking is the ability of the closed cylinder to retain a known air pressure.

That's still a pretty wide variation tho - 90psi vice 120. Did you build this engine, or buy it? If you built it, I might have some questions for you...

5-90
 
5-90 said:
Got a leakdown gage? Typically, 90% or higher pressure retention is acceptable, 95% or better is good, 98-99% is excellent. "Needs checking" is 80-90%, and "Needs service soon" is 80% or less. Again, this is using a "leakdown" gage rather than a "compression" gage - what you're checking is the ability of the closed cylinder to retain a known air pressure.

That's still a pretty wide variation tho - 90psi vice 120. Did you build this engine, or buy it? If you built it, I might have some questions for you...

5-90
Click to expand...

I don't have a leakdown gauge...I purchased the longblock and had it installed by a trusted mechanic. Ironically longevity/reliability were my two highest factors in this project. Go figure. I'm calling the builder tomorrow to update him and see how he responds.

Matthew
 
You can change the seal without using air. Just locate the piston at TDC, then stuff a 3/8" piece of plastic tubing under the valve - between the valve and piston. I used a clear plastic flexible tubing and replaced all 12 valve springs using this method.
That said; if you have an audible leak you probably have a bent valve and the head needs to come off.
 
I spoke with both the engine installer and engine builder this morning. Learned something about my engine that I didn't know. The valves and springs are from a SBC -- New guides were pressed in etc. Both people think that the elevated leaking from #1 is due to carbon deposits on the valves caused by the oil leakage. The engine builder offered to replace the seals for me if I wanted to bring the truck to him (about a 4 hour drive). My mechanic estimated 'a couple' of hours to do the job. I'm out of time this week and my schedule is hectic. I think I'm going to have my mechanic do this process.

The engine builder is also going to check for me if with the piston at TDC if the valves can completely drop into the cylinder or not (ie non-recoverable). He's fairly confident that they won't.

My question now is this -- assuming that this is in fact the problem on all affected cylinders (bad valve stem seals), and assuming that the leakage is caused by carbon deposits on the valves and or valve seats, what does this mean for my engine? Will they go away over time (with no more oil leakage). Will they cause my valves and seats to get burnt?

Matthew
 
Personally, this would drive me nuts, I would want to pull the head, clean and lap the valves, just to be sure they seal the next go around....and replace the seals of course. :)


If you ran a compression test and it shows 100 psi max on a new engine, that sux big time.

Good luck
 
If it is carbon buildup, run a can of BG44K. It will nuke the carbon.
 
user name said:
Personally, this would drive me nuts, I would want to pull the head, clean and lap the valves, just to be sure they seal the next go around....and replace the seals of course. :)


If you ran a compression test and it shows 100 psi max on a new engine, that sux big time.

Good luck
Click to expand...

Only with the engine stone cold which is not a valid test. Warmed up and running I was showing 200 psi...

Believe me, this is driving me nuts...

Matthew
 
tetsulo said:
Only with the engine stone cold which is not a valid test. Warmed up and running I was showing 200 psi...

Believe me, this is driving me nuts...

Matthew
Click to expand...


I must have missed the part where you stated warm compression test was 200psi...your in good shape then.
 
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