LEATHL_WS6

Let me start by telling you my problem. I upgraded froma 224 228 cam and a crappy set of heads to the pp 5.3 and the texas speed 231 237 cam. Car seems to run very well is responsive no popping had a 12.8 to 13.0 AFR on the dyno but only made 400rwhp. This was weird seeing how I made 392 with the crappy heads and 224 cam. I have been chasing the wanted HP fpor a while now.

I did a compression check on all cylinders and the results are really messed up.

1- 180
2 - 210
3 - 210
4 - 215
5 - 230
6 - 220
7 - 165
8 - 210

What's up with that? I cranked all cylinders untill pressure stopped rising. I thought this cam should only be about 165..

I also did a leakdown all cylinders were under 8% with most being under 4%.

Any ideas what could cause this? OR what it should be?

I have a set of Harlan Sharp Roller Rockers torqued to 22ftlb's. I did check preload as the directions said and I got between 1/2 and 3/4 turn of preload before hitting 22ftlb's Heads are unmilled and I'm running a stock length pushrod.

Thanks Rob

Z28Venom

iTrader: (13)

I recently did a compression test on my car with the TR230 cam.. I wasn't aware that the actual compression changed based on the cam..

My numbers were:

1-150
2-150
3-150
4-150
5-145
6-150
7-145
8-150

Does this mean that my 5 and 7 cylinder are jacked?


I'm not tryin to highjack your thread. I'm confused also..

LEATHL_WS6

No your fine thats what they should look like. As long as they are with in 10 psi of each other your good. Those numbers are determined by the amount of overlap a cam has. yours probably has some good over lap to have numbers in the 150 range. Overlap is the amount of time both the intake and exhaust valves are open at the same time. Mine should as well. But for some reason I dont. Thats what confusing me.

Rob

2fast2z

Im new to the board so ill say hey first off. Im pretty sure this is not your 1st comp test just wondering did you disable the fuel to prevent fuel wash down to produce different readings? Did you keep equal cranking times? Tried another comp. guage? If all is correct have you added a small about of oil to the cyinder to see if pressure goes up? If it does you may have a ring seal issue. Just a few thoughts. Later

mike m

iTrader: (6)

It seems you may have gone from one set of crappy heads to another. There are alot of pp 5.3 guys making under 420 with that cam. Are you an auto or an m6? You should have had the old set of heads and the new set of heads flow checked to see the difference in the cfm. before installing them to eliminate that as the cause. I hope for your sake it is something to do with preload, wrong size pushrods etc... and not the heads. Good Luck.

mike m

iTrader: (6)

Also do a leakdown test to see if the valves are sealing correctly.

LEATHL_WS6

Thanks for the reply. Yes I've done a few. I cranked each cylinder unitl the pressure stopped going up. This was about eight crank rotations. Yes I did disable the fuel pump. I only tried the one guage but this one worked fine last year on this car. I can try to get another just to be sure. The leak down tells me the rings are ok. So no need for oil in the cylinders. I was hoping to lower the pressure anyhow not raise it. The high number tells me that the valves aren't opening correctly too soon too late not enough who knows. Just not right I believe my pressure should be in the 160's.

technical

Did you ever perform a comp test on the old setup?
#7 ain't right. maybe try again. otherwise i'd say bad valvejob/valve or they just aren't closing on #7, since you said leakdown was ok.
#1 ain't looking to good either.

LEATHL_WS6

Mike heads seem to be fine. Thanks for the bash. plus heads would not cause these types of readings. Last heads flowed in the low 280's these in the low 300's

Car is an M6.

As I stated earlier I did a leakdown and all cylinders were fine.

Sure guys are making under 420 but I've yet to see anyone post compression test readings like these. Something is wrong and its not the heads. II'm gonna try the stock rockers tomorrow and see if that makes a differance.

Rob

LEATHL_WS6

Tech old setup was 190 or so across the board. But this cam is susposed to have more overlap and is susposed to be in the 160 range. 7 and 1 are closer to what all cylinders should be.

as for trying again I did all cylinders 2 times and did 7 and 1 four times because I couldn't believe it.

technical

ok, this is going way out on a limb...
Was there excessive carbon buildup on the pistons in the cylinders that were high?

Never heard of this one...normally I'm looking for the low cylinder(s) ( because something's wrong) not the abnormally high

StickSS

Could be that you have a cam lobe problem or a bad lifter to me. Sometimes a new cam is defective and is not hardened correctly, or it was installed with out enough lube. After 15 minutes of running a cam lobe could get wiped out. Check the lift on the bad cylinders and some of the good ones with a dial indicator gauge. If the lift is a lot lower on the bad cylinders this would indicate a bad cam lobe, Or possibbly some of your lifters may have gone bad or collapsed. Did you reuse the old lifters? If they are old I would have replaced them. Also check the rocker arms to see if they are to lose, worn etc.

Hope this helps

strokedls1

iTrader: (1)

If your using comp or crane lifters 1/2 to 3/4 may be a little too much preload on some. I do 1/4 to 1/2 on the aftermarket lifters. As stated above, could also be a flat lobe or dead lifter. Was the cam degreed in at installation or just dot to dot?

racer7088

Cam could be installed way advanced?

LEATHL_WS6

Tech Nope all cylinders had the same amount of buildup which I removed.

LEATHL_WS6

Stick

I always use assembly lube when assembling and engine or changing lifters cam etc. I covered the cam with assembly lube before installing it.

I also agree I think the cam is ground wrong. I find it hard to believe that 6 lifters went bad. The motor only has 16k on it so I just reused the old lifters. I will get a dial indicator and check that out. rockers are all still tight and look good.

Thanks Rob

LEATHL_WS6

Cam was installed dot to dot. Stock Lifters with only 16k on them. I did put some assembly lube on top of the lifters could that screw them up?

technical

Spark plugs not seated/sealing as good on 1 & 7?


Sorry for all the quick posts, but this one is real interesting...just trying to brainstorm some ideas.

LEATHL_WS6

No problem Tech.

I tried those cylinders 4 times each so I doubt the hose was in wrong 4 times. I'm going to re run the test again tonight with a different gauge and see if I get the same results. Then I'm going to put the stock rockers back on and test it again.

Real intresting but driving me nuts.....

Rob

technical

I'm sure it is making you nuts.

Sometimes a bad valve guide can do this as well ie Leakdown would look ok, but during compression the valve would rock and loose a little pressure. I'd hate to think that since they are new heads. Good luck tonight, let us know.