Can anyone tell me the right way to do a compression check on each cyclinder. I have all the plugs out, unhooked the coil wire then I pumped the gas first while turning the motor over to skirt gas into the cyclinders to wash the oil off the rings and walls. I then put the carb throttle at wide open . After screwing in the gauge do I turn the motor over until the gauge quites moving OR do I only turn over the motor so many times like 3 or 4? Thanks, Rick __________________
test Looks like you have a good handle on the process. I do not "wash down" the cylinders. But the important thing is to always do it the same way. Follow the same steps next time you do it to see if there is any change. I turn the engine over until the gage stops, which is usually 3 to 4 compression strokes. Are you doing this to find a problem, to get a baseline, or to "explore"? If you find a problem, I recommend a leak down test which is where you inject compressed air into the cylinder thru the spark plug hole and see if the valves, gasket or rings are leaking. Or you can squirt oil in a low cylinder and repeat the compression test. If the pressure comes up then the rings are bad. - Bill :TU:
The reason I'm doing this check is I recently added a ATI supercharger to my 455 and I'm now getting oil blowing out of my valve cover breather, out the front under my dampner and a little out of the cover plate where my mech. fuel pump used to be. I'm thinking mybe I've got blow by with bad rings or I've blown an intake gasket. Rick
I've got blow by on my rings:af: I decided to pull the motor, replace the hyperutectics with a TRW forged dish piston and moly rings. The rings had about 40,000 on em, don't know what kind they where. I added an ATI supercharger to it last year WITH OUT an intercooler so I guess the added hot compressed air caused them to wear out faster. Rick
I determined it probably is the rings because of the smoke coming up through the breather on my valve cover and by talking to alot of other BUICK machine shops and telling them my problem. :ball: I've now got it out, stiped down to the short block and loaded in the back of my truck headed over to a machine shop to have new rings and forged pistons put back in it.:grin: Well just got back from machine shop:af: my cyclinders are out of round which was causing my rings not to seat :ball: so now getting it bord from 30 to 40 over with a torqe plate. Rick
Sorry to hear about your bad news Rick......... Just a thought, but while the motor is out of the car and taken apart, it may not be a bad Idea to 1/4 fill the block with "HardBlock" to add some rigidity to it..... I wish I had the last time I pulled it down for a freshen up............ Halo girdle would be a good idea as well..... Rich
I wish I had the extra $$ to buy a girdle and modified oil pan! This little set back with the egg shaped cyclinders was an unexpected hit to the wallet! If hard block isn't to much I might look into doing that. Rick
Combination.... You've got it all out and all apart so........I read you complained about what looked like reversion into the intake. What are the specs on the cam your running? If its not a blower cam it would be benefical to go with wider lobe centers and alot more exhaust. Usually street blower cams are good about not having reversion problems. You could probably get by with just cam and lifters. Its just horsepower and I'd hate to see you pass it up with the motor all apart, that is IF its not a blower cam already. Not to knock o-rings but with the stock short block I would stay away from the o-rings. A head gasket is alot cheaper than a short block. I ran nitrous with no problem on stock Fel Pro's and stock head bolts. I wouldn't blame your supercharger for the rings. Something simple as running rich will trash rings just as easy causing accelerated wear. Look at all the high mileage street Turbo Regals and GN's making alot of power with fewer cylinders. They don't complain about there engines wearing out in 40,000 miles.
Hey Rick, the cam I'm running is not a BLOWER cam, I got it 2 years ago. It's a TA 413 ground on 110 degree lobe seperation. The cam has 234` intake and 244` exhaust with 500` lift on both intake and exhaust. After taking it to the machine shop, they told me they checked the cyclinders and each where out of round. They also said it looked like the rings never seated properly. I should have known that after having new bearings put in but haveing the same 30,000 mile rings put back in it with just a honning job was a bad idea. I now have to have it bord to 40 over to make them round agian. I now remember thinking how odd it was for the oil to turn black quickly right after changing it, ( carbon getting into the oil because of blowby ). This time I'm switching to forged pistons and putting in a set of NEW moley rings. I'm also going to have some of the dish area in each piston cut out to lower the compression to 8-1. Felpro has a new performance intake and head gasket for a 455 that I'm going to use. Your right about not blaming the supercharger, I just had alot of blowby because of the rings not seating right. I really hadn't thought about changing cams. I talked with ATI and they said what ever I do, make sure to reinstall it straight up, not advanced. I had installed 2` advanced before I got the supercharger. Thanks for your input, Rick:TU:
