Cylinder wash

jonalley · #1 (**permalink**) 05-20-2012, 06:23 AM

Sorry,This is a bit long but tell me about cylinder wash and possible fixes. I'm really in the dumps. 302 with 48 IDAs. Engine runs but,in trying to tune, discovered the left front carb not pulling. Idle mixture screw also does not change rpm as other three do. Engine has been started and stopped for a total of maybe one hour on a total rebuild- there's still assembly lube showing on parts and I did prime the system before anything.I have good oil pressure.Timing light shows life in the no.1 plug wire. With valve cover off, valve train on number one cylinder showing movement to match other cylinders. I did a compression check on a cold engine and the numbers are all over the place-e.g.no. 1 just about showing and no.6 at 150#
So... tell me my bad feelings are wrong. Would a cold engine produce these low numbers? Would the rings not have seated as yet and in this irregular way? You can tell I'm looking for a happy ending here. I did have problems with the floats being set poorly when I first got the carbs but if the cylinders did get too much fuel in those short runs what is my course of action to repair??Of course I don't want to pull everything apart to find the fault someplace else. If this is the infamous cylinder wash,can I pull everything apart in the car and electric drill hone the cylinders? Do I need to change ring sizes???? Regards, Jon

Rick Parker · #2 (**permalink**) 05-20-2012, 11:04 AM

Couple of things... are the valves completely closing? If it is a solid lifter cam is there lash when springs are relaxed? If it is a Hydraulic cam, maybe reseting the preload on the lifters??
Next...it is not unheard of for the cylinder that is not firing to have the throttle butterfly closed (not exposing the idle port) when the other cylinder on that carb is functioning properly. This is sometimes caused by a slightly twisted shaft. If the syncronizing tool that you are measuring the airflow shows that both cylinders on the suspect carb ARE drawing an equal volume of air then move to the idle jet and see if something is plugging it, next remove the idle mixture screw on the suspect cylinder and blow small amount of compressed air into it, reset it to correct opening about 3/4 - 7/8 of a turn open.

jonalley · #3 (**permalink**) 05-20-2012, 01:35 PM

Rick, I was hoping to hear from you. You've helped in the past. The motor has hydraulic lifters. Arms appear to be going through about the same movement as others. Also, I just redid the compression test ,again cold, and no.1,3,4,&6 all have no compression( just bought a new meter and it works fine on the other cylinders-175-180# range)
I put things back together and am going to try a compression test after heat up. Hopefully that will show some results. The motor runs a little rough but runs and I can't believe it would do that if half the cylinders were down.I'm hoping the rings just have not totally seated and not that I put some in upside down or something stupid like that.
The front left carb was the one that started this all-just no reading on the syncro tool at all on the front stack and a very small draw on the second.
I'll blow out jets and take out the mixture screws for a cleaning at your suggestion.I think I also need to revisit the valve lash settings just to exclude that issue. Thanks Jon

*13* · #4 (**permalink**) 05-20-2012, 02:31 PM

What do the plugs look like? Are the carbs stock or pre jetted? You should get some vacuum reading even if it's not firing. Did you install the intake? Was the sync too reading vacuum when you first ran it? Yes, check the lash & let us know.

jonalley · #5 (**permalink**) 05-20-2012, 03:22 PM

Plugs, like the compression ,are all over the place color wise- Some sooted and some not. I bought the carbs stock but Rick Parker suggested a different idle just early on. I also spoke with Jim Inglese and he got me to change most everything based upon the engine description I gave him.The parts that came with the carbs were more for a larger displacement I think. An old post here will show that I was complaining about fuel spurting from the stacks. Like reversion but at idle. It was scarey but turned out to be the floats. They were all set wrong. Changed/adjusted them and the spurting stopped.
I'm going to go over this thing tomorrow and look at some of your suggestions. I felt like I was so close to getting this car done and now this seems like a real confusing set back.Thanks, Jon

Gaz64 · #6 (**permalink**) 05-21-2012, 02:27 AM

150 is healthy, zero is not.

You must have valves not seating in the affected cylinders.

Time for a leakdown test, will reveal more than a compression test.

Don't even bother trying to restart the engine until your leakdown is under 10%.

Intake valve loss is heard through the carb throat, exhaust valve through the pipes, rings heard through the oil cap.

jonalley · #7 (**permalink**) 05-21-2012, 08:23 AM

Ok I'm feeling a bit better. Valve leak. I did a poor man's leak down test ( pressure directly to cylinder with schrader valve removed from my compression tester line) and, sure enough, both intake and exhaust are leaking big time. Pulled a valve cover and removed the rocker pressure on the tested cylinder and the air rush almost ceased. So.... Got to go back and check the lash settings on this engine. Must be that. Have Edelbrock Performer heads with the small valves and stock push rods and lifters. I'm assuming it's not the push rod length.
I do thank you all for saying something other than cylinder wash. Regards, Jon

Gaz64 · #8 (**permalink**) 05-21-2012, 12:23 PM

Jon,

Did you place each cylinder at exactly TDC compression before hooking up your air supply?

It's the only parked position of the piston where both valves are closed.

jonalley · #9 (**permalink**) 05-21-2012, 05:12 PM

Thanks Gaz64. Yes, I understand that. The no.1 cylinder was actually were this all began as that was the one over the carb that had no draw on my syncrometer when I was trying to balance them. I just finished redoing all the valve preloads again and did a quick rerun on the leakdown on no.1. Looks good. I'm going to try to start things tomorrow and see where I am. regards, Jon

*13* · #10 (**permalink**) 10-16-2012, 11:17 AM

I also,I know others have experienced this, have had this issue in the lower rpm's that turned out to be an idle screw port with debris in it. Pulled the carb & the idle screw. Look Down through the hole & see no light. Blow or carefully clean the debris & cylinder acts normal again.

Rick Parker · #11 (**permalink**) 10-16-2012, 12:24 PM

The hole in the bottom of the idle jet will generally become blocked before the idle discharge port because the fuel hole is dimensionally smaller (ie .55, .60, .65 mm) in the jet where the foreign material is picked up VS the 1.00 mm discharge port in the throttle bore. If you find your engine suddenly running on 7 cylinders (or less) inspect the idle jets first.

*13* · #12 (**permalink**) 10-17-2012, 03:11 AM

Yes, I don't know what happened exactly. I pulled the jets & they were clear.