SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: CenCalCruiser on August 08, 2009, 08:20:43 PM
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Not boat related but maybe you guys can lend a few ideas...
I have a '64 chevelle with a sbc 350. The motor came out out of a '93 suburban that my father and I tore down and rebuilt. Only modifications made was an edelbrock performer cam, edelbrock performer rpm heads, 1.6 roller rockers, rpm air gap manifold etc etc. We have built several motors without any issues; however, this time we're baffled! We broke the motor in @ 2k for 20 min, changed oil and everything seemed fine for the first 500 miles. Then the motor developed a slight lifter-sounding tap that would come on and off. Things we have done: rechechecked rocker arm torque, thought maybe we had a collapsed lifter so we replaced and broke in once more, changed out rocker arms. The tap seems to be coming from the back of my motor and seems to be more noticable when hot and and over 14-1500 rpm. I called edelbrock and the first thing they asked was if I had the hardened pushrods that were .0100 longer....yes I do have em!
A few other things that I have not checked that could I suspect could be screwed up: bent or cracked flexplate, stripped distributor gear. I made plexiglass valvecovers and each side is getting plenty of oil being pumped up. Very good oil pressure. What do you think it could be? It sounds like a lifter tap but the rocker arms are fine when I check it. Also, it's not a simple exhaust leak!
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Have you inspected the flexplate ???, cause if it was in the valve train, I think you would hear it more at idle than anything, not at a higher rpm.
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Very good point...I've bumped it over a few times and have inspected it somewhat but I don't see anything (very hard to tell though). I've been told that even a hairline crack can cause a tapping.
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Ya that be the bummer part, not being able to inspect it good enough, without going through a lot of work :mad:
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rebuilt a 350 once had same issue turned out to be bad mech fuel pump, not saying thats your issue but check it out cheap to replace.
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rebuilt a 350 once had same issue turned out to be bad mech fuel pump, not saying thats your issue but check it out cheap to replace.
"96 5.7 don't have a fuel pump boss....has to be an electric.
I think you have a broken flexplate at the crank circle, seen it a lot. see if you can find a plumber buddy that has a bore scope/camera to inspect it from the block side and look for some very slight rust coloring arount the crank hub..
My first car was a '64 Chevelle SS, my second car was a '64 Chevelle SS, but with a four speed instead of an automatic :thumbup:
Another wierd deal..when I put a '92 Corvette tune port 5.7 in my '72 Blazer, the block had a funny issue of being 1/4" shorter at the rear of the motor (between the motor mounts and the bell ousing mount), make sure everything fits right.
Also, which torque converter do you have?, did you check the crank pilot for proper fit?, That one bit me in the butt.. :banghead:
GT
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I did not check the crank pilot for proper fit...I went out this morning, let it warm up and had the ol lady rev it up while I was listening for the ticktap. It sounds more noticable from underneath the car and at the very rear of the engine (on the passenger side). How do you check for proper crank pilot fit? I'll jack it up a little later and try to inspect the flexplate a bit more thoroughly.
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Check all the valvetrain, make sure every pushrod is seated in the lifter and rocker correctly.
Is it a consistant ticking? Or is a tick here and there? If it's not consitant then it's not the flexplate
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It is not consistent. You can not hear it at idle...its only when the motor is above 1500rpm and even more noticable when hot and above 1500rpm. From what I've heard...a cracked flexplae will expand at higher temps and rpms and will thus cause a tapping? Any other takes?
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Just took it for a ride and this is what happens...At idle everything is fine and seems to purr like a kitten. I'll leave it in third (TH-350) doing 35 @ 13-1400 rpm and there is still no tapping...however, when I drop it into second the rpms will go up to 18-1900rpm and there is a distinct tapping that sounds almost like a lifter tap. This occurs in all gears once the engine is rev'd up to 18-1900rpm and above. Before the drive, I took both valve covers off and checked valve lash and everything was perfect! WHAT COULD IT BE???
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Revision...Almost sounds like a knock compared to a tap. I'm seriously thinking it's something in the transmission area. Torque converter, flexplate....???
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Probably not the same concern but we had a motorhome with a 8.1L Chevrolet engine that was making a chirping type noise from the bottom end area. R&R'd the trans to look at the flex plate with no problem found. We were just about to pull the pan when we found the rubber oil fill tube sucked shut when running. We decided that it was trying to ventilate through the rear main seal (chirping noise), loosening the oil fill cap would stop the chirp :screwy:
What we found was a failed PCV system (built into the intake manifold).
Replacing the intake manifold corrected the problem.
Good luck in your search ;D