I have a 350 crate (goodwrench) motor, stock Rochester 2bbl, I changed the distributor to HEI, changed plugs/wires. Ran great for about 5 minutes, when I put it into gear to double check the idle settings, it picked up a mean shake?? minor at idle, picks up to about 2k rpm and is at its worst, (balances out) above that and lessens but still there?? I took it to a mechanic, they said vacuum leaks, they fixed them and indicated the carb was only running Half (one side was not squirting fuel) and intake manifold leak on 6 and 8?? ( I had just rebuilt the carb and I checked it, looks fine, fuel squirting on both sides OK?? sprayed carb cleaner on the intake manifold, got no response checking for leaks?? I am at a total loss, I think the mechanic is FOS due to the Carb diagnosis.. any suggestions? I checked plug wires for correct placement 4 times with 2 different buddies. no problem there...
What causes engine shake?
67 RS style
21 - 40 of 45 Posts
Gary glad to see your on top of things... Have you check the temp on the exhaust manifold/headers to see at a quick start up drop a little mist of water on each exhaust port to see if they are all pretty equal. Something tells me its a miss fire.
This Goodwrench 350 engine, how equipped was it?
Was it a long block with oil pan and timing cover?
If it was, and the original engine was a 2-bbl, i.e., 327 CID/210 HP, everything should have transferred over from the original to the new engine without any problems whatsoever.
You say the engine ran good for 5 minutes of initial start-up. With this statement, I believe your torque convertor theory doesn't hold water. You would have known an imbalance from the begining.
FYI - the flexplate is neutral balanced, meaning the flexplate looks the same configuration 360°, a stamped center plate with a ring gear welded on. A weighted flexplate will have a weight welded on the circumference, only for 400 CID V8's. Also, on 210 HP V8's there was no harmonic balancer bolt, it was pressed into place. Adding a bolt certainly does not hurt.
Check the tailpipe with a sheet of paper. If the paper blows out or gets sucked in, exhaust valve is too tight.
Any noises fromt he engine? I don't think so, otherwise, you would have mentioned.
Dinner's called, I must go. Back later.
Was it a long block with oil pan and timing cover?
If it was, and the original engine was a 2-bbl, i.e., 327 CID/210 HP, everything should have transferred over from the original to the new engine without any problems whatsoever.
You say the engine ran good for 5 minutes of initial start-up. With this statement, I believe your torque convertor theory doesn't hold water. You would have known an imbalance from the begining.
FYI - the flexplate is neutral balanced, meaning the flexplate looks the same configuration 360°, a stamped center plate with a ring gear welded on. A weighted flexplate will have a weight welded on the circumference, only for 400 CID V8's. Also, on 210 HP V8's there was no harmonic balancer bolt, it was pressed into place. Adding a bolt certainly does not hurt.
Check the tailpipe with a sheet of paper. If the paper blows out or gets sucked in, exhaust valve is too tight.
Any noises fromt he engine? I don't think so, otherwise, you would have mentioned.
Dinner's called, I must go. Back later.
Joined
·
142 Posts
again thanks very much for the insight, almost like having educated best friends at your beck and call.. gotta love the internet OK,, so not really sure how the 350 was equipped, thinking CHEAPLY... interesting on the balancer bolt, but how does the paper tell you about the valve? I would assume it should always blow out right? if it goes in then that indicates a problem?? am I getting that correct? going to stuff some in and try the water on the manifold soon, let you know what goes on..oh, i was thinking the flex plate or converter had something go wrong at the 5 minute mark, maybe external weight fell off? something like that, I don't know enough about them to really know the answer,, of course if I did, then I would not need you guys huh???
Joined
·
142 Posts
oh, well then crumbling it and stuffing it in the pipe was NOT what he meant?? funny.. I did that and it fired right out.. do you think that tells me anything? he he.. the exhaust manifold did seem to burn the water off at a slightly different rate 6&8 were slightly slower, somebody earlier suggested putting the timing light on each plug wire and see if they are firing. I did that and they all seemed to fire OK... so even more confused now...basically back to square one,, I am solving one problem, the rodents in the garage must be dying off given that I have run the engine with the garage door closed 
this arctic 65 degrees prohibits me from opening it up.. jokes aside, I have been opening the door but still stinks..
this arctic 65 degrees prohibits me from opening it up.. jokes aside, I have been opening the door but still stinks..
Joined
·
142 Posts
Skeeter, by the way, that is one really NICE 69 you have there, hope mine looks that good someday.. starting with good bones, just need to work out the stupid kinks...
Gary how do the plugs look at 6&8 vrs the rest.... I had the same problem that temp was reading different and the plugs at #3 was getting little black spots only on 1-side. All that said turned out to be a crack on the inside runner on the inside of the intake manifold, it was running just like you described. A leak down test should tell you something.
Joined
·
142 Posts
I will pull the plugs when it cools and let you know, thanks very much.. need to look up what a leak down test is
Thank you for the complements... I went threw the same thing like all others. I'm not in anyway a certified mechanic just talking from exsperence... Some one will get on this thread by now and hit it right on the head.
Joined
·
142 Posts
ok, found the leak down test, if anyone is interested, I attached it here, has some really good diagnosis info.. need to get a tester in the morning...A leak down or "cylinder leakage" test is similar to a compression test in that it tells you how well your engine's cylinders are sealing. But instead of measuring pressure, it measures pressure loss.
A leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead center (both valves closed) when each cylinder is tested. Most people start with cylinder number one and follow the engine's firing order.
A threaded coupling attached to a leakage gauge is screwed into a spark plug hole. Compressed air (80 to 90 psi) is then fed into the cylinder.
An engine in great condition should generally show only 5 to 10% leakage. An engine that's still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.
The neat thing about a leakage test (as opposed to a compression test) is that it's faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn.
A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems.
A cylinder that has poor compression, but minimal leakage, usually has a valvetrain problem such as a worn cam lobe, broken valve spring, collapsed lifter, bent push rod, etc.
If all the cylinders have low compression, but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.
If compression is good and leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery (bad injector) or ignition problem (fouled spark plug or bad plug wire).
A leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead center (both valves closed) when each cylinder is tested. Most people start with cylinder number one and follow the engine's firing order.
A threaded coupling attached to a leakage gauge is screwed into a spark plug hole. Compressed air (80 to 90 psi) is then fed into the cylinder.
An engine in great condition should generally show only 5 to 10% leakage. An engine that's still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.
The neat thing about a leakage test (as opposed to a compression test) is that it's faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn.
A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems.
A cylinder that has poor compression, but minimal leakage, usually has a valvetrain problem such as a worn cam lobe, broken valve spring, collapsed lifter, bent push rod, etc.
If all the cylinders have low compression, but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.
If compression is good and leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery (bad injector) or ignition problem (fouled spark plug or bad plug wire).
Hey Gary just by chance is 6&8 crossed. Double check if you have time... http://www.joby.se/corvette/misc/firing_order.gif
Joined
·
142 Posts
all good there, looked them over again, no luck, they are all correct...
Joined
·
142 Posts
yep, let you know tomorrow how it turns out, hopefully I turn up something...this one reallly has me stumped,,, fun and challenging though,,, a good puzzle keeps the mind sharp... Happy holidays to all...
Joined
·
8,373 Posts
Yeah! You didn't let Xmas get in the way of working on your car did you?
Joined
·
142 Posts
sorry guys, but as stupid as it seems, I can't find any guage ( or anyone ) that is for leakdown?? do you use a compression tester? been to all the local parts suppliers?? no luck, compression testers, vacumm guages, but nothing for leakdown?? what gives??? and I did get a vacuum guage, a good 17 (shaky but only on the 17) does not shake more than 1/2 either way...
Summit has them;
http://www.summitracing.com/search/?keyword=leakdown tester&dds=1
and most any implement store would also.
With 1" total swing, one cylinder has a slight problem.
http://www.summitracing.com/search/?keyword=leakdown tester&dds=1
and most any implement store would also.
With 1" total swing, one cylinder has a slight problem.
Is this crate motor flat tappet or roller cam? If flat tappet these need break in oil and an initial start up run in varying between 2500 and 3000 RPMs to properly wear in the cam lobes and tappet bottoms that mate with the cam. Drain the oil and run break in oil for first 1000 miles after which you can use conventional oil with a zinc (ZDDP) additive such as Red Line zinc additive with every subsequent oil change. Failure to follow proper initial run in can leave you with a brand new cam sporting flat lobes.
One other diagnostic is to run the engine up to its shake rpm then unplug one spark plug wire at a time until you unplug one that does not change the engine shake. It's a shot in the dark but I've cracked my share of plugs installing them especially if there are headers involved and found my share of cracked plugs using this diagnostic.
It certainly could be related to a torque converter fastener issue or cracked or incorrect flex plate. Perhaps a balance slug dislodged from the flex plate. Does it shake whether in drive or reverse? The connections from the flex plate to the torque converter are easy to check so start there. Also double check all your motor mount fasteners.
Best of luck in resolving the issue.
One other diagnostic is to run the engine up to its shake rpm then unplug one spark plug wire at a time until you unplug one that does not change the engine shake. It's a shot in the dark but I've cracked my share of plugs installing them especially if there are headers involved and found my share of cracked plugs using this diagnostic.
It certainly could be related to a torque converter fastener issue or cracked or incorrect flex plate. Perhaps a balance slug dislodged from the flex plate. Does it shake whether in drive or reverse? The connections from the flex plate to the torque converter are easy to check so start there. Also double check all your motor mount fasteners.
Best of luck in resolving the issue.
21 - 40 of 45 Posts
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
