Engine knock upon start-up

[corey wilkins]

Help my fellow Buick Brethern!!! Rebuilt engine with less then 5,000 miles engine knock on start-up has got progressively worst. use to only do it on cold start-up, but now does it intermittently on warm start-up now. Bearings? Rod-Knock? Dont want to spend another $3,000 on rebuild. can i have the oil-pan removed and have my mechanic replace bearings. whats the best case and worst case scenarios? 68 buick 430 motor.

[bob k. mando]

best case? your oil pan got dented and one of the crank weights is hitting it.

you wouldn't think that would get worse over time though.

i've also heard of a torque convertor bolt hitting stuff.



use to only do it on cold start-up, but now does it intermittently


uh, yeah. you shoulda figured out what that problem was when you first started hearing it. it might be a pretty serious issue by now.

did you rebuild this yourself? if a shop did it, have you reported your problem to them?

if you built it yourself, do you know that the cam bearings MUST be installed with a properly clocked position, otherwise you'll starve the drivers side rockers.

how is your oil pressure? do you have a gauge or just an idiot light? are you sure the sensor is functioning properly? have you plumbed the block to read pressure from rear of the oil galley ( i prefer Henderson's solution )?

http://www.buickperformanceclub.com/Oilmods.htm


i don't suspect a problem with your pump clearance because it's a cold issue. the pump clearance issue would get worse as the oil warmed up / thinned out. you should pack the pump with petro jelly and prime the oiling system before first firing though.

http://www.buickperformanceclub.com/oilpumpwear.htm

this would be a good time to look at upgrading to the 5/8" oil pickup and possibly looking at the block and timing cover mods:

http://www.buickperformanceclub.com/oilflow.htm

http://www.buickperformanceclub.com/OilingMods.htm



so far as troubleshooting goes, i would:
1 - get a mechanics stethescope
2 - hook a charger up to the car battery
3 - put car in park
4 - pull all spark plugs
5 - have someone crank the engine over on the starter and use the stethescope to try and locate the knocking sound more exactly

[corey wilkins]

Thank-you for your reply. I reported it to machine shop but its out of warranty. I now know about the oil-mods after the fact. can i go thru the oil-pan and replace bearings to buy me some more time before i have to go full rebuild again? If so please explain the process for my winter project!!!

[bob k. mando]

and you're certain the rod bearings aren't a problem here?

all those oil mods aren't actually essential for a normal street driven cruiser, but if you're doing a major rebuild it seems kind of pointless NOT to do them.

oh, also DO NOT USE FRAM FILTERS. they're crap. use AC-Delco, Wix or Napa Gold or the like.


from the 67 chassis manual for the 430:
http://www.teambuick.com/reference/l...chassis/60.php
"1. Since any service condition which affects the crankshaft bearings may also affect the connecting rod bearings, it is advisable to inspect connecting rod bearings first."

[Dr. Frankenbuick]

I would think if a bearing is hurt the corresponding journal is also hurt. You can't usually solve those sort of problems with just a bearing, and if the cause is not found, it is very likely to happen again.

[telriv]

Very common problem on the 350/400/430/455 engines with the oil filter on the timing case cover. As said DO NOT use Fram filters. You have an oil drain back problem/loss & the engine has to build oil pressure upon initial start-up. One way to gain some longevity is DO NOT try & start the engine immediately. Don't set the choke by pumping the gas pedal. Let it crank until the oil light goes out & while still cranking then pump the pedal. Doing this will only help the longevity issue. The problem is already there & MUST be repaired. Bearings have TOO much clearance & are more than likely already worn to copper.
Just my thoughts on the subject.


Tom T.