Pontiac GTO Forum banner

1 - 20 of 24 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Recently had 1964 GTO 389 professionaly rebuilt. Have appx. 1500 miles on it and have changed oil 3 times using Lucas zinc additive. After sitting and cold in the morning, it rattles like rod noise until pressure is up (2-3 seconds). It is getting progressively worse and I was told there is an oil check valve/spring where the oil filter mount bolts to the block that may be bad. I wonder if it is just a loose motor? Carries 50-60 psi once running. Any ideas?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #5
389 rattles

Not sure video would detect rod noise on initial cold start. Have been told that advanced timing (about 36 deg) and 91-93 octane produces "Ping" and along with decked heads and block may be running 11 to 1 compression. Had a mechanic tell me the motor will self destruct with cold starts and dry bearings as a result of loose clearance / worn bearings after 1500 miles??
Suggests: dished pistons to reduce compression, new bearings,rings, and polish crank. Hopefully has not been hurt. Is already .010 under.
 

·
Former Super Moderator
Joined
·
9,919 Posts
If that is in fact what's going on, it could have been caused by not priming the oil pump durring assembly. Now that the pump is working, replacing the rod bearings might be all that's needed. I would be sure to use some plasticgauge on them to check clearances when installing the new bearings.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #7
389 rattles

Thanks for responses. Maybe at this point new bearings will work if crank is not hurt. Is the advanced timing, higher compression, and pinging a factor in the bearing failure?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #9
Do you run pump gas / octane boost? Maybe I can save this motor without major rebuild by just replacing rod bearings. Just want a dependable car.
 

·
Registered
Joined
·
475 Posts
Recently had 1964 GTO 389 professionaly rebuilt. Have appx. 1500 miles on it and have changed oil 3 times using Lucas zinc additive. After sitting and cold in the morning, it rattles like rod noise until pressure is up (2-3 seconds). It is getting progressively worse and I was told there is an oil check valve/spring where the oil filter mount bolts to the block that may be bad. I wonder if it is just a loose motor? Carries 50-60 psi once running. Any ideas?
the spring in the oil filter block is blocked filter bypass. it has nothing to do with oil pressure.
hard to tell what the noise is without hearing it. could be lifters or bearing noise. lifters are more of a clatter. bearing noise is a more solid fast rattle.
 

·
64-67 Expert
Joined
·
8,561 Posts
An engine will not ping on start up and at idle unloaded. Only under load. I have seen engines and have torn down engines that had the lower con rod babbit destroyed by pininging/detonation. It does not take long. I'm in the same boat: I built the 389 in my '65 GTO in 1981, and it's high compression with the original bathtub heads. It does have forged pistons. I need to run racegas mixed with 91 or a now-defunct lead additive to make it run ok. Have had recent esperience with dished pistons in a 389 (9:1) compression with stock iron heads and an XE268 cam, and that engine runs as hard as mine does.....and it does it on 89 octane. The reason I hardly ever drive the '65 is because of the high compression......I drive my '67 ALL the time, because I dropped the compression down to 9:1 and can use cheap pump gas.
 

·
64-67 Expert
Joined
·
8,561 Posts
As a PS, I broke the lands off of 4 or 5 pistons in a 428 I was running on pump gas back in the mid '80's. Never once heard it ping, but detonation was the cause of the failure. A co-worker recently finished installing his SECOND set of rod bearings in his '96 Ford F-150 with a 302. Less than 80k on the clock. Cause? Detonation. Pinging that his 19 year old son could hear, but his 50 year old ears couldn't. You'd think there'd be a knock sensor on a '96 Ford.....go figure. He ditched the Ford and got a Honda Ridgeline, which HAS a knock sensor!!!
 

·
Registered
Joined
·
9 Posts
Discussion Starter #14
Thanks for the education. It is starting to make sense now. The "Pinging was under slight load and I was running pump gas 91 ? octane. If the pinging can roach the rod bearings, then that is what sounds like happened. Don't know if I can drop the pan on my '64 GTO or maybe will have to pull the motor to replace / check rod bearings. I assume if I run an additive or higher octane, and retard the timing a fuzz, that will prevent this from happening again. Just hate doing it all over again after only 1500 miles. Better fix it now though.
Thanks again.
 

·
Registered
Joined
·
475 Posts
Thanks for the education. It is starting to make sense now. The "Pinging was under slight load and I was running pump gas 91 ? octane. If the pinging can roach the rod bearings, then that is what sounds like happened. Don't know if I can drop the pan on my '64 GTO or maybe will have to pull the motor to replace / check rod bearings. I assume if I run an additive or higher octane, and retard the timing a fuzz, that will prevent this from happening again. Just hate doing it all over again after only 1500 miles. Better fix it now though.
Thanks again.
you have to pull the engine to check bearings. i would want a better diagnosis before i went to all that work. first thing i would do is pull the oil filter and disect it. if the bearings have deteriorated you will see evidence in the filter.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #16
Thanks. Will pull filter first. Not sure I'll find anything. Rod noise on initial cold start for about 2 seconds, but I think it is getting progressively worse. Have changed oil 3 times in 1500 miles. Valvoline 10-40 and NAPA Gold 1049 filter. Local Napa machine shop did the motor and is willing to go back through the motor if I pull and bring in. A good friend in our club is the head mechanic there and has done others for me w/ no problem.
Is the "Pinging" octane issue / timing the culprit or do you think it was just a loose motor from the start? Just don't want to have to go through this again.
If we have to pull it all the way down, I'll run the dished pistons, but he said the ones they used were Pontiac replacements for the 389.
One thing I failed to mention: I put 200 miles on engine break-in w/ Lucas zince, changed oil to same specs and ran about 900 miles to WV and back at moderate speed 60-65.
 

·
Registered
Joined
·
475 Posts
Thanks. Will pull filter first. Not sure I'll find anything. Rod noise on initial cold start for about 2 seconds, but I think it is getting progressively worse. Have changed oil 3 times in 1500 miles. Valvoline 10-40 and NAPA Gold 1049 filter. Local Napa machine shop did the motor and is willing to go back through the motor if I pull and bring in. A good friend in our club is the head mechanic there and has done others for me w/ no problem.
Is the "Pinging" octane issue / timing the culprit or do you think it was just a loose motor from the start? Just don't want to have to go through this again.
If we have to pull it all the way down, I'll run the dished pistons, but he said the ones they used were Pontiac replacements for the 389.
One thing I failed to mention: I put 200 miles on engine break-in w/ Lucas zince, changed oil to same specs and ran about 900 miles to WV and back at moderate speed 60-65.
i highly doubt detonation would hurt rod bearings in 1500 miles with normal driving.
i have a stock 66 that i have run for years on pump gas with no problem.
any chance you can do a video with the sound?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #18
I'm not good enough to do video, sorry. It is definitely rod noise on cold start up. Oil must drain back off loose bearings? Or what keeps oil in valve train, rods, and mains so there is lubrication on start? Once the oil pressure is up, next start up is fine, no rattle. I will go ahead and pull motor and let them figure it out. I just want to prevent it from happening again.
 

·
64-67 Expert
Joined
·
8,561 Posts
Oil will generally stay put in the bearings, lifters, etc. for a fairly long period of time. Synthetic oils have better "cling" and will stay on parts even better over time. If you have your rattle every morning, after just sitting for 20 hours or so, you probably have too much oil clearance in the bearings as you suspect. This could be a bearing problem from detonation, even with as few miles as you have, or as the result of borderline oil clearances from the get-go, which is what I suspect. Motor needs to come out to verify for certain. There is a good chance there is no damage to the crank, etc, since there is no noise after pressure builds up. Do the oil filter thing first, though. If/when you do pull it apart, measure ALL the bearing clearances, not just one or two. I always double check the machinist's work by measuring everything before I assemble a motor. I've even run into brand new, mis-boxed bearings that said ".010" oversize and were actually standard. Guaranteed rod knock. Clearnace checks will tell you what is loose.
 
1 - 20 of 24 Posts
Top