Need Help With Engine Problem
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Need Help With Engine Problem
Hi guys,
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I’m new here trying to get some help for my son on a 1982 302 engine he just rebuilt.
It had been rebuilt 2 to 3 years ago. Just about every thing that could be done was done as far as boring and turning with new pistons and oversized bearings, heads worked etc. It did fine for him till about a couple of months ago when he blew a head gasket and it ran hot.
He pulled the heads and took them to the shop and had them pressure tested and they were supposed to be ok. He put them back on and it still wasn’t right so he checked the compression and it was off. Then he pulled the engine and took everything to the shop and had it all checked again and they found a cracked head.
He replaced it and once again went through a total rebuild, but this time he decided to replace the stock cam with one with a little more lift. That’s where the problem comes in, I guess. It wasn’t broken in right and he finally discovered that a tapping noise was one of the lifters worn down. He checked them all and only found one bad.
He said the cam lobe looked okay and decided to just drop a new lifter in and see what would happen. While doing this he changed the oil and told me that he couldn’t see any metal in the oil, so he cranked it and it ran okay with no more apparent valve problems, but the oil pressure was crazy.
The oil pressure gauge was like a tack. At idle it was 20 to 30 lbs and when revved would go all the way up to 80 lbs. Up and down like a yo yo.
He’s now decided to go back with the stock came, but we still have the oil pressure problem.
Is the pick up screen stopped up or are metal particles in some passages? What would you guys suggest as the next step?
<O></O>
ffice
ffice" /><O></O>I’m new here trying to get some help for my son on a 1982 302 engine he just rebuilt.
It had been rebuilt 2 to 3 years ago. Just about every thing that could be done was done as far as boring and turning with new pistons and oversized bearings, heads worked etc. It did fine for him till about a couple of months ago when he blew a head gasket and it ran hot.
He pulled the heads and took them to the shop and had them pressure tested and they were supposed to be ok. He put them back on and it still wasn’t right so he checked the compression and it was off. Then he pulled the engine and took everything to the shop and had it all checked again and they found a cracked head.
He replaced it and once again went through a total rebuild, but this time he decided to replace the stock cam with one with a little more lift. That’s where the problem comes in, I guess. It wasn’t broken in right and he finally discovered that a tapping noise was one of the lifters worn down. He checked them all and only found one bad.
He said the cam lobe looked okay and decided to just drop a new lifter in and see what would happen. While doing this he changed the oil and told me that he couldn’t see any metal in the oil, so he cranked it and it ran okay with no more apparent valve problems, but the oil pressure was crazy.
The oil pressure gauge was like a tack. At idle it was 20 to 30 lbs and when revved would go all the way up to 80 lbs. Up and down like a yo yo.
He’s now decided to go back with the stock came, but we still have the oil pressure problem.
Is the pick up screen stopped up or are metal particles in some passages? What would you guys suggest as the next step?
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From: Virginia
It's normal for the oil pressure to raise and lower with the engine rpm. 80 is a little high, but if he put a high output pump on it, that could be the cause. And also it may run that high after you first start it since the oil is thick(what weight oil is he running?).
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5w 30 is what he used. He didn't put a high output pump in.
I understand a little fluctuation is normal, but the pressure didn't move say 20 lbs. It was up to 80 down to 20 or maybe 40 depending on the engine speed. Warm or cold it did this.
Shouldn't it start out at a high and as the engine warms up go down a little and hold at idle, then go up just maybe 5-10 lbs as the engine speed increases?
It was also a new guage installed at the rebuild point. I'm just guessing its not the guage.
I understand a little fluctuation is normal, but the pressure didn't move say 20 lbs. It was up to 80 down to 20 or maybe 40 depending on the engine speed. Warm or cold it did this.
Shouldn't it start out at a high and as the engine warms up go down a little and hold at idle, then go up just maybe 5-10 lbs as the engine speed increases?
It was also a new guage installed at the rebuild point. I'm just guessing its not the guage.
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From: Denver Metro Area, CO
I understand a little fluctuation is normal, but the pressure didn't move say 20 lbs. It was up to 80 down to 20 or maybe 40 depending on the engine speed. Warm or cold it did this.
Shouldn't it start out at a high and as the engine warms up go down a little and hold at idle, then go up just maybe 5-10 lbs as the engine speed increases?
It was also a new guage installed at the rebuild point. I'm just guessing its not the guage.
Shouldn't it start out at a high and as the engine warms up go down a little and hold at idle, then go up just maybe 5-10 lbs as the engine speed increases?
It was also a new guage installed at the rebuild point. I'm just guessing its not the guage.
For example, my relatively freshly rebuilt (about 3k miles on it) 400 M-block has 75 psi at cold idle, down to 50 or perhaps even a bit below at warm idle.
With a fully warmed-up engine, oil pressure is generally 65-75 off idle (in motion).
But what strikes me is this change in behavior comes with the 2nd rebuild:
He replaced it and once again went through a total rebuild
Which tells me something was changed that causes this behavior you're seeing, where the needle bounces around like a yoyo in response to engine RPM.
I have only seen that kind of behavior on what I consider to be worn-out engines, where the pressure at idle is something near 0.
Given that this was recently rebuilt, I would guess it wasn't broken in properly or maybe the wrong size bearings were used.
Presumably you've got a flat tappet cam; did you use that special red moly assembly paste on everything the cam touches, and also use high-zinc-content oil for the first 30 or so minutes?
Tuned
Joined: Sep 2005
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From: SE Missouri
I agree with ctubutis, if it is a flat tappet cam and you didn't use high zinc oil for break in that very well could be your problem. Most oils today do not have it and it was very important in the flat tappet day's. Most diesel oils still have it, I use Rotella when breaking in a new engine with flat tappets and have never had a problem.
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For sure he didn't break in the cam right. This was his first new cam and I never put in a new cam either. So, I was ignorant too and didn't have any advice to give him. After the fact he learned what he should have done.
The machine shop checked everything before the rebuild. Heads, block, pistons, crank (which was polished) and sold him the parts including the new cam. So, I guess they sold him the right bearings. They installed the cam bearings while they had the block.
The thing that gets me is the running after the reassembly had normal oil pressure the best we remember. We would have noticed if it was doing what it is doing now.
It was after he found the bad lifter and replaced it last weekend that we noticed the change in the oil pressure. That's the only thing that has been done since the rebuild.
The machine shop checked everything before the rebuild. Heads, block, pistons, crank (which was polished) and sold him the parts including the new cam. So, I guess they sold him the right bearings. They installed the cam bearings while they had the block.
The thing that gets me is the running after the reassembly had normal oil pressure the best we remember. We would have noticed if it was doing what it is doing now.
It was after he found the bad lifter and replaced it last weekend that we noticed the change in the oil pressure. That's the only thing that has been done since the rebuild.
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From: Denver Metro Area, CO
I have never replaced just one lifter and don't know how good or bad of an idea that is to do.
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The single lifter was just a shot in the dark or maybe a, do something even if it is wrong deal. All the other lifters were new and okay, so he just put another new one in.
I thought of something else.
When he changed the lifter, before he took off the intake manifold he went ahead and pulled the distributor instead of working around it.
Could something have happened to the oil pump rod maybe?
I wasn't there when he pulled it, but I was there when he put it back in.
He had to try a couple or three times to get it back in the right position, but it finally just dropped in and he locked it down.
Could something have happened during this to affect the oil pump and the pressure?
I thought of something else.
When he changed the lifter, before he took off the intake manifold he went ahead and pulled the distributor instead of working around it.
Could something have happened to the oil pump rod maybe?
I wasn't there when he pulled it, but I was there when he put it back in.
He had to try a couple or three times to get it back in the right position, but it finally just dropped in and he locked it down.
Could something have happened during this to affect the oil pump and the pressure?
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From: Virginia
You could pull the dist back out and make sure the teeth on it look ok. That is what drive's the oil pump. I am assuming they probably used a new driveshaft during the rebuild? It looks like a hex shaft.
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From: Denver Metro Area, CO
I have a hard time imagining how the fault could be with the distributor and oil pump; to me, it's one of those things that either works or doesn't.
I know it'd be a lot of work to do this, but the root-cause-analysis side of me is saying to put the old lifter back and see if the problem goes away with it.
I know it'd be a lot of work to do this, but the root-cause-analysis side of me is saying to put the old lifter back and see if the problem goes away with it.
Old School Hot Rodder
Joined: Feb 2006
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From: Exmore, VA
I would suspect possibly a sticking relief valve in the oil pump. I had a reman 4.6L that blew the oil filter off the engine, not once, but twice. The culprit was a tiny piece of carbon that jammed the relief valve.
My 66 Shelby 289 used to idle at 45 psi and run about 65 psi over about 2000 rpm. This was with a Melling high volume pump, 10W-40 oil (8qts.) and an external oil cooler.
My 66 Shelby 289 used to idle at 45 psi and run about 65 psi over about 2000 rpm. This was with a Melling high volume pump, 10W-40 oil (8qts.) and an external oil cooler.
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We are at a stand still on this. We had planned to use the 3 day weekend to try and see what we could do, but TS Lee is right on top of us and we work under an open shed.
We have had torrential blowing rain at times, so we postponed it until next weekend.
I thought my son was going to go back with a stock cam, but that’s not the plan now. He stopped by the machine shop that did work for him and sold him parts Friday and talked with them. He left with a new non-stock cam (not the same as the last one) just over stock, new lifters and some other advice. He tells me the cam is one step above stock whatever that means.
On the oil pressure problem one of the guys thought along 85lebaront2’s theory. He told my son to remove the oil pump and clean the heck out and we will include the pressure relief valve. Then we will install the new cam and break it in right.
Any more suggestions or advice.
We have had torrential blowing rain at times, so we postponed it until next weekend.
I thought my son was going to go back with a stock cam, but that’s not the plan now. He stopped by the machine shop that did work for him and sold him parts Friday and talked with them. He left with a new non-stock cam (not the same as the last one) just over stock, new lifters and some other advice. He tells me the cam is one step above stock whatever that means.
On the oil pressure problem one of the guys thought along 85lebaront2’s theory. He told my son to remove the oil pump and clean the heck out and we will include the pressure relief valve. Then we will install the new cam and break it in right.
Any more suggestions or advice.
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After I posted yesterday my son announced he was going to start tearing into his engine.
The weather was a little better yesterday and we (I was the assistant) managed to get the oil pan off and oil pump out and the cam out.
The oil pressure release valve was stuck open and the pump itself was in pretty rough shape. The cam had one lobe in bad shape. That’s a mystery to me, why just one lobe?
We went and got a new oil pump, gaskets, and all the other necessities to put her back together late yesterday. The plans are today to reassemble and break in the cam right this time.
I’ll update on the results of the new cam and oil pump.
The weather was a little better yesterday and we (I was the assistant) managed to get the oil pan off and oil pump out and the cam out.
The oil pressure release valve was stuck open and the pump itself was in pretty rough shape. The cam had one lobe in bad shape. That’s a mystery to me, why just one lobe?
We went and got a new oil pump, gaskets, and all the other necessities to put her back together late yesterday. The plans are today to reassemble and break in the cam right this time.
I’ll update on the results of the new cam and oil pump.
Fleet Mechanic
Joined: Jul 2011
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If I'm correct, you should be able to tell if that lobe is as bad as you say while the engine was running. It'd act like it'd have a hiccup to it at the exhaust. Loose rockers and badly adjusted valve lash will make for poor engine running too.
It won't matter now, because there's a new cam in it. But, just thought I'd throw in my $0.02.
Old School Hot Rodder
Joined: Feb 2006
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From: Exmore, VA
You hit it right on the head. Lack of break-in lube will destroy cam lobes. Follow the cam installation instructions, particularly with regards to engine rpm buring break-in. Cam lobes are lubricated mostly by "throw-off" from the crank. If the instructions say 2500 rpm for 30 min, they mean it.