Vintage Mustang Forums banner

41 - 60 of 89 Posts

·
Registered
Joined
·
588 Posts
It's situations like this when I think back to when my dad was plant manager at AGAP (AKA nationwide engine rebuilders/ Signa pro)in Fort Worth. They used to sell assembled long blocks and every one went on the spin tester to verify oil pressure and cam break in before it left the building. The very few engines they got back as failures were short blocks or bare long blocks(no valve train installed). 99% of them were all installer error and almost always not pre oiled. They rarely had any failures.
It's unfortunate things went the way they did and the company was sold to an investment company and it went under. With suppliers like them I never built my own engine as it cost more and you had no one else to back up the work.


One thing I almost never do is use a standard oil pump in an engine. I always use a high volume pump which basically has bigger gears or a HVHP pump in some engines but high pressure is usually not needed.

I will agree that assuming no valve train interference or way too stiff of valve springs and good fit of cam bearings that the only other conclusion is a lack of oil at the cam. Was the oil pump on tight and how about the pickup (loose/sucking air).
 

·
Registered
Joined
·
5,020 Posts
"Just got done with cam break in. It was successful but not without a problem. Tough to start. Cranked for 5-10 sec a couple of times, no go. Fiddled with choke, gave it a little gas and got it started (but it seemed like I got lucky). Ran pretty good, got idle up to >2K and started the clock. All the physical gauges looked good. Around 5 minutes in I went to vary the idle and dropped a little below 2K and it died. Would not restart. Tried 3 or 4 times for 5 secs or so and no go.

Noticed some vapor coming out a hole where the choke used to be (as I took it off…broken). Bolted the choke housing back on. Still no start. Verified I did not run the carb bowl dry (it was at the proper level). Thinking now must be timing issue. I decide to cap off the distributor vacuum canister (and carb port). Now it fires right up. Get idle set, and watch and wait. Decide to check timing. 40 BTDC?? How, why? I assume some of the mechanical advance may be coming in or maybe I botched the initial timing. I adjusted to 20 BTDC and adjusted idle to compensate. Ran the additional 25 minutes (30 min total) varying RPM from 2000-2500. Water temp never exceeded 195F. Oil pressure was 60 PSI to start and levelled off at about 25-30 PSI."

All oil galley plugs (3 front 3 rear) are installed and still in place after tear down, including the single 3/4" plug on the top rear. Yes, I did check distributor shaft to driveshaft compatibility and engagement. When I primed I got 60 PSI cold and then the same 60 PSI cold and 25 PSI or so hot at 1250 RPM. I know I had oil pressure the entire break-in, but did not monitor the 2nd day other than at start-up.

@Tallguy, I took the liberty to quote what you posted on your break-in thread. I've only done this to make sure those who are trying to help figure out what may have happened see how your break-in went and also to keep in mind that you have determined your rpm's actually varied from 1000-1250 due to the tachometer being switched incorrectly.

I'm not sure if initially running at 1000 rpm for the first 5 minutes and it dying as you were trying to idle up to 2500 rpm (actually 1250 rpm) would be a reason for such damage or not.

I do hope it helps get more suggestions to help get to the bottom of your problem.

Again, wishing you luck and hoping you find what caused the problem!

Allen
 

·
Registered
Joined
·
931 Posts
Discussion Starter #43
"


@Tallguy, I took the liberty to quote what you posted on your break-in thread.


Allen
Thanks! I have no secrets and this is a great add to the thread. I just got off the phone with my machinist. He has no explanation and reiterated that melted cam bearings is not a usual failure. We are working out a time for him to come by to look at all the parts. May send the block back with him to double check everything and install cam bearings. I am 99% sure I did it right, but my experimentation with cam bearing installation is complete.
 

·
Registered
Joined
·
8 Posts
From everything I have read, sounds like you did the build correctly. I don't think you had an oiling problem. First, only the cam bearings were affected. Second, oil pressure is really head pressure from the oil meeting resistance at the bearing clearances. The fact you had oil pressure indicates oil was getting to the bearings. And if getting to the main bearings, it is getting to the cam bearings, unless each passage to the 5 cam bearings is block. Worth checking but highly unlikely. The damage to the bearings suggest a pounding action. The cam journals have actually moved into the bearing material. Can't be from the timing chain being too tight because that would affect the #1 cam bearing most, but very little effect on the #5. Since damage is uniform on all 5 bearings and on the bottom side, it suggests pounding coming from above. The only thing I can think of that could pound from above would be valve spring bind. Would not take much, but as soon as the spring goes "solid", the softest metal will deform first. The softest metal would be the cam bearings. Also, breaking through the oil film could allow metal-to-metal contact, generating lots of friction heat.

I would not hesitate to recommend you try again with your engine, but play close attention to how close your valve springs come to binding with the amount of lift you have. Once your lifters pump up (assuming its a hydraulic cam), it can slightly alter how much your springs compress. Also, the longer push rods could slightly change the geometry. You could be dealing with just a few thousandths of an inch making the difference between no problem and the one you are having.

Not saying I am right, but it's the only scenario I can think of that fits the facts.
 

·
Registered
Joined
·
47 Posts
Hi,
Just to eliminate all possibilites, you had the right cam thrust plate bolted to the block the right way? So that the gallery in the front does not spray all the oil on the chain instead of the cam bearing. Not long ago someone posted, that using the wrong plate can cause big trouble.


Alain
 

·
Registered
Joined
·
5,524 Posts
Interesting issue, given all the due diligence you've done. I think you've been given some great advice on directions to go. Personally, I'd start with Randy's timing chain theory, as it sound the most plausible and knowing Randy's history, we also know he likely has more experience than everyone else posting in this thread, combined.


The only other thing that stands out to me is the hot oil pressure does seem a little low when compared to other SBFs I've dealt with. Yes, 25 psi at 1250 meets the rule of thumb minimum, but typically anything above idle I see 50+ psi.



And just a note, changing the cam in this scenario definitely saved you more damage, but for future reference, your break in procedure was fine. Yes, they tell you to break it in with one continuous run and to not shut it off and restart it, but I'd bet more engines are shut down during the break in, than not. Just by nature of a break in, running the engine at RPMs and not moving, engines get hot and people shut them down. Also on new builds, there can be fuel or water leaks that lead to them not making it through a continuous break in. It happens, and although it can be a problem, it typically isn't. If you complete the break in, and you're concerned about it, just pull the lifters and inspect them. You'll be able to tell if there was an issue in break in. Even if you shut it down 10 times, if the lifters and lobes look good, they probably are.
 

·
Registered
Joined
·
931 Posts
Discussion Starter #47
From everything I have read, sounds like you did the build correctly. I don't think you had an oiling problem. First, only the cam bearings were affected. Second, oil pressure is really head pressure from the oil meeting resistance at the bearing clearances. The fact you had oil pressure indicates oil was getting to the bearings. And if getting to the main bearings, it is getting to the cam bearings, unless each passage to the 5 cam bearings is block. Worth checking but highly unlikely. The damage to the bearings suggest a pounding action. The cam journals have actually moved into the bearing material. Can't be from the timing chain being too tight because that would affect the #1 cam bearing most, but very little effect on the #5. Since damage is uniform on all 5 bearings and on the bottom side, it suggests pounding coming from above. The only thing I can think of that could pound from above would be valve spring bind. Would not take much, but as soon as the spring goes "solid", the softest metal will deform first. The softest metal would be the cam bearings. Also, breaking through the oil film could allow metal-to-metal contact, generating lots of friction heat.

I would not hesitate to recommend you try again with your engine, but play close attention to how close your valve springs come to binding with the amount of lift you have. Once your lifters pump up (assuming its a hydraulic cam), it can slightly alter how much your springs compress. Also, the longer push rods could slightly change the geometry. You could be dealing with just a few thousandths of an inch making the difference between no problem and the one you are having.

Not saying I am right, but it's the only scenario I can think of that fits the facts.
THanks. I will be checking valve geometry very closely. I can't figure out how it can be a problem with the components I have chosen, but maybe the "quoted" clearances/capacities are not accurate.



Hi,
Just to eliminate all possibilites, you had the right cam thrust plate bolted to the block the right way? So that the gallery in the front does not spray all the oil on the chain instead of the cam bearing. Not long ago someone posted, that using the wrong plate can cause big trouble.

Alain

Thanks for the suggestion. Yes, I have the "idiot proof" thrust plate that can only go on one way and also has "this side down" or whatever it says..
 

·
Registered
Joined
·
522 Posts
I gather you are looking for any suggestions, even WAGs. I haven’t built an engine since the 70s (and then various 4 cyl English designs), so take this for what it’s worth.
I agree with @bobmannel that the damage suggests pounding coming from above. I’d suspect either spring binding or valve-to-piston clearance issues. Did you check out the value train, and adjustments, with light break-in valve springs? A really, really out-there thought was that you don’t have the cam you think you have and the lift is greater than you expect causing binding.
I feel your pain and hope for the best. Good luck.
 

·
Registered
Joined
·
931 Posts
Discussion Starter #49
I gather you are looking for any suggestions, even WAGs. I haven’t built an engine since the 70s (and then various 4 cyl English designs), so take this for what it’s worth.
I agree with @bobmannel that the damage suggests pounding coming from above. I’d suspect either spring binding or valve-to-piston clearance issues. Did you check out the value train, and adjustments, with light break-in valve springs? A really, really out-there thought was that you don’t have the cam you think you have and the lift is greater than you expect causing binding.
I feel your pain and hope for the best. Good luck.
At this point even SWAGs are welcome!

I measured every cam lobe and though there is some variation in lobes, it is the cam I ordered.

My head springs are 1.8" installed height, 1.130" coil bind. With my lift of .299/.303 cam and .477/.484 (after 1.6 rocker multipier) and ~.040 valve lash, I have significant clearance (~.140" which is double what safe minimum is). Now of course I will check when I rebuild but I do not see a path to coil bind. Also all pistons and valves look perfect (given the velocities and forces, I would expect massive damage to the piston and bent parts with piston to valve contact). I also heard nothing while the motor was running.

So this still leaves me with no smoking gun.
 

·
Registered
Joined
·
931 Posts
Discussion Starter #51
I was not clear - hydraulic valve lash. about 5/8-3/4 turn after take up up and down slack in push rod. On a 3/8-24 stud that it is .042" per turn so mine is more like .030". My understanding is you add this to your potential lift as if the lifter goes dead hard you get an "extra" amt equal to the lash.
 

·
Registered
Joined
·
931 Posts
Discussion Starter #52
Update:

My machinist came by the house this weekend to inspect the parts. He was not able to provide any smoking gun as to how the cam bearings failed. We talked about all the theories presented here on VMF, and the verdict is try again, but measure more clearances to see if anything is out of whack. He has never seen cam bearings fail like mine did. Some of the wear on the mains and rod bearings he thinks is debris from the cam bearings.

I have all new cam, main and rod bearings and now after doing clearance checks, I now know that my motor was machined on the very “loose” end of spec. I guess there was a misunderstanding between the machinist and I. More I did NOT understand what he was doing at the time to ask the right questions. I was not clear on my usage for the and directed him to machine for a possibly high revving motor. He align bored the mains, balanced it all, etc. Clearances never came up. I have read a lot of stuff online and there is a lot of debate on clearances (and some of that right here on VMF)

Clearances:
Mains – Mic and Dial bore gauge - .002 to .0025, with plastigage – all show about .002
Ford Spec Desired - .0005-.0015, Allowable - .005 - .0025
Crank main Journals are at the low end of the Ford Spec, all 2.238 (.010 undersize)

Rods – Mic and Dial bore guage – all .002 except 1 is .0015, did not do plastigage (last time they were .0015 to .002 with plasti)
Ford Spec Desired - .0008-.0015, Allowable - .008 - .0026
Crank rod Journals are mid to high end of Ford Spec, 2.113 to 2.1135 (.010 undersize)

Cam - .003 on #1, 2, have not measured 4,5 yet as cannot get to them with dial bore yet as motor still on stand and can't reach #3
Ford Spec .001-.003 with wear limit of .006
Cam Journals are all dead on at exactly the middle of the Ford Spec

Lifters - .003 (based on .874 lifter). This is pretty consistent on all 16 bores (clearance lifter OD to bore)
Ford Spec Lifter to Block - .0005-.002 desired, .005 wear limit
This one does not surprise me as there are no bearings and this is a well-used old block.


So that said, with a standard oil pump, am I too loose?. My oil pressure at 1250 RPM hot was 25 PSI on previous failed motor.

Crank is already .010 under. I could go .020 under and go tighter on clearance but I’d like to stop the bleeding at some point. But not at the expense of “bleeding” more babbitt!
 

·
Registered
Joined
·
1,270 Posts
Sportsroof69 ,
thank you for the kind words but I must correct you Bob Mannel is extremely well versed (if not obsessed) with the Small Block Ford. He has multiple books on the subject which are MORE informative than any other books on the market even the one I helped with in the late '70s. While Bob disagrees with my past experience , and now that I have seen pictures of the actual bearings , I have to disagree with his opinion ( respectfully). The springs are not coil binding according to tallguy's information. "Normal" babbit cam bearings can handle ridiculous loads from valve springs . My current 331 has each spring at #260 psi on the seat and well over 600 psi over the nose. It has Durabond bearings and has 17 years of running on them. With the additional information tallguy offered about the engine shutting off abruptly during break in , I am wondering "IF" there was enough heat and an abrupt enough stop to cause a sieze situation between the cam and the bearings. "IF" there was , the starter motor has enough torque to "rip" it loose again from the softer babbit material and would also continue to tear up the loaded part of the bearing ( bottom half).
If you had an oil supply issue , the MAINS would be trashed as they get oil BEFORE the cam bearings. While oil is still flowing at 25PSI , The BIG drop in uncharacteristic it should have been 45 or higher . The loss indicates a pressure bleed situation . In your case the cam bearing were toast at that point and causing the low pressure. A high volume pump would NOT solve the issue only mask it. Oil pressure alone does not eliminate metal to metal contact. On a Ford style ( gerotor) pump ( Chevys are a different style) high volume versions are a waste of money. How many use them WITHOUT even thinking about increasing the pick up tube diameter??? THAT will increase oil flow volume just like making the oil passages in the block larger. The biggest pump in the world won't flow much if the inlet and outlets are restricted . Sort of like a human heart and plaque.
Back to the topic , the only other scenario ( along the lines of Bob's thinking ) is "if" the rockers were binding on the studs ( which would leave a witness mark on the stud. That "might" cause enough bind to kill the bearings like I see. A bent cam will not do what I see either. Prelube the engine this time around and turn the engine over a few times when you are priming it .
Randy
 

·
Registered
Joined
·
8 Posts
>>"if" the rockers were binding on the studs<<

Hadn't thought of that. An old Ford TSB says, “Although similar in appearance, the 240 and 300 CID six‑cylinder engine rocker arms are not interchangeable with those used on the 221, 260 and 289 CID V-8 engines. To minimize the possibility of installing the incorrect rocker arm on any of these engines, they are identified by a cast letter on the upper surface of the push rod end of the rocker arm. The cast letter ‘E’ is used to identify the 240 and the 300 Six rocker arms. The cast letter ‘A’ identifies the 221, 260 and 289 V‑8 rocker arms.”

I also remember reading about having to open up the slot on the rocker arm with some grounding in certain conditions.

If using longer push rods with normal installed spring heights, the rockers could be tipping far enough to run out of travel. Something to check would be that the correct rocker arms are being used and that there is sufficient travel when installed.

I have to be honest in saying I have never seen damage on cam bearings as your pictures show. It is specific to the bottom half and deeply penetrated. The engineer in my asks myself what kind of force could do such a thing? All I could think of was pounding. Nothing else fits your scenario that I can think of. Then the question becomes, what could produce such pounding.

Keep looking for the cause. There has to be a reason for this failure.
 

·
Registered
Joined
·
931 Posts
Discussion Starter #55
gt350hr, bobmannel, and everyone else

Thanks for taking the time to continue helping me work through this problem. As much as I want to give up and write a check for a short block, I also must find out why this happened so press on (the engineer in me). I don't lose sleep over many things, but this is one of them.

The only original Ford parts on this build are the block, oil pan, and rods (though modified for ARP bolts).

Here is a pic of the valve train set-up (before any pre-oiling so lifters not pumped up). Pistons and valves still look new and undamaged as do all other valve train components. I will be checking everything extensively before moving on to each build step. I'd make more progress if I could get the right parts from Comp Cams but that is proving to be a challenge as they seem to think it OK to put Chevy lifters in a Ford box (bygones...)

I hope I am missing something and find some kind of valve train binding but time will tell. I am still concerned about my clearances being on the loose end.

Top End Pic.jpg
 

·
Registered
Joined
·
5,020 Posts
"Loose is fast."

I don't think being loose on some of the tolerances would cause what happened. The only thing I see is that the lifters are outside of spec (although within wear tolerance) and I wouldn't think that's an issue either.

Still baffling. I've just never seen cam bearings look like that (not that I see engines every day either)...

Allen
 

·
Registered
Joined
·
8 Posts
What follows might not apply to your configuration since you are using non-Ford parts, but the principle might. In Ford's Muscle Parts catalog, this was said about the stock rocker arms, "It may be necessary to remove 0.030" from the valve end of the rocker arm slot to obtain rocker arm stud clearance with higher lift mechanical cam." You had earlier mentioned when talking about push rods, "I ended up with about .125 longer than stock at 6.95". You are setting your hydraulic lifters correctly by taking the lash out while the piston is at TDC, then tightening an additional 3/4 turn. The lifter will adjust itself for zero lash. By-the-way, most recommend lifters be put in empty of oil (right out of the box) and allowed to pump up on their own. Otherwise they can have too much initial oil and increase valve lift (and more spring compression) while not allowing the valve to fully seat closed. There are tools for checking that you have the proper length push rod, but I have not checked into them. Checking that there is sufficient rocker slot clearance with the rocker arm stud is not something you might see on assembly. If you can compress your valve spring with the rocker arm a little more when it is at max lift, you are probably good on this clearance. One source I read mentioned .060" is the desired clearance between rocker arm slot and stud at max lift.
 

·
Registered
Joined
·
2,603 Posts
cam bearing failure

Tall, sorry I didn't write earlier. It looks like you put the cam brgs in wrong. Do you have the oil outlet holes @ 6:00 ? thats wrong. They are supposed to be at 3:00 or 4:00. Look in the instructions in the front of the Durabond catalog. Never had a problem with Durabond in 30 yrs. LSG
 

·
Registered
Joined
·
931 Posts
Discussion Starter #59
Tall, sorry I didn't write earlier. It looks like you put the cam brgs in wrong. Do you have the oil outlet holes @ 6:00 ? thats wrong. They are supposed to be at 3:00 or 4:00. Look in the instructions in the front of the Durabond catalog. Never had a problem with Durabond in 30 yrs. LSG

I wish that was the case but that can't be right for my '68 302 (at least with the Dura Bond F18 or FP-18 bearings). There is only a single oil hole at 6 o'clock on the block (except #1 which has 2 holes). The bearings have no grooving at all, just a ~1/4" slot. I have aligned the slot with the hole on all bearings.

If I am mistaken, please let me know as the new cam bearings and cam are already installed the same way.

Thanks for the reply. I MIGHT have found the smoking gun though. More to follow shortly
 

·
Registered
Joined
·
6,746 Posts
My 331 comes up cold with 40 and drops to 25 once the engine gets heat into it. As soon as I rev it some it pegs 60 which is the pressure relief point with the oil pump I am running now. I replaced the high volume pump with a performance Melling standard volume pump. I have fired it up and run it around the neighborhood enough by now to find an oiling problem if I had one. The other thing I did was ditch the Royal purple in favor of Valvoline VR1 oil. I'm not sure this last thing make any difference but I am running solid cam and lifters.
 
41 - 60 of 89 Posts
Top