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Freshly rebuilt 455 issues... Need some advice
Hello all,
I worked with a local machine shop to build a 455 for my 73 Grand Prix. Here are the specs: 73 455 block, bored and honed to fit .030" over Butler/Ross forged pistons, zero decked, checked/magnafluxed etc. Pistons are the aforementioned Butler/Ross forged flat tops with their recommended rings, mounted on Eagle H beam rods. Stock 455 crank turned down 0.020" on the mains and rods Melling HV pump, Milodon 7 quart pan and Milodon pickup for said pan 6X-4 heads, ported with new Ferrea valves/springs/retainers, etc. Butler hydraulic roller camshaft that mimics the RAIV 041 cam, with Morel hydraulic roller lifters and Harland Sharp 1.5:1 rockers. I have a Butler flat valley pan with PCV fitting. Rotating assembly was balanced and I mated it to a Super T10. I have 2 major issues. Oil consumption and oil pressure. Since day one the engine has been pulling oil into the chambers. I can see oil on the piston tops with my borescope and the plugs foul out pretty quickly. I have maybe 300 miles on it at this point and it has never run right. the last time I tried to start it I gave up, the plugs were oil fouled and it wouldn't light off unless I pulled them out and cleaned them again. I think I maybe drove 50 miles since the last time I pulled and cleaned them. The second issue is oil pressure. When the engine first starts oil pressure is GREAT, 50psi or more. Drive it 20 minutes and everything gets warm, and if the engine is allowed to idle oil pressure slowly drifts down to almost zero. If I goose the throttle it will come back up to 20 for maybe 10 seconds then slowly drift back down. I am watching it on a digital gauge and reading it from the port on the oil filter housing. The only things I did that are "not standard" were to drill a 0.030" hole in the galley plug in front of the distributor to improve oiling to the distributor gear, and I replaced the front push in plugs with threaded plugs. I tore it down and as far as getting the heads off. I pulled the passenger side head, the valves and springs and seals all look fine. The guy who did the porting and set up the heads used to work at the GM tech center (long before my time there) and he knows his stuff, so I don't think the oil is coming in through the seals. Could it be that the PCV isn't getting enough flow through the slits in the valley pan? Or is the engine just pulling oil past the rings? The machine shop said that they used the correct grit for the rings. With the head off I see some cross-hatching, but the cylinders feel really smooth. I'll try to get some pictures of what I'm seeing in the next couple days. I really took my time with this build and thought I followed every step in Jim Hand's book. I can't figure out where I went wrong and its driving me nuts. If the engine has to come back out so be it. But even then, I'm not sure what to "fix" as so far nothing looks to be amiss. If I put it back together as is I'm sure I'll get the same results, so something has to change. Any ideas where I should be looking? I'm all ears! |
Flat valley pan, meaning the PCV valve is seeing direct oil splash.
Stock baffled or equivalent Tomahawk valley pan would be the first thing I’d change to solve the oil consumption. Flat valley pans are for race engines as far as I’m concerned. Could be some crud holding the oil pump check ball off of its seat, I’d check that. Or perhaps your bearing clearance isn’t tight enough. |
Have you confirmed oil pressure with another gauge?
Did you or machine shop assemble? What are the bearing clearances? - machine shop should be able to advise? The front threaded plugs confirmed they aren’t too deep blocking the oil passage? Any ticking or tapping noise to go with the low oil pressure? If oil pressure is confirmed low, that engine needs to go back to the builder. I assume you’ve consulted with him before pulling the head? |
are the back side of the intake valves on the head you did not pull yet showing oil wetness?
You may have installed the number two ring the wrong way during assembly. |
Is there oil inside the PCV vacuum hose?
A guy here had no end of problems with aftermarket heads that had been ported, the way I remember it is that first he fixed oil coming down the rocker studs into the intake ports, and then he had to fix excessive porting that broke-through the pushrod pinch area, so the intake ports were drizzled with oil from the pushrod hole. How were the rings compressed to get the pistons in the cylinders? I once bought an Asian knockoff of the wonderful Made-in-USA Lisle wrinkle-band ring compressor; the knockoff had the slots for adjusting the diameter punched into the metal from the wrong direction. The INSIDE diameter of the ring compressor had a dozen SHARP edges. Using that ring compressor, the last thing you did to the pistons would be to score the ring band, and ruin the rings as the pistons slid down the ring compressor. I explained to the counterman why the ring compressor was faulty. He gave me my money back...but I'm pretty sure he just hung it right back on the tool display. How much blowby does this engine have? More than the PCV system can handle at idle in neutral? More than the PCV system can handle at fast-idle in neutral? Excess bearing clearance could both sabotage oil pressure, AND flood the cylinder walls with more oil than the rings could scrape away. |
Once again, lots of good possibilities have been listed above. If you trust the quality of the machine shop that did the work, start by doing a little testing just to see what happens. As B-man said, a single layer valley cover is for race cars. Believe me if Pontiac could have saved 10 cents in production by using a single layer cover they would have done so. I would block off the valley PCV system and just go open breathers just to experiment. If the problem goes away, put a stock style lifter cover on and your done. If the problem stays the same, then go deeper. As mentioned, ported heads can allow oil into the intake stream from multiple places. Valve cover bolt hole break through, rocker studs, push rod bulges to name just a few. Finally excessive blow-by from improper cylinder wall to ring interface is a possibility. I would think any competent machine shop could achieve at least a decent ring seal, but anything is possible I guess. Call me an old school dinosaur, but I still use a 4-step plateau honing process on the vast majority of hone jobs I perform. The grit count and amount of removal varies with the exact ring pack. For the Ross pistons you mention from Butler with a channel molly ring pack, my process is: Hone to .003" with 70 Grit stones. Hone to .001" with 220 grit stones. Hone to finish size with 280 grit stones. Then 4 strokes with a 400 stone set at 20% load. Rings will be fully seated in 15 minutes with this process.
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I have seen similar issues with the Butler valley tray with the PVC provision fouling plugs. It is a sketchy design. You won’t necessarily find oil in the PVC line to indicate that is the problem, and it does not take very much oil in the line to make it a problem. Either add a PVC catch or like B man said, put a Tomahawk tray or stock tray on. Or plug the PVC and switch to vented valve covers. Sort that out before you get to deep into it.
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Ahhh them Cam Bearings were honed for cam to turn. Oh how nice. My non-favorite diagnosis.
Get eyes on the cam bearing edges from above to see if PB-lead slag has come out. If you know you know. So, how is the idle blow-by? Blowby deoesn't esplain the low-no idle PSI. Real lack of PSI will develop clatter noise at long idle. PMD Valley cover is 2-piece for promoting condense-cooling of oil vapor, buuut that ain't it here huh. Swapping not a solution, just an incremental improvement. Maybe break-in need to be continued under hard-load? Original poseter may have left the chat. |
I would check to see if the 2nd ring set was installed correctly. If they are correct, do a careful magnified inspection of the ring's wear pattern for an even pattern. With today's lack of quality control sometimes the rings don't have enough tension or uneven heat treating causing them to float on the oil film on the way down. We just encountered a set of rings that only had 8-10 lbs of tension after breaking in an engine in on the dyno. Half a quart of oil in less than 10 minutes of run time. It's now getting a fresh hone and different rings.
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" I replaced the front push in plugs with threaded plugs."
Did you perform the drilling & tapping before the block went to the machine shop, or after it came back? |
Thanks for all the suggestions all!
I did look in the intake ports of the head that I removed. I don't see any oil in the intake ports. Looking at that Butler valley pan, the PCV provision had just 2 slits and they are barely bent up. I wonder if lack of PCV flow causing the crank case to build up pressure and push oil past the rings? I do have a breather on one of the valve covers and one would think that it would relieve any pressure. I didn't really check blow by before tearing into the engine, probably should have done that. The cam bearings - the machine shop noted that one of my cam bearing holes was oversize and they bought a set of cam bearings and used just one for that single hole, the rest were standard bearings. The cam slid in just like any other build I've done, but I didn't mic the cam bearings and cam journals. I DID mic the crank journals and rod and main bearings and they were all great, I have the numbers written down and can get them next time I'm out in the shop. I even used plastigauge to double check the bearing clearances and everything looked good. For the low oil pressure... Am I just pumping all the oil up to the top end and starving the pickup? I did read up on the Morel hydraulic roller lifters and Butler's site said you don't need restricted flow pushrods with the Morels, so I didn't use them. Perhaps using restricted pushrods would help? I could spring for a set I guess. I'll definitely dump the flat valley pan and order a Tomahawk to replace it. I'll also take pictures of everything tomorrow when I can get back outside to the barn. Maybe you guys will see something that I'm not seeing... I've assembled 2 other Pontiac V8s and several small block chevies and have never had this much trouble. |
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Oil pressure dropping to zero sounds like a bad pump, ort more likely, excessive rod brg clearance. That would flood the cyl walls with oil causing high oil consumption.
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I’ve had engines with excessive bearing clearance. From a windage tray that was dragging on my crank. It wore the bearings and I was trying to get it thought the race season I never had oil fouling of the plugs and it had zero oil pressure at idle. Similar to yours. So I don’t think that’s the issue.
I also never , ever run a PCV I plug that crap and put breathers in , on boosted applications I run a vaccum pump . But not on N/A Again never had an oil issue like your having. First think I’d do is plug that thing and run breathers in the valve cover see if it helps it’s cheap and easy woukd be. Logical first step If it was a break through in porting it would show up in one or two cyls not all of them unless your porter really sucked. All your plugs are fouling if I understand this correctly. ??? This leads me to belive it’s a systemic problem that was repeated - rings installed incorrectly , finish on cylinders done incorrectly. I’ve heard of machine shops swearing they didn’t hone right only to find yes it was in fact wrong . Who put the ring packs on and how? Are we certain they were done correctly? But first things first block the PCV quick easy and cheap. Best of luck with it and please make sure your post back when you find out what it was could save someone alot of headaches down the road. |
I think there can be a issue with threaded plugs if they are put in too deep.I have seen some plugs that are tapered on the inside.Just throwing that out.Tom
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Any chance you could prime the pump and see how much oil gets up to the head ? With the valley cover off you could maybe see some big bleeding.
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If you use threaded plugs to seal off the front oil galleys then the passenger side pipe plug needs to be a shallow one to not partially block off a oil feed passage.
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i found a faulty sending unit giving me fits.
i re-used my old tried and true oil pressure sending unit and after a few months with my new build i was having low readings at full warm up... but there was no noise. i changed the sender...bingo. is your engine making noise at full warm up? |
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No after market valley pan has proper baffling for the PCV system except the Tomahawk valley pan. Others suck oil into the intake manifold. You need a factory piece or a Tomahawk.
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