The Stovebolt Site Forums The Shop Area Engine Shop High oil pressure after installing new head

On my 1954 235, i just put a fully professionally rebuilt head ( new hardened seats, valves, springs, guides, the whole works), as well as discovering that the 40 over pistons had standard rings.It was a rebuilt engine from before I purchased it. The blue smoke coming out of the tailpipe was a clue. When I did the head I also put correct rings in as well as honing the cylinders. The oil pressure gauge reads 30 ( the max on the dial). Wondering what I should check. Before rebuilding,I noticed when i installed the rocker assembly that the oil tube had a couple of crimps on it. These were there when i disassembled the rocker assembly when I took it off to take to the rebuilder. The engine was a rebuild by some PO and I don’t know the story. What should the normal range of oil pressure be?

Snowman51 A 51 6400 with a 235 full pressure came to me with one of those noises that you can here the oil pressure shut it up. I installed -.002 rods and mains fixed it !! It now keeps the 30 pound gauge pegged summer and winter,have driven it 9000 miles so be happy like me. Also couldn't see much wear on the shaft,figured it would lock it up ,didn't ...turn by hand on the flywheel,start run ride and drive !!

Snowman 51 book says 35 lb. is normal I put in those hard seats to burn propane.guides too,got seats from Goodsons put in 12 called them for more the guy says don't use for propane ! Well I don't think my engines know what they're burning,but been fine so far now the 9000 mile one still has soft seats in it. Think those seats are a stainless alloy,thought I would work my head over then install the fenton split,have a one barrel aluminum intake for it.

The gauge in your truck was intended for a 216 engine, which struggled to make 15 pounds of hot oil pressure. The 235 runs anywhere from 25 to 50 PSI depending on engine temperature. The "reconditioned" oil pump we put in John's 261 engine when we built it would put out 70 PSI on a cold start, and drop to 30 or so at a hot idle. Somebody had probably tinkered with the relief valve on that one! It sounds like your engine is doing what it's supposed to do. Any oil pressure at all indicates the pump is producing more oil volume than the engine needs for lubrication, but most people like to see that gauge at midrange or above all the time. It's theoretically possible to lubricate an engine properly at zero oil pressure, but all of us like to have a little buffer zone where oil pressure is concerned.

If you can find a dash gauge for a GMC stovebolt, it's got a 60 pound full scale. Original gauges are a little scarce and pricey, but I think some of the resto-ripoff guys have newly manufactured clones for sale.
Jerry

I feel better now that I know what is “normal”. Glad there are so many qualified wrenches out there- definitely a great site where professionals can share a wealth of information for the collective GM family. Thanks again.

Hotrod Lincoln I was under the impression that with oil pressure on a round and properly clearanced journal and bearing that it was harder for the journal to touch the bearing under a load. You know you see performance engines tore down where the bearings still look new !On the other hand you see 60 year old dippers where the babbitt rods look fine too. One of mine that was rung in 82 and didn't need shimming still runs fine and it has had some workouts getting out of the woods loaded to the gills. Wish I had another dipper to fix-up,my local crank turner is getting old need to use him before he dries-up on the vine,of course rods are expensive now !!

Hotrod Lincoln One other thing I may be drying up on the vine too LOL !!

If a bearing gets one drop of oil from the pump every time a drop goes back into the pan from seepage, the bearing will be fully lubricated with zero oil pressure. That's why I say that even one pound of oil pressure at every place that needs lubrication means that the pump is supplying more oil than the engine needs. The only reason pressure builds up is the fact that the pump is supplying more oil than necessary to lube the engine. The trick is getting that oil flow all the way to the last bearing in the chain. On a hydraulic lifter engine, the lifters probably consume a lot more oil than the bearings do. On the small block Chevy race engines with solid lifters, we put 1/16" diameter restrictors in the lifter galleries to force more oil to the lower end, especially when running increased-clearance race bearings and/or a crankshaft ground .001" undersize. A brand new race engine has more clearance built in everywhere than a 100K mile street engine. Doing race engine stuff on one that's built for street use is beyond stupid- - - -we expected to get maybe 1K miles from that round track engine before it wore out or blew up.
Jerry

I put a 62 - 235 high pressure motor in my 46. I used a after market oil pressure gauge for the block, which reads 40. And hooked the factory gauge to a fitting at the top of the head that reads 15,right in the center. It also helps in knowing what is going on, I broke a push rod a few years ago and the factory gauge hooked to the head went to 0 and the block gauge stayed right at 40.

Hotrod We got a green Merlin3 block 540 for 4 x truck pulling,first year had to get mains worked but lasted 5 seasons with some rod bearings lost. Had it's mains worked,bores straightened,nother cam has lived about 10 years now. Due for a bearing inspection this winter,so will go for it in 2022. our best lesson has been the green block problem.

I had to line bore a MOPAR cast iron hemi block my neighbor used for pulling a few years ago. Every time he torqued the thrust bearing main cap the crank would lock up, even after we did the line bore. It turned out the block had been in a high speed wreck that totaled the car and broke the crankshaft, and the main cap had deflected .015" from the impact. He put a new main cap on, we line bored it again and it lasted several seasons in an unlimited class 4X4 on alcohol and nitro.
Jerry

Try cycling that Merlin from 3500 RPM to 7500 100 times in a 50 lap dirt track race a couple of times a week and see how long the rod bearings last. About half a season was average on the engines we built for a lot of years. If one didn't hand grenade by midseason, we'd put the backup engine in and freshen up the one we started the season with. Having a sponsor with a deep pocket and a dedication to winning races helped. It's always more fun to go racing on the other guy's money!
Jerry