Thread: Oil pressure drop after top end rebuild

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383 SBC GM block My oil pressures when warm were 35 at idle and 70 at 3000rpm. I should add that engine was built by American Speed and has a Schumann BM55 hp oil pump. Engine had covered 4000 miles when a rocker from RPM fell apart. No damage apart from a bent valve.
I decided to replace some of the valve train with top quality parts so.
I replaced the roller cam with an identical one in billet steel from Comp. I fitted Comp endure-x lifters with pressure feed to the rollers. Comp pushrods and again comp shaft rockers. Also replaced timing gear and valve springs. At the same time I ditched my distributor for an EDIS system and put in a MSD oil pump drive.
Upon reassembly the engine runs great but I have a @15 psi pressure drop across the board 20 at idle and 55 at 3000rpm. Whilst these pressures are not something to worry about in themselves I would like to know what has caused them. I can only think that either the lifters and or the rockers are flowing more oil and that this has caused the drop. I would welcome any comments from you guys. same oil nothing else touched no restrictors in the lifter galleries.

Jeez! I thought that some of you knowledgeable people would have had something to say!
My conclusion at the moment is that the direct oiling of the rollers on the lifters is causing more oil to flow and hence the pressure drop and/or that the shaft rocker system is flowing more oil and causing the drop. I do not think that fitting std type restrictors will be good even though it will raise the oil pressure before them in the system it will lower pressure after them hence reducing oiling to lifter rollers which are known to suffer on street engines. Next maybe I should consider restrictive pushrods?

sounds to me like you answered your own question .. and i supprised you didn`t get a response also .. perhaps now you will

Originally Posted by webby

Jeez! I thought that some of you knowledgeable people would have had something to say!
My conclusion at the moment is that the direct oiling of the rollers on the lifters is causing more oil to flow and hence the pressure drop and/or that the shaft rocker system is flowing more oil and causing the drop. I do not think that fitting std type restrictors will be good even though it will raise the oil pressure before them in the system it will lower pressure after them hence reducing oiling to lifter rollers which are known to suffer on street engines. Next maybe I should consider restrictive pushrods?

well did you nick the cam bearings ? did you mic the cam journals for size . your direct lube lifters will lower the oil psi abit . why would you restrict the push rod .all you going to do is dry up the top end were valve springs will not last long if your driving this on the street and you think your getting all the top end oil you need you can use restrictors in the back of the block just step up on the restrictor hole size till you get were you want

Besides the cam journals maybe being a little smaller, or nicking the cam bearings on the way iout or back in with the cam---yes the direct feed rollers will lower the pressure some and also did you put o-rings on the MSD oil pump drive?

Sorry, but I never saw your post before

And it isn't that no one wanted to help, but sometimes we just don't have an answer. Diagnosing something over the net is at best a guess most times.

Don

Thanks Guys I was feeling a little lonely.
I didn't mic the journals so that is a possibility. I fitted the endure-x lifters because they have direct oiling to roller. I have heard that solid rollers in street engines do not last without that facility. So if I use std restrictors it will also reduce flow to the new lifters which I am not keen on because of the above. I did not use the o-rings on the oil pump drive because the block is not chamfered to allow them to fit and original dizzy did not have them. my research tells me that small blocks are prone to over oiling at the top end hence why a lot of people fit std restrictors. I thought that restrictor pushrods would give me the ideal solution if they dry up the top end so causing spring failure etc why do comp make them?

Originally Posted by webby

Thanks Guys I was feeling a little lonely.
I didn't mic the journals so that is a possibility. I fitted the endure-x lifters because they have direct oiling to roller. I have heard that solid rollers in street engines do not last without that facility. So if I use std restrictors it will also reduce flow to the new lifters which I am not keen on because of the above. I did not use the o-rings on the oil pump drive because the block is not chamfered to allow them to fit and original dizzy did not have them. my research tells me that small blocks are prone to over oiling at the top end hence why a lot of people fit std restrictors. I thought that restrictor pushrods would give me the ideal solution if they dry up the top end so causing spring failure etc why do comp make them?

to sell you new valve springs .if you restrict at the back of the block your turning the top end oil off abit its going to get to the lifters first . you can look at it that way but your still going to dry up the springs abit .i used hippo lifters was never a big deal on oil psi on the big block but never used a set on a sbc. you can buy a smaller hole push rod TREND pushrod makes them to. i would put the restrictors in the back of the block BUT YOU WANT TO JUMP UP ON THE HOLE SIZE DRILL IT OUT ABIT BIGGER the oiller from GM is about 1/4?stock have to check on at the shop. there 4 holes in the restrictors i would add up the 4 holes and drill them out till your = to 3/16 ,why i would use the restrictors there cheap and i like oil on my valve springs for street use. new push rod s are $$ .the O ring never help much i played with and with out,its a good way to go if the dist hole edge is rounded for the o ring first thing i do when i prep a block .. . i have seen oil psi drop i did a Zo6 but oil pumps are not to hot .. with T&D rockers with spring oiler s and that did take the oil psi down but many road races and now its back on the street still running .i just did not see your post this stuff jerry and i do. so i am always happy to add my two cents .as for the hippo lifters for the street there good way to go but your going to get some oil splash off the crank rods that will hit the cam .low speed idle is hard with out a lifter with out hippo some lifters hold up better then others i ran solid rollers on the street for many years spring lbs and cam lift comes in to play on the street smaller cam s= lower spring lbs with good rollers lifters can have a good life span

One other thing that may be relevant is that I used a priming device to pump oil to all new parts before starting the engine. I have a mechanical gauge on my accusump which is plumbed in after the filter. This gauge was reading over 100psi after the priming.
Could I have damaged the relief spring or something in the pump?

Further thoughts. from above if I had 100psi on gauge could I have collapsed my filter because oil lines were empty after it when I hit full speed on my drill and priming device?

Nah I am getting 70 psi when cold so plenty of pressure after filter. dropping as engine warms up I guess my new parts are flowing more oil and so reducing pressure. I hope so anyway.