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Discussion Starter · #1 ·
Built a 598 BBC nos motor, makes 1000hp on motor.
question is what do guys see @ idle with similar applications.
1100rpm's
here are some specs.
motor is very new, only 6 passes and 50 street miles
4-5% leak down cold
.028 & .032 ring gaps w/med tension oil rings
running a moroso 4 vane pump on a wet sump system.
2.5"crank pulley and 5" on pump.
the pump was new last season and is clean with Rotella 15w 40 oil
I put alittle air into the motor and found a leak at the collar on the distributer. sealed it up, motor seems to hold air now, no other leaks found.
the engine only starts to pull VAC after 2500 rpm. I even flipped over the vanes in the pump with no change. Im not so worried because it is pulling 12" @7200 threw the traps.
I was thinking of going to a STAR pump but i dont think this will change???????????
even put on new vac gauge and the pump does pull some vac if you put your hand over the intake. also seems as there is still a leak.................but it engine DOES hold air for a while.

Is 0" @ idle ok?????????Thanks for your help in advance. This is one of those things that bothers me alittle.....Ray
 

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My 565 with well over 100 passes on it idles at 5 inches of vacuum. I run a Moroso enhanced pump. Put a shop vac on the motor and look for leaks. Air in the crankcase will seal any oil seal like the timing cover and rear main. Maybe use the shop vac and some smoke from a cigarette or something.
 

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Ray did you check if air is coming through behind the belt drive.sombody on here just had that going on with a jessel.
 

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Discussion Starter · #4 ·
this was the same deal with the 565 engine, thats way i bought a new pump and same deal. WHY???????????????????
 

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The air leak through the jesel was me but mine was because the engine assembler left out two of the three cam bolts, luckily I found it before firing the engine. In the end though I still have a couple of small vacuum leaks and not yet perfectly sealed but I am pulling the exact same #s as the thread starter here reported. I am not satisfied but content to run it till fall and pull it back out.
 

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Discussion Starter · #6 ·
found it............leaking from front nut on oil pan to timing belt cover. sealed it up, will let it drive and fire it 24hrs.
 

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We run an older style 3 vane Moroso pump on our 540 and it pulls 5-7 inches at idle.* We clean the pump before every race by disconnecting the lines and spraying a good amount of brake kleen into the pump.* Spin it over to wash out the gunk and you're good to go.We built a vacuum canister out of an old nitrous mother bottle using a ball valve and -12 line that we connect to the intake of our air compressor.* We pull around 17 inches of vacuum on the bottle, close the valve, connect the -12 line to the valve cover and slowly open the valve to pull a vacuum on the engine.* If there's a leak, you'll hear it.* Better than pumping air into the engine, easier on seals and gaskets.* We do this everytime before we put the engine into the car, easier to locate the leaks.The last time we had a problem with vacuum, there was a stud in the manifold that we were using for a ground for the nitrous solenoids.* The stud was tight, but still leaked enough around the threads to keep the engine from holding vacuum at idle.* Little teflon paste and the engine instantly went to 5" at idle.* It doesn't take much of a leak to keep the vacuum down at idle.Hope this helps,Martin
 
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