Ok, please educate me....what is and how do I do a leak down test?? I assume we are talking about a vacume test per cylinder??

The leak down test is done using a tool consisting of two gauges and a shut off valve .( summit or jegs sell them)
The test is done by filling the cylinder with a regulated air pressure then measuring the leakdown % past the rings , valves, head gasket ... piston must be @ top dead center on the compression stroke.

Depending on the crank size, oil level, oil pan, and rpm, you could just be dealing with crank windage. Windage is oil getting aerated by the crank spinning at high rpms, it creates a vortex in the crankcase and makes pressure, usually just pushing out the dipstick. Good oil pans with windage trays will help prevent this, but wont solve it entirely depending on how much stroke you have.

My 598ci N/A has less than 20 hours on the rebuild and is leaking down virtually nothing, yet I still have to spring the dipstick to keep it from pushing out. And this is with a good oil pan with kick outs and a windage tray. It doesnt blow anything out the breathers, at all. I have 4 breathers on it, so I know it is getting enough ventilation. If your valve covers/air filter is staying clean and free of oil, then your blowby probably isnt the problem.

My 598 was blowing out a quart of oil onto the valve covers every 2 hours of run time before the dropped valve and subsequent rebuild, and that was with 4 breathers with 6" extensions stuffed with stainless scotchbrite pads to catch the oil. Now THAT was blowby.

I had the same problem. Mine was from the breathers in the valve covers. I used plastic inserts and tubes to air cleaner. No more issues.

Wow Phil, thats pumping oil.

90% of the time you can fix this with dual breathers with the little filters on them, but a vacuum pump is the best solution for 598.

Engine must be awesome though...


Uncle Dave

I had two breathers on each valve cover, with a 6" tall extension on each one that was stuffed with fuel cell foam. only problem was, that got clogged up in about 15 minutes and started pushing out seals all over the engine. The blowby was tremendous.

Like i said, now I have no breather extensions and it doesnt blow out any oil at all. I have 4 of the filter breathers on the valve covers, and am certain that I could do with just two, one per side. Prior to the rebuild I was leaking down at 10-15%, the ring gaps were set up huge, anywhere from 35-45thousandths. Now we are leaking down at 2-4%, with ring gaps in the 22-23thousandths range.

It doesnt even push much oil out of the dipstick without the spring on it, just a few drops an hour. With the dipstick spring it doesnt leak at all.

Engine is pretty sick, sounds bad at 6000rpm. Still making in the mid 700hp range with the hyd lifters, dropped down from 800hp with solid lifters. i can live with giving up some hp based on the added reliability.

What you are describing is what Im probably going to move my tunnel hull to next a 598 N/A BBC- simple effective.

It's probably a (roaring) kitten at mid 7 HP too. good low rpm stable idle id bet. Thats also something I can deal with if I have issues. I can actually FIX a BBC.

Ive been pretty impressed by my ilmor 710
700hp out of a 505 and still idle well and never have a speck of soot on the transom is awesome.

As it should be for what it cost.

another downside of the technology based engine Is that I dont have the ability to do much of anything to it but change fluids plugs and filters. If it stops there isn't a whole lot I can do but check the basics.





Uncle Dave

Viagra or Cialis:party-smiley-004:

It certainly gets the job done. Single 1050 Dominator is old school, but much cheaper than a nice EFI setup, plus much easier to work on.

It idles like a champ at 800rpm in neutral, 600rpm in gear. Throttle response is great, though it doesnt much like running below 3000rpm as it doesnt get all its timing until then. Nice 3500rpm cruise, and it really comes alive at 4500rpm. With the solid roller cam, I was spinning it to 6300-6400rpm with a labbed 32p Bravo 1. CMI sport tubes dry to the tips certainly help with the sound.:coolcowboy: