Question for Jake.. Type IV's leak down

It could be a simple as a tight intake valve clearance...

Fact is most people do not complete leak down checks correctly..

Have the fellow pop the rocker arms off and then ensure that the piston is at TDC and HELD THERE while the air is being introduced into the cylinders.

If the piston is at BDC the numbers are not correct as you will almost always have ring leakdown with the pistion at BDC due to piston rock...

If the engine has more than 5% leakdown it'll need attention.

Hope that helps.

It could be a simple as a tight intake valve clearance...

Fact is most people do not complete leak down checks correctly..

Have the fellow pop the rocker arms off and then ensure that the piston is at TDC and HELD THERE while the air is being introduced into the cylinders.

If the piston is at BDC the numbers are not correct as you will almost always have ring leakdown with the pistion at BDC due to piston rock...

If the engine has more than 5% leakdown it'll need attention.

Hope that helps.

well Jake. if I get it and its no good, then I guess I get you to build me one. Its got a DTM shroud on it.

"Tried to do a leak down and got some leakage through intakes 2-4. #1 was ok. It's very weird that the intakes could be leaking not the exhausts. I did it the same way I would do a valve adjustment on T1. TDC on #1 and then back 180 degrees for 2-3-4. "

thats his reply..



Michael

On this topic should all cylinders read the same?

Jake, (or another who can answer)
Need some info, was thinking of buying a Type IV off the web used but doing a leak down he states that he is getting leakage from the intake? I thought it was usually the exhaust valves that get burnt? If he is getting untake leakage but not exhaust, what does that? Could the heads be warped? is that possible if the heads are torqued properly or did the valve adjustment just get done wrong?

All cylinders should read virtually the same.. 1% is the margin of error on most gauges unless someone has a funky set up, but they can be hard to read.

Also ensure that the gauge used for this has TWO gauges to view. The set ups that have one gauge with a red or green reading background are worthless. They will tell you all sorts of weird things that are not true. The dual gauge unit shows the pressure being introduced into the cylinder and the pressure being held by the cylinder. If you have 100PSI on one gauge and 90% on the other then you have 10% leakage, as an example.. The singe gauge set ups don't have this feature. Listen for the leaking air to exit the valves on intake or exhaust and also pop off the oil cap and listen for leakage past the rings, ending up in the case.

If someone does NOT pop off the rockers it is very easy to have a cam that preloads the intake valve and makes a leak when its not there.. Thats why I always tell the novice to remove the rockers to make sure the reading is correct- this way nothing can open the valve.

remember: A leak down check done cold is also pretty worthless- the engine needs to be warm. Also MAKE SURE THE PISTON IS AT TDC!!! BDC readings are absolutely worthless and inaccurate..

Jake..
thats what he told me..he heard leakage thru the carbs...so my guess is the valve seats?


Michael

Yes... BUT how much leakage and WERE THE VALVES CLOSED??? As i said its very easy for a false reading if the test is not done correctly. Cams with more overlap will try to barely bring the valve off the seat and create a false reading. Have hi remove the valve cover when the air is applied to the cylinder and if that intake valve does not have lash the test is worthless.. Thats why removing the rockers is so worthwhile..