Too much crankcase pressure

[vwfan79]

I modded a 5hp briggs with .300 cam, billet lifters, heavier springs, new valves, eyebrows shaved, mikuni carb, billet rod, 3hp flywheel and coil, timing advance, honed and new rings. I have way too much crankcase pressure and I'm running 2 breather tubes right now, 1 to a fuel pump and 1 is just onpen tube but is getting catch can. The pressure is pushing oil to the top end and causing it to smoke. I didn't measure ring gap but all was good before modding, no smoking. I pulled the oil cap while it was running and there was a lot of pressure. Any ideas on how to fix this or what caused it, I know blowby will do it.

 

[1stlegendtx]

You could try a PCV valve.

 

[george3]

is your breather pluged, damaged or hose cloging it. If ok too much compression going by the rings?

 

[vwfan79]

You could try a PCV valve.

Already have 2 vents

is your breather pluged, damaged or hose cloging it. If ok too much compression going by the rings?

New 2 vent valve cover and hoses.

 

[1stlegendtx]

Already have 2 vents


New 2 vent valve cover and hoses.

A PCV valve only goes one way (different then a vent). Ask Kart racers in the unlimited class.

 

[vwfan79]

A PCV valve only goes one way (different then a vent). Ask Kart racers in the unlimited class.

Ya I guess I wasn't thinking the breather is actually pulsing and if I put in a pcv it will only let air or not back in. Worth a shot.

 

[Hounddog]

I have seen this before with a built briggs motor with two breather vents. The rider was blowing lots of oil out into the catch tank and all over the motor etc...It turned out he had overfilled the crankcase with oil with 32 ounces of oil! Maybe drain the oil and refill with correct amount. Many racing briggs motors use less oil than the owners manual....

 

[vwfan79]

I have seen this before with a built briggs motor with two breather vents. The rider was blowing lots of oil out into the catch tank and all over the motor etc...It turned out he had overfilled the crankcase with oil with 32 ounces of oil! Maybe drain the oil and refill with correct amount. Many racing briggs motors use less oil than the owners manual....

Well I know it's not over full, when I put it back together a couple weeks ago I used about half a quart.

 

[jim210]

Steel bore or cool bore? Did you offset the ring gaps or did you line them up? How were the valve guides? How about using intake manifold for the fuel pump pulse and venting the second vent?

 

[vwfan79]

Steel bore or cool bore? Did you offset the ring gaps or did you line them up? How were the valve guides? How about using intake manifold for the fuel pump pulse and venting the second vent?

I think it is steel bore it's a fun power block, the ring gaps were offset, valve guides are good. I was thinking about using the intake I just need to pull it and weld in a fitting.

 

[vwfan79]

I was wrong I have a cool bore block. Now I wonder if I go the right ring set.

 

[jim210]

Yea you could have the wrong rings. also cool bores can wear out so much that reringing doesn't do any good. A mikuni manifold should be thick enough to tap it for a npt fitting, no welding needed.

 

[vwfan79]

Yea you could have the wrong rings. also cool bores can wear out so much that reringing doesn't do any good. A mikuni manifold should be thick enough to tap it for a npt fitting, no welding needed.

How would I go about getting a Briggs part number for the right set of rings? My manifold is pretty thin, the guy that made it said I probably won't get any threads in it because the walls are too thin, he told me it would be best to weld a fitting in.

 

[vwfan79]

I found my oil was full of gas, I know this will wash the cylinder walls of oil but will this also cause the rings not to seal? Could this be my problem?