BLOWBY

[Anonymous]

Hi Guys,

After doing a few burnouts in a skid comp my motor had excesive blowby. Thinking it was the rings i have pulled the block apart expected to find worn / broken rings. All the rings are in good shape and the bores still fresh after a recent rebuild, so it has be baffled.

I have a feeling that it could be valve train ware ie, valve seats etc due to the cam.

Can this cause blowby or is there any other reason it could occur.

Cheers

Simon

 

[xctasy]

Backlash and Aussie7Mains are the men. They have worked on these things for years, and would be the best bet.

There are a few types of valve seal that can have differing results. If they cop too much heat, the exhast seals may have lost it.

The rings, if its post 85, are low-tension, and prone to fluter over 5000 rpm, apparently. Crankcase holds a lot of cavitating oil, and there are areas where it can pool for quite some time on the head itself.

Simple things like the PCV valve, and normal valving can stop working if heat gets too much.

As for me, I think you've done the right thing. Although a really good read valve in the header can be made to suck out excessive blow by, a Falcon six is only designed for 5500 rpm max as a 3.3, and 4800 rpm as a 4.1. Alloy heads can pull out rocker studs and all suffer plasticine rod bolts over about 5300 rpm. By doing a strip, you ensure you'll have a rock solid machine, and you'll hold your honour next time.

The worlds Scariest burn-outs are ones where a guys nice, newly rebuilt 351 Cleveland windows the block or splits a bore. When our sixes cop a mean donut, V8 guys are pi#%% it didn't blow up!