Dutton Kit Cars and their owners
Hi all, hope everybody's been out Duttoning in the sun!
I've recently been running the trusty Pinto up to 7k rpm, mainly because I can. Previous self-inflicted red line was 5k rpm. Engine oil is blowing from the cambox breather and the dipstick tube (lifted the dipstick), nothing from the crankcase breather pipe.
I have twin 40 DCOEs and no connection between the crankcase breather and the inlet manifold.
Can I assume that the crankcase breather is a one-way valve that needs to be gutted to provide crankcase breathing?
I was under the impression that the standard conrods were only good for 6500 rpm or so. I don't know how accurate that is. Have you got different ones or are you living proof that the rumour is wrong?
It's all a question of balance. A well built and balanced shaft will perform at much higher RPMs than other engines. Even if that exceeds the normal RPM limit.
6350 is the factory max continuous speed, with 6500 the usual red line that most people use. You can go higher but the stock rod bolts will fail after a while. A few detail tweeks and a set of arp rod bolts and they'll go to 8000 just. The stock rods are well balanced as they come so long as they are a set. If the engine has been rebuilt and a mongrel set used then balance could be a problem. Pinto cranks especially the 205 ones with rolled fillets don't tend to suffer breakage but pistons will be a weak link above 7000 as the oil control ring groove is slotted and this is generally where the crown parts from the skirt. Beware also 2.1's built with V6 pistons as they have a mean piston speed limit that's lower than stock Pinto pistons.
Good balance doesn't increase performance just engine service life.
To answer your original question,
At high revs the oil control rings struggle and the crankcase pressure builds up, the oil drains back from the head via two drains at the rear of the engine. with the build up in crankcase pressure the oil cant drain back and instead blows out of anywhere it can. If you arn't running a mechanical fuel pump then a hose can be connected between the pump location and the cam cover. Likewise take out the turbo blanking plug from the right hand side of the crankcase and feed a hose to a catch tank via the cam cover. This allows that crankcase gasses to bypass the oil drains so the oil can get back to the sump - important as if you hold the engine long at high revs then you could use up all the oil in the sump :
Take out the valve you mentioned and pipe into the catch tank and fit a Sierra oil filler cap with the hose stub on and feed that into the catch tank too. Make sure the catch tank has plenty of breathing capability to as there's a lot og gas to shift and don't use one of those silly breather filters that are mean't to look like a mini air filter - you might as well use a bottle stopper for all they are worth.
That should help.
That's an interesting bit of info BV, I will file that away for later, sooner rather then later :-)
Thanks for all the replies, I'll be modifying the crankcase breather, fitting a catch tank and keeping the revs down to 6k. Sounds good at 7k rpm though!
Cambox breather and crankcase breather fitted, no further lifting of the dipstick and no oil from the cambox breather tube with a max of 6k rpm. Some oil from the crankcase breather.
Top tip: when rummaging under the carbs to fit the crankcase breather, check that you haven't loosened the HT lead at the coil, it might fall off 20 miles later. Which would be embarrassing.
I know that feeling.