1700 crossflow problem

[S2K]

Ive put this on the main engine/transmission bit but just in case somebody who looks at this has the knowledge I'll ask here as well . My locust runs a 1700 crossflow that is suffering from excessive crankcase pressurisation, I suspect the P.C.V. valve could be the cause of the problem but I can't see how it is held in the block, I was told it's just a push fit but I can't budge mine, can anyone help please. Thanks.
Andy

[Mr2Mike]

If you have the original "tin can" style crank case breather, then there is a small bolt that secures it to the block (1/4" I think), and the inlet at bottom of the breather is simply a very tight fit in the block.

[Norfolkit]

Concur with Mike but also is the vent hose from the PCV gubbins connected to the inlet mainfold because if it isn't there won't be the necessary vacuum to open the PCV valve and the crank case will pressurise. If it's not vented through the inlet manifold you have to remove the PCV valve and vent to a catch tank (or into the rocker cover then a catch tank). Been there, done that, mopped up the oil.

[Comadis]

standard carbs or weber sidedraughts?

if webers have been fitted i pressume the original crankcase breather in form of a tin-can has been replaced by a 90degree alloy-ellbow which should end in a catchtank or mabye the environment.

if you have a shortened oilsump, but still using the original indicator marks on the dipstick for the oil-level it might be a problem there: your sump is overfilled and the crank is splashing the oil around.

do also a compression test and tell us the result for each cylinder, please.

[Mr2Mike]

Comadis said:

if you have a shortened oilsump, but still using the original indicator marks on the dipstick for the oil-level it might be a problem there: your sump is overfilled and the crank is splashing the oil around.

If you use the original dip stick marks (as you always should) then the oil level will be no different from standard, though there may be more or less total oil in the sump if it's been modified.

[Sam_68]

Comadis said:

if webers have been fitted i pressume the original crankcase breather in form of a tin-can has been replaced by a 90degree alloy-elbow which should end in a catchtank or maybe the environment.

You definitely shouldn't be venting the crankcase breather back to the manifold if you've got twin Webers or similar, as all the gases would go into a single inlet runner and lead to problems with charge contamination and mixture on that cylinder.

For what it's worth, my experience is that all tuned Crossflows tend to breathe quite heavily (the standard system can't cope with the higher revs, even if the engine is in perfect order), so you're much better off simply getting rid of the PCV valve and venting to a catch tank. Personally, I just vent the catch tank to the atmosphere, but if you're obsessive about environmental considerations, you can vent the catch tank back to the intake system (air box, if you're running multi carbs) via a PCV valve.

There is a very good 'idiots guide' to breather systems in the Burton Powertune catalogue, incedentally, and they'll sell you a new PCV valve for the grand sum of £6, if you really want one.

[S2K]

I'm running twin webers and the P.C.V.valve is of the alloy elbow type direct to a catch tank, as i said I can't get the thing out to check it and if I do discard it altogether ( once I've managed to get it out ) what do I put in the hole, is there some sort of adaptor available. I spoke to Burton power and was told that you cannot get the P.C.V.valves any more.Thanks again.
Andy

[Comadis]

Mr2Mike said:

Comadis said:

if you have a shortened oilsump, but still using the original indicator marks on the dipstick for the oil-level it might be a problem there: your sump is overfilled and the crank is splashing the oil around.

If you use the original dip stick marks (as you always should) then the oil level will be no different from standard, though there may be more or less total oil in the sump if it's been modified.

oops..my mistake: it should say: if the sump has been shortened and somebody also changed the position of the marks on the dipstick or even took a differnt length of dipstick--tube than it might be that the sump will get overfilled using this "new" marks.

your alloy ellbow breather is a tight fit and often impossible to remove without using a big gripper or similar. this alloy thing is NOT a PCV valve!! this ellbow consists of nothing than itself...this means there arent any internals, also this ellbow cant get blocked. try with a wire.

so we are still missing some info from your side:

1. values of the compression test
2. result of a pressure-leakage test
3. where does the most oil come out: crankcase breather or rocker-cover?

Edited by Comadis on Sunday 28th June 16:03

[S2K]

No compression test done yet, also no form of leakage check, thanks for info on ally elbow, no point in trying to remove that then. Most oil seems to be coming out of the filler cap which is a clip down affair and also the dipstick tube so maybe it is overfull. Thanks so much for all your help.
Andy.

[Comadis]

filler cap?

do you use the standard steel rocker cover or alloy one?

do you use a filler-cap with a hose connected to your catchtank?

have you checked if there is a splash-shield underneath the filler-cap neck of the rocker cover?

the alloy ones do normally use a bayonet-cap without hose.

on an alloy rocker you normally have to fit yourselves a breathing-hose connector and most people forget to "install" a splash shield in front of this outlet.

[S2K]

Sorry, been away for a couple of days, pretty sure now that I'm going to have to live with the problem. I intend to remove the rocker box cover ( it is an aftermarket ally one and the filler cap is of the clip down variety, no breather of this )and carry out some modifications to it so that the results of the pressurisation are directed to the catch tank and not to the floor. Many thanks for all your help.
Andy.

[Mr2Mike]

Are you using the mechanical fuel pump, or do you have an electric one fitted? If the latter, ensure the fuel pump blanking plate has an oil splash shield to prevent gobs of oil getting blown out of the crank breather.

Crossflows tend to breath a fair bit if used hard anyway, they are not exactly the precision machines that modern engines are. You need a breather in the rocker cover, if you don't have one then simply drill it out and fit a barbed connection for a breather pipe. Both the crankcase breather and rocker cover breather should go into a catch tank if you are running sidedraft carbs.

[Norfolkit]

The other thing is, what sort of oil are you using. On a crossflow it needs to be LARD, seriously it should be 20W50, don't use modern synthetics they're way too thin, VALVOLINE 20/50 is by far the best with Duckhams Q 20w-50 Classic Engine Motor Oil an easier to get alternative.