SD1 + Holley + breather pipes?

MissMoppet · Post by **MissMoppet** » Mon Oct 20, 2014 5:36 pm

I run a Stag with a SD1 (10A engine)+ Holley 4160. I've had it for two years and it runs OK but not as smooth or as nippy as I feel a V8 should run. There are two breather pipes run from each rocker cover to the pancake air filter but studying my Haynes I believe one R/C should have a flame trap open to air and the other ran to a branched hose to each SU PCV outlet. I have tried to duplicate that by installing a small PCV from Real Steel for one R/C and then hose to the large PCV inlet on the Holley. BUT, but it runs very poorly, spitting and coughing.

Any ideas most welcome.

Dave

DaveEFI · Post by **DaveEFI** » Mon Oct 20, 2014 5:49 pm

Take it SD1 SUs won't fit under the Stag bonnet?

MissMoppet · Post by **MissMoppet** » Mon Oct 20, 2014 8:32 pm

Doubt it, but bought it with a Holley and apart from cost, presume Holley is an advance.

DaveEFI · Post by **DaveEFI** » Mon Oct 20, 2014 11:08 pm

MissMoppet wrote:Doubt it, but bought it with a Holley and apart from cost, presume Holley is an advance.

I wouldn't bank on it with a standard engine. Especially at low to medium revs.
And only if in perfect tune - which most aren't.

Darkspeed · Post by **Darkspeed** » Tue Oct 21, 2014 6:52 am

Not really clear on how you have piped it

Could be that the PCV spring is not strong enough for the Holley signal and it's being pulled open prematurely resulting in a weak mixture and hence coughing and spitting back.

As said getting a Holley tuned right is a task and in most cases results in less power than the original set-up.

You need an model 8007 as your basis then a secondary metering plate, a selection of power valves, pump cams and, secondary springs, and about 5 pairs of primary and secondary jets. From that you have a chance of getting a Holley to work.

The RV8 should do smooth but nippy in stock form in a Stag compared to a modern

especially if on the back of an auto of the same period.

Remember the old rule - if you think its the carb then its definitely the distributor

MissMoppet · Post by **MissMoppet** » Tue Oct 21, 2014 8:21 am

Many thanks for that. The PCV is a weight not a spring so I've simply mounted it vertically on top of the Rover rocker cover outlet. Then led a pipe to the PCV outlet on the Holley. (This PCV from Real Steel was recommended on a TR7 forum - v old post).
I have played around with the Holley - float level on the primary tank - and idle jets so I know it can run OK - but just feel that as the Stag is so much lighter than the old SD1 it should have a bit more go and be smoother. I do have the recommended correct main jets.
And that various forums say that you should have Positive Crankcase Ventilation for this SD1 - which at the moment I don't have (no effective connection to the carb)

Darkspeed · Post by **Darkspeed** » Tue Oct 21, 2014 4:07 pm

My explanation of the sprung PCV is back to front as the spring is to open the valve when idle vacuum drops off so the spring would have to be too strong for the Holley signal.

No idea how a non sprung / weight one works

MissMoppet · Post by **MissMoppet** » Tue Oct 21, 2014 4:29 pm

Gravity.