Stock 3.0 SC...do I need cams if I want PMO's?

[D911SC]

I built a 3.2SS with 46mm PMO's and S cams. It is a great engine and while the cams give you some decent torque down low the temptation to rev it out is often too great.

I'd like to go EFI but the carbs are still fantastic, as long as you can handle a poor idle while it's cold and difficult starts if you don't drive it all the time.

[rennch]

Ok kids...talked to Richard Parr the other day. Nice guy, and very knowledgable. I totally get the fax thing now, btw. Apparently, EVERYONE calls him and asks him a million questions, so he puts a good barrier of entry in front of them. Smart.

Anyway, I'm getting PMO 46's to start with. I need to measure my intakes to see if I've got 34mm or 38mm. If I've got 34, I'm going to have to bore them out. Any threads on this procedure?

[snbush67]

It's not your intakes but rather your intake ports on your heads. It's not something you can do with the heads still on the motor.

For the time being you will have to buy intake manifolds that match your intake ports. Hopefully you have a 78-79 motor or Euro ROW with the large ports.

Also, I think you can probably get away with the larger manifolds for a while, even if you have small ports, it's only a small step. I don't know for sure though.

[911pcars]

Gentlemen,
With all due respect to the fine products from PMO, Webers/PMO carbs are a waste of money without a commensurate upgrade to other significant engine parts.

However, carbs do look racy, and if that's the objective, great. Go for it. However, that look will cost $2500-$3500 with only a slight bump (if any) in power. Perhaps better throttle response. Congrats. Not sure how people think carburetors are superior to fuel injection. Maybe being able to tune carbs in their garage with minimal instruments and skill is key. 930 engines use CIS. Should their turbocharger(s) be "upgraded" with a carburetor too?

Other than Webers/PMOs, compatible pistons and more aggressive valve timing completes the correct mix of equipment for more torque and power, but that requires a serious expenditure of budget. Even then, it's more a function of increased volumetric efficiency (i.e. + compression ratio) and better breathing than just dumping more fuel in the engine.

To summarize:
- Aggressive valve timing isn't compatible with CIS pistons due to structural interference
- The benefit of carburetion is limited by CIS piston design and emissions-centric valve timing.
- Weber/PMO carbs look and sound sexy. CIS equipment is complicated and looks clumsy in comparison.
- There is no substitute for cubic inches (or cubic centimeters)

Sherwood

[rennch]

Sherwood, thanks for the input. As the car becomes more and more of a dedicated track machine, My next step will indeed be cams and Pistons. One step at a time though...my CIS has been an absolute mess for over a year now, and I can't wait to ditch it.

[Josh D]

Just got done going through your build thread. Impressive! You've done a lot of work to that car and it's certainly deserving a motor that matches it's looks.

From this picture from your thread, it looks to a be a 80-83 US 3.0. It has metal fuel lines and what looks to be the smaller intake runners.

[jpnovak]

For less money I would put the Bitz EFI kit on there. Tune it and enjoy it. You can still add compression and cams later and then just retune.

[rennch]

Again, I'm trying to get as authentic RSR as I can, without completely breaking the bank. I'm ordering some PMO 46's today. I *do* have the smaller intake runners. (34mm) Richard said he'd swap me out when I did the heads and got the larger bore. I'll do cams and heads sometime next year, perhaps. Any issues with running 46's with the 34mm runners that you know of?

[snbush67]

You wont be using the 34 runners, the carbs use manifolds and there should be no issues, they are shaped and come with spacers to cover up the injector notches.

[911pcars]

Originally Posted by emptyo

Again, I'm trying to get as authentic RSR as I can, without completely breaking the bank. I'm ordering some PMO 46's today. I *do* have the smaller intake runners. (34mm) Richard said he'd swap me out when I did the heads and got the larger bore. I'll do cams and heads sometime next year, perhaps. Any issues with running 46's with the 34mm runners that you know of?

RSR engines used MFI - not synonymous with "not breaking the bank" (however, no clue as to the size of your bank account). Even RS engines used MFI. Completing the look of an "RSR" body is another big ticket item.

46 Webers are over-carbed for a 3 liter factory SC engine and unless adequately compensated with more modest venturis and rejetting, fuel mileage and perhaps throttle response will suffer.

Perhaps shop for the 46 Webers now, then install them with more compatible pistons/cylinders, head, cam and exhaust at a later date? Again, confirm with your checkbook.

Folks on these threads have no hesitancy to spend other people's money.

Sherwood