Carburetor Question?

CRH911S · 05-02-2002, 01:19 PM

I am pulling my engine and trans to deal with some minor leaks and to perform some maintenance. I have been giving some thought relative to the PMO carburetors endorsed by Randall Aase. Presently I have a 2.7 CIS that serves me well. I am looking for input positive or negative. Thanks in advance.

Clinton R Hodges II
Anchorage, AK

pwd72s · 05-02-2002, 02:33 PM

My GUESS is that the carbs wouldn't add much power without other engine changes as well.

CRH911S · 05-03-2002, 10:50 AM

pwd72s, in your opinion would the carbs help toward bringing out the true character of the S cams. Back dated exhaust in place already.

Clinton R Hodges II
Rennlist/PCA member
Anchorage, AK

Formerly Steve Wilkinson · 05-03-2002, 11:37 AM

I've got PMOs on a 3.4-liter SC with headers, S cams and twin-plug heads. I did it purely for the fun of it--FI is too easy. Also, being 66, I'm from the generation that didn't feel manly if we couldn't play with our SUs and Webers. Having said that, it certainly has reminded me what archaic devices carburetors are. They may make a little more power, and add some snap, and they look cool and sound neat, but my mpg is ridiculous and I hate to think what I'm emitting. God knows they're better than CIS in many ways, and I do enjoy tuning 'em...

Stephan

Early_S_Man · 05-03-2002, 11:56 AM

Clinton,

There seems to be a lot of confusion by 2.7 CIS owners as to what 'S' cams are ... and no CIS engine ever came with what are commonly referred to as 'S' cams, and can't be retrofited with them unless the pistons are changed to forged pistons with large valve relief pockets! The cast CIS pistons with the 'odd' emmissions crown design doesn't permit using aggressive 'Solex,' 'E,' or 'S' cams from the earlier high-revving engines! So, unless a change in pistons & cylinders is done along with a cam change to accompany the change to PMO's ... the money spent is NOT going to return much of a power increase! That is what Paul -- pwd72s -- meant by ' other engine changes as well.'

J P Stein · 05-03-2002, 12:10 PM

The world wold be a boring place if we all agreed about everything. I think pwd72s and I would agree that your CIS, S cams and his S cams have little in common.

The "true character " of the CIS cams is that they are not exactly "deep breathers". Nice flat torque curve, but they're all done bout 6K.

IMO, the PMOs and back dated exhaust will give a tidy hp increase and far better throttle response. You're the only one that can decide if the expense is worth it.

PMOs or Webers really come into their own on a modified engine, but you gotta' learn to deal with them. As Sephan said, it doesn't
bother those of us that grew up with carbs.

CRH911S · 05-04-2002, 11:35 AM

I stand corrected here and appreciate everyone's feedback. I have been considering a conversion to carburetors because I can afford it, I like the way they look and sound, and I like the future performance enhancements possibilities.
I realize the conversion to carburetors requires time, patience, and knowledge. I'm short on knowledge and working on that. That's why I am here on the Pelican bb; a super group of people with one thing in common.
I am looking forward to Wayne's new book and have expressed an interest in obtaining an advance copy. I think some time after that I'll decide what direction to go as far as p/c's and cams are concerned. My understanding is that the magnesium case is structurally limited.
Thanks again and any input is greatly appreciated.

Clinton R Hodges II
Anchorage, AK

porsche74 · 05-04-2002, 12:50 PM

Clint:

IMHO, converting your car to PMO's would make it LOTS more fun to drive and the throttle response increase belies the power changes.

Any carburetor requires some patience & expertise to have a troublefree installation and I'll tell you sir, that carbs (properly configured and jetted) make damned good power.

From a mileage perspective, carburetors can do very well if one is disciplined to keep one's foot out of the throttle but, this is not why people do such things, yes?
MFI is no better and even an EFI installation isn't that much better on fuel, if you drive it briskly. CIS-type cams make good mileage if you are prudent.

The magnesium cases (7R version) are only an issue above 250 HP and for street use, they are just fine provided they are properly upgraded.

Mr. Wilkinson and J.P. are right on the money here and offer good advice. You might ask Stephan off-line who helped him get setup with his engine project and provided some guidance. There is no reason to be afraid of a carburetor setup on your 2.7 provided that you get good qualified help and support.