E cams in an rs spec motor

[930chef]

i just got a new car. 1975 with a supertec rs spec engine with pmo's and a close ratio 915 with 7.31 r&p. i found out that he had e cams installed and it has no top end really.
what are some options to wake this motor up on the top end w/o sacrificing too much on the bottom end?
i sold a monster 930 with 503 crank hp and bought this car and was prepared to give up raw hp for handling(it handles like no other car ive driven, and i mean that in a good way). but there must be something cam wise i can do.
any suggestions?
also how involved of a job is changing the cams? is it expensive labor wise? it is a relatively new motor so it shouldnt need anything else (while im in there) parts.

thanks for your expert input.

kevin

[Tom C.]

This is certainly not expert input, but since you are running PMO's I was wondering what their 'setup' is. Mostly their size 40/46 and the Venturis you are running in them. Your top-end issue could be more a tuning fix vs. a cam fix. My fiddling with PMO's has taught me there are two configurations for my motor . . . Performance vs. Drivability. And it is a compromise either way.

[BURN-BROS]

Hi Kevin,

Tom is correct in pointing to carb setup. Verify what you have as far as venturis and jets.

That said, the DC 40 (ModS) from Dougherty Racing cams provide both good midrange and Good Top end performance.

[larrym]

I once ran E cams in a 2.8 in vintage racing - they pulled well from about 1000 rpm, ran out of ooomph at 5800 rpm, tho you could keep winding to 6500 - no good for racing but great for street & autocross

I now have (as claimed by p.o.) solex grinds in a 2.7 rs, they pull a long level curve on chassis dyno from 2800 to 7000, but are crummy for street, and worse fuel economy - i'd gladly trade 'em away for E's since I no longer race the car, so if ya decide to sell your E cams let me know

in both cases above the carbs are the same set - 34mm venturi redline-weber 40's, pmo tall manifiolds

I agree with Tom ... can't have it both ways

[911pcars]

Originally Posted by 930chef

i just got a new car. 1975 with a supertec rs spec engine with pmo's and a close ratio 915 with 7.31 r&p. i found out that he had e cams installed and it has no top end really.
what are some options to wake this motor up on the top end w/o sacrificing too much on the bottom end?
i sold a monster 930 with 503 crank hp and bought this car and was prepared to give up raw hp for handling(it handles like no other car ive driven, and i mean that in a good way). but there must be something cam wise i can do.
any suggestions?
also how involved of a job is changing the cams? is it expensive labor wise? it is a relatively new motor so it shouldnt need anything else (while im in there) parts.

thanks for your expert input.

kevin

If the engine has RS-spec pistons, then it should be just a case of installing S cams (or equivalent). Typically, no other changes other than "while you're there" upgrades. However, it would be prudent to check for proper valve-to-piston and valve-to-valve clearance near TDC before running the engine (check a cylinder, both banks). In addition, the PO may have cut the cylinder head sealing surface and/or trimmed the cylinder heights which further reduces that clearance. Don't assume too many things with a previously owned engine.

Sherwood

[kandhmfg]

Originally Posted by larrym

I once ran E cams in a 2.8 in vintage racing - they pulled well from about 1000 rpm, ran out of ooomph at 5800 rpm, tho you could keep winding to 6500 - no good for racing but great for street & autocross

I now have (as claimed by p.o.) solex grinds in a 2.7 rs, they pull a long level curve on chassis dyno from 2800 to 7000, but are crummy for street, and worse fuel economy - i'd gladly trade 'em away for E's since I no longer race the car, so if ya decide to sell your E cams let me know

in both cases above the carbs are the same set - 34mm venturi redline-weber 40's, pmo tall manifiolds

I agree with Tom ... can't have it both ways

I had a 2.7L with RS P/C with a Webcam 120/104 grind a "mod-S" type like the DC40 basically I believe. Carbs were PMO 40's have run 34 and 36mm venturis, not a ton of difference. Car is '71 RS Clone, light, used in autocross and track. Good powerband from 3500-6500 and pulled to rev limited 7000. For the size of engine, I like the S cam. Many TTOD in PCA autocrosses in Phx area.

[larrym]

it would be interesting to see a chassis dyno chart on your engine (and for others who've posted here) - they are not too expensive, and worth the knowledge

Originally Posted by 930chef

i just got a new car. 1975 with a supertec rs spec engine with pmo's and a close ratio 915 with 7.31 r&p. i found out that he had e cams installed and it has no top end really.
what are some options to wake this motor up on the top end w/o sacrificing too much on the bottom end?
kevin