SC Engine from CIS to Webers Which Cam?

[Lucky9146]

Have heard the CIS Cams may not be the most optimal for use with Webers.

79 SC 3.0 motor headed to my 914-6 conversion with factory metal flares

The 3.0 CIS will be fitted with Dual Weber 40 IDA 3C carbs

Carrera tensioners

MSDS 1 5/8 inch headers for 914-6

Jerry Woods complete distributor rebuild/re-curve

MSD 6-AL Ignition box, MSD Blaster high vibration coil

Mazda RX-7 front oil cooler

Rich Johnson engine conversion mount

Perry Kiehl 914-6 engine conversion wiring harness

Think the sums up the engine set up just trying to figure out the best cams to use.
Thx

[Flat6pac]

Your problem is going to be with the face of the piston. There is little room to have the valve open at TDC.
Bruce

[fred cook]

Originally Posted by Flat6pac

Your problem is going to be with the face of the piston. There is little room to have the valve open at TDC.
Bruce

Yep, you will need to use something like the 964 cam grind or change pistons. If it was my choice, I would do both! Good luck!

[Lucky9146]

Originally Posted by fred cook

Yep, you will need to use something like the 964 cam grind or change pistons. If it was my choice, I would do both! Good luck!

Have heard the 964 cams are a good choice but what does that do over the current CIS cams? Thanks for the replies

[JmuRiz]

Longer duration and higher lift, but not so much that the valves hit the piston tops.

[fred cook]

Don't have my rebuild notes in front of me, but I think the SC cams had lift specs of about 450/400 (intake/exhaust) and duration of 284/256 (intake/exhaust). The 964 cams are somewhere around 465/406 lift and 304/276 duration. Main diff is about 20 degrees more duration. If I find something different, will post.

[BoxsterGT]

This is a bit off topic, but can you tell us about your Mazda front oil cooler and lines setup? Perhaps in another thread.

I am working on a Six conversion that will need a front cooler.

Thanks,

Len

[Forrestkhaag]

Boxter GT / I can help as I have a front oil cooler setup done and functioning pm if interested / On the cam grind issue / WebCam reground and rehardened my 82 SC cams to a 20/21 grind with stock pistons and cylinders and recurved dizzy to match the grind. I can send webcam spec sheet if helpful

cheers

[Robman]

I have the same question except I have a 79-80 ROW 3.0. How hard is it to change the cams to run carbs?

[safe]

Originally Posted by Robman

I have the same question except I have a 79-80 ROW 3.0. How hard is it to change the cams to run carbs?

Its not that difficult, but its quite a lot of work, many fiddly things. With the engine out an experienced mechanic can do it in 8 hours (guessing).
But to change to something the CIS can't handle you will need to change pistons too, as said above.

[Forrestkhaag]

Not sure why some are saying you need to change cams rather than have them reground and hardened with a recurved SC dizzy. That is what I did and it works fine with no issues.

[banda]

I have Web Cams, 20/21 Grind, on my 78 SC motor with Webers and SSI's and they work excellent. Good low end Torque but they still pull. strong on the top end. Here's the link

Web Cam Inc. - Performance and Racing Camshafts / Porsche 911 SOHC 12v Timing Card

[juanbenae]

I am currently working through a rich at idle situation with a fresh 3.ol rebuild with JE 9.5-1 that was volume confirmed to just a hair under 9.4-1, single plug, webcam 120/104 grind & weber 40's. JWE did my dizzy recurve and around 30* advance, jetting is currently 180AC, 160 mains, 50 idles with f3 ET's. started with a 60 idle and a 170AC.... and not much diff post jet shuffle. works nicely AF & power wise as soon as the mains chime in. I'm wondering if the wecbam grind I chose was too rich for street & spirited canyon use?

[Trackrash]

Originally Posted by BoxsterGT

This is a bit off topic, but can you tell us about your Mazda front oil cooler and lines setup? Perhaps in another thread.

I am working on a Six conversion that will need a front cooler.

Thanks,

Len

There is another thread around recently discussing these. My search isn't finding it however.
These work well when you are moving.

[Trackrash]

Originally Posted by juanbenae

I am currently working through a rich at idle situation with a fresh 3.ol rebuild with JE 9.5-1 that was volume confirmed to just a hair under 9.4-1, single plug, webcam 120/104 grind & weber 40's. JWE did my dizzy recurve and around 30* advance, jetting is currently 180AC, 160 mains, 50 idles with f3 ET's. started with a 60 idle and a 170AC.... and not much diff post jet shuffle. works nicely AF & power wise as soon as the mains chime in. I'm wondering if the wecbam grind I chose was too rich for street & spirited canyon use?

I can't get my motor to run with 60 idle jets. I need to run 65s. Do you have an AFM? When is it rich? Idle or progression? How does the motor run? What RPM does the power come on? Do you have large or small ports?

[juanbenae]

Gordon, sorry I did not check back in here. settled on 55 idles which have maintained the good upper end & transition. problem is I'm still very rich at idle monitoring the single right side bank with an AEM AF gauge and stay rich until just before the transition to the mains where all is good. no loss of power throughout as long as I run rich on the idle circuit. will not run on 50 idles.

I wish id done more research on the cam profile about now, but coming from a race car I really forgot what driving a street 911 was like so the 120/104 sounded great, "hot street & track". I think I may have chosen the wrong cam for my application to stay on topic. I'm talking to the people ive know all along about how to solve this when I should have gone to them before I had my hasty cam selection made. I was going to post a thread this weekend as to what ive been thru & solicit some advice regarding hot cams in a street, carbed 3.ol with the bigger 78-79 heads. motor also is fresh.

[Trackrash]

Those of us who have been hot rodding motors for a while have all made the mistake of trying to run too much cam.

In your case with a lightweight car and low gearing, something like an S grind might make sense. Not sure how your cam compares to an S grind and I don't know if your cams are causing any of the trouble for your carbs. Maybe the real experts on board will chime in.

I am using GT-2/102 cams in my motor. They have slightly less duration and slightly more lift compared to an S cam. I wanted response and torque right now. I did not want to have to wait until 4K rpm for my motor to start pulling. Torque and response are worth more to me on the AX course than horse power in the book. Now, on a race car on the track you can keep the revs up and use the extra RPM, not so much on the street or at an AX.

My motor is built from a '78 SC 3.0. It is still a 3.0 with large ports, single plugged, but with 9.8 to 1 CR using JE pistons, weber 40s, old style heat exchangers with a sport muffler, and K&N air cleaners.

I still have some fine tuning to do on my carbs but my A/F runs about 12.5 to 1 through out the RPM range. It runs a little richer at part throttle acceleration , around 11.5 and at light cruising around 13.

I am running 36mm venturis, 155 mains, 170 SC, 65 idles and 120 idle airs.

[RSstop]

All good advice above.
Remember that your stock compression ratio is only 8.5 on a 1979. Besides clearance issues, you need more compression to take advantage of a more radical cam. Otherwise it is a wasted expense.
It also depends greatly on how you intend to drive the car. If you redline every shift go bigger cams. If you like nice tractable torque, and only occasionally rev above 5500, bigger cams don't help, and can reduce lower rpm torque. That is were carbs are hard to tune; at low rpm transitions.
Today's fuels are designed for injected cars. I am convinced it is more difficult to tune carbs today.
EFI can be tuned so much easier, but at a higher entry cost.
Anyone need a set of 46mm PMO's?