Cams for my 2.4 Project

[grotvik]

I have a 73.5 T motor that I will be converting to S spec with stock 2.4 S pistons. I will have the heads ported to S spec also. I will be running carbs, most likely PMO 40's. It has been suggested that I go with a cam grind somewhere between E and S spec. Which cam should I use/buy as cores for the grind I need? Can the 73.5 T CIS cams be reground?

Thanks for your feedback.

Greg

[MST0118]

I’d probably just have new camshafts smade from a blank by John Dougherty or Elgin because by the time you pay for a used set of good S cams and pay for a regrind, it almost comes to the same price as a new set unless you can find a good deal on a core set. I think the 73.5 T cams wouldn’t be a good set to use because I think they would need to be welded which might make them weaker than new ones. Would be interested in what the experts think though.

[Trackrash]

+1
All true. I recently went through this.

Go to Dougherty's web site and see what is available. I think mod solex is what you are talking about. Ask John any questions he is the camgrinder here.

Dougherty Racing Cams Porsche 911, 930 and 964 camshaft profiles

[horizontallyopp]

Mod Solex is the DC-30 grind (in case it isn't obvious from John's list).

Greg you may want to read up on the use of S porting and come to our own conclusion. The take away I got was that with the right cam profile, carbs and a bump in compression, that the smaller ports give more low end grunt vs. the high revving nature of the S motor (which also had to do with its camshaft). Depends on how you're going to drive the car and what your intended use is, of course.

[grotvik]

Thanks all. As always, you guys are spot on. Here is John's reply to my cam inquiry yesterday.

---------------
Hi Greg,

The DC30 profile will work well in this. Strong 3500-6500 rpm power band. Not as aggressive as 911- S camshaft and not as mild as the 911-E.

Only available on new blanks ($1049 pair) unless you can find a good set of original E or Solex camshafts to grind ($415 pair).

Thanks,
John Dougherty
-------

Keith, what port sizes do you recommend? My goal is a good driving daily driver and canyon carver on an occasional Sunday morning. Simply said, a combination I will be happy with for years ahead.

Greg

[Matt Monson]

Have Steve Weiner at Rennsports Systems, also in Portland, send them out for regrind for you. There is absolutely no reason to spend the money on something ground from new blanks on a build like yours.

[cmcfaul]

love the DC 30's on my old 73 E. Had a bit more compression then your S (I opted for the JE pistons) but it was a screamer.

Chris

[Trackrash]

Originally Posted by Matt Monson

Have Steve Weiner at Rennsports Systems, also in Portland, send them out for regrind for you. There is absolutely no reason to spend the money on something ground from new blanks on a build like yours.

The CIS cams need to be welded in order to get the profile he wants. Not worth it.

[horizontallyopp]

Originally Posted by grotvik

Keith, what port sizes do you recommend? My goal is a good driving daily driver and canyon carver on an occasional Sunday morning. Simply said, a combination I will be happy with for years ahead.

Greg

Greg,

I'm going with DC-30 cams as well and opted to stick with smaller T/E ports - the engine will run out of breath at higher RPMs, so the peak will not be above 6000 rpm. But I'm looking for punch between 3500-5000 rpm anyways.

Here's one good topic:
2.2 S pistons with E-cams ?

Cheers

[grotvik]

Originally Posted by horizontallyopp

Greg,

I'm going with DC-30 cams as well and opted to stick with smaller T/E ports - the engine will run out of breath at higher RPMs, so the peak will not be above 6000 rpm. But I'm looking for punch between 3500-5000 rpm anyways.

Here's one good topic:
2.2 S pistons with E-cams ?

Cheers

Thanks Keith. I will check out the thread you included. Have a great weekend.

[Matt Monson]

Originally Posted by Trackrash

The CIS cams need to be welded in order to get the profile he wants. Not worth it.

Been using welded cams in builds for 2 decades. To each their own.

[Steve@Rennsport]

I've been using welded cams in various motors and have no angst if:

1) The welding job is done properly

2) The rocker arms are properly refaced (not as easy as you think)

3) Correct break-in procedures are followed

4) One uses a good engine oil

[Trackrash]

Who will weld and grind cams for less than $900? For a little more you have new AND you don't have to ship your cams to the grinder.

[Matt Monson]

Money is money. I’m $15k into parts on my engine build. The price delta between regrinds and new is almost a set of intake valves. We each draw our line for ourselves. I bought brand new Mahles and will use welded regrinds. The next guy might use used or reconditioned p&cs and new billet cams.

[grotvik]

Can early S cams be re-ground without having to weld material onto them?

[Trackrash]

Most likely. You should verify with your cam grinder.

[grotvik]

Thanks, Gordon. I just emailed John. I will post his answer when he replies.

Greg

[grotvik]

Yes, per John, he can grind S cams to the DC30 spec.