SC Cams –vs- 964 Cams w/ new Ps&Cs?

[Porsche_911s]

’74 2.7 (~ 4000 miles) - EFI - RS Dizzy - Street car

To all those who know much more than I (mostly everyone), I am in need of Internet advise. This summer when the temperatures are reaching 105 w/ 80% humidity, I’d like to drop the engine and change out my Cams. I am in a dilemma as to what grind and the amount of money I should put into my 2.7 that has about 4k on a rebuild. (I finally got a working odometer so I can keep better track of the mileage.)

The car currently has the standard 2.7 Cams running MS EFI with a RS Dizzy. I have spoken with several Pelican members who were amazed by the SC grind in their 2.7. Even if they continue to run CIS, their experience has been bliss. (Better running & more powerful car.)

My question is this, would changing out the Ps & Cs for 9.0:1 compression & the ability to run the 964 grind be worth the extra power? I plan to do the work myself except for the final timing of the Cams. Here is what I have listed as a break down of what I think it might cost.

** 4 bearing cam towers already purchased
** Cams tools borrowed from fellow Pelican

Keep the 3 bearing Cams – Regrind between SC & 964
$350 for timing Cams at local shop
$100 Gaskets & hardware for work???
$300 Regrind of my current Cams, between SC & 964 (DC10 most aggressive for stock Ps&Cs)
~($200) Cam towers

~ $550

SC Grind
$350 for timing Cams at local shop
$150 Gaskets & hardware for work???
SC or Carrera Cams
$200 used
or
$300 regrinds
$60 For Carrera Cam hardware

~ $860

964 Grind
$350 for timing Cams at local shop
$150 Gaskets & hardware for work???
964 Cams
$300 used
or
$300 regrinds
$60 For Carrera Cam hardware
Ps & Cs to allow 964 grind
$700 used Ps&Cs
$700 New JE pistons only if I have Mahle cylinders
$200 rings

~ $1,800


Couple of notes, since I only put about 2k to 4k a year on my car, going with used or regrind is not something that concerns me. Resale of the 2.7 is so low; I cannot see a reason for dumping new parts in to an engine that has little resale value. Sort of like Wayne’s example with the Boxster, high price parts for a low resale item.

The follow are what I am wrestling with:

Regind –vs- OEM used

Type of grind –vs- $$$$

[Early_S_Man]

Stephen,

I would suggest Web-Cam 20/21 grind if you go with the JE pistons and valve reliefs ... you might want to try 'S' cams or GE60s, someday, along with ITBs!

Even if you have Alusil cylinders, you could bore them out to 92 mm and have them Nikasil plated ... no difference in price of 92 mm JE pistons! You might be breaking into new territory with an EFI 2.8.

[Porsche_911s]

Thanks for the reply Warren.

I looked at ITBs when I first decided to go to EFI. One thing to consider (per people who have done it) was overlapping Cams. I don't understand it 100%, but I think if you get too aggressive with the Cams it creates an unstable vacuum for the ECU, either with ITBs or the single TB I have now.

I have seen big bore kits ranging from $700 to 3k. The $700 ones are steel kits. I guess they are the Internet China special I see every now and then.

ITBs are out of my price range, but you are correct about looking towards the future and what I might get the urge to do later.

I would also pose the question if the 4 bearing Cams & towers were a worthy upgrade, especially since I already purchased the Cam towers.

[SP2]

Originally posted by Early_S_Man
Stephen,

I would suggest Web-Cam 20/21 grind if you go with the JE pistons and valve reliefs ... you might want to try 'S' cams or GE60s, someday, along with ITBs!

Warren,

I thought you need higher compression than 9.0:1 for 20/21's, no? I think that is what Webcam recommends.

Stephen,

I recently put in 964 cams in. As far as regrinds, John Dougherty is highly regarded, did mine (fantastic) and is not as expensive as $300. He is aka camgrinder on this board, and very helpful over the phone. He can regrind to SC, 964 and I think he has something called a 330 which is a bit milder than 964 or 20/21 but stronger than SC.

Here are links that taught me about these cams. They refer to SC engines, but the discussion I think you will find helpful.

Best Cam Profile For A Stock SC?

964 cams in 204 bhp sc

[Porsche_911s]

Thanks James! After the game I'll read up. The DC10 are a Dougherty grind that is in between a SC and a 964 for the 2.7. Probably similar to the 330.

[SP2]

Your welcome! BTW I think you should time the cams yourself. If you are removing and installing them, then you have all the tools you will need except a $15 dollar dial gauge indicator from harbor freight and a tube of assembly lube. I am, or was, a total newbie and timed them myself 3 weeks ago. It is harder to remove them. Putting them in just flies by. Also, regrind your rockers, whatever the condition. I had them done for $4 a rocker and they were perfect.

[Porsche_911s]

I hope to persuade the fellow Pelican that is letting me borrow the tools to help me time them. I have heard it is easy once you understand the concept; I was just going to play it safe. We shall see...

[SP2]

It is easy if you have Wayne's engine rebuild book. It is actually easier to tighten them with one person than with two, because then you don't have to coordinate how much force each person is applying. I would recommend the digital dial indicator. It is 22bucks at Harbor Freight, but worth the extra 7 bucks.

[Porsche_911s]

Bump for more opinions...

[Superman]

I put 20/21 cams in my engine when I freshened it. No other new stuff. Stock P&C's. 9.3:1 CR. Stock CIS. My impression is strong indeed. These cams make the engine MUCH better. Much wider power band. More power at both ends, especially down low. I enthusiastically endorse this grind.

I would also suggest you time them yourself. If you can remove an engine and remove the cams from that engine, you can certainly time cams. Certainly. In fact, it's a piece of cake. Also, you can time them so they are at this or that end of the range. My hazy recollection of my decision in this regard was to advance them. This helped create the low-end torque.

[camgrinder]

Originally posted by Porsche_911s
Thanks James! After the game I'll read up. The DC10 are a Dougherty grind that is in between a SC and a 964 for the 2.7. Probably similar to the 330.

The DC15 is the 330 grind. Also called Sport SC.

The DC10 has a slightly higher powerband, usually 3500 and up.

I also have a new profile listed, DC-19. Similar to that other profile.

[Jeff Alton]

Go with what John says! He has done a few sets for me and I have yet to see a dissappointed customer. He even did a custom (ish) grind for my 3.4...

Cheers

[SP2]

Hmm, DC 19. That sounds awesome. If John says you can put that in there, do that dude.

[Porsche_911s]

Originally posted by camgrinder
The DC15 is the 330 grind. Also called Sport SC.

The DC10 has a slightly higher powerband, usually 3500 and up.

I also have a new profile listed, DC-19. Similar to that other profile.

John,

Just to make sure I am clear, for my 2.7 EFI street car with stock Ps&Cs, you are recommending the DC19?

What is your opinion on the number of journals? I currently have the stock three bearing but did purchase the later cam towers for the four bearing cams.

Thanks!

[camgrinder]

Stephen,
I have not sold the DC19 for a 2.7 with stock pistons. I doubt they will fit without notching the pistons. They will work with EFI.
Its best to use the early cam towers on the 2.7. There are some late 2.7 4 journal, 47mm housings. But they would need to be drilled for oiling on the extra journal.

[Porsche_911s]

John,

What do you recommend? My original post was a dilemma on money for the performance gain. I don't want to spend the time or money switching out Ps&Cs to get a more aggressive grind if the performance gain from the grind is minimal. (I say this understanding higher compression pistons will provide more HP)

I guess what I am saying in a LONG way; can you recommend a grind that will work now?

[camgrinder]

I would use the DC10. It fits the 2.7 cis-s cores (911105144,911105143) and will clear the pistons.
Unless you do some head work, change the pistons etc, the more aggressive profile is not really an option.
The higher lift cams will benefit from some port work. They will need a better valve spring. The retainer to guide seal clearance will need to be checked etc.
A piston with higher compression will gain you low and mid range torque. The gains above the torque peak with a compression ratio increase, are sometimes minimal. They will however give you the piston to valve clearance for more aggressive camshafts.

[Porsche_911s]

Thanks John! I'll be contacting you as soon as I can schedule a window for the work to be done. (I have too many projects going on for such a small work area.)

You recommend going over the rockers as well correct?

[Superman]

Reconditioning rockers is the conventional wisdom......but Porsches are not conventional cars. One of our more experienced drivers and mod guys went to a machine shop with this question. He had an engine apart and was wondering if his rockers needed to be resurfaced and then of course re-hardened. He and the machinist did a little research and learned that the factory did an unusually good job of hardening them in the first place. So.....they put a rocker on one of those peening devices that tests the hardness of surfaces. Apparently, the business surface of a 911 rocker is just slightly softer than a diamond. Sure, that's an exaggeration but the machinist assured Eric that the business surfaces of his rockers are the same today as they were when they left the factory. No need to recondition. It would probably result in a new rocker surface that is the same as before, but with a less aggressive hardening treatment,

YMMV