Cam Selection for 2.7L

[jksinuc]

I have a 2.7L CIS. I am currently gathering parts and information for a re-build. What cams should I be looking at for the following conversion. The Bruce Anderson handbook recommends "E" cams. I have posted similar questions before and someone said that the "E" cam would be too revvy.
Any advice would be greatly appreciated.

Upgrades Already:
11-Blade Fan
Pressure Fed Chain Tensioners
SSI Heater Boxes with B&B Sport Muffler
Breakerless Ignition

Planned for Rebuild
PMO 40-IDA-3C Carbs
Euro RS P&C's 9.5:1
Heads Rebuilt with 36mm ports (new valves/guides)
Port and Polish
Align bore the Case
Timecert and Raceware studs
New Cams when I figure out which one.
Re-curve the distributor
Re-build kit (Bearings, gaskets, etc.)

[Bill Douglas]

Read Matt's post http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=54183 It's enough to get my little heart beating....

[RoninLB]

GE-60 is a fine cam. My attitude is its intended use. Street and track are different worlds. I would like to know how long plugs last on the GE-60 I will install E-cams because it fills my needs. '65-'66 Solex with some porting is a great street set-up. I had an engine in days of old that needed plugs every Mon. morning after a weekend of street racing. Didn't bother me then because that is what I wanted. It wasn't good enough to win, someone had to lose.

[Early_S_Man]

I do not understand why people fail to understand that the larger displacement of 2.7 and 3.0 engines 'tames' the 'S' cams characteristics from what people have read about (and I have to assume they have NEVER driven a 2.0 or 2.4 'S' car to compare their 'peaky' nature) from the days of the 2.0's! The 2.4S is NOT that peaky, and the RS 2.7 ... EVEN LESS SO!

The RS 2.7, using the same cameas my 2.4 has, has more torque than my 2.4S has at PEAK (216 Nm @ 5200 rpm) all the way from 3300 rpm to 6700 rpm! That means considerably MORE FLEXIBILITY, NOT a 'peaky' character!

And, finally ... people talk of the GREAT torque of the 930/10 "Euro' SC engine, yet the RS 3.0 engine with its' peaky 'S' cams had MORE torque than the best SC engine! Try ... 203 lb-ft vs 189 lb-ft ... on for size!!!

__________________

I assume by: "Euro RS P&C's 9.5:1" ... you mean that JE 9.5:1 pistons with valve relief cuts will be used in Nikasil cylinders, as there weren't any 9.5:1 'euro' 2.7 pistons!

My recommendation is for 'S' or GE-60 cams.

[RoninLB]

All thoughts well considerated. Bottom line IMHO is that all different cams do different things in different aplications. Thankfully I can try what feels best for my needs and change it [no big deal] when ever.

[kstar]

Originally posted by Early_S_Man

I assume by: "Euro RS P&C's 9.5:1" ... you mean that JE 9.5:1 pistons with valve relief cuts will be used in Nikasil cylinders, as there weren't any 9.5:1 'euro' 2.7 pistons!

My recommendation is for 'S' or GE-60 cams.

I am now in the midst of re-rebuilding my MM 2.7.

I have found that Andial has a 9.5 to 9.7:1 90mm custom Mahle piston! I want more compression than the standard Euro RS which is 8.5:1, I think.

I was going to have WebCam regrind my Solex cams to "S" spec, but you have me looking at the GE-60 now!

How much do the GE-60s run in $s? I was looking at around $600 for the Solex to "S" regrind job . . . or can WebCam regrind to a GE-60 profile?

Also, are more robust springs and Ti retainers a must for a top-end that will see excursions to 7300RPMs+?

Thanks in advance!

Best,

Kurt

[911pcars]

Don't forget that a change to aggressive cams must be accompanied by verifying there is adequate piston-to-valve clearance, then machining deeper valve pockets in the piston crown accordingly. In addition, if you're starting from a CIS-based engine, any agressive camshaft must be accompanied by a change to pistons with the proper non-CIS crown shape. Even swapping an S in place of an E cam (or whatever) is not recommended without verifying there is sufficient clearance as the piston/valves are dangerously close at the TDC, overlap position; more so if the pistons are supplying a high compression shape. You don't want these parts to "kiss" at any speed.

Sherwood Lee
http://members.rennlist.org/911pcars

[jksinuc]

Thanks for all the input.

Warren, you are correct. I was attempting to refer to the the JE 90mm 9.5:1 P&C's which I now know is different from the Euro RS P&C's.

[Oldporsche]

The "E" or "Solex"(slightly more agressive than the "E") cam grinds are probably the best compromise for the compression ratio of the euro-rs pistons for street use. (EuroRS piston=8.5:1)

Cam choice has to do with a delicate balance of compression ratio and relative useable rpm range. This evolves into an effective-mean cylinder compression discussion.

If you have more compression you can use a more agressive cam profile without hurting your low rpm street use. As your displacement grows your agressive cam profile becomes softer. This again is related to your effective-mean cylinder discussion.

I would suggest your read Steve Weiners Web-site notes completely. He's been there and done that many times!

Good Luck,
David Duffield

[jluetjen]

Where can we find Steve Weiners Web-site notes???

[cds72911]

Good stuff....


http://www.rennsportsystems.com/~porsche/2.html

[J P Stein]

The Rennsport site pretty much covers it all, but don't pass up the part about your intentions for use of the car.

I was faced with these decisions a while back.
My 2.7L has 9.7:1 Shasta pistons, Webers with the long aux venturi, a bit of port polishing. My use is street and AX....so, cam choice. I did Solex and am not sure I'd do it again. Above 4K rpms, the engine is wonderful, but driving around at 4K on the street is a PITA. Since my car is light, there is enough torque down low, but all that cam overlap effects running smoothness at low rpm. It's kinda herky, jerky.
I am still at work to resolve this by some ignition and carb tuning tweaks, so the final verdict is not in. More lower end grunt would be nice at the AX, but the shape of the torque curve is *mostly*
influenced by the cam grind/ compression.

Cam overlap is overlap. "Stuff" flowing the wrong way is just more noticeable in a smaller engine.

I was thinking about an S grind, originally, but Mr. Weiner talked me out of it based on the car usage. It was good advise, me thinks. He spoke of the "reversion" causing tuning problems
with Webers.
I probably should have gone with E's.

I suppose, the only way to find out what one wants/needs/likes is try a grind and live with it a while.

A pair of Solex cams (one NOS and one unused since being "touched up" by Web Cams)were $300 from a good fella in Canada. Spending $1K on a set of "maybe" cams doesn't appeal to me.

[RoninLB]

JP......Stoddard has E-cams that list for $625 for set. With my std. 10% disc. and 10% winter sale the total should be $512

[jksinuc]

In addition to the conversion information, I probably should have included what I am going to the use the car for. I may do a little autocrossing at some point, but I also want a car that is still streetable. I am willing to give up a little performance to have some low end torque and the ability to drive to the store and not keep the car above 4000 RPM the whole way.

I guess that I am leaning towards the GE-60 and the "S" cam.

[J P Stein]

The way I read the specs for these various cam grinds.....

Best bottom end to worst:

E, Solex, S, GE60.(maybe a toss-up between these last 2)

A 'T' grind is better than any of these. Torque starts right off idle, but it runs outta gas about 6K. Prolly sooner in a 2.7L.
Just my .02.

[john walker's workshop]

if you want good bottom end, the solex cams are hard to beat. the S cams in a 2.7 pull well on top end, but the bottom end lacks, and the engine feels like you need to downshift to get the revs up when you're cruising around with light throttle. it's annoying to drive at the local speed limit of 30-35 MPH. the solex cams are so smooth, you could lug it down to 1500 RPM in 4th, and accelerate up to speed again without downshifting.

[J P Stein]

Lug it down, eh?

Here's some specs:

duration deg- lift- lobe center deg
E- 229/223 (int/ex)- .408/.393- 102
Solex- 244/234- .439/.406- 97
S- 267/235- .459/.396- 97

While setting the cam timing (around 4mm @ overlap tdc)I could look into the intake port and see daylight thru the exhaust.

The Solex are nice cams, about half way between the E and S , but there isn't a huge amount of difference between them and the S. Bottom end isn't a strong suit of my engine...........but I'm workin' on it :-).