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View Full Version : Compression question for those with Steg's big cam.



David Neibert
08-27-2004, 06:00 PM
I'm at stock 8.2:1 static compression and using the Stegimeier 240/240 cam. When I tested the compression last week all cylinders were 130-135 psi. It sounds kinda low to me. It's probably because of the overlap because I'm only getting 7 inches of vac at idle/park and 5 inches in gear.

Anyone else with this cam tested their compression ?

David

XR7 Dave
08-27-2004, 10:02 PM
I'm at stock 8.2:1 static compression and using the Stegimeier 240/240 cam. When I tested the compression last week all cylinders were 130-135 psi. It sounds kinda low to me. It's probably because of the overlap because I'm only getting 7 inches of vac at idle/park and 5 inches in gear.

Anyone else with this cam tested their compression ?

David

David, I think Gary's was only a little higher but he has a higher compression ratio. According to my sources, that is about right for your combination.

XR7 Dave
08-27-2004, 10:04 PM
With my cam the same motor would do about 155psi. :cool:

Bacondoggy
08-28-2004, 03:58 AM
With my cam the same motor would do about 155psi. :cool:


8.2:1 static compression

you guys are wierdos :-P LOL I have had an aftermarket cam in my SC (doesn't matter because it is currentlly trashed - if I can fix it I will see you at the MN12 nationals - your not gonna miss it?!?!)
is there a way to tell how it was a regrind? I mean I got the sc with crazy mods. It is not the same, I but the stick gears back init it hat 3.27 gears in and bored 30 over (whoever did all this madness put bottom spacers in the top of the crank so no oil could get to the rod - the cylinders still had hone marks on it!)

ok maybe I am as strange as you, but I don't know about inches/vac in park.... but you all have AOD's so you THINK (haha) you would smoke me... LOL my car would be going sideways while you are 50' ahead...

David Neibert
08-28-2004, 09:41 AM
Bacondoggy,

We may be weirdos....but what does that have to do with compression ratios and cylinder pressure ?

Sorry I won't be at the MN12 Nats this year and will be attending the SC Shootout instead. If you can get your car running in time, you should really consider attending. BTW, If you make it I'll be happy to race you and see who smokes who.

David

RancherV6Lee
08-28-2004, 01:13 PM
man, 240/240 seems like WAY too much cam to me. With my mild 205/216 .477/.495 lift cam my car made peak HP @ 4700rpm N/A and peaks over 5500rpm with the vortech supercharger (I say peaks over 5500rpm because I had them stop the pulls at 5500rpm and the HP was still climbing good.

Whats the lift on that badboy? seems like that much duration would kill the best aspect of a roots blower, low-mid range torque.

David Neibert
08-28-2004, 04:21 PM
Rancher,

With the rockers I'm using (1.6) it only lifts the valves .539. The vacuum sucks too and wouldn't be enough in a 93 or newer SC to operate the brake booster. I liked my old cam much better (same as Chris Wise had) and it only had 226 intake and 239 exhaust with .600 lift using the same rockers and had twice the vacuum and alot more snap off the line.

Like the old one, this one peaks around 6000 and still has enough bottom end torque to light the tires up at will, but does require overdriving the supercharger a little harder and advancing the timing another 2 degrees to feel like the old one. Instead of 23% overdrive, I'm now maxed out at 26% (18-19 pounds of boost) which is hard on the blower bearings and seals, not to mention the amount of power required to spin it that fast.

The only good thing about it, is that it's not as rough on the valvetrain which is something I broke about every three months with the other cam. Revving it to 6500 probably didn't help either.

David

XR7 Dave
08-28-2004, 09:49 PM
man, 240/240 seems like WAY too much cam to me. With my mild 205/216 .477/.495 lift cam my car made peak HP @ 4700rpm N/A and peaks over 5500rpm with the vortech supercharger (I say peaks over 5500rpm because I had them stop the pulls at 5500rpm and the HP was still climbing good.

Whats the lift on that badboy? seems like that much duration would kill the best aspect of a roots blower, low-mid range torque.

That's because you have a Vortech. :p That blower always skews HP higher than normal because it is building boost at a faster rate near redline than it is at any other rpm. That same cam would peak HP at about 4900 on a roots car.

My 210/220 cam with .513" lift peaked HP at 5200 on my M90 car and 5500 with the AR. With an auto performance below 2500 is a non-issue and once you get to 4000 (about .5 seconds in David's car) torque has evened out and the 240 duration is happy all the way to 6500rpm. Of course in David's case, his M90 is not happy at all above 6000rpm so it's a catch 22. :cool:

David Neibert
08-29-2004, 10:21 AM
Dave,

As soon as I get this 347 turbo SC road ready, I'll be looking to upgrade my MPII to a 1.7 AR. Until then, I'm just gonna overdrive the crap out this M90 and hope it's enough to hang with the whipple and autorotor equipped SCs.

David

XR7 Dave
08-29-2004, 11:36 AM
Dave,

As soon as I get this 347 turbo SC road ready, I'll be looking to upgrade my MPII to a 1.7 AR. Until then, I'm just gonna overdrive the crap out this M90 and hope it's enough to hang with the whipple and autorotor equipped SCs.

David

Hehe, not a chance. :p