SteveG75

Here is the current situation.

Currently running an Comp Cams XE262 cam with 1.6 rockers in a 355 (4.030 x 3.48) with 10:1 static compression. I feel that I have too much dynamic compression ratio based on the relatively quick intake closing event of this cam. I have had to retard the timing a couple of degrees on pump gas and I have so much low end torque that traction in first is a serious issue.

I was thinking about stepping up to something in the 230+ at .050" lift range. I was thinking about either a Comp Magnum or a Crane Powermax series. I like the fact that the lobe separation angle is slightly wider on the Cranes as well. (Previous cam was a Crane).

I was also looking at solid lifters as well. Dyno 2000 shows that I won't loose as much low end with the solids vice comparable hydraulics. I know about the lash requirements but I figure that good rollers with polylocks will help there.

I was looking at the following:
1) Crane Powermax 278 solid. 238/248 @.050" with .480/.500 total lift. 3000-6500 RPM range.
2) Crane Powermax 288 Hyd 226/234 @ .050 with .458/.473 total lift. 3000-6000 RPM range.
3) Comps web site is harder to look at but probably something like a Magnum 270 or XE274 from them.

The motor has 5000 miles on a rebuild. 2 bolt mains with ARP bolts so I figure that the occasional blast to 6000 rpm is my limit. The Vette is also now a true weekend/fair weather car since I just got a new 2003 Avalanche last week (sweet truck) so the bigger cam should be easy to live with.

As for vacuum considerations, Hydroboost and electric lights are on the list for the winter.

Any ideas, criticisms are welcome.

MotorHead

CC270H is a great cam if you have good open exhaust :D

cardo0

How ‘bout a tighter lobe sep angle (LSA)? This will increase overlap and reduce dynamic compression. Iskenderian (Isky) has a Mega Cam with a 108* LSA. Vizard (the wizard) says the 108* LSA is optimum for a 350 Chevy producing the most torque. With 10:1 c.r. I think the 270-Mega Hydraulic would be a good match. This cam has 221* at 0.050”. But you mention having to retard timing and widening the LSA will make this worse unless your duration is large enough to increase the overlap. No free lunch here. Now the wider LSAs will make more power top end and the 108 is best for mid range torque.
I’ve never driven a large cammed car but the Crane charts for Powermax 230* at 0.050” say rpm range is almost 3,000 to 6,500 where the Isky 270* is 2,000 to 6,200 rpm. But if you do go with the large cam please post your impressions good or bad. :D

Matt Gruber

i am :confused: .
i have the xe262 w/1.6 in my 72. it uses 87 octane and runs great. 9.65:1.
Perhaps the 5 speed has too low a 1st gear?
Maybe too much air in tires? Try 24 psi.
No spare?(ballast)add tools, spare tire,
I think a 3.08 rear would solve the problem(what is in there now?)


[Modified by Matt Gruber, 8:29 AM 10/7/2003]

The Money Pit

I know everyone has there own opinion of the perfect cam for the perfect combination,but this is of course subject to the opinion of the owner of the car. I called Comp Cams when choosing mine,and against my better judgement,listened to them and got a smaller cam than I'd planned. As it turned out the 406 shreaded the tires and ran out of rpms too soon. I recammed the engine using the cam I thaught would work,and it suits me fine.This is my opinion,someone else may not like the lumpy idle.

In all the dyno tests and buildup articles I've read,it seems once you exceed 230 degree intake duration,the peak torque numbers begin to drop,though the hp numbers go up do to rpms.The trick in a street engine is to keep the most useable torque in a range you can still play with the rpms for the "fun factor" I would try the Comp XE-268 ,or 270H in a 350,and certainly nothing larger. These should keep the peak torque up,and still hit 6000 rpms for fun.

SteveG75

Matt,
The Tremec has a 3.27 first. Combined with my 3.36 rear, first gear is pretty steep. I don't want to drop to a 3.08 since right now I cruise at 70 at 2000 rpm and don't want to go much lower. The XE262 is designed to build cylinder pressure with a very quick intake closing event. With my 10:1 compression, I figure I can go to a bigger cam without too much trouble.

Dyno 2000 (I just uses it for trends really) shows that the Crane solid will lose about 30 ft lbs at 2500 rpm and pick up 50 HP at 5000 rpm. Peak moves from 5000 to about 5500 rpm which is fine with me.

I am also thinking that solid lifter will be fun. The other option is a Comp XE274 but that may move the power band too much.

bertmeister

I am also thinking that solid lifter will be fun.
Adjusting solid lifters means less driving time :steering:

Matt Gruber

go with the crane solid. with a rev limiter.
checking the lash once a year is no big deal.
the 114 LSA will give better mpg too! :steering:


[Modified by Matt Gruber, 7:03 AM 10/8/2003]

tsw71

I had thought about the crane 278 solid, but ended up going with the comp 282s. The crane will make a bit more power up top, but will peak later than the 282S and torque down low will suffer. With your near stock shortblock, the 282s will make good power and torque with out the need to rev past 6000rpm. The comps torque curve is very flat making close to peak torque right of an idle and remaining past 3500.