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View Full Version : Camshaft Suggestion - from Comp Cams - thoughts?



bingham72
08-06-2008, 05:46 PM
Ok, so I've gotta get a new camshaft because I rounded off a lobe on the old one. I filled out the form on Comp Cams website and they got back to me with this recommendation.

I think it might be too much for my car. What do you guys think?
Car specs.
358 SBC
EDELBROCK PERFORMER RPM HEADS
LT-1 port matched factory manfold
780 Holley Street performer carb
HEADERS
MUNCIE M-21 4 speed
3.55 rear end

Comp Cams XR294HR-10

INTAKE MASTER 3317S
EXHAUST MASTER 3318S
ENGINE CS XR294HR-10
GRIND NUMBER CS XR294HR-10
INT EXH
HYDRAULIC Y/N YES DUR @.050 242 248
INTAKE EXHAUST LOBE LIFT .3600 .3750
VALVE ADJUSTMENT HYD HYD ROCKER RATIO .00 .00
MAX GROSS VALVE LIFT .540 .562
DUR @ .006 TAPPET LIFT 294 300 LOBE SEPARATI 110.0
ADVANCE 4
VALVE TIMING OPEN CLOSE VALVE SPRINGS 987-16
.006 INT 41 73
EXH 84 36
THESE SPECS ARE FOR CAM(S) INSTALLED
106.0 INTAKE CENTERLINE

Lowend
08-06-2008, 05:57 PM
That's pretty big for a 358 with not much gear

bingham72
08-07-2008, 08:04 AM
That's pretty big for a 358 with not much gear
Thanks, that's what I was thinking. Back to the suggestion box.

Blown353
08-07-2008, 11:29 AM
I ran a XR294HR in my 353 years ago; 200cc Dart Pro-1 heads, Dart single plane later changed to an RPM air gap. 1.6 rockers on the intakes.

The cam had a nasty idle but and was really soft below 3500 rpm.

Made 455 hp / 435 ft-lbs on a SF-901 engine dyno. Peak HP was at 6100 rpm.

Sounded nasty but didn't work so hot in my 3700# Chevelle with 3.42 gears, it was just an all around mismatched combo. Not enough bottom end power for the weight and the gears. Started to get entertaining above 3500 rpm but was a total dog below that.

In a much lighter car with lower gears it would have been a lot of fun-- but even then I agree that the XR294HR is too big for 358 cubes.

Lowend
08-07-2008, 11:50 AM
I'll recommend the Crower 0470 (http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00470&x=0&y=0)
more suited to your setup.

I would even go so far as to get a wider (112 - 114) lobe separation in this engine assuming the compression is around 9.7-1

bingham72
08-14-2008, 06:39 AM
I'll recommend the Crower 0470 (http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00470&x=0&y=0)
more suited to your setup.

I would even go so far as to get a wider (112 - 114) lobe separation in this engine assuming the compression is around 9.7-1

Ok, so comparing the cams, the Crower looks like it has a shorter duration, but more lift on the intake side at .550 and a little less on the exhaust side at .560. Both have a 110 lobe separation.

How is the Crower work better for my setup?

Lowend
08-15-2008, 05:40 PM
It's a more aggressive lobe with less duration. It will tend to keep the engine in the powerband at lower RPM. The cam will go to 7000RPM if you ask it to in that motor.
Realistically the higher duration comp cam will just cost you torque on the bottom end, and with the RPM heads it won't really gain you anything on the top

yellow heap
08-15-2008, 05:56 PM
What Is your comp ratio gonna be?
I would go a bit smaller than even the listed Crower with rpm heads
unless your compression is at least well into the 10's.
With the m21 3.55 combo your first gear is close to my second gear,with a xr294 and even the Crower your car would be a dog until 5000rpm.
I would start lookin at a cam in the 220-230 range with a lsa of 108-110 to build some torque.
If your lookin to stay with a Comp hyd roller I would start lookin at a XR276hr or any other cam company with a similar spec for your setup.

DeltaT
08-18-2008, 01:17 PM
I like the Comp XFI cam for your motor and gears:

P/N 07-466-8, 218/224 on a 113LSA
RPM 1800 to 5800
Lift .570/.565" w/1.6 rockers

You will not regret going slightly small on the cam, but I often see people regret going too big.

Jim

bingham72
12-15-2008, 06:33 PM
ok, back to the top... since it is Christmas and I still haven't gotten a replacement cam, I'm looking.

So I've decided on a more standard setup, flat tappet camshaft. I downloaded the Compcams software to make an informed decision.

My 2 choices are these
XE268H or XE274H. I think the later might have a little better top end with the former more torque, but it seems it's a wash to me.
both around 420 hp, 430 ft/lbs Any thoughts, there

Also, in toying with the application to see what other engine adjustments might make a difference, I changed the intake selection from DualPlane - High Performance to Dual Plane - Max Performance and the numbers JUMPED to the 470 range.
That seems like a HUGE jump for an intake swap, so my question is this; what would you guys think is the difference between a High Performance Dual Plane manifold and a Max performance one?? Would it be porting, runner length?
I estimated a High performance manifold base on the semi-stock LT-1 intake I'm using (1970's LT-1 that is). I've gasket ported it to match the Edelbrock heads. Any ideas what this would really convert to and what might be a better choice?


Thanks in advance! I hope to have the car back out after Christmas and maybe validate these numbers on a dyno soon there after!

CarlC
12-16-2008, 10:58 PM
I the long run a dual plane will be nicer to drive. The Airgap has been shown to perform better overall in both street and drag racing applications for engine builds like yours. I'll find the link on my other computer.

I'll also try to dig up the link to a mag article on a previous engine that I had. 350, XE268, ported cast iron Bowtie, dual plane, etc. Very similar to your proposed build. It was fun to drive and made 440hp on the dyno.

bingham72
12-18-2008, 08:02 PM
I the long run a dual plane will be nicer to drive. The Airgap has been shown to perform better overall in both street and drag racing applications for engine builds like yours. I'll find the link on my other computer.

I'll also try to dig up the link to a mag article on a previous engine that I had. 350, XE268, ported cast iron Bowtie, dual plane, etc. Very similar to your proposed build. It was fun to drive and made 440hp on the dyno.


I'd be extremely happy with 440hp. 400 would be fine with a nice torque curve. We'll see what Santa brings. I'll definately be browsing Ebay for an AirGap Intake now.
Thanks!

CarlC
12-18-2008, 09:40 PM
Here's a little light reading for ya.

http://www.classictrucks.com/tech/cl_0312_choosing_carburetor/index.html

http://www.popularhotrodding.com/tech/0406phr_edelbrocks_air_gap_performer_intake_manifo ld_tech/index.html

bingham72
12-29-2008, 10:02 AM
Thanks for the reading assignments Carl.

I got a XE274 instead of the XE268. I've pulled the motor apart already and pulled the old cam. I'll have to post some pictures because one of the lobes is rounded off. Makes me wonder where all that metal went. I'll post some photos of the subsequent installations and break in this week. Should be fun to hear the motor fire up again!

streetk14
12-29-2008, 12:27 PM
Looks like you made a choice, so my advice is really not relevant any more. But...... I'm glad that you did not get that XR 294HR. I had that cam in a 360 ci small block with AFR 195 heads and a TKO trans (3.27 1st) and 3.89 gears. It was fine with my very aggressive gearing, but is not for what you have. I also had very good flowing heads to better take advantage of the high rpm power. Not that the Edelbrocks are bad, but not ideal for such a cam.

I would have advised going hydraulic roller, the only downside is the price. Something like the GMPP Hot cam would have been very nice. I actually had that cam with Edelbrock RPMs years ago and it was a very good street combo.

Anyway, look forward to seeing what your new combo can do.

bingham72
12-29-2008, 01:30 PM
I really wanted a Hydrollic roller for all the reasons, but just cannot manage the additional cost. I just want to get it on the road now. I need the therapy only muscle cars can provide.

Skip Fix
12-29-2008, 02:51 PM
"Makes me wonder where all that metal went." Bearings and oil passages!
Better think of a tear down and clean up.

FWIW alot of the Pontiac guys are using the 288HR in bigger motors. Think their 290+ is a little big.

If using another flat tappet are you going to break it in with just the outer springs first? Use a high ZN oil or additive? If not another flat lobe can sure happen.

bingham72
12-29-2008, 05:12 PM
"Makes me wonder where all that metal went." Bearings and oil passages!
Better think of a tear down and clean up.
That certainly crossed my mind today.



If using another flat tappet are you going to break it in with just the outer springs first? Use a high ZN oil or additive? If not another flat lobe can sure happen.
I've considered taking out the inner springs, but DEFINATELY using the ZiNC oil additive (Comp cams PN 159) with Diesel oil for break in. Kinda sucks it's such a pain now.

Skip Fix
12-30-2008, 01:14 PM
There are some companies like Crower than have 1.3 ratio break in rockers where you don't need to pull the springs.

Cut your old oil filter apart, if there is metal it needs a tear down before it hurts more things.

bingham72
12-30-2008, 05:22 PM
There are some companies like Crower than have 1.3 ratio break in rockers where you don't need to pull the springs.

Cut your old oil filter apart, if there is metal it needs a tear down before it hurts more things.

do I really need to reduce the spring load? This is turning into a complete PITA. Time to break down the oil filter.

yellow heap
12-31-2008, 11:32 AM
That's the reason I run rollers now-flat tappet break in now seems to be a roll of the dice-I would pull the inner springs(Fix the dice) and what ever else possible.
By the way-good choice on the xe274.

bingham72
01-02-2009, 11:41 AM
That's the reason I run rollers now-flat tappet break in now seems to be a roll of the dice-I would pull the inner springs(Fix the dice) and what ever else possible.
By the way-good choice on the xe274.

Cool, thanks! Have you run this came before?
I'm definately going to pull the inner springs. I've got the spring compressor from a past replacement, just have to locate the sparkplug tool to keep pressure in the cylinders while I do it. I've been battling the a winter cold, but hope to bring this bad boy back to life this weekend.

yellow heap
01-02-2009, 06:05 PM
I built a 327 with E rpm heads and that cam-It was strong and had decent manors and sounded nice.

bingham72
01-03-2009, 11:08 AM
Awesome! I just returned from the local speed shop with breaking fluid, a new fuel pump and regulator. It won't be long now..