IrocZS383

I am having trouble deciding which cam would go better with my combination of parts in my new engine. Here are my specs:

.040 350 (357)
Ported and polished iron heads, 2.02/1.6, 3 angle valve job, 58 cc chambers
Speed Pro skirt coated hypereutectics 2 valve relief (10.4 on 58 cc)
Pete Jackson Gear Drive
Siamesed Base, stock runners, ported plenum, stock tb, airfoil
Flowtech headers and y pipe, no cat, flowmaster
700-R4, stock converter, 3.23 rear gear

I would like to upgrade in the future to AFR or comparable heads, slp runners, better headers, possibly higher stall converter, bigger throttle body . . .

but this is the setup I have no so which cam would be better for now and in the future. I know I need a custom prom either way so thats no prob.

XR270HR
270/276 218/224 @ .050
.495/.502 (.528/.535 1.6 RR)
110 LSA

XR276HR
276/282 224/230 @ .050
.502/.510 (.535/.544 1.6 RR)
110 LSA

Thanks in advance for your help

BadBlue91RS

I'd go with the bigger of the two. Cuz the lift isn't THAT HIGH, but down the road, whe you do the other mods...you can slap a ser of 1.6 RR on it and it'll be like switching cams.

Just my .02

IrocZS383

Thats what I had originally decided to go with but I was concerned because Comp says the 270 is the largest cam for use with the stock converter. They say you need a 2000+ stall for the 276 cam. I am not concerned with regular drag racing, I just want a quick car for the street. I didn't know how big a deal not having the right converter would be.

gen3z

use the 276 and ditch the gear drive,i have seen proof that a gear drive pulls more than 25hp from the motor,yeah they sound cool but not at the cost of that much hp!!!!!!!!!!!!

Dyno Don

iTrader: (7)

Also you might want to go with 112 LSA 110 would be a bear to tune on a cam that size with TPI.

IrocZS383

They don't offer than cam in a 112 LSA for the hydraulic roller retrofit. I decided to change part of my combo. I am going to go with 64 cc heads which will give me 10.29:1 compression with .040" quench. Just a small change. Thanks for posting

SnkSknrZ28

iTrader: (2)

They can do a custom grind, same specs but with a 112lsa, problem solved! Shouldn't cost any more money either..

And definately go with the 276! They always put that crap about, this is the biggest u can do! Dont pay attention to it, HOWEVER make sure you check your vavle springs, you may have to change those to make that cam fit, but thats no biggie, it'll be worth every penny! good luck...

jimmy_mac

Here are a couple, they are listed as the same part # for retro fit and non retro fitl

XM270HR 12-417-8
270/276 218/224 @ .050
.495/.503 (.528/.536 1.6 RR)
112 LSA


XM276HR 12-418-8
276/282 224/230 @ .050
.503/.510 (.535/.544 1.6 RR)
112 LSA

http://www.compcams.com/Technical/Ca...ML/128-169.asp

I'm using the non retro fit xm270hr 8-417-8 with 112 lobe, wish I had gone with the xr276hr with 110 cause I'm running with a carb. The xm270hr is pretty mild but for TPI might be right.

GASGZLR

the 270hr is close to what a HOT cam is and it runs great. If you want it to be streetable without having to run a really high stall go with the 270. You could always put 1.6 RR on it too.

IrocZS383

I had looked at that cam after Dyno Don suggested 112 LSA. Its the same part number for retro and non retro but on a different cam core. I wasn't sure about it because it doesn't say anything about a car, just recomendations for marine applications. But if I just need to compare specs then that cam would work great. So you would recommend

XM276HR (12-418-8)
276/282 224/230 @ .050
.503/.510 (.535/.544 1.6 RR)
112 LSA

The cam listed for the computer controlled hydraulic roller is

XR276HR (08-503-8)
276/281 224/230 @ .050
.503/.510 (.535/.544 1.6 RR)
112 LSA

The only difference I see is the one degree reduction in advertised duration on the exhaust. But it does have the 112 LSA. What would the difference in the LSA do cause a choppier idle? Thanks for replying I'm actually getting somewhere.

jimmy_mac

I do believe the bigger lobe seperation will give you more vacuum to run the fuel injection. Although I don't know how much you would be giving up with 2 degrees. My brother runs the xr282hr with 110 lobe sep. in his 383 and has no vacuum issues with his brakes or anything. But he is using a carb also. But hey comp cams thinks 112 is better for computer controlled cars and all of GMs high perf cams for late model cars have big lobe seperations, so there is probably something to it.

Comp Cams is funny with all their part numbers. I got the XM270HR because the specs where what I wanted for the time when I was using TPI. And a guy was selling it cheap. The specs were identical to the computer cam so I figured what the heck. Well when I got it and the box said XM270HR but XR269HR was etched in the end of the cam. I looked that up and it was the computer version for cars. And the specs where identical So I think they put different part numbers on the same grinds.

On a side note I got a manifold real cheap from a guy on ebay. He thought it was a single plane and didn't know it was for vortecs. It came off a boat and said MARINE POWER on it. But in the picture you could see it was a vortec manifold and dual plane. So I got it for 50 bucks in almost new condition. The dimensions are identical to the performer RPM vortec manifold. So there are quite a few parts that interchange between marine applications and street cars.

IrocZS383

I was checking on the marine cams again and the XR276HR, the xtreme energy cam, is listed as being installed at 106 degree intake centerline and the XM276HR, the xtreme marine cam, is listed as being installed at 110 degrees intake centerline. This can be varied by where you install it as far as advanced/retarded, right? Someone please verify this for me. Thanks

IrocZS383

I forgot to ask has anyone installed one of these cams, and used all the recommended springs, retainers, seals, etc. I was adding up the cost and its like $900. Is all this necessary, I am especially curious about using the recommended seals. The cylinder heads I am getting will be cut for the 1.437" springs but I will be installing my own springs from Comp Cams, the heads come with PC seals but the seals Comp recommends are umbrella seals and they require the guide to be cut down. Is this required or will the pc seals work. Thanks again