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roller cam selection for my monte ss

4K views 37 replies 8 participants last post by  redbandit98 
#1 ·
Yes, i am the guy that you hate because I started another cam thread. So be i need some help here. :confused: Ive putting together a 355 chevy for my monte carlo ss. It will have 3.73 rear gears, a 2k to 2500 stall, ~9.2 compression with the 62 cc iron vortec heads im putting on it. The block is still getting worked over at the machine shop. My plan is to get the shortblock done, and install some "upgraded vortec heads" from scoggin dickey. They have the bigger springs and the valve guides cut down to accept up to a .575 lift roller cam. I was going to go with the "hot cam" kit, but read if i use the 1.6 rockers that come with the kit, i would have to mill out my pushrod holes due to cleareance. I dont want to do all that. Im looking for bolt on and go. I called comp and they suggested a xr282hr. I think that may be a bit much for what im wanting. It will be strictly a street driven car. I do want it to have some growl to it, but I also want it to have plenty of vacuum since i will be running power brakes, vacuum operated hvac etc.. After all of this, i think a good option would be teh comp xr276hr cam using a set of stock 1.5 rockers. A nice roller cam with a little thump but good street manners. I may be totally off, and if anyone has better suggestions, please let me know. Also, im not dead set on a comp cam, thats just what i have been looking at. I had a lunati cam take out a 4k dollar ls1 that i built for my trans am so im not to hip on them.

EDIT: I forgot to mention that this will be a factory roller style cam, not a retrofit. Not that it matters a whole lot i assume. I have a factory roller one piece seal block to work with.
 
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#27 ·
redbandit98 said:
well, its too late for that now. I went and picked up the short block the other day. I just told them i wanted the flat tops in them, didnt specify a part number. Apparently they didnt deck the block any and used the 345np cast sealed power flat tops. (.040 over)

nope the 345's. I was going to get the hp345s to replace them. I thought i read they were the right height. I would look at federals website but its useless.
 
#28 ·
Seriously why are messing around with all these crappy pistons, get a forged two valve relief piston. TRW sells a set for 300 bucks. They weigh a little less than your hypers and are twice as strong and are designed to come out to -.010 in the hole with no machining. You are about to drop a lot of money on the top end so spend a little extra on the bottom and do it right. Just my opinion...take it or leave it.
 
#29 ·
Double_v23 said:
Seriously why are messing around with all these crappy pistons, get a forged two valve relief piston. TRW sells a set for 300 bucks. They weigh a little less than your hypers and are twice as strong and are designed to come out to -.010 in the hole with no machining. You are about to drop a lot of money on the top end so spend a little extra on the bottom and do it right. Just my opinion...take it or leave it.
x2
Just like Double_v23 says above,do it once and do it right.Getting your quench area right should be of concern to you.Having your rotating assembly balanced should also be on your "to do" list.
Guy
 
#31 ·
alright, Im gonna leave you guys alone after this. I have one more question. Like I said, im putting the kb-120 pistons in it now. This should put me back to where i need to be as far as the quench height. I have pretty much decided on the comp xr276hr cam, it was between that or the xr282hr. I think the 276 will do better for my street duties. Now the last question, I am trying to decide on heads. I am leaning toward the aluminum fast burns from gm. They are a little more than the cast vortecs, but not quite as much as some of the higher end brands such as the afr's. Do you guys think it would be worth it to upgrade to the fast burns or not?
 
#36 · (Edited)
Be sure you follow KB's instructions on the top ring gap, which needs to be 50% larger than what most other pistons require.

I suspect you'll be OK with 10.2:1. Somebody on this board mentioned that he had no detonation problems with an engine basically the same as what you're building, except for a Comp 268 cam.

I checked Comp's site just now and couldn't find a CR recommendation, but I found Crane's recommended range for their 276* hydraulic roller, which is 8.75 to 10.75:1.
 
#37 · (Edited)
well, its getting down to the nitty gritty. I did some number crunching, i think im pretty close on it. With the standard size deck, pistons (7cc flat tops), and .035 gasket the calulators i used came up with a 9.74 cr with 64cc heads. With 72cc heads, it put me at 8.98. I dont know if im comfortable running that high compression with the 64cc iron head vortecs. I mean I hear oh yea thats fine , then I read in some magazine article that your crazy to run anything over 9.2. on iron heads. I dont know. :sweat: . As far as the 10.2 that is thrown out the window. I emailed keith black and they told me their figures are all based on a zero deck block.
 
#38 ·
ok, the numbers are in. I picked up my shortblock today and got it home and measured it. The piston to deck height was .024 I emailed keith black and they told me their pistons were designed to be ran from .040 to .055 quench. With the gm .028 gasket i would be in their recommended quench. The only thing is Im worried about the compression with the 64cc heads. Ive convinced myself to go ahead and get some 76cc heads. This would put me right at about 9.1. I have been searching for some good iron 76cc heads. I saw where rhs makes some vortec heads that actually have the 76cc chambers. The only thing is I cant seem to find any with a straight plug that are already assembled. No huge deal but i would like to find a set that are ready to go. The thought of buying some in a 64cc in aluminum has crossed my mine, but they are some serious coin.
 
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