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Old 05-16-2010, 07:18 PM
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Recommended cam for roller 355 LT1 heads

Hey guys I've been debating on a cam change for my 355 4 bolt. It has fully ported LT1 heads, 1.7 rockers modified to work on GENI blocks. It has hyp. flat top pistons 2 valve reliefs. It currently has a zz4 cam in it. I am looking into going stronger but would like an opinion. By the way the heads are ready for big lift. Intake is a 300-36 Holley and db Holley 750.

Any suggestion would help.

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Old 05-16-2010, 11:21 PM
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Wait... are we talking about LT1 or LT-1? Late model LT1 heads won't work on a first gen block.
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Old 05-16-2010, 11:33 PM
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Quote:
Originally Posted by curtis73
Wait... are we talking about LT1 or LT-1? Late model LT1 heads won't work on a first gen block.
They will with proper work done to them Curtis, Bogie went through this recently on another thread.

355Nova, if you can get me all the info on the motor, I'll run it up on DynoSim and help you choose a cam that will work. I need head flow 0.100" through 0.700" with valve sizes and static compression ratio.

Was there no high-rise intake that would work on these heads?
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Old 05-17-2010, 07:50 AM
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Quote:
Originally Posted by techinspector1
They will with proper work done to them Curtis, Bogie went through this recently on another thread.
Agreed, but welding and machining a casting just to swap factory heads seems a little out of the budget for most folks.

I've seen it done once.
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Old 05-17-2010, 02:29 PM
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Specs

Well heads were welded and redrilled with a mig welder. Not costly though. Suprisingly it was 150 a head. The 300-36 intake fit perfect but I had to weld and redrill the sucker also lol! It has a very very fast response.

Flow is .400, Static compression is at 10.73, valves 1.94 & 1.50, I believe the flow was around 221 cfm flow after the port work. I couldn't really go bigger in valve size they were pretty much maxed out. Block is 4 bolt 350-.030 over
I don't really know the specs on the Holley 300-36 I've looked all over but no success yet.
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Old 05-17-2010, 02:35 PM
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Quote:
Originally Posted by 355Nova
Well heads were welded and redrilled with a mig welder. Not costly though. Suprisingly it was 150 a head. The 300-36 intake fit perfect but I had to weld and redrill the sucker also lol! It has a very very fast response.

Flow is .400, Static compression is at 10.73, valves 1.94 & 1.50, I believe the flow was around 221 cfm flow after the port work. I couldn't really go bigger in valve size they were pretty much maxed out. Block is 4 bolt 350-.030 over
I don't really know the specs on the Holley 300-36 I've looked all over but no success yet.

221? Are you sure? That's awfully low.
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Old 05-17-2010, 03:24 PM
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If you didn't get a bar chart with the head work, how do you know anything about them? Did you just walk in and tell the guy to grind on 'em and you would hand him money?

Scroll down and look at this orange and blue bar chart from Racing Head Service. This is what I would expect to see when I picked my heads up and I would expect it to reflect some improvement over stock for my money. If you didn't see a before and after comparison of the flow, the heads could be worse now than they were stock. I hope you see where I'm coming from with this.
http://www.racingheadservice.com/Inf...Charts_New.asp

If you flew into this whole head porting thing blindly, you have more money to waste than I do.
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Old 05-17-2010, 03:29 PM
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Of course

Not a problem I did recieve a document like that one. I will get those numbers in as soon as I can you for.
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Old 05-17-2010, 04:24 PM
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.100 72 int 56 exh
.200 140 int 104 exh
.300 195 int 144 exh
.400 231 int 171 exh
.450 236 int 172 exh
.500 262 int 184 exh
.600 260 int 193 exh

Exhaust / Intake Index
72.01 %

Flow Index
921.09 I can barely make this one out paper is faded a little

Please let me know if you need any other information.
Thanks a bunch!
JD
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Old 05-17-2010, 08:17 PM
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Well, flyin' by the seat of my pants, I have figured the static compression ratio at 10.57:1 and have researched and found the specs on a ZZ4 cam. Intake opens -8, intake closes 36, exhaust opens 42.5, exhaust closes -1.5 for an intake duration of 208 and exhaust duration of 221. Lift with 1.7 rockers is 0.532"/0.541". Intake centerline is 112, exhaust centerline is 112, lobe separation angle is 112.

I never thought I would find myself sayin' this, but leave this motor alone. If you want more power, build a bigger motor. This one is maxed for a 355 street motor. More cam will make 20-25 more hp, but the best cam I tried will not make more torque than the ZZ4 cam makes in this motor. In my opinion, it would be foolish to change cams just to make a little more hp and the same or less torque than you're making now. Here is your motor on the DynoSim. Gobs and gobs of torque right from the git-go. If you're not rippin' the tires off from an idle, then your tune is off.

RPM HP TQ
2000 159 416
2500 211 443
3000 253 444
3500 300 450
4000 342 450
4500 375 438
5000 395 415
5500 405 384
6000 372 326
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Old 05-17-2010, 10:03 PM
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First off Thanks Techinspector! Yeah the engine accelerates very very quickly. Very good engine. I don't spin tires but I did crack a TH350 tranny twice. I had to go to a 400 tranny. Sounds good I will do as you recommend. I'm going to post it on craigslist and get going on a big block. Time for a new thread lol!

Thanks,
JD

Last edited by 355Nova; 05-18-2010 at 12:25 AM.
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