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Discussion Starter #1
Thoughts on these cam specs for a twin turbo 347 looking to shift around 7500 + and make around 1350 + hp:

I can't say that I've ever ran a turbo cam with so much lobe separation before...any ideas of what the idle quality and lower rpm power response will be, if any, with this cam?? I've also never seen so much extra exhaust duration. My last HR cam that shifted a whole 1000 rpm lower was 241/243 @ .050, .601/.608 on a 114 lsa...had noticeable lope at idle, about 8 inches of vacuum and was very snappy on the bottom end. I made about 1150 hp with the HR cam and 25 psi boost.

Valve Adjustment: .016” .016”
Lobe Lift: .447” .445”
Gross Valve Lift 1.60 Ratio: .715” .712”

Duration @ .050” Tappet Lift: 240* 256*

Lobe Separation: 118*

Recommended Intake Centerline: 114*

Specs at 114 Degree Intake Centerline:
Valve Timing at Open Close
.050” Tappet Lift: Intake: 6.0* BTDC 54.0* ABDC
Exhaust: 70.0* BBDC 6.0* ATDC
 

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I'm interested to hear what others say. That's much different than my cam. But honestly I'm completely ignorant when it comes to turbo camshafts.
 

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Discussion Starter #3
From doing some researching, it appears that you design your cam lobes FIRST for the application and then the LSA is calculated from there??
 

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I am no cam designer but the specs that were for my twin 320” sbf are as follows

278/244 on both intake and exhaust lobe

.427 lobe lift with 1.7 rockers
115 lsa 112 icl will be shifted about 8,000 rpm

the large split in duration on your cam is what requires the larger lobe separation to keep the overlap minimal.
 

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Is that 278I/244E?
My cam is .673/.673", 264/264 degrees @ .050
114 lsa, 114 icl
This is a 406 sbc with decent 23 degree heads that don't start backing up until .800 lift.Turbos twin gt45's. Light car loose converter that stalls 7000, shift 7600, finish line 8200.
I ran the cam advanced 3 degrees most of the season. At the end of the season I tried 114 icl, and it seemed all around more responsive. But a blown head gasket prevented runs that day.
It is very important in bracket racing that it respond instantly onto the two step and build some boost. So I was reluctant to go big with a cam. But now I am second guessing my cam choice. I operate in a narrow and relatively high rpm range. Maybe a little more cam duration and lift would be useful.
 

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Often the conversation ends about here. You can't blame those who have great camshaft information for not sharing a valuable commodity. The thing for me is that I'm not one to get one opinion and order from them without verification of some sort that what I am buying makes sense. So it is a bit of a challenge. This grind was offered to me by a friend at no charge. It happened to be somewhat close to what a pro was going to sell me. But the friend didn't have much experience with the grind either. Certainly it was a starting point. I have yet to have someone tell me I am leaving a lot of easy pony's on the table because of "this" aspect of the cam.
 

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I don’t think you will get that either... people have made more power with much less cam than the one you mentioned, and I am sure people have made less with more.

you need to chose a designer you trust and stick with what he tells you.
 

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I don’t think you will get that either... people have made more power with much less cam than the one you mentioned, and I am sure people have made less with more.

you need to chose a designer you trust and stick with what he tells you.
More power than what?
 

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Oh sorry about that.

I don’t think the cam you spoke about will have any issue going to 8200 as long as the rest of the combo can get there.
 

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Discussion Starter #13
The only thing I can figure, is that I told my cam designer that I wanted to make that power through full exhaust with mufflers. There seems to be some logic behind the extra exhaust duration and the wide LSA and what I'm trying to do. Well, I'll find out this Spring how the cam works.
 

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It would be ok in a supercharged application. It will be a turd down low and will spool like shit. I just sent a cam to a guy in Australia that had some jackass sucker him into building the engine after a lifter hurt the block/cam. Ran ok on chassis dyno but gave some excuse why two-step wasn't hooked up. Got car home and it wouldn't spool on proven converter even added converter dump but still no good. I spec'd a new Comp Cams solid roller and it is working awesome now. The cam I spec'd was more aggressive than your setup, max effort deal with twin GT4788 turbos on methanol but same cam issues you may encounter.
 

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It would be ok in a supercharged application. It will be a turd down low and will spool like shit. I just sent a cam to a guy in Australia that had some jackass sucker him into building the engine after a lifter hurt the block/cam. Ran ok on chassis dyno but gave some excuse why two-step wasn't hooked up. Got car home and it wouldn't spool on proven converter even added converter dump but still no good. I spec'd a new Comp Cams solid roller and it is working awesome now. The cam I spec'd was more aggressive than your setup, max effort deal with twin GT4788 turbos on methanol but same cam issues you may encounter.
What do you mean by "more aggressive"?
 

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Higher duration and lift but way less duration split. I think the big split is what will cause issues.
 

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Higher duration and lift but way less duration split. I think the big split is what will cause issues.
Interesting, thank you.
The OP's cam and mine (posted above) are pretty different animals. And so are the applications. But I would guess that my lobe is much less aggressive with the longer duration and shorter lift. Ought to be easy on valve springs. I'm sure I am leaving some on the table with the short lift though. The heads don't back up on the flow bench until 1"
 

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Is that 278I/244E?
My cam is .673/.673", 264/264 degrees @ .050
114 lsa, 114 icl
This is a 406 sbc with decent 23 degree heads that don't start backing up until .800 lift.Turbos twin gt45's. Light car loose converter that stalls 7000, shift 7600, finish line 8200.
I ran the cam advanced 3 degrees most of the season. At the end of the season I tried 114 icl, and it seemed all around more responsive. But a blown head gasket prevented runs that day.
It is very important in bracket racing that it respond instantly onto the two step and build some boost. So I was reluctant to go big with a cam. But now I am second guessing my cam choice. I operate in a narrow and relatively high rpm range. Maybe a little more cam duration and lift would be useful.
I dont see how you would have any issues with that much rpm available on the converter. Those turbos should spool instantly. That cam aint bad at all and looks like most turbo cams i have seen. Duration seems enough to be strong in the 7000’s rpm but abit more wouldnt hurt much i dont think
My old 246/252 hyd roller spooled twin 72-68’s to 7 psi in less than 2 seconds at 4400-4500 rpm 2 step
 

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I dont see how you would have any issues with that much rpm available on the converter. Those turbos should spool instantly. That cam aint bad at all and looks like most turbo cams i have seen. Duration seems enough to be strong in the 7000’s rpm but abit more wouldnt hurt much i dont think
My old 246/252 hyd roller spooled twin 72-68’s to 7 psi in less than 2 seconds at 4400-4500 rpm 2 step
You are right, the combo does, and has to come right up on the two step and makes some boost in less than a second. I have to remind myself that instant response was a priority for this application. I should be able to sneak this thing into the 6's this next season at 190+ mph. Going to add a wing, so that may hurt mph a bit.
 
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