Not my point though.

Unless you (and he) have the EXACT same setup SANS the cam, your recommendation/assurance to PLRX would be -- as risky as PLRX telling Red that 11:1 would be fine in his motor.

It's NOT apples to apples.

Look how hesitant Brian was to say yes/no and he's the one building the most engines in this thread, right? Did he refer to SCR or DCR?

I might as well vs try to make a point here!

 

I live in california; we have 91 octane max. Ran an small block, 11 to 1static compression ratio, cast iron heads, with no problem. The "secret" if there is one, use a cam with lots of duration. which you probably are anyway

 

It's NOT that simple but, yes, using a "big" cam lowers DCR.

The "secret", if there is one, is to learn/understand dynamic compression, get your quench right, get your tune right, adjust cooling temps/system (if necessary)*, and remove any sharp edges on the pistons (or cchambers) that could cause "hotspots" -- leading to pre-ignition.

 

No, I don't know how to compare a L98 to a LT4 because I don't have to.

Why should I care about a L98?

Looks like you have all the answers, give the guy your input, you take the credit and glory.

 

Because a lot of us in this forum have them, like them, and prefer interaction from others who feel the same.

 

I guess no one has noticed that Red, the original poster of this thread , (Remember Him) has bowed out of this completely and we haven't heard from him in 2 pages now. I thought we were suppose to be helping him, but thats not what Im seeing now,just arguing..Guess he got tired of the pissing contest and went elsewhere.....WW

 

WW7...the feedback Red got in this thread was:

1) Explanation how to use DCR guidelines to stay safe.
2) Being told nothing is scientific -- to ape GM.
3) Other's saying 11:1 is doable w/o details on how/why.
4) Other's saying to change course and do a known combo
5) Bail on the CF and get advice from his builder

The pissing contest to which you refer was a simple challenge on why 11:1 was not a safe bet -- with Red's cam. Would you rather see suggestions w/o debate? Answers w/o reasons?

As someone who's gone thru this, solid reasoning is good to see/have. Without that, it's not worth the money/risk to alter a motor. I empathize with Red's concern and I certainly noticed his lack of participation for the past couple of days. From my perspective, it started when people said he should bail on his current path and go with a "known build". (That there was no science to figure this out). IOW, there was little effort aimed at helping him get his current parts to work -- with explanation of why/how.

Are you surprised at the result?

 

WW7...the feedback Red got in this thread was:

1) Explanation how to use DCR guidelines to stay safe.
2) Being told nothing is scientific -- to ape GM.
3) Other's saying 11:1 is doable w/o details on how/why.
4) Other's saying to change course and do a known combo
5) Bail on the CF and get advice from his builder

The pissing contest to which you refer was a simple challenge on why 11:1 was not a safe bet -- with Red's cam. Would you rather see suggestions w/o debate? Answers w/o reasons?

As someone who's gone thru this, solid reasoning is good to see/have. Without that, it's not worth the money/risk to alter a motor. I empathize with Red's concern and I certainly noticed his lack of participation for the past couple of days. From my perspective, it started when people said he should bail on his current path and go with a "known build". (That there was no science to figure this out). IOW, there was little effort aimed at helping him get his current parts to work -- with explanation of why/how.

Are you surprised at the result?

FWIW: I hope the points made here give Red reason to talk to a builder, learn more, and return with add'l questions to help him feel confortable about his course of action.

 

WW7...the feedback Red got in this thread was:

1) Explanation how to use DCR guidelines to stay safe.
2) Being told 11:1 is doable w/o details linked to his cam/setup.
3) Being told nothing is scientific -- to ape GM.
4) Other's saying to change course and do a known combo
5) Bail on the CF and get advice from his builder

More debate on items 1 or 2 would have improved this thread (IMO), but no one else is willing/able to (earnestly) participate**. As someone who's gone thru this, solid reasoning is essential. Without that, it's not worth the money/risk to alter a motor. (It was obvious Red feels that way.)

FWIW: I hope the points made here give Red reason to talk to a builder, learn more about what makes a given combo work, and return with add'l questions to help him feel confortable about his course of action. If you're not going to build a known combo, it's wise to gain the insight necessary to deal with the alternate path you decide to go on.





** Thought: As time goes by, this (C4) forum is bound to dwindle to look more/more like C3, C2, etc... IOW, fewer people will participate as newer models arrive to spark interest. How much of that do you think is happening now?

 

Sounds like he has a small setback

http://forums.corvetteforum.com/off-...s-morning.html

 

That sucks !

 

I had the feeling he was "distracted" by other issues. I think his choice will work out for the better -- and hope it does!

 

There is a thread on this board with the engine builder putting together a 383 that will turn 400hp at the rear for one of the members. Why not ask him. Been a nice guy, my bet is he will give you the answer or better yet a parts list. His kit seemed affordable to me.
http://forums.corvetteforum.com/c4-t...-w-photos.html

 

There was never a claim (in that thread) by me to turn 400 hp at the wheel. We intend to build a solid, reliable, engine that will work well with the parts the end user owns. The build will also be geared towards many optional future upgrades. The hp and torque that we get, we will accept. There is no quest to build the "perfect, leave no power on the table" combo by me.
It is just a 383 small block. Ain't no big thing. It's been done to death.

 

Sorry I didn't have time to read all the responses on this thread... so (My Apologies) if this type of stuff has been mentioned already:.....My personal 93 octane pump-gas engines (and customers engines) commonly get set-up with 10.7(on the low end)....and up to 11.7 to one compression ratio's on the upper end....but more often than not, what ends up being the supreme factor for the detonation threshold is what EXACT cam specs will be run in the engine, and how that particular cam bleeds off cylinder pressure as a result.....We have found that as long as were around the 200-205 cranking compression range, on a basic (nothing wild technology wise) assembly, were more than ok with no detonation of any kind......and can push things as high as 215-220ish (cranking compression) if many (or ALL) of the detonation threshold raising practices have been implemented for that particular engine set-up.....For example: on my current Forged 388 LT-X stroker.....were at an honest 11.7 to one....and I have the quench distance set @ .35 thou... the piston's crowns & skirts have been friction & thermal coated... my combustion chambers have been CNC machined and contoured to have no real sharp edges...spark plugs are the perfect heat range for the set-up... and their ground-straps have been rounded (IE: nitrous plug prepped) to remove any sharp edges.........With a VERY mild (custom grind) street cam in the mid-high 220's @ 50, on a 112 LSA, & just under .600 lift....I'm cranking 216-218 PSI cranking compression...and it's showing ZERO signs of detonation of any kind.....No knock retard.....and the plugs look perfect when studied under a magnified scope......The previous (larger) cam that I had in was in the 240's @ 50 on a 110 LSA with about the same .600 ish lift, and the cranking compression was down in the 205 range so we were even further away from problems.......PS: I also have some buddies that are in the honest 12.5 -12-7 to 1 range with super large 280's @ 50 roller cams running 93 octane pump gas with zero detonation issues.... so my point is that there's never really just one answer for compression ratio.....if you not interested in really maximizing the compression set-up for 93 octane , just use one of the tried and true set-ups that most go with in the 10.5-11.0 compression range , and pick a cam in the 220's to 230's @ 50, on decently wide lobe centers (IE: 110-112 LSA's are great for the street on FI engines) and you'll be more than fine.........good luck with your engine.......Joe

 

He has an L98, anyone read that? 383, small cam (213/219)

If he cranks the compression up high with that its gonna ping.

 

The entire explanation by 95NOSVette provides a good practical correlation between DCR to SCR. With a little thought, I think we could come up with a decent chart to follow -- if we wanted to. (It could look something like: Cam duration, Cam lift, compression range, water temp range.) Obviously, a DCR calculator is good too.


From all the source I "polled" on this subject (mentioned earlier in this thread), that's consistent with their recomendation. As such, I would agree with that.

With the smaller .450" lift/213 duration voodoo cam selected by Red, cranking pressure WILL go up because of the reduction in actual duration (seat-to-seat). Because of the increase cranking pressure, the SCR should be lowered to compensate. In terms of static compression, 10:1 is the boundary I think Red should stay under -- if he really wants to be certain of flawless operation.

95NOSVette, please say whether you agree with my lower 10:1 SCR recommendation using the Voodoo cam specified. Whether it's yes or no, that should be helpful to Red (and other readers).

FWIW, Red will use 1.6 (vs 1.5) rockers in his application. Since we all know bigger rockers make the cam operate with a more aggressive profile w/o letting add'l cranking pressure bleed off (like a higher lift/longer duration cam would), those new effective figures won't raise the recommended compression range/limit.

 

Thanks Ron! I probably get too technical and wordy (even though I hope people want to learn). But, your short/simple answer is perfect.

One thing people who haven't built a 383 might not realize is compression goes up because of the longer stroke.

 

knowing the intake, headers, and compression Im looking to run...how I intend to use it, and how Id like the tune to end up....what VOODOO hyd. flat tappet cam would you all reccomend?

60103?

Advertised Duration (Int/Exh): 268/276
Duration @ .050 (Int/Exh): 227/233
Gross Valve Lift (Int/Exh): .489/.504
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 1800-6200

 

I gotta chance to look at the IK200 specs tonight. Assuming you were interested in the NON-CNC'd option, I have to say you would be much better off looking at the AFR195's to go with the cam you bought. The biggest thing that will accomplish with the "383's special needs", is significantly improving the air supply. With up to 25cfm more flow at the lift you're hitting, that would translate into a possible 50 more HP.

If you don't consider a head that flows well above 250cfm (for a 383), you might just be better off selling that cam and buying a "bigger" one. (Of course, if you do that, you could do that higher compression thing!)

Edit: I was typing this while you posted above. I'll post back later tonight on your cam request. In the mean time, reread what 95NOSVette posted on cam specs.