So what cam is LPE running in their turbo packages? GT2-3?
Phillip

 

I just called some of the "big boys" and they said to run a 206/220.
Phillip

 

Nice how nobody agrees eh?

 

well FWIW

mine is 251/244 .695/.683 115LSA 113 ICL
.025 hot lash

Sounds nasty, idles at 1200 RPM, and made over 800rwhp at 12psi

Has FAR better throttle response than my last cam, and seems to get the job done

BTW, cam is from Futral/Cam Motion

 

"big boys" = Lingenfelter Performance Engineering, shoot they have one of the fastest turbocharged LS1s in the country.

 

But again, 90% of the turbo cam spec is going to depend on your intake/exhaust pressure ratio - and what lingenfelter runs in their setup is going to be different than what you or someone else see.

That is why no one "agrees" - a log manifold 60mm is going to want a wayy different cam than a 76GTS, etc.

 

So much for me asking what size would be good for my future build.

Ok, here it is anyway, looking at a 8.5 or 9:1 CR 382stroker, guessing stage 2 or 3 heads w/ 2.055/1.6 valves, looking at the QMP single T76, and what about my current cam- TSP 231/237 wrong split, or good?

 

Cat3.. your not alone. I am having similar decision making issues... to thicken the plot, Im planning on the AFR heads of which we have no useful information.

 

Was thinking the AFRs as well just for the thick deck and less lifting hopefully. I only want a lot of boost

 

The thing is to copy a good setup not a bad setup. I would say to stick close to what LPE has done, but then again you have other kits using different Turbos whether they are single or twin. I would look at the power they make and where that power is made at and how well it translates throughout the RPM band.

I was thinking about this cam to put into my current setup. A 228/224 116lsa but with a 112 center line. My current cam is a 224/224 114lsa on a 110 center line...any thoughts about performance gains if I switch to this cam?????
Thanks.

 

WRONG
they have one of the fastest C5R's around, or is Ronnie Duke's C5R faster.

Rob Raymer had (coarse he sold it) one of the fastest ls1 around, least FI, aluminum with stock cubes.

then Steath had one (not sure if he sold it or not) with an Iron block

and of coase Harlan will probably have one of the faster-est ones if he'd just get a full pass on the track.

Compare apples to apples C5R =! LS1

 

Here's my thing....It just doesnt make sense in my mind to run a reverse split. After building import turbo motors and seeing almost 100% of them run straight up or normal split cams, I just can digest the idea. I even looked through the comp cams catalog and all of their turbo cams were like this except for one. I am just looking for the reasoning to run a reverse split. Here's my reasoning on running a normal split....

1) Your forcing air into the engine therefore you dont need to assist the engine with more duration.
2) The exhaust is restrictive so IMO you would need more duration on that side

Why assist the engine where it doesn't need it?
Phillip

 

I don't remember LPE running a C5R during that 1/4 mile run...better check again....C5R's don't come with a TH400 tranny last time I checked. If you mean C5R as in the GM Factory Racing Block Core that comes from GM for $6000 that Katech uses to build the C5R race cars then big deal....it comes with a bigger standard bore with stronger journals, and 7/16" rod bolts (stronger case)...one could use a Darton Sleeved Block and have just as strong a motor.

The LPE TT 650 (346cid) averaged 224 mph in one test. I just don't see too many cars doing that type of stuff...

I am not trying to call you a liar SmokinHawk just asking if you will please show me where LPE used a C5R in any test??? I don't remember them ever using a C5R for anything unless you are just talking about using a C5R 7liter motor...in which case would be the same as using any 427 ls1 with TT's...but LPE did adapt the TH400 tranny to it....which there is a guy who makes them as a swap in now.

 

Call Comp cams. They can give a much better explanation than I ever could.

Also, check out the turbo cam specs on this page:
http://www.cmotorsports.com/engine/l...ft-design.html
All reverse pattern.

I think Harlans engine is a great example of what power a reverse split pattern can make and its only a 5.7! Even with his old setup, he was make great power.

 

All lingenfelter C5's that run below 10's have the C5R block. I personally saw the pewter TT C5 in Kentucky and it had a C5R block.

Yes! Its on sale!

 

Anyone have an explanation why to run a reverse split?
Phillip

 

Are you sure you are not smoking Kentucky Blue Grass out there....

I would really like to see your 1/4 mile run at 9.50secs on street tires...do you have a video or somebody to vouch for you...because if you did or do...that is pretty fn amazing!

Like I said C5R Block....and you don't need a C5R block to get any LS1 into the 9's. Wade Stevens at ARE has a 422 with a 200 shot in the hi 8's..without a C5R block.

 

FWIW. ET Streets are DOT approved. There is your street tire.
I agree you don't need a C5R block to make it into the 9's or 8's. Or an iron block. There will be a lot of LS1 powered cars doing just fine this season.
Also the Incon kit is setup real similar to the LPE Vette kits. I'm running a large straight up cam on a 115lsa and seem do be doing just fine. We will be trying a large reverse split on the 382 though.

 

The exhaust can be restrictive, but that is a neccecary function of the turbo. Say you are running a 2:1 exhaust/manifold pressure ratio - you look at two cams - a reverse split and normal split. The reverse split is going to have much less overlap than the traditional split (assuming intake lobes are ~).

Now what happens during valve overlap? We have say 20psi on the exhaust side and 10psi on the intake side - which way is the system going to flow? Exhaust flowing back into the intake probably isn't what you want. Now there is still some inertia from the airmass moving, etc. but the more overlap you have the more you are going to start to backflow into the intake/get exhaust back into the cylinder.

Why more intake duration? To fill the cylinder - even though you are pressurized, etc. you still probably aren't achieving 100% fill at what ever pressure you are at. It may not be as much of an issue as it is NA, but it still is a pretty big issue - basically, you can only get air in the chamber when the valve is open.

So if you want as much intake duration as you can get, but want to limit overlap, you end up having to go smaller on the exhaust lobe.

But there isn't some huge change when you go from traditional/single/reverse split, it is all a progression. You may very well not end up with a reverse split - if you are running a 91mm thumper and seeing very low backpressure then you can get away with more overlap/more exhaust lobe - and more valve time in general is good since that is the only time your engine is "flowing".

So I guess the answer is that no, reverse splits aren't the way to go neccecarily - you probably will tend to see them more here as these motors tend to move a decent amount of air, especially the larger cubic inch ones. The turbo's people are using are smallish in general (compared to what import people are using vs. their engine's cfm flow, for example). There was a post on turbomustangs.com - an individual with a T-76 and a ~350" ford motor was seeing over 60lbs of backpressure at 20psi of boost. That type of situation is where you really need to limit valve overlap. On the other hand a T-88 at 10lbs of boost on the same motor may only see 20lbs of exhaust backpressure. In that situation you could get away with alot more overlap.

 

Nice times.

I never really considered MT/ETs a street tire..but your right they do have a DOT approval. I think of Street tires as like my Michelin Pilot Sports. There was a 427 TT out here that ran a 10.98 1/4 with a 2 sec. 60' time. I find that impressive. My goal right now is to measure perfomance on the stip and track as I use the car on the street. Then I will be throwing on the Slicks and hoping nothing breaks!