Im looking at gettin this comp cams cam that is for sale in the classifid section. these are the specs the guy gives "CompCams Custom Solid Roller cut for turbo motor 6000 RPM peak HP 224/224 541/541 112 CL".

Im in the process of building a 383 4 bolt main motor with the BBSdesign single turbo kit (T62-1 turbo). was just woundering if this cam is enuff or alittle small?

im also goin all fordged internals on the motor, havent decided on a EFI set up yet or heads. pretty much ill just match the heads with the cam so everything is matched.

also im tryin to get more then 650hp out of this motor , not sure how much boost but id like to push it to 20lbs at the track and the motor will have an intercooler.

 

IMO that cam would be garbage for a turbo engine. There's way too much intake duration and way too narrow lobe sep.

Turbo's generally run approx twice as much backpressure as they have boost pressure, so you have to take this seriously when planning your valve events. Because of this, the requirements for a turbo cam are much different than that of a supercharged, or N/A engine.

In another sense you can run a turbo with any camshaft and see a power gain. Don't let that fool you to think that is what the turbo wants. You may give up as much as 50% efficiency, have severe turbo lag, and encourage detonation by using a mismatched camshaft.

Stock camshafts generally make much better power with a turbo than most aftermarket extended duration grinds. If you're on a strict budget then a stock cam isn't a bad way to go.

 

Why do all of the "turbo" cams I see listed have a longer intake duration than exhaust duration?
Wouldn't you want more exhaust duration if the backpressure is higher?

 

Basically, intake duration will determine rpm range, HP peak etc. Exh duration will have an effect on these as well but I've yet to find a clear enough explanation to cover all the bases on a turbo motor. The rev split is due to the fact that a decent street turbo set up will have 2x boost pressure in the exh. So you will not get intake flow into the cyl till the exh valve is shut and piston has moved far enough down for the pressures to equalize. From the one person who had the cash and the willingness to post results. He went 224/224 113Lsa plus a few other setups. IIRC, the 224 made the most HP above the HP peak by far. But had a rough idle which he didn't want. His conclusion was the extra overlap from the short lsa helped on top. I've heard similar from pro's who sell the 1000hp stuff to the big bucks guys. He ended up with a 1.6rr 219/219 114 lsa CC HR and makes 840rwhp or so on an LT1 afr headed 355 with an HSR style intake & 18 or so psi w/2 T61's. The heads and exh will determine how much split is needed. The exh includes the turbine housing. So there are a lot of variables. Best to copy someone elses combo to some extent.
As far as a 224 being to much intake dur is BS!
Plenty of 302 turbo stangs running around with them and making lots of power. Never mind the fact this is for a 383!
Not that a better cam isn't possible. But 700+ rwhp is plenty. (at first). The 224 is a FMS cam and cheap so lots of people have them already. They just swap pistons and throw on a turbo so to speak.

The above mentioned pro used a CC XE SR 230/224 115lsa in a LS1 to make 900+hp at 19lbs or so.
So your single T62-1 turbo is a little small for that cam and and a 383. And IIRC a 62-1 won't support 650hp. You cam it based on the rpm you want and boost it for the desired hp. So you then swap the specs around till you get what you want. For only 650fwhp, a 219 HR or so should be plenty and only 5500 or less with good heads.
For all around flexibility, you might look at a single T70.
It will fit in the same spot as a 62-1 (close) but will move a lot more air. And it can be turned down into the 550fwhp range. At 20 psi it would be in the 800hp range if you have the right heads. Meaning big enough. If you plan on racing a lot. Go straight to a T76 and at least a 215 head.
Mostly street and under 800hp, a T70 and a good 200cc head will work fine. 800 hp is close to the crossover for needing a Dart block and a billet crank btw.
You can get you hp goal with a 355. The 383 will make just that much more torque and spin the tires even sooner.
But it will have better under 2500 rpm power. Above that you should be in boost already on a good setup and the tires will be spinning shortly if not already.

What I came up with for a combo for 750 or so fwhp @15 psi or less is a 355, T70/.96tang turb, 221-219 HR cam spec'd by Cammotion, Brodix RR200 heads, 8.3-8.5 CR depending on shelf pistons used. Just turn the boost down for less hp.
Or run a smaller cam for even better driveability and leave the boost up and only loose a little hp. Though IIRC, the 95 LT1 spec'd above gets 21 mpg with a T56. And does 9's! Do a search on Turbomustangs for screen name "INTMD8". His setup is what I based mine on. Just cheaper and less HP.

To get a 62-1 size to push 650 hp you need a custom unit with a TS04 back plate and a different compressor wheel.
I happend across the setup during a search. The T70 is basically a shelf unit and ends up the same price but will support more HP.

 

For ball park cam sizing @.050
Use (int dur + exh dur)/4 - LSA. Should be in the -10 to +2 range. The bigger the cam the more lsa you need to stay under +2. The small stock style cams are in the -10 to -6 range. Use this to compare with the cams I posted above.
And also look up the E303 and F303 FMS cam specs as a comparison of what people have gotten away with in the
600+rwhp range.

Another way to look at it is:
The smaller the exh housing, the smaller the cam since the small housing will not support a lot of rpm. That's how you do the junkyard small turbo stuff. And don't forget
a T3 exh with the same AR as a T4 will not flow the same. It will flow less. You have to go to a stg 3 or something T3 to equal a T4 with similar AR.

 

[QUOTE]Originally posted by Z69
[B]For ball park cam sizing @.050
Use (int dur + exh dur)/4 - LSA. Should be in the -10 to +2 range. The bigger the cam the more lsa you need to stay under +2. The small stock style cams are in the -10 to -6 range.



What if a cams is less than -10? The stock cam (LT1- 201/208 117° LSA ) I was going to use comes to -14.75. Engine will be a 350 or 383( haven't decided yet), 8 to 8.5 CR, aluminum heads (hopefully, havent decided yet), twin T-03 turbos (garrett 60 trim compressor wheel A/R.42 compressor housing and A/R.48 turbine housing), intercooled (with water/meth inj.), tpi manifold, 42lbs. inj., 730 ecm, $58 code. I was wondering how this cam will do, it's not a daily driver but more like a weekend cruiser? I was looking for a redline of around 5500-6000rpm and lots of midrange torque. The car is an auto right now, but switching to a T-56 soon. Thanks.

 

All of the .42 A/R compressors I have seen are 45 trim. Where did you find a 60 trim compressor marked .42 A/R? What vehicle did it come from?

J

 

I don't keep good track of those small turbo specs.
None of them available locally for me to consider using.
IIRC, they are only good for 600hp on a 350 when ran as a pair. Wouldn't do them on a 383.
They are real popular on the budget 302 setups.
There's a board dedicated to them on Turbomustangs.
The exh housing is too small to allow a 350 to rev much beyond 5k IIRC. So that LT1 cam is almost too big for them.

The lower the number, the lower the HP peak basically.
So a -10 isn't going to make a big number up top.
Also, the more corked up the exh is, the lower you want the number. So if your were running a bigger turbine, you could go to a 110 lsa with that small cam. If you don't like it, you can always change the cam. For what your doing, I wouldn't worry about it.

 

Couldn't agree with you more Z69. After reading your earlier comments on the cam selection, it makes sense that going to the lower side of the -10 to +2 yields a more bottom end cam. After reading what you wrote and doing some searching I decided that I will throw a new cam in my setup when I pull the engine to do the intercooler install this winter. Your post pointed me in the right direction.

I looked up info on the garrett T3 .42 A/R compressor, .48 A/R because you see them for sale on ebay all of the time and are common in the junkyard. I ended up buying a pair for cheap at a yard that were in excellent shape. And they ain't gonna make 650hp as a pair. The target vehicle is a 4500lb truck with a stock 350ci w/ a cam and a TPI on it. The cam is good from 5500rpm, and the TPI is good for a max. of 5000 rpm. Pushing it is 5500rpm.

If you look at a 45 trim compressor map you will see that these things can push a max. amount of air of about 220HP. At 8ish psi they will support maybe 400hp as a pair (probably 370hp). So yeah, my dog 4500lb vehicle that needs more torque will benefit from a couple of quick spooling undersized turbos. As for a thirdgen, I would only install them if you are looking to learn about turbos or only want low to midrange power. I am guessing it is going to fall on its face about 5000rpm. They will get you started though and you can always upgrade later.
If they are truly 60 trims, then chuck the .48 A/R turbines for some .63+ housings. With 60 trim and good housings you might get 650 fwhp, but I think that is pushing it.....real efficient intercooler = massive bar & plate.
J

 

wow you guys gave me some awesome info. i think ill just end up finding a cam that is a good combo for the turbo. since i already have the turbo set up i cant really dump another grand or so for a bigger turbo just yet.

maybe ill just do a 355 set up and then if i want later on down the road ill do the 383 with the t76 or if i find a good deal on something bigger.

i think ill call Compcams and see what they would recommend, then go from there. i didnt know there was so much math and science behind all this. i knew there was but you guys just opened a whole new ball field.