After many years of thinking, looking, and thinking some more I found a used procharger kit for cheap on Ebay for a C4 and snapped it up. It has the P1SC head unit that will need repair due to some damage to the impeller and some small misc peices seem to be missing.

My goal is 650 RWHP. I've read the intercooler provided with the kit is a little small for that goal, but I'm unclear if it is small because of the lack of cool airflow or too much restriction on the hot side. I'm not opposed retrofitting a larger core to the housing if needed as I'd rather do this than use alcohol injection. I plan to run around 14 PSI and realize I'll need a cogged belt setup or an 8 rib conversion.

On the engine side, I plan to build a 396 with a forged, internally balanced rotating assembly from Eagle. I have not decided on a cam as of yet, but am open to any suggestions. Heads will be ported and polished LT4 castings and a ported LT4 intake unless the new Edelbrock LT4 intake is out by then and there are proven benefits to using it. I have a set of EM long tube headers that should be arriving any day now and will probably settle on a B&B 3" exhaust.

I plan to tune with LT4 edit.

Any thoughts or suggestions?

 

Here's the one thing that I see that doesn't make sense to me. If you are planning on running 15 psi, which seems about right for you hp goals, then you are going to want 8.5:1 compression. You might be able to get away with 9:1 but that might be pushing it if you are going to be running pump gas.


If you are planning on using actuall LT4 heads with their 55cc(?52? don't remember) chambers you are going to have a hard time getting to 9:1 let alone 8.5:1 where you should be.

Are you planning on using 6" rods or something shorter? The shorter the rod the more dish you can get in the piston, but the worse rod/stroke ratio.

I would suggest going with a shorter stroke 383 maybe or going with AFR 210 heads and get some 76cc chambers. With those you can build the 396ci and the compression shouldn't be a problem. The problem is with those heads and the compition porting will run you $3k or more.

 

That has been a concern of mine with a 6" rod 396. I haven't done a lot of searching to see what pistons are available at this point, but was hoping to find something around 9:1. My second choice was to build a 383 and that may be what I end up doing since there would be less block modification required. I doubt the tiny difference in stroke between the 383 and 396 would make that much of a difference anyway.

I was planning to stay with the factory LT4 castings since I already have them. As you said, the aftermarket heads fully worked are going to be pretty expensive. Then again, I could sell my factory castings and make back some $$. Or just keep them if I decided to go back NA one day. Hmmmmm.....

 

to help a little without breaking the bank, you could sell off the LT4 castings and grab a set of trickflows for a few bucks over what ya get for yours ready to bolt on with good springs and such. they flow a little better then the stock casting LT4 heads and have the 62cc chamber which will help get the compression down.. I own a set of these and am VERY impressed with the quality!

Chris

 

I just completed a 383 build and sent the customer home in his car. This car made nearly 620 RWHP and 600 RWTQ with a 383 build. the blower is a Vortec T trim making 12 PSI. The engine is a 383 with 8.7:1 compression with 70cc AFR Competition CNC ported heads. Even with the 70cc heads we ended up using a set of custom Ross pistons that yielded the target compression that we wanted.

If you are going to use a set of LT4 heads you will need a HUGE dish in the piston. Which will compromise piston strength, and if you are planning on running 14 to 15 PSI you want all the strength you can get. I used the 70cc heads along with the shorted stroke of a 383 to gain additional strength. 13 inches won't make much difference as far as power gains go, not enough to warrant sacrificing strength. With the shorted stroke and a shallower dish you can get a much stronger piston, and be sure to spec out a 2618 alloy. This allow is much more resilent and will take more abuse than the more brittle 4000 series forgings. The downside is that these require a bit more clearance and therefore a bit more noisey as compared the a hyper or a piston made from the 4000 series aluminum.

Another thing is that we were maxed out on the T trim that we were using. And seeing how one can't install a larger blower without extensive hacking, 12 PSI was enough. At that rate the engine was making well over 700hp at the crank with the numbers we got at the wheels. Also it takes over 100hp to drive the blower to the levels that we were making power at. So in saying that with 100+hp in parasitic losses to just drive the blower, 20% drive train loss, I figure we were making over 800hp which is more or the limit of what the T trim can support. We just plain ran out of blower.

One other thing, you had better plan on studding the heads. At those boost levels any amount of head or block movement will cause you to loose a headgasket in a hurry. This can happen with detonation or improperly torqued heads. Do it right the first time and you won't be sorry.

 

tjwong, how much more clearance are we talking to run the different alloy in the piston? I just rebuilt a stock LT1 and was amazed at the clearance that still falls within factory specs on one of these.

I do want to build it once and not go the trial and error route. I am a professional engineer so I'd rather something be overdesigned than underdesigned. I do plan head studs and main studs as I'm a firm believer in that being the best way to get an accurate torque reading.

How big was the cam were you running in the 383?

How do the AFR LT4 heads compare to the TFS LT4 heads?

 

Dave, I am an EE but never went for my PE Anyways to answer your question. The 2618 alloy pistons are set at around .006 to .008. We are not talking about a lot, but due to the inherent design of the skirt and alloys these make a bit more noise when they are cold. Once warmed up they are quiet. As far as heads go, TFS as far as I know do not make a true LT4 design. I do know they make a 195 LT1 head that can be ported extensively. I go with the AFRs because they can be ordered with larger valves and will come 100% CNC machined, and they will outflow the TFS heads that have been ported out of the box. Plus the AFRs have exceptional mid lift flow numbers which is very important for good mid range to peak numbers. Who cares about 650+ lift flow numbers, how many people do you know that run lift numbers that big? Some do but valve guide wear with lift numbers like that is high on daily drivers. The only problem with AFRs is the wait time can be prohibitive to some.

The cam I ran in this instance is a 234/242 ground on a 114, basically it is a GM 847 ground with a 114 LSA with 4 degs of advance ground into the cam. With these specs the 847 has a decent but very noticable idle and will deliver enough engine vacuum to be suitable with a normal vacuum brake booster without having to use a resorvoir.

That is good that you plan on using studs. I used a F body LT1 block as a foundation. And I used a set of Program Engineering splayed billet caps in the 3 center locations, and their billet front and rear caps. All secured with ARP studs. This was probably overkill, but like you I like to over design in the begining and not worry about failure later. I also did a partial fill on the block to strengthen the bottom end. Rods were a set a Lunati billet 4340 steel, these are a bit on the heavy side but at 700+hp who cares This thing made peak power at 6000 RPM and carried 600hp to the redline of 6500. It will carry 590 to 7000 RPM as well. And get this, my friend got it smogged in So Cal, but of course it would never pass a visual because long tube headers are a no no, but she sniffed rather clean, for a cam that size! I am not sure if it sniffed clean enough for a 96 model year, but it was definitely suprisingly clean for what it was.

 

Haha...I would've stopped at my BSME if I didn't need the PE to make a good living in my profession.

I like the sound of the combination you're talking about. I just have a friend with an 03 cobra that put down 644, so I'd like to surpass that even if I've already got him by almost 1000 pounds between the cars and drivers. So I'd like to squeeze an extra 50 HP out, maybe the extra 2 PSI would do it?

Do you think the P1SC would get me where I want to be?

I'm looking at the AFR catalog right now. Did you run the 210cc 'competition package' heads on that combo? Whats the chances of getting a duplicate of that cam?

 

We did run the Competition ported heads and the optional larger intake valves. Getting a duplicate of that cam would be easy. I have the part number that you need at my shop somewhere. I am not sure if the P1SC would do it. The problem is, getting the power into the blower to make the boost. And that means at a minimum a 8 rib belt, and if you are doing a Pro-Charger that means a total custom setup. Now if you do a Vortec call Greg at BlowerWorks. He can help you with the same setup I am installing on these cars. We already have a working pulley combinations with NO Slippage! This was confirmed using a optical tach on the blower pulley.

In our cars we can get 12 PSI and thats it. That is after descreening the MAF and adding Gregs divider in the inlet plenum. The T trim is about maxed out at this power level. And getting another blower with a larger trim is not an option. At least not without major surgery.

As for your friends Cobra, what has been done to that? If its a stock bottom end, it won't live long at those power levels. And was that power measured on a Dyno-Jet? They are notorious for punching out higher numbers. Not to mention that I have seen several of them Cobras scatter their guts on the pavement with modified KB blowers. They do make very respectable power but their bottom ends are weak.....very weak. Their rods will kick out the sides of their blocks at those levels unless some decent forged peices are installed.

The numbers I gave were from a Mustang in my shop. And its tight with the numbers, not to mention the curve that I posted for Glens car show low numbers in the lower RPMs. The reason is because I had to "gently" roll into the throttle, otherwise I would blow the tires off the rolls. I am sure I took away a few hundred miles of tire life from the tires during the dyno tuning sessions.

An extra 2 pounds of boost would do it. But getting there maybe hard, especially with a very free breathing engine. Remember, boost is more or less back pressure, the more free flowing your engine is (higher efficiency) the less boost you will show, that is unless your blower is capable of flowing way more air than can pass through the engine. Where I beleive we ran out of blower in this car. Had we had a YS trim there wouldn't have been a problem. I have a friend in So Cal that is running a YS trim and is running 9's His engine is similar 383 build, you can check him out at:

http://para.noid.org/~lj/

Our engine is very capable of handling it but we had to live within the restraints of the C4 chassis and utilizing the Vortech blower bracket with the T trim. It is very streetable, and fairly docile. Boost starts in at around 2800, after that RPMs build very fast as does boost pressure. During Glens trip home to SoCal the car registered 23MPG but that hasn't been verified.

 

I forgot you were running on a Mustang Dyno. That puts me right there where I want to be.

I saw in an older post where Bruce had a cogged setup on his Procharger and am thinking about something similar for mine. From what I've read on Procharger's site, it seems the P1SC will get me there, its just the belt slip issue that seems to be the problem. That and I'm not sure on the capacity of the intercooler.

As for the Cobra, he is running the stock bottom end with a KB right now. They seem to have pretty good luck around here keeping them together at about 600 rwhp. Much above that and they start coming apart pretty quick.

I never would have believed there were so many high HP cars in this area until I joined some of the local boards and went to some events. There's a 900 WHP EVO8 and lots of other high HP cars. Of course, thats on racing fuel. To me, streetcar=pump gas. I gave up trying to compete and now I just want to have a good reliable (ha!) high HP GS.

Thanks for your help, by the way. I'll PM you about that cam.

 

If you move to the R series blowers from ATI and a custom IC, they will definitely get you there and then some. At the levels that a D1R can deliver, I am sure you will run into the practical limits of the factory computer system.

Aaron