capncrunch

Hey guys, been away from the forum for a good while. I am back and building another LT-1 for my '94 Z28. I plan to use my old Powerdyne SC, and maybe add a FMIC. I have some questions for those who have already done this:
How much boost can I run on a 'near stock' lower end? (I know, it's all about the details, so...)

Here's my 'near stock' parts-list:
Sealed Power Speed Pro standard bore Hypereutectic (10.5 to 1) pistons w/ Hastings moly Rings
Comp Cam #07-500-8 (.258/.264 dur. .480/.488 lift, w/112* LSA)
Sealed Power Speed Pro stock style Roller-Lifters
Crane Push rods, with Crane Gold 1.6 Rockers
Melling stock style Timing Set
Federal Mogul Rod Bearings & Main Bearings
Durabond stock style Cam Bearings
Melling stock style Oil Pump
Melling Freeze Plugs
FellPro Gasket Set
ARP Crank and Rod fasteners
Gasket-matched, fresh grind and seals, Alum LT-1 heads,
K&N CAI, MSD 6AL, Edelbrock 'Shorty' headers and Borla exhaust

I realize I probably should run forged pistons, but bought this Master Kit years ago, so unless it's absolutely imperative to buy new pistons, I'll just have to live within its limits.
I need different springs to handle the .513(ish) lift with the 1.6 rockers, too. I plan to go with the single ovate Beehive springs. I was looking at Howard's springs (here- Howards Cams Performance Valve Spring and Retainer Kits 98113-K12) because they are about 1/2 the price of Comps and Howard's gets their springs from the same source as Erson and Manley, which should mean they are good, right?
Also, should I get different head gaskets- say Cometic or other aftermarket?

So, with the parts I currently have, what are your suggestions?
Would it be worth the time/money investment to add a Front Mount Intercooler?
I ran the stock engine on 4.5 lbs boost for 70K miles, before blowing a head gasket and overheating it. I'd like to get at least that much out of it this time around. Can I run a 6.5 lb pulley and expect longevity, with this setup? If not, what would I need to change?

FYI- The car is the coupe below- for mods list.
The trans is a fresh 4l60e w/ B&M Transpak and 2200 B&M stall.

Thanks in advance for any input or suggestions!
John

squarehead

Hi John,

I do not have supercharger experience but turbocharging is similar which I do have. The hyper-eutectic pistons may be a better choice for your project. I am pretty sure their best attribute is dimensional stability with temperature change. The supercharged engine will run hotter so it might be a better fit.

I think the case for forged pistons is since they are stronger they can thus be made lighter which is beneficial if you are headed to high rpm operation. The main reason to go lighter in high rpm is so the rod tension is lessened during the exhaust stroke by having less mass in the piston to stop and re-accelerate back down the bore. I believe this is the stress that the rod designer is most concerned about.

If you are planning to set the engine up to make power up higher in the rpm band you may want to get the forged pistons but with slightly larger gap in the bore to accommodate their expansion. If you are going to use the increase torque available from the supercharger just in the regular power band you could stick with the hyper-eutectic.

The math to support these arguments is in Corky Bell's book "Maximum Boost". It is a very enjoyable read an he certainly has the qualifications to write on the subject. He also wrote a book called, "Supercharged" which you can get on Amazon and elsewhere. I have not read this one but I want to just for fun, he is quite the sage guy!

I know from experience that the intercooler is a great maker of horsepower on 10 - 15 psi turbo engines but not certain it gives the same level of reward on 6.5 psi applications.

Good luck!

capncrunch

Thanks for that info squarehead! I didn't know about half of what you wrote, and am glad to hear it! I'm hoping someone will weigh-in on the Howard's Springs and other things as well.

Injuneer

There's a thread on the Advanced Tech forum discussing hyper cast vs. forged in forced induction applications. The most interesting post is #16, a quote from. KB Tech article. Note.... not all hypereutectic pistons are created equal. Not all hyper pistons are “light”. Not all are suitable to forced induction applications.

I would investigate the design of the Speed Pro pistons in terms of weight, for example, vs. the KB comments. Are they specifically designed for a forced induction application?

https://www.camaroz28.com/forums/adv...ations-240775/

capncrunch

Thanks Injuneer Fred!
I looked and it seems that what I am doing will be okay, since the hyper pistons are better than the stock ones (& since I have probably got some of the last USA made Speedpros). I couldn't find any empirical data on piston weights for these specific units, mostly just the KBs- which would be great. But, I really can't justify spending much more than I already have, as this car will be a 'luxury' (toy) and not my DD like it was before.
I went ahead with the Howard's Springs, too, which raises my total for this rebuild to well over $1,000 but not to $2,000 yet- not counting the trans. Hopefully it'll be a dependable and strong vehicle.
I do want to 'surprise/play' with the new Mustang GTs, as I work at Ford and my Focus ST is capable of that (w/ some big mods). Other than that I suppose my performance goals are pretty moderate, so it should be fine.
BTW- your build-list is AWESOME! Wish I had the money to do something like that. Maybe on the next vehicle...