Hey guys, Got a few question if anyone has some time to give me advice.


Im building a 383 l98. Its pretty much assembled allready minus brand new AFR 195 heads sitting on my floor.

The cam i have in is the lt4 hot cam.

My question is i have decided to go with a ATI install aswell. Is the LT4 cam a very good choice in a supercharged 383 ?

Im a novice here hence why im asking. I like the keep the car streetable, I guess im asking is by swicthing to a bigger cam how much power increase could i see on a 383 with a ATI. Is it worth the extra 500 bucks to do so.

Way I fiqure a mild 383 with my hot cam and ATI with slp headers and AFR heads with all new internals .Should put me in the 450 to 500 hp range. Or is that a understatement ?

I know a bigger cam will give me better horsepower but , money VS finding somone to put it in, VS keeping streatable is it that much better then the LT4 cam.

stupid guestion to some but honestly i just dont know what to expect with a motor of this horsepower range.

 

With a 383 and supercharger, I'm thinking the real benefit would be with larger port heads. 195 is a bit small for that amount of cubes being force fed. Getting much bigger on the cam won't help a heck of a lot because your small intake ports will be reaching stall air speeds I would think.

Try searching around a bit and see how anyone is doing with an SC and those 195's. Seems a bit small to me...

 

When I think about suddenly "adding" a supercharger to a combination that was originally spec'ed to run NA the first thing I worry about is compression ratio. Not the cam, not the heads, not the intake.

Trust me when I tell you that a blower motor neither wants or needs anywhere near as much compression as the same motor running NA.

I don't know what compression ratio you were shooting for on this motor but I suspect it's probably over 9.5:1. Aluminum heads or not it's going to be too high to run any meaningful boost on pump gas without flirting with detonation (which is MASSIVELY destructive on a boosted motor). If you want to put any kind of boost to that motor I'd get compression down below 9:1, and probably below 8.5:1, depending on whether it's intercooled, how much boost you intend to throw at it, etc. Whether that means swapping pistons or using heads with larger chambers is at your discretion.

I wouldn't worry about the cam too much. It may not be ideal for a blower but it probably isn't going to make a huge difference in power output unless you're really trying to squeak every last bit out of the combination. And if you were after that you'd have spec'ed it out as a blower motor from the get-go.

 

Thanks guys for the advice , im learning as i go with this.

Hum now im kinda stuck on what to do. I really dont want to dig back into the internals of the motor because frankley it was hell finding somone to build it for me. Not awhole lot of preformance engine builders around my part of the woods. The guy i did find i had to pull him out of retirement after i beg him lmao..

Option two totally forgot about the compression aspect of it. I just dished out 1400 bucks for AFR heads and waiting for 8 weeks for them. Not really wanting to go that route either lol

What could bring my compression down , im running dished pistons. Using thicker head gaskets would help correct ?

What else could i do ? Or am i pretty much screwed ?

i was looking to run just the standard 6-8psi with ATI Not awhole just that extra 100 hp or so...

I really like to make it to the 500 hp range? Thats my goal and my limit ... Any ideal's

again i know these seem like dumb questions but unfortuanally i never had a dad or a machine shop near my house when i grew up that i could learn from.. so pretty much im gathering information as i go..

 

That depends on what the dish is (measured in cc's). You *could* run a thicker head gasket, but generally you don't want to do that because the thicker head gaskets can fail easier than a compareable gasket that's thinner. Besides, the most you'll get out of that is maybe a 1/4 to half a point if you're lucky. You might find out if someone makes a thicker copper head gasket for a three-fiddy block.

What cc are your heads? 64? 72?

 

I would strongly recommend against using thicker head gaskets. More important than the actual compression ratio is the quench area. If you widen the quench distance from its 0.040" (optimal), you risk detonation. The whole purpose of the quench area is to create turbulence. This reduces the chance of hot spots in the chamber. The K-B silvolite website had an article on this very topic. You'll notice that even dished pistons have an area that is flat and at deck height. This is to maintain the quench area.

 

You really need to know your compression ratio. Like said, detonation, even just once, can ruin your engine. Also, I wouldn't change those heads. They will be fine. Don't get too concerned about port size, its the flow rate that is more important. I am running AFR 190s and am planning on a ATI blower!! I KNOW I will be just fine!! Knowing your compression ratio and what kind of pistons, ie cast, forged, etc, is your biggest concern. Don't fudge there or you will really hurt yourself later. I would say anything between 9.2:1 and 8.5: CR is good for you, the lower being a little better. Since ATI uses intercoolers your engine can stand a little more compression...