Alrighty my idea right now is boost. I dropped the na idea. how much boost with 9.0-1 or 10.0-1 compression ratio engine will be completely forged. Also since this is a daily driver how many miles would this engine last? I was think like 9psi or 10 but I dont know still kinda new to forced induction world.

Edit: Forgot to add this would be intercooled.

 

I started with 9. After blowing an engine, broke the new motor in with no boost. Then went to 7, now 10-11 (12 psi rated).

9 or 10 psi is a lot to start out with, but a forged bottom end will take this and more. Just hold on, you won't believe the power increase

 

A low compression/higher boost combo makes more hp and is less prone to failure than using a higher CR and lower boost. Aim for ~8:1 if you are going to use a big blower that can provide high boost. If you don't need a lot of hp, a "small" blower producing ~10psi and a CR of ~9:1 is a good combo.

A "small" blower would be on the order of an S-trim or P600B. These can make 10psi on a typical small block.

A T-trim or D1 is a "big" blower that can produce 14-15psi even on stroker.

An F1 or a YS-trim is a "huge" blower that can probably blow up your stroker with ~20psi.

Don't even think about anything bigger

Rich Krause

 

I probably would be best with a t trim then. that way if I fell the need to turn the boost up I dont have to upgrade head units.

 

Yeah, but a motor built for 10psi and pump gas will self destruct at 15psi on the sme fuel. So don't get greedy with the boost if you build a relatively high CR shortblock. I re-read what I wrote originally, and 9:1 is still on the high side for even 10psi. The problem with LT1 heads and street or street/strip blower cars is that the small chambers make it difficult to get a low enough CR. A 355 with a -31cc piston and a .039" gasket is ~8.75:1 and that's what I would do for lack of the ability to make the CR even lower. A thicker gasket is a bad idea due to the effects on quench.

Rich Krause

 

Well, lets say I go by the book, and I finish building my 4bolt lt-1 with a CR of 8.75:1 or 9:1. (355ci, intercool, 10psi)

How long will it last if I drive the car 70 miles every day (24miles of those in hevy philadelphia traffic, maybe more traffic in the high way too!). My concern is more base on the heat and traffic than anything else.
I guess noneone can give a clear answer for this question, but I don't loose anything by asking.

leo

 

Leo: it will last as long or longer than the OEM motor if you stay out of the boost. The harder you run it though, the sooner something will break or wear out. That is the nature of all things mechanical. If you are reasonable* as to how you use it, a combo like the above should give decnt longevity.

*Use high octane fuel, don't get into the boost much under terrible conditions (really hot, humid day), be sure it's tuned right (rich, AF ratio in the low 12's), etc.

Rich Krause

 

Alright thanks for all the info i really needed that I just have one more question where can I get pistons with that a big enough dish to get me below 9.0:1 because i noticed everytime I look for the the closes I can get is 9.0:1 because like you said are heads 58cc and suck.

 

The CR calculator I use at http://www.rosspistons.com/CR%20Calculator.htm gives 8.5:1 with a 4.030" bore, a 3.48" stroke, a 0 deck, a 58cc head and a -31cc piston.


Rich Krause

 

how much rwhp are we taking about? (10psi, intercooled, 355ci, lt-1 heads -> 175/195 (.600 lift), custom blower cam, longtube headers )


leo

 

I am running 10 Psi of boost on a 383 with stock heads. I dont have dyno numbers or track number yet but I drive it 600Miles a week in traffic and on the highway without any issues. Right now I am running too much of a conservative tune but I will get it tuned later on the Dyno with WideBand O2s. See link in sig for full details. I currently put about 20K miles on this motor with about 11K being blown and I drive it everyday.

thx,
Claude

 

warning to all my car be a sleeper and I am coming after you houston people!!!!!!!!!!hahahahaha coming in jan.

 

Thought I would chime in here.

Not intending to disagree with any previous posts, but I think the trend is to drop the compression too far.

For example (actual results) taking a heads/cam stock compression LT1 car down to 8.5:1 compression, required upping the boost from 8# to 10# just to get the power back by lost compression.

I commonly use 9.2 to 9.3:1 with 10# intercooled boost. This will work if properly tuned & live on a regular basis. My 9.3:1 383 motor was used extensively for 3 years of daily driving (32mi each way to work) with 10# boost, 93 octane, no octane boost, no water injection. Not sure of the HP, but it ran 10's with a 6 speed & 3.42 gears.

I have used 11# on pump fuel & 9.5:1 compression..... yes 9# with stock 10.2:1 is borderline. I know of a few people using 12# on daily drivers with 9.2:1.

Consider working the heads to have a 65cc chamber & then you can run a 9.2/9.3:1 383 (16cc dish) or 9.5:1 355 flat top motor.

My advice is to think out your combination before building. Don't build the bottom end for 15# boost if you never intend to run over 10# or your performance will suffer.

Hope this helps.

 

So you're running stock heads and a small cam (cc305) in a 383? (that's a little confusing... did you ran out of money?)

how did the car ran with a 9:1 cr and no blower?? I guess it wasn't that bad... after all you put almost 10kmiles that way.

leo

 

I dont think your seeing his point. he is not say 9.0:1 is not possible what he tring to say is with a ratio of 8.0:1 to 8.5:1 is just for liabilty reasons. why let your end go to waste when you stop at the pump to get gas and its bad which then causes predetnation then bye bye motor. With a smaller compression ratio its peace of mind. But 9.0 to 9.5 to 1 is possible but not quite a risk but I rather have insurance because I went with a smaller compression ratio.