I've decided to buy a set of AFRs... but I'm still up in the air on the chamber vol and whatever head milling, if needed.
I would prefer NOT to be limited to using 93 octane, gas is expensive around here.
But if I'm in the mood to play hard I'd like to be able to switch to hi octane and make some timing adjustments, if nessecary.
So that's the sort of comp ratio I'd be aiming for, sort of borderline.... whatever that might be.
I'd like suggestions on that.
My cam will be either the Comp XR269HR (118/224*@.050), XR276HR (224/230*@.050), or GM hotcam (118/228*@.050)
So.... Questions:
#1 What CR should I be looking at using with either of those cams to make this motor compatible with lower octane fuel?
#2 Once I've determined what the right CR is, would it be best to use a small chamber head with dished pistons or flat pistons with a larger chamber?
This will be for a 383, TPI (LT1 intake coming)
This combo seems like a pretty popular one. Let me hear from you, I'd like to know how your setup is working and what you think about my combo.

Thanks, as always

 

C'mon Fellas.... you're not trying

 

Go to www.ChevyHiPerformance.com and do a search for "Agent 87"

It was a build up of a 355 that ran low, low 13's on 87 octane. They were using Vortec heads, but the same could be accomplished with AFR's if you use the same approach.

 

I would keep compression at 10:1. Since you have aluminum heads you should be fine.

Use flat top pistons as they give the best flame travel of any piston, get the 74cc heads, deck your block to .01, get your #1010 felpro gasket with .039 compressed. This will give you the optimal quench area of .040, which is another big factor in octane needed(besides compression and cam overlap)

 

Thanks.... very helpful.

 

It all depends on what you want to do with the car. How fast do you want to go? Is this your daily driver? Do you care about gas mileage and idle and all that other crap?

Need more info.

 

Yep, I do care about gas mileage and idle.
Part of my reason for going with a stroker is I'd like 400+ hp without a radical idle. This is Cali. and I feel better driving a car that at least sounds legal.
If possible, within the above mentioned limitations, I'd like a 12 sec machine.
Got any suggestions?

 

89 GTA 383...
Need more info??

 

What more do you want? That article I gave you the link to pretty much explains what you have to do. Like what SCR to aim for as well as DCR with the same cam you're using, just the flat tappet version.

What more do you need to know?

 

Much thanks for the link to that article AJ 92RS, it is very helpful and very thorough as well, especially considering it's a magazine article. ...Greatly appreciated.
89gta383 replied yesterday asking for more info, re fuel consumption/ idle quality. It sounded like he might have something to add.

 

I read this, and you describing a supercharger, but I dont think on porpose.:lala:

 

I meant 400hp at the crank, not the wheels....Or whatever it takes to get me into the mid 12s.
I just don't want a 'conspicuous' idle.
And I'd like my car to get at about 7 mpg better fuel economy than my truck (that would be about 24 hwy)
And to be able to cruise on regular gas (premium is about $2.10/ gal here)

I'm thinking, something like this is what I want: https://www.thirdgen.org/techbb2/sho...threadid=84340
Only different....Add some AFRs, an LT1 intake, and 7* more cam duration to Mikes Crews (see link) formula and it seems like that ought to put me there.
400 hp might be high but I think mid 12s is realistic, that's the important thing.

 

24 mpg and 400 hp? That doesn't sound like a combination that's able to mix. You might get 24 mpg with a stock 305/350. I have a built 355 with a medium cam (zz4 cam .474/.510 with 1.5 rockers), it used to idle lumpy. I got rid of the old stock chip and had a custom chip done. Now it has all the power in the world, gets better mileage, and that lumpy sound turned into a somewhat smooth idle. From what I was told, you can even have the chip programmed just for taking it to echeck. I'd look into a custom chip if I were you. LSRacing did mine and it's great. Best mod i've bought yet.

 

I might have to compromise on that 24 mpg, huh?
From what I've been reading in my searches the CC XR269HR has a pretty steady idle tho.
Some of the guys say the hotcam can be kind of rough.

It sure is cool, being able to find out what guys have to say about all the stuff they've tried.
Thanks everyone