I am looking at a hardcore racing stroker kit, but the compression ratio is 11.1 to 1 with a 72 cc head, and standard deck height. my question is there any way to lower the ratio, im going to use AFR heads, and i believe they are 74 cc. the main reason i ask is because i want to run this motor on pump gas (93) thanks for your help

 

Well, we could help you if we knew a little more about your engine????

Auggie

 

Welp, im doing homework now for a 383 buildup. this will be my first engine build, its a 74 vette 350 block, im going to use AFR 195's most likely and fuel injection. its going in my 87 IROC. Id love to give more details but i dont know too much.

 

Well, I really don't think that your C/R is that far out of line.

Bore = 4.03"
Stroke= 3.75"
Cyl head cc's = 74
Deck clearance = .025"
Head gasket thickness = .038"
Valve reliefs cc's = 2

Compression Ratio = 9.79 to 1

Auggie

PS: That's the best I can do with the info you gave me
Them heads have some real large flow numbers if you are
going to use them on the street.

 

not positive on the heads, i might stick with a pair of 190's. any ways what else do you need for info. sorry if these questions sound dumb, but im new to this and trying to learn some. thanks for your time

 

Well, I just guessed at a few of those figures, but if you can give me the velve events I could calculate your most importent C/R which would be your effective C/R.

Auggie

 

velve events ? what are these. do you mean valve? as in size of valves?

 

No, the valve size on AFR 190's are 2.02" for the intake and 1.60" for the exhaust. Valve events would be the duration in degrees that the Intake or the exhaust valves are open. You said that you were new to this sort of thing and so was I at one time. I just went to the libury and checked out a bunch of books on engines and read them from cover to cover. Very poor at that time so the free reading was great.

Auggie

 

so to find that out i would need to know what cam i was using, right? yes i have a few books that i have glanced at , but havent had the time to really read them, i will soon though.

 

Yes.

Auggie

 

Actually, the AFR 190's and 195's are street heads so I dont think you will have a problem with them in that way. One thing is though that I would go with the AFR190's because they both flow practically the same numbers. The only difference is that the intake port is a little taller(or at least shaped differently) in order to work better with a couple of the large single plane intakes. The 190's will probably line up better with your intake. What kind of fuel injection are you planning on using?

Ben

 

What kind of power are you looking at? What power range? Is it mainly street, strip, roadcourse? Give us all the details and we an pick out a good cam and such for your motor. Then we can find out the dynamic (or effective) compression ratio with those cam specs.

 

well, for intake i was looking at either the stealth ram, or the super ram.

as far as use it will see mostly spirited street use but will also be a wekend warrior at the track on ocassion.

as far as power i am looking for 400-450 at the motor, something cappable of getting me well into the 12's

I will be using a 700R4 that will be rebuilt

thanks for your help, i was mainly looking for weather or not this setup could run on 93 octane, but the more info i get the better, more to learn. i appreciate it

 

Well, everyone has their owen ideas but I think that the AFR-180's (180 = port cc's) are a much better all around street/strip head for a 383. You have to think about what persentage of time you will spend useing your car on the street compared to drag racing. I would guess 90% and you want good crisp throttle responce for the street. Big cams and heads make for a lazy bottom end. Have you given any consideration to a set of Vortech heads??

Auggie

 

Dude, the AFR 190's +195's are made specifically for street use. Look at their website. They were designed with keeping velocity up in mind. This is what keeps the low end. I might agree with you on the 180's if we were talking about a 350, but even then I would probably still use the 190's. On a 383 you flow a lot more air than a 350 and will really benifit from the extra flow. Heck, I don't think he is going to be lacking on torque with a 383 no matter what his choice. As far as the vortec heads, they are a good flow per dollar option, but if he has the money for the AFR's I think he will be much happier with them. If you get the vortecs they dont have screw in studs and wont support much lift without machining down the guide boss, and enlarging the spring seat. I have not seen anyone that was really dissapointed with their low end on a 350 with the afr 190's, so I really doubt you are going to be on your 383. I would bet you will still have a very hard time getting traction.

Ben

 

Ben, you could be right, but I have seen many a disappointed guy's running big carbs, cams and heads on the street with stock stall convertors wondering why they lose from stoplite to stoplite. To each is owen

Auggie

 

I was going to use the AFR'S because i have heard and read great things about them. Plus they are only 1250 ready to bolt on. I dont consider that an outrageous amount of money. I like to get the best thing i can the first time even if it means waiting another month to get it.

As far as the TC goes, i wasnt planning on using the stock one.

Traction will be part 2 of my project. yes i know i will have problems but i want to do my motor and tranny 1st, then next summer go about the traction

 

I am not arguing that it is real easy to get caught up in the bigger is better philosophy even though it doesnt work that way. I was just pointing out that in my opinion the AFR 190 falls into the too big for a 383 catagory. Now maybe if he was looking at something like the 210's or 220's which are designed for track use I would agree that they were to big.

KMAN,
I wasnt trying to say that you didnt realize that you would have to do some traction mods. I was just stating that with the 383 I didnt think you were going to have to worry about not having enough low end.

Ben