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drag engine questions. 383 sbc
Posted: Mon Jan 30, 2012 2:48 pm
by 71 chevy
hi,
my buddy is finishing his 383 sbc. he is replacing the double humps that came with it with AFR and wants to know how much power to expect, and what size heads to buy
it is 12.5:1 compression
solid flat tappet , 550 lift, 250s@ 50 duration
edelbrock single plane intake running e85 with an hp 950 carb
car is a first gen firebird, about 3400lbs race weight
g force 101a 4 speed transmission
29.5 tire
questions
1. how much honest power would a combo like this typically make with AFR heads?
2. what size heads. He leaning towards the AFR 195s
3. should he upgrade the headers from 1 5/8 to something bigger?
thanks for the replies
Re: drag engine questions. 383 sbc
Posted: Mon Jan 30, 2012 6:59 pm
by supernova
I would say 195 heads and it might make 500 hp. I would also go with 1 3/4 headers, more will not hurt but less will. The 950 carb wiil be too big for those heads and cam combo. I ran trick Flow 195's on a 385 with a 750 carb on gas and a cam with almost the same specs and it made 485 hp. I tryed a big carb and it didn't like it.
Re: drag engine questions. 383 sbc
Posted: Mon Jan 30, 2012 7:25 pm
by 71 chevy
thanks supernova. i'll let him know what you said.
he was hoping for 550hp plus based on what the head mfgs are telling him.
Re: drag engine questions. 383 sbc
Posted: Tue Jan 31, 2012 8:01 am
by spib
my 385 had 550 on engine dyno
has 210 cnc heads and a 630 roller cam and a lil over 13to1 compression
Re: drag engine questions. 383 sbc
Posted: Tue Jan 31, 2012 8:03 am
by spib
spib wrote:my 385 had 550 on engine dyno
has 210 cnc heads and a 630 roller cam and a lil over 13to1 compression, that is a big carb for that small of a cam
Re: drag engine questions. 383 sbc
Posted: Tue Jan 31, 2012 12:33 pm
by clutchdude
With more cam it would make 550, with the setup he has currently has 500, and yes i would say the carb is to big.
My old 383 made 550 to the wheels on a chassis dyno with AFR 210's, my car is also a 4 speed car so the drivetrain is very effiecient...maybe it makes 600hp?
I also used 1 3/4" headers. when i last ran the car with a carb (750cfm) it ran 10.20s @ 130 mph at 2800 ft. elevation, and the race weight was 2900 lbs.
Re: drag engine questions. 383 sbc
Posted: Tue Jan 31, 2012 8:41 pm
by Craig W.
I agree with the 210 AFR recommendation. The 195s make great power on a mild 383, but with the 12:1 compression and more aggressive cam, you might as well turn it up with the bigger heads.
Re: drag engine questions. 383 sbc
Posted: Tue Jan 31, 2012 11:37 pm
by 71 chevy
thanks for the replies all.
i feel a realistic target is 500-525 but my buddy thinks it should be closer to 600.
he is looking into upping the compression to 14.1 since everyone is now saying that is safe with e85 fuel
Re: drag engine questions. 383 sbc
Posted: Wed Feb 01, 2012 7:41 am
by Craig W.
The 195 heads with a moderate hydraulic roller will make right at 500. The 210s with more compression and larger solid roller cam should be somewhere north of 550 but maybe not quite 600.
Re: drag engine questions. 383 sbc
Posted: Wed Feb 01, 2012 7:42 am
by Craig W.
How is this engine gonig to be used? How fast is he looking to go?
Re: drag engine questions. 383 sbc
Posted: Wed Feb 01, 2012 8:26 am
by supernova
IMO if it's going to be a street car I would use the 195 heads with the cam you posted but if it's going to be a track car with big compression I would go with the bigger heads and a bigger cam.
Re: drag engine questions. 383 sbc
Posted: Wed Feb 01, 2012 9:08 am
by Craig W.
I agree. For a hot street car, the 195 heads with a milder hydraulic roller and less comprssion would be really nice.
I recently builts a 9.0:1 383 with AFR 195 heads, Comp XR288 hydraulic roller cam, 750 Holley, Peformer RPM Air Gap intake and 1.6 rockers. It made 506hp at 6100 rpm with a torque curve that was table-top flat. Very torquey. It'll be a real hoot to drive on the street. The low compression was to allow a small supercharger later on if the owner feels the need for more power.
Re: drag engine questions. 383 sbc
Posted: Wed Feb 01, 2012 10:25 am
by 71 chevy
Craig W. wrote:How is this engine gonig to be used? How fast is he looking to go?
he is looking to go 9.99 at 3400lbs. manual trans clutch car.
car is 80 percent drag, 20 percent other(pro touring, standing mile) for now though it is 100% drag and he wants all the power possible out of it.
i mentioned increasing the compression and that is not out as an option
Re: drag engine questions. 383 sbc
Posted: Wed Feb 01, 2012 10:27 am
by 71 chevy
clutchdude wrote:With more cam it would make 550, with the setup he has currently has 500, and yes i would say the carb is to big.
My old 383 made 550 to the wheels on a chassis dyno with AFR 210's, my car is also a 4 speed car so the drivetrain is very effiecient...maybe it makes 600hp?
I also used 1 3/4" headers. when i last ran the car with a carb (750cfm) it ran 10.20s @ 130 mph at 2800 ft. elevation, and the race weight was 2900 lbs.
he is not a member here but he has read the thread. he loves the way your car leaves. can I ask what front shocks you have.
now, I do have to say, 130mph at 2900 does not come out to 550 at the wheels. my slide rule shows more like 500 at the flywheel.
Re: drag engine questions. 383 sbc
Posted: Wed Feb 01, 2012 11:04 am
by clutchdude
Maybe the dyno is lying?
The Dyno was also at a sea level and the 10.20's @ 130 mph were at 2800ft elevation, where 5000 ft d/a's are common?
And for the original posters info i dont see the car running in the 9's without a 210 cc head and a bigger cam and or nitrous.
My 383 in its current configuration with AFR 210 heads runs 9.50's @ 138 Add the birds 450 lbs and i would have a hard time running 9's, and thats in a dedicated race car.