Any guesses on HP for this 403
- Thread starter Csilvy2000
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Only the 1/8 mile local to me. Yes 9.7 in the 1/8 mile, equal to 15.13 with my similar 403. I went from 9.9 or 15.44 to a 9.4 in the 1/8 or a 14.66 in the 1/4 by just bumping the compression from 8 to 1 up to 9.6 to 1 plus 2"/1.625" valves with ported #6 vs stock #8's, the same 204/214 cam with 1.72 true roller rockers added in place of stock 1.6 non adjustable rockers on an Olds 350.
Now in my opinion, that's a nice street car. You don't have a fortune wrapped up in it, you don't have something everyone else has, and you built it with your own hands. I'll keep my eyes open for that head swap.
Alright, I go straight down the list you gave me. If a entry doesn't make scenes, just use the generic entry. Valve angle and runner volumes, I'm not to sure on.
Bore-4.35
Stroke-3.385
Rod length-6.0 inch
Piston in hole-zero deck
Piston valve relief-recessed dish-.15 deep x 3.25 dia
Compressed gasket thickness- .041
Head chamber size-83cc
Intake and exhaust valve dia.-2.0" and 1.5" respectively
Head type-45 degree. ?
Rocker ratio-1.62
Intake runner size- flows 185 at .400 lift
Exhaust runner size- flows 115 at .400 lift
(Not sure those numbers will do you any good)
Type of exhaust- headers with 1 5/8 primaries
2 1/4 exhaust dia, duals
Carb- Demon 650,
Intake-Edelbrock Performer RPM
Thanks
Attached is t he output from the Dynomation5 program. I had to make some guesses but i think the output is pretty close to real. If you see anything that I got wrong, let me know and I can make changes and run again.
Cool program but very optimistic. I would say 50 high on hp and torque. I think the torque curve would be flatter as well. I think my 2400 RPM converter was too loose for my 403, I think a 1900 stall stock D9 2004R converter was better, used more of the torque curve. My car was terrible slow with 2.56 gears, I gained .6 going to 3.42 gears. The stock 4A heads suck pretty bad on the exhaust side and mine measured at 86CC.
I agree about the torque being a little high but this program takes into account things like pressure wave reversions and gas pulse dynamics (?).
In making some of the assumptions, I may have hit on a sympathetic combination of specs that raised the output. I don't think it is too far off though, I had a 406 SBC set up with open chambered heads and a cam similar to yours that dyno'd just under 500 ft/lbs of torque (on a real dyno) The torque curve started and ended a little higher in the rpm band but not much. My SBC dropped dead at 5300 rpm, so there was no point winding it up higher than that.
If you can get me more specifics (especially all of the cam specs and head flow numbers), I'd be curious to see what happens. Send me the head casting numbers and I'll see if i can find some flow numbers on the web. Remember that I don't know chicken squat about Oldsmobiles.
In making some of the assumptions, I may have hit on a sympathetic combination of specs that raised the output. I don't think it is too far off though, I had a 406 SBC set up with open chambered heads and a cam similar to yours that dyno'd just under 500 ft/lbs of torque (on a real dyno) The torque curve started and ended a little higher in the rpm band but not much. My SBC dropped dead at 5300 rpm, so there was no point winding it up higher than that.
If you can get me more specifics (especially all of the cam specs and head flow numbers), I'd be curious to see what happens. Send me the head casting numbers and I'll see if i can find some flow numbers on the web. Remember that I don't know chicken squat about Oldsmobiles.
Mike, you've gone above and beyond. Thanks for putting that together for me. I think the averages tell a lot. I don't think they'd be too far off. I'm not sure what the program figured the comp. ratio at, but my guess is about a 7.9 to 1. I'd be interested in seeing what a 9 to 1 cr along with an exhaust valve of 1.62 would do for this engine. I'm thinking I could probably locate some early heads, get them built, have about 800 to 1000 dollars wrapped in the swap and would be disappointed in my cost to performance increase. On with the SBC build. Thanks again Mike!
Glad to do it.
Your compression ratio came out at 8.42/1. I used 18cc for the piston dish which may be on the small side.
Your compression ratio came out at 8.42/1. I used 18cc for the piston dish which may be on the small side.
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