HP/TQ estimate

[CamaroAdam73]

What do you guys think my 403 will be able to push? I'm more interested in the TQ it's going to make lol.

Specs...

Olds 403

.040 Over
Stock spec pistons
Fel pro gasket, compressed thickness somewhere between 0.037 - 0.040, not 100% sure there

350 Rocket heads from 69, had them CC'ed, 66CC
Stock valve sizes, 1.94 int/ 1.63 exh i believe?
They have been ported, had my machine shop check them out and they told me i really lucked out here.

Cam
Comp cams thumpr, dick miller recommended me this cam profile
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1463&sb=0

Lift : 491 / 476
Duration: 278 / 296
Range 2000-5800

Intake
Edelbrock 3711 performer low rise
Range idle - 5500
Dual plane

Ignition
Stock dizzy recurved, DUI DYNA MOD ignition module/ coil.
Moroso adjustable vacc advance
Moroso Pickup

Carb
Factory 850 CFM 403 Q-jet, built to this motors exact specifications by Ken @ Everyday Performance

Exhaust
Hedman headers
Primary Tube Diameter (in):1 3/4 in.
Collector Diameter:3.000 in.
2.5" full dual exhaust the whole way back.

Beyond that, the car is an 88 Monte carlo SS, TH350 B&M rebuilt, 3.73 gearing in the stock 7.5 rear.

 

[pontiacgp]

it's about $75 or less for a dyno run so why guess?

 

[CamaroAdam73]

Not in my area man, there's only one dyno and it's over 100$, 45 miles away and they only let the public play once a week so the waiting line sucks.

Believe me i do plan on getting her on a wheel dyno. I'm just bored and curious right now.

 

[pontiacgp]

That sucks, did the guys at the machine shop who checked out the heads give an opinion on what the hp and tq might be?

 

[DoubleV]

Hard to guess. Some thoughts; What is your actual CR? It's probably lower than what you think because cast stock replacement pistons are short on height. I can't believe Dick Miller recommended a Thumpre cam because those things are made to sound 'cool' ( if you get into that lopey idel sound ) without actually making as much power as a milder cam. Not that they won't make power, it's just that a different one would make more and idle better too. Your carb is 800 cfm, not 850. If the head porting was done right, it could give you a nice bump in power but if it wasn't done right and/or not that much was even done, then you won't be getting much more ( if any ) out of them.

So assuming the heads were done right, your CR is adaquate ( like in the low 9's ), and it's properly built and tuned, I'd guess around 350 gross.

P.S. I didn't even know you could bore a 403 .040 over...at least it's not recomended to do so. There has to be like only a sliver of iron between those cylinder walls!

 

[shanghaismith]

I think you will have between 325 and 350 HP at the crank. My 403 is .040 over, no problems but I have light weight pistons and the rotating assy. is balanced.

 

[Kwik_Cutty88]

Not in my area man, there's only one dyno and it's over 100$, 45 miles away and they only let the public play once a week so the waiting line sucks.

Believe me i do plan on getting her on a wheel dyno. I'm just bored and curious right now.

I'm around the Myrtle Beach area, I know of a tuning shop in Wilmington that a friend had his car dyno'ed/tuned at a while back, just have to dig up the name.

 

[CamaroAdam73]

Kwik it's been awhile since i updated my profile, i'm in western PA right now. I won't be back in wilmington/ CB till next year.

DoubleV, I was actually aiming for the low to mid 9's, i didn't want to raise the CR too much. There are allot of different profiles of the thumpre cam, i trust dicks opinion so i hope it rips. I thought i might have been off with the CFM, knew it was at least 800 though. Well my shop told me the work is quality, i noticed it when i got the heads so i wanted to have the work checked out to make sure i didn't have to have them ported again to fix any mistakes made by the last guy.

About being 0.040 over, at first i thought i was only 0.030 over and alittle worried but again dick miller, and my machine shop ( the guy races olds motors so that's why i go to him, has a super rare 70' GT37 too) said i will be fine, especially because i'm not pushing too hard.

If i end up with around 350 HP i'll be totally happy, i'm really really hoping to peak TQ around 425-450. That should reallllyyy make this gbody chassis move!

 

[lilbowtie]

300 to 350 hp should have you in the low 8's to high 7's in the 8th

 

[olds307 and 403]

I would see how far the pistons are in the hole. With close to 0 deck, it will be low
9's compression wise. It will put a smile on your face.