I'm second guessing my engine HP
Thread Starter
Burning Brakes
Joined: Dec 2002
Posts: 1,069
Likes: 2
From: Sherwood Park AB
I'm second guessing my engine HP
I bought a 400 sbc last year from a local repair shop to replace my L82. I was told it was originally built for his mid 70's camaro, and it did a 13.3 quarter mile. The camaro was 3900 lbs. I was told 400 hp and 450 tq.
Engine Specs: 400 block, 262 XE cam, 462 double hump heads (ported and polished) and 1.5 roler rockers. It had a performer RPM intake, but I changed that to a performer to fit my Q-jet. I don't know the compression ratio, but it ran fine on 87 octane.
I put on 1 5/8" hedman headers and am using the stock HEI distributor with new plugs, wires, rotor, etc. I am using a modified Q-jet carb. I have a 4 speed with a 3.70 rear end.
This summer I had a few problems with tuning the carb and timing. The problem was, my vette never really felt fast (or as fast as I thought it would.) I only drove it 160 km, but put a full tank of gas through it. The engine runs smooth, and doesn't smoke at all.
Any guesses on the actual horsepower numbers on this engine?
Engine Specs: 400 block, 262 XE cam, 462 double hump heads (ported and polished) and 1.5 roler rockers. It had a performer RPM intake, but I changed that to a performer to fit my Q-jet. I don't know the compression ratio, but it ran fine on 87 octane.
I put on 1 5/8" hedman headers and am using the stock HEI distributor with new plugs, wires, rotor, etc. I am using a modified Q-jet carb. I have a 4 speed with a 3.70 rear end.
This summer I had a few problems with tuning the carb and timing. The problem was, my vette never really felt fast (or as fast as I thought it would.) I only drove it 160 km, but put a full tank of gas through it. The engine runs smooth, and doesn't smoke at all.
Any guesses on the actual horsepower numbers on this engine?
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
Hard to say without knowing compression ratio- maybe somebody can run it through DD w/ a ballpark guess. The cam is mild for a 400 so it looks to have been built for torque. If the Q-Jet has been jetted for a 350 it's likely to be pretty lean. Have you checked to make sure the secondaries open all the way at full throttle? If they don't that could really make a difference. Also, there's a spring that adjusts the tension for secondary opening rate if I remember right. What's your total timing & how fast does advance come in? All of these things can add up to much better power when they're set up right. Good luck.
Melting Slicks
Joined: Feb 2004
Posts: 2,435
Likes: 0
From: largo florida
take it to the track or put it on the dyno and find out what it does. The at the track, the mph will be a good indicator of horsepower. Other then that, you have to use the "bench dyno" and they notorious for being inaccurate.
Melting Slicks
Joined: Feb 2004
Posts: 2,435
Likes: 0
From: largo florida
depends on weight, but.. http://smokemup.com/auto_math/hp_mph.php
assuming 3700 pounds including driver would put you at 230 hp at the flywheel. Sorry, dont know what they weigh
assuming 3700 pounds including driver would put you at 230 hp at the flywheel. Sorry, dont know what they weigh
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
does any body know if the truck weigh stations on the interstates will let you weigh yoiur vehicle (free or for a fee)????
if not, anybody know how you can weigh a vehicle (with driver)
if not, anybody know how you can weigh a vehicle (with driver)
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Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
the places i buy land scape stones from all have scales....you weigh your car befor the stones get put in and then after and pay for the additional weight....i bet some coffee and donuts could get you a weight.....
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
this is one of the reasons I jumped at buying GrandsportC3's motor. I've seen with my own eyes this motor propel his car to mid 12's on street tires.
If I'd had one built, I'd always be wondering if the output numbers the builder claimed were real.
If I'd had one built, I'd always be wondering if the output numbers the builder claimed were real.
Thread Starter
Burning Brakes
Joined: Dec 2002
Posts: 1,069
Likes: 2
From: Sherwood Park AB
I didn't think it was 400, but the nastee 383's reply of 355 hp/430 tq doesn't make me feel too bad. I guess I will have to wait until May and take it to the track. Unfortunately, now I think I will get smoked by a co-workers 03 Mustang Cobra, although his best time is 13.6. Maybe a new cam is in order. 
Around here, there are a number of unmanned scales where you can weigh your vehicle, one axle at a time. Sometimes you get lucky on a roadtrip and find one. I weighed my vette once with the back full of camping gear. I am not going to
the numbers because I can't remember... I know it was fairly close to 50/50 distribution though.
Around here, there are a number of unmanned scales where you can weigh your vehicle, one axle at a time. Sometimes you get lucky on a roadtrip and find one. I weighed my vette once with the back full of camping gear. I am not going to
the numbers because I can't remember... I know it was fairly close to 50/50 distribution though.