A little disappointed in my 451

[rustyst]

I just got my 451 back on Friday for my '73 Charger.  Although its a lot better in terms of power than the stock 400 I gotta say I was expecting a little more. 

I have the original thermoquad 4 barrell that was rebuilt, also the original heads that were ported, the intake is a edelbrock performer and a 2500 stall from hughes. The gears are the original 2.73's (ran out of money) will a gear change to 3.55 or 3.73 give me the head snapping power I am looking for?

Any input is appreciated, thanks.

[Blown70]

Well I would think the gear will make a big difference.  Did you Dyno the motor?  This can be helpful in the intial tuning of the carb and timing.

Just a thought.

Tom

[rustyst]

Did not dyno the motor, nothing around here.  If the timing is off how much will that effect the power?

[Blown70]

Did not dyno the motor, nothing around here.  If the timing is off how much will that effect the power?

My last motor was A LOT..... Could have swore I was driving a 4 cyl.  I guess I would check a lot of things.... Fuel, spark, Timing. to start.  I know due to an issue with a balancer the timing on the last one was off 5 degrees.

Tom

[rustyst]

Right now I wouldn't want to race my wife in her Mitsubishi with the Charger, somethings wrong.

[MOPARHOUND!]

I just got my 451 back on Friday for my '73 Charger.  Although its a lot better in terms of power than the stock 400 I gotta say I was expecting a little more. 

I have the original thermoquad 4 barrell that was rebuilt, also the original heads that were ported, the intake is a edelbrock performer and a 2500 stall from hughes. The gears are the original 2.73's (ran out of money) will a gear change to 3.55 or 3.73 give me the head snapping power I am looking for?

Any input is appreciated, thanks.

Edelbrock Peformer is worse than a stock intake, a Chebby design adapted to a Mopar.  Get a Eddy Performer RPM if you have room for a tall intake, or a Holley Street Dominator.  You've got RB cubic inches trying to be fed by a relatively smallish B intake.

Gears will make a world of difference, especially switching from 2.73's.  My Dodge truck went from dogging with 3.21's while towing, to pulling away with ease from a stop with 3.55's.

Do you have a 8-3/4??

[BigBlockSam]

try advancing your timing alittle.

[moparguy01]

id swap to a set of 3.55 or even 3.73 gears (yes they make them for mopars now)
and maybe toss a holley carb or speed demon on there, 750-850 cfm. and i bet it'll pick up ALOT.

[firefighter3931]

What cam is in the 451 ?

Ron

[Headrope]

Gears can make a huge difference, but shouldn't have anything to do with the engine being less now than it was before. From your description the gears are the only constant between the two builds.
And not to start the whole "which manifold is better debate" but I've found the Edelbrock Performer to be much better than what many on this site made it out to be.
I too am curious about your cam.

[rustyst]

camshaft specs are as follows

cam lift 302, valve lift .491 duration@.050 228
cam lift 308, valve lift .522 duration @.050 234

I was told by the guy who built the engine that the bottom end was way over built for what I had with the heads, cam, intake and carb.
Maybe I shouldn't have stressed the driveability issue so much.

[RD]

camshaft specs are as follows

cam lift 302, valve lift .491 duration@.050 228
cam lift 308, valve lift .522 duration @.050 234

I was told by the guy who built the engine that the bottom end was way over built for what I had with the heads, cam, intake and carb.
Maybe I shouldn't have stressed the driveability issue so much.

302/308 duration is kinda big when you only have a 2500 stall, plus add to that fact that you have 2.73 gears... wow, i bet its a slug off the bottom end of the rpm scale huh?

You need a bigger stall like a 32-3800 and some steeper gears to awaken that bad boy up.

Your heads, you said were ported right...did you get bigger valves also?  how much do they flow?  you know that performer intake may be hurting you also, i would have put in a performer RPM instead.

oh and the dirt-o-quad is a good carb, just not the best out there.

last bit of advice... listen to the firefighter feller, he is a pretty smart cookie when it comes to this stuff.

[rustyst]

I'm waiting for his .02.

Thanks for the reply.

[firefighter3931]

camshaft specs are as follows

cam lift 302, valve lift .491 duration@.050 228
cam lift 308, valve lift .522 duration @.050 234

I was told by the guy who built the engine that the bottom end was way over built for what I had with the heads, cam, intake and carb.
Maybe I shouldn't have stressed the driveability issue so much.

Well, it has a bit of duration at .050....228*intake/234* exhaust at .050 valve lift. That is the critical number that defines the powerband of this engine. The 302/308 numbers are the advertised numbers that determine seat timing and influence idle quality. Ok, enough with cam 101.

Basicly that cam will want around 2800 stall and 3.55 gears inmo. It will feel sluggish out of the hole because you're a little short on stall and woefully undergeared. The lowdeck "performer" is not that bad of a manifold. The rb version is comparatively worse. If the car is heavy you'll want to keep a dual plane on it for better throttle response and increased torque. I'm not a fan of thermoquads....that engine is screaming for a 750 holley. Timing and ignition advance need to be looked at and adjusted for maximum performance. A cam like that will want at least 15* of base timing at idle and 36-38 at 3000 rpm. I would start by tuning the ignition curve to see if that helps....once that's taken care of you can move on to carburation. For sure it needs more gear in the back end.

Ron

[is_it_EVER_done?]

My opinion is that your cam is much to big for your combo/gears/converter. You didn't say what the cams centerline was, or what it was installed at, nor did you state your compression ratio or what your intended purpose is, but I'm going to guess that the cam is far too much for the rest of your combo and vehicle weight.

with your gear ratio, manifold, carb, weight, heads, etc., a stock type "Magnum" cam would be far better. There was a post a while back wherein someone used a 590 cam in a mild build, and produced dismal power on the dyno. A change to a more suitable cam for the build produced dramatic improvements in every area. However, the 590 cam is a known performer (to the extreme) in it's proper environment. You may be in the same situation.

Another thing to consider is the TQ carb. I love them with a passion personally, but I would never use one in a "performance only" environment. They can deliver exceptional driveability, gas millage, and decent performance, but they are a compromise in all areas, and only excel in general mileage/performance applications.

You need to post all your engines parameter, including vehicle weight, compression pressure (from a compression test), carb CFM/jetting/metering rod specs, your cams full specs w/installed centerline, and desired performance goals. That is the only way to get specific recommendations.

Lastly, don't get in to much of a hurry. It takes time to tune an engine to it's max potential. It sounds as though you have a solid 25% - 30% power still in yours (not uncommon in a new build). Just take it one step at a time and you will soon be amazed.

[rustyst]

Thanks much for all the replys, I guess theres still a lot to do.

[Chryco Psycho]

the 302 / 308 # are Valve lift at the Cam / Cam lift NOT duration
the 228 * / 234* duration is a nice smaller cam & should work Great ,
I would start by doing it to death to see how much is left in the package , often ther is a lot of power in tuning , then maybe change gears to 3.23 or 3.55 for more Feel