Help Predicting 351W Chassis Dyno Gains ?

This was a unmodified FMS 351W/385 crate motor
Flat tappet cam 230/240 Duration / .520L,
Compression 9:1
BG 650 Speed Demon, V-Jr,
GT40X heads /1.6 Rockers
Motor pulled 346RWHP with this set up

Recent upgrades are :
Brodix ST 5.0 heads ported w/enlarged 190cc intake runners, larger valves, flow tested at 300cfm/.6L
- V-Jr Intake port matched
- Heads milled to increase compression to 10:1.
- Rockers upgraded to 1.7 from 1.6( lift increase from .520 to .550?)
- Larger Holley 750HP carb

Any guess on potential power gains with these mods ?
Dyno is scheduled for next week.

No guesses ? Okay...I will post the numbers regardless as soon as we get the car out of the shop later this week.

You already have 365 RWHP, I would guess you added another 20 - 35 RWHP with your new setup.

Sounds like you built a high RPM Motor with the add on's... but the windsor does not like to go high RPM's to take advantage of your new components. So you will not make a lot more power then you already have.

May have lost some torque too.

I'll say +40hp with an increase everywhere.

In several magazine tests, the 385hp 351 has pulled over 400 horsepower, when baselined on the dyno. In those tests they used a larger carberator, and various forms of dyno headers. Obviously, a chassis dyno will be significately less. At 340 - 350hp, on the rear wheels...you are in the ballpark for your current setup. personally, I think you need a larger carberator to get the full potenial out of that package - others would likely disagree.

Of the changes you are making; raised compression, better flowing heads and increased lift (i.e. higher ratio rocker arms) will add to the top end, but should also help from 2500 on up too. I would expect your rear wheel, chassis numbers to be in the 370 - 380hp range once the tuning is done. Your torque should be in the 400 - 425f/lb range.

Let us know how it shakes out?

Wow ! My buddy had plans last season to measure gains but I could not lis all the 'ghosts" that had to be purged from this car at that time !!
Anyway...the dyno is scheduled TODAy AT NOON. I will post results of this FMS 351W/385 crate motor after adding a good swet of heads and upgrading to 1.7 rollers rockers !

Okay..the results are back. The guy's motor pulled 387RWHP @ 6000rpm making 248RWTQ @ 5100rpm. It had to be jetted down to 76F/86R. It's a very usable power curve as it lands in a great spot after a shift. At the end he turned on his nitrous bottle and sprayed 125HP and pulled a whopping 481RWHP !

Sorry. I made an error. The improved dyno measured 387RWHP @ 6000rpm and 348RWTQ @ 5100rpm. took 100tq away from the guy after all his hard work !
Nitrous pull remained the same @ 481RW.

Originally Posted by Mikes66

You already have 365 RWHP, I would guess you added another 20 - 35 RWHP with your new setup.

Sounds like you built a high RPM Motor with the add on's... but the windsor does not like to go high RPM's to take advantage of your new components. So you will not make a lot more power then you already have.

May have lost some torque too.

I think that is what I said.... Loose some torque.... I did not expect he would loose 100 pounds of torque though..... Yikes...!!!!

Original dyno stock crate motor he pulled 346rw. You guys are on target. So...making a gain 41RWHP with better heads than the GT40X's is one area of gain. But what we saw as more impressive was the power curve. His torque peaked at 5100rpm changed from the last @ 4500 rpm. Yet...the torque band was real close to the peak everywhere from 4000rpm upward to the peak rpm. I mean the motor makes it's power flat with much more punch when he shifts. Good stuff.