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  #1 (permalink)  
Old 06-25-2012, 06:48 PM
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Default 351W dyno rwhp

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Just got back from a dyno trip and am not sure if I am where I should be. Here is what I have.

351W .30 over
Trick flow TW 170 heads
comp cam 508/532lift 222/232dur
dual quad edelbrock 500cfms
MSD ignition on a 6AL
Timing at 34 total advance

My results on a mustang dyno all numbers are at the wheels
max tq 289lbs @ 2800rpm
max hp 280 @ 4700rpm

TQ remained almost flat across the dyno thru 5200
HP started at 160 at 2800 and rose at a 45 degree angle thru 5500 up to 280hp.

I am just not sure if this is the right numbers for the set up I have? I know I can make more if I go single large 4bbl.
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Old 06-25-2012, 07:21 PM
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Exhaust pipes/mufflers as well as transmission and rear end type play a big roll in RWHP numbers......for instance, a toploader will "eat" more HP than a modern 5 speed transmission as an IRS rear end will do the same compared to a 8.8 or 9 inch rear end, not to mention restrictive side pipes/mufflers.....

Using 350 HP at the flywheel and a 15% driveline loss, you should be around 297 RWHP.......it's not unheard of to pick up 20 to 30 RWHP with a good tune,carb jetting/timing, just takes some time on the dyno with an expirenced operater....

David
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Old 06-25-2012, 07:35 PM
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4700 rpm? Something is not right.
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Old 06-25-2012, 07:35 PM
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I am running a tremec 3550 and 8.8. I was not aware that the loss was so much thru runnning gear. Also it was hot in san antonio today around 100 when we ran the tests.

Am I correct in assuming that I am about where I should be based on the setup?

My AFR averaged at 14.3.

The car definately feels like its more responsive so I dont feel that I wasted my time.
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Old 06-25-2012, 07:37 PM
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Jeff

I just double checked the dyno sheet it reads 4900 sorry on the typo
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Old 06-25-2012, 08:12 PM
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Keith Craft told me that when he dyno-ed motor, installed it into a Cobra and then chassis dyno-ed the car he typical saw a 20% loss.

I have a 302 stroked to 354 fuel injection, KC Brodix heads, TKO 600 and a 8.8 rear end. I dyno-ed last year at 402 hp and 416 tq at the rear wheels.

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Old 06-26-2012, 12:10 AM
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dual quad are probubly killing you. I would try a dule plan intack and a 650 cfm carb. A stock 351 W with some rubing on the heads will do 310 hp
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Old 06-26-2012, 01:56 AM
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I've seen 100hp drops from flywheel to rear wheel on Cobras. Sidepipes and drivetrain losses are usually killers.

A good single carb intake and carb package would probably wake that thing up a little bit. It should pull a little higher than 4900, so something is amiss somewhere.

Any signs of valve float at higher rpm? Usually the springs that they put on these heads (especially small heads like a 170) peter out pretty quick.
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Old 06-26-2012, 02:46 AM
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Can this thread be moved to the "Official RWHP Thread" ?
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Old 06-26-2012, 05:33 AM
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Not only driveline loss,but don't forget the loss form the water pump/alternator/power steering and anything else belt driven on the front of an engine.........
Years ago, a guy had a 360 Dodge engine on a dyno,this particular dyno didn't have it's own water pump,so the engine had the water pump on it and in this case the alternator also.......when they began making pulls,at about 5000 rpms, it would throw the water pump/alternator belt off everytime, pulleys were not lined up properly.....
On one pull it was noted that there was a 14 hp increase as soon as it hit 5000 rpms and threw the belt!!!!!!!!!!!!!!!!

David
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Old 06-26-2012, 10:26 AM
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Quote:
351W .30 over
Trick flow TW 170 heads
comp cam 508/532lift 222/232dur
dual quad edelbrock 500cfms
MSD ignition on a 6AL
Timing at 34 total advance
Based on the limited info,I'm comparing this engine to another 351-W I know of with very similar specs, dynoed at around 325 HP at the flywheel......assuming your engine makes 325 hp at the crank and it made 280 at the rear wheels, that is a 13% loss,which would be outstanding......
I'd say for what you have,those numbers are in the correct ballpark..
Switching to an air gap dual intake and 600/650 double pumper and a good tune, I'd bet another 20 to 35 hp would be possible....

David
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Old 06-26-2012, 11:55 AM
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Thanks to all-

Seems the to be concensus that with the set-up I have I am about where I should be.

I am going to enjoy this set up and master controlling then will look into making more hp.

Appreciate everyones input-
Beastly
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Old 07-06-2012, 08:30 AM
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Just because no one else mentioned it -

170 heads on a 351? The consensus I get lately is minimum 185 -195 would pull another 35hp and leave the curve up against the rpm limiter. On the bottom end, it would still be able to keep the same hp and begin building sooner.

HP is a tricky game, we see a lot of magazine dyno tests where they claim gobs of additional hp, but what really happened right there in the charts is it was robbed from the lower end, and the engine is just more peaky. Since MOST of the engine rpm is less than 5,000 rpm, I'm no fan of making the engine weaker where it will be used the most. I've gotten a bit cynical when I read one of these churned and spun stories selling some new parts.

On the other hand, plenty of tests show the newer bigger heads aren't killing the low end, which is why they are worth the money. If you see increases starting at 1,800 rpm, then something right is happening.

Another factor is the LCA of the cam, and whether it's appropriate for the intake. This seems to be another of those finesse points finally coming up to the surface, and a lot of the discussion is about getting that detail of cam timing right to match what you run - not just taking whatever it ships with. People are talking improvements measured in multiple tens of horsepower, so it's significant. Sure, on a 300hp motor that might be just a 5-8% improvement - or another way of looking at it, up to 25 hp.

Add three or four of those little finesse points, and it adds up quick.
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Old 07-06-2012, 09:20 AM
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I would bet that the numbers would increase and your car would run better if you changed the carb’s to dual 390's instead of the dual 500's. I believe 1000 CFM is too much for your motor.

Although I could be wrong & I am sure that I will be told so and to keep my opinion to myself.
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Old 07-06-2012, 06:08 PM
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This may sound too simple but is your throttle opening up all the way? When I first dynoed my mild 302 it only pulled 160 rwhp. Guys at the shop said that was about right. I searched the Internet and a poster at ford muscle said to check the throttle opening. I did and it was only opening up about 1/3. I adjusted it, took it back and it pulled a little over 280 RWHP.
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