Thread: Desk Top Dyno....anyone?

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If anyone has a desktop dyno that they believe to be fairly accurate could they run this combination for me.I have this engine in my 32 roadster.Thanks!

BBC 454 bored .030 over
Eagle Rods H-beam rods
Eagle crank
Pistons Speed Pro forged
Heads are Merlin Rect 345cc intake runners...2.30 int. 1.88 exh. 119 cc'd
polished combustion chambers and port matched.
Isky hyd roller...110 lobe center .608 ex. lift .578 int.lift... 238 deg int. 248
deg ex. at .050 .....284 deg int. 294 deg ex. at .020... 72 deg overlap
8-71 Blower...10% under driven
2-750 cfm double pump Holleys
static comp 9:1....effective comp 12:7
Headers 2 3/8 primaries...4 1/2 collecter with cone

Originally Posted by Blown32

If anyone has a desktop dyno that they believe to be fairly accurate could they run this combination for me.I have this engine in my 32 roadster.Thanks!

BBC 454 bored .030 over
Eagle Rods H-beam rods
Eagle crank
Pistons Speed Pro forged
Heads are Merlin Rect 345cc intake runners...2.30 int. 1.88 exh. 119 cc'd
polished combustion chambers and port matched.
Isky hyd roller...110 lobe center .608 ex. lift .578 int.lift... 238 deg int. 248
deg ex. at .050 .....284 deg int. 294 deg ex. at .020... 72 deg overlap
8-71 Blower...10% under driven
2-750 cfm double pump Holleys
static comp 9:1....effective comp 12:7
Headers 2 3/8 primaries...4 1/2 collecter with cone

Hi,and welcome to the club.
I am not trying to pick your combo. apart but rather help you.
The heads are very large for this comination.
I run the same port volume heads on my 540 with a 8-71 and 10% over-drive and a mech. roller cam
Even though I am not a big fan of the desk-top dyno I am very curious about this combo.

heads are way too big for that cam correct? should be in the 7's with those , and also some more cubes or some heads with smaller runners, that is the same size i will be running on my 632ci bbc, but i am new to some of this as i was a small block guy so don't take my recomendation to heart but from what i have been doing research on that is my conclusion

Question: since this is a blower motor, the port velocity will be plenty high enough even with the big runners, no? Granted, with the force-feeding, smaller ports will work just fine, but I wouldn't expect the large runners to hurt performance any

Just wondering....

-Chris

Originally Posted by skids72

Question: since this is a blower motor, the port velocity will be plenty high enough even with the big runners, no? Granted, with the force-feeding, smaller ports will work just fine, but I wouldn't expect the large runners to hurt performance any

Just wondering....

-Chris

Chris,you bring up a very good point.
I have not done enough dyno testing to know for sure but I can tell you about a customer of mine who has a very similar combo.
He has a set of 357 fully CNC'd AFR heads.
We tried his 357 cc heads first and our tq/hp where very poor below 3,500 rpm's.
I had set of 305 cc heads and the hp/tq picked up down below.
I guess we can lok at cam specs. ,boost levels,etc.
You can "overhead" a blown aplication also but it is much more difficult.
In the 454 listed above I am not sure what 10% under means as far as PSI.
I will try and see if I can find some of the dyno results.

Thanks again guys for the help.
As to the large heads my train of thought was to allow the engine to breath very good even at low rpm due to the fact that I set the motor up with 9:1 static compression to start with so if the blower was to much for the street I could remove,change cam and put a new intake and carb and still have a short block with descent compression.Not my first engine build by any means but my first blower motor.
Figured if it was able to breath good it would cut down on heat and possibly get away with 9:1 to start with and prevent detonation with 93 octane pump gas.With the a 61 tooth pulley on the blower and a 55 tooth on the engine my effective compression is at 12:7.So far no detonation after 1500 miles.I know I'am not pushing alot of boost but I have the option to change pulleys and overdrive the blower and make much more power on race gas.
If I reverse the pulleys it will make about 15:1....16:1 compression and much more power but also heat.That is the reason I o ringed the block so I can overdrive and really see what power the combination will make.

For best results you need flow numbers and cam timing to input into DD.

Decent estimate though IMO .......... Kitz

Originally Posted by Blown32

Thanks again guys for the help.
As to the large heads my train of thought was to allow the engine to breath very good even at low rpm due to the fact that I set the motor up with 9:1 static compression to start with so if the blower was to much for the street I could remove,change cam and put a new intake and carb and still have a short block with descent compression.Not my first engine build by any means but my first blower motor.
Figured if it was able to breath good it would cut down on heat and possibly get away with 9:1 to start with and prevent detonation with 93 octane pump gas.With the a 61 tooth pulley on the blower and a 55 tooth on the engine my effective compression is at 12:7.So far no detonation after 1500 miles.I know I'am not pushing alot of boost but I have the option to change pulleys and overdrive the blower and make much more power on race gas.
If I reverse the pulleys it will make about 15:1....16:1 compression and much more power but also heat.That is the reason I o ringed the block so I can overdrive and really see what power the combination will make.

I think without the blower, your low end torque and throttle response will be sluggish with the big heads because the intake charge velocity will be slow, but they will support alot of power at higher revs. As with just about every aspect of an engine build you're balancing low-end vs. high-end... big intake runners = high-end... (smaller runners = low-end)... as I mentioned before... I think the blower negates these impacts to some degree because you're forcing the charge in.

-Chris