James

Finally (after a year) I got my 385 on the DTS engine dyno yesterday. This is a motor I'm building for 1968 Rally Sport Camaro I have. I had a 110 GPH Holley mechanical fuel pump that I was hoping to re-use on this motor. Looks like this pump can't pump enough fuel according to the information collected from the only pull we made. So any suggestions on what mechanical pump I should try? What mechanical pumps are you guys using? I was wondering if the holley 130+ pump would be enough of a jump to fix the problem. When the motor goes back in the car the pump will be plumbed to the factory 3/8 inch fuel line which is still in place. Hopefully I can get by with the 3/8 inch fuel line if not I will address that later. Thanks for your help.

Guru_4_hire

You maxed out a 110gph pump. Dang!

James

Last week they dyno'd a 1969 factory spec DZ302 Z28 motor for a guy. He had some kind of a factory replacement fuel pump on it and it fell short too. I let them try my 110 GPH pump and it worked perfect on his 302. I was kind of surprised when it could not supply enough fuel for my 385. His 302 dyno'd almost right in spec of what the motor was rated from the factory at. Kind of cool!!! I need to order something today so any ideas you guys have I would appreciate it!!!!

gkull

I only within the last two years replaced my original 79 pump with from NAPA AC-Delco original type return line mechanical. I can almost bet that your smallish 385 does not put out the power of my 434 motown unless you are using power adders like blowers or lots of juice.


Maybe you have not tuned for correct BSFC on the dyno.

billla

I'd agree with gkull - I can't see how you're leaving the pump behind unless that 385 is making 500+ HP. I'd spend some serious time with the lines and filter - and VERIFYING pump output - before going too far down the route.

James

I was kind of surprised too. I'm just going off what he told me and I trust what he says. He is a very well known high end performance enige builder and racer in the area. GKULL I have the dyno sheet from the one pull we made that I can send you via e-mail if you want to take a look at it. BILLA - This is a DTS engine dyno not chassis dyno so lines are not an issue at this point. I think the columns he pointed out to me were BSFC and fuel pressure. Again I'm just trying to figure out what the best solution is and how to proceed. Thanks.

billla

I missed that Probably still worth checking pump output.

James

No problem at all.
I'm always open to any input anyone has to say from here!
Thanks again.

gkull

I was just wondering if your fuel log to your double pumper has a return feed? Do you see fuel pressure drops during the dyno run? I was trying to figure out why the dyno operator was saying you don't have enough fuel.

James

The carb is holley 4160 750 Vac secondary carb that has been worked over just a little bit. It is a dual feed carb. Pretty positive the way it is hooked up on his dyno right now there is not a return fuel line plumbed into the current setup but I did not look at it super close. I think it just dead heads at my carb but again not 100% sure. I know the pump did not require a regulator because its hard set @ 7.5psi.

gkull

For everybody, James sent me the dyno printout. The fuel pressure has a steady drop from 6.1 down to 3.7 and an A/F ratio of solid 8.3 at all rpm

I don't think that a motor would be running very well at 8.3 and this might be true because the dyno run starts at 3900 rpm. So the operator could not get the motor to take a full load at lower rpm.

IMO - the 3.7 psi is not a big deal because you never leaned out and in fact Your BSFC was constantly climbing and your hp did not drop off hardly at all from 5500 - 6300 rpm

Gordonm

I ran my "smallish" 385 on a chassis dyno with 3/8 fuel lines. I made 409 rwhp and I had a fuel pressure gauge tha tI was looking at during the whole run. It started at 6.5 psi and maintained 6 psi through 6500 rpm. I run the Holley fuel pump. Nothing special. I agree with the others this pump should supply all the fuel you need.

Fonz69

I used a RACE PUMP on my 540 and it has worked great!

First in my jetboat on a blown 540 pushing over 1000HP and on the dyno the pump never varied more than a 1/10 of a pound

Its now on my 540 in the 69 vette and has been still working flawlessly

And thats on SS factory replacment fuel lines on the vette too with a motor dynoed at 650+HP running a quickfuel 850 DP

http://www.racepumps.com/

DRIVESHAFT

In theory you need 1/2 lb of fuel per horsepower, per hour.
For a 600 hp engine, that means that you will need 300 lb of fuel per hour.
Fuel weighs 6 lbs per gallon, so 300 lb = 50 gallons per hour.
Your 110 gph pump should have no problem keeping up unless its defective.
If I were to upgrade to a higher output pump, I would go straight to the 172 gph Carter pump. http://store.summitracing.com/partde...5&autoview=sku