Power Loss--Need Help

[DangaCustom/10]

Hi all,
I have a 1972 Custom/10 Deluxe that I had just finished restoring. It has a 375 hp and 400 ftlbs torque 355 small block backed by a 1993 700r4/4l60 overdrive transmission with a 2200 stall converter. It has a single piece driveshaft and a auburn gear posi unit with 4.10 Richmond gears in the rear end. I was thinking I was putting together something, which in theory, should be relatively fun to drive, however, after I hit 2nd, 3rd, and 4th, there is a huge power loss. if feels as if there is no guts or power being put to the ground in low rpm. I can step on it and it won't do much. I did fix a problem with my fuel pressure, which did help a little bit but now I'm at a loss for ideas. Truck cruises nicely at 115km/h at 3000~rpm on the highway which is nice but it take a while to get there.

We have noticed that the distributor "pings" and the carb needs to be rebuilt. I'm thinking timing will be a big factor but I feel I went the wrong path with my rear end gears and transmission.

Any ideas??? Any help is greatly appreciated.

[leftybass209]

A 700r4, and 4.10 rear gears are a recipe for serious low end torque. If an engine is properly set up for a 4.10 gear and the low first of a 700r4, your tires should want to break loose at the slightest blip of the throttle. What camshaft profile is in that engine? What intake is on it? If your engine is set up for high rpm, and your trans and rear end are set for low rpm torque, you have a serious deficit and will never get them to see eye to eye.

First thing is first though, fix the problems you know you have, or you'll chase issues that may not exist. Get the carb rebuilt, tune the engine, then describe your issues.

It's like saying why don't my brakes work good, but you know you need front brakes and a master cylinder.

Diagnosis should be done after known faults are fixed.

[DangaCustom/10]

Thats what I was thinking. Seems to be a pretty dead on answer there by getting my known problems fixed first. The engine is setup to max out at 5500 rpm. It has a scat crank, 0.030 over hypereutectic pistons, comp cams xe268h cam, vortec heads, gm performance intake, all topped off with a edelbrock rpm performer carb. The engine builder set it up to be for ripping up a street. Should be at 350~ ftlbs torque @ 2000~ rpm according to the "dyno" sheets. Just want to get some ideas flowing.

[geezer#99]

I assume you have a fuel regulator!
What's your fuel pressure?
What's your timing curve like?
What initial?
How much mechanical?
How much vac advance?

[DangaCustom/10]

We had to add an electric booster pump because my truck was slumping around 3psi with only my mechanical. Added the pump and now the gauge reads between 5-7psi.
As far as know for any of my timing, I only know off handedly that my total timing is 34. Sorry if that isnt much help.

[geezer#99]

Originally Posted by DangaCustom/10

We had to add an electric booster pump because my truck was slumping around 3psi with only my mechanical. Added the pump and now the gauge reads between 5-7psi.
As far as know for any of my timing, I only know off handedly that my total timing is 34. Sorry if that isnt much help.

3 psi still works. I ran that little with a pair of carbs on a dual quad intake.. Never ran out of fuel.
You need to limit your fuel pressure to 5 psi max. And lowering your floats a little (1/8") helps too. That's needed because of atmospheric pressure. Lower pressure lets the fuel level run higher.


Your power loss is in your lack of initial timing. You need more timing in the 1000 to 2500 rpm range.
34 total only gives you 8-10 initial.
At elevation like where you live (2700 feet) you need to start the burn process a lot earlier. You need to recurve your distributor. You need about 18 initial with 14 mechanical and a limited 10 degrees from your vac advance.
Look here on distributor mods.
http://www.crankshaftcoalition.com/w...EI_distributor

I live out here at sea level but learned how to get maximum power out of motors with timing tweaks because I lived west of Red Deer for 40 years.

[DangaCustom/10]

We will be giving that go here in the weekend. I have a good family friend mechanic that knows his way around building engines and dragging them on the strip. Thank you for the information and I will be reporting back with my results! Hopefully that will cure my problem. Good to hear from another fellow Albertan!