poor acceleration

[Shovl]

that's the only real problem, starts, idles & cruises easy. but seems to really struggle to accelerate. 1st is OK, 3rd is the worst (4 spd). it's an 80" shovel, dual plugs, super E, dyna ignition. compression is 150 front & back, new fuel filter, clean plugs, acceleration has never been great but has gotten worse this year. any ideas what to look for? would a dyno tune-up be worth the $$? thanks

[junior]

check the acce;erator pump adjustment screw (the one on the right) seat the screw lightly (in is less fuel) and then back it out 1/2 turn at a time while blipping the throttle. adjust for best response then road test. fine tune from there.

it's a start....

also- check the pilot jet size you might only need a 29 or so. i think they come with a 31. it might be too fat and causing a stumble...

j

[Heretic]

Junior.....one of these days I am going to find something to disagree with you about.......it is not today though...LOL

[JD]

+1 I'd also start there.

Could also be an ignition timing/advance issue.

[rwpatton]

+1 I'd also start there.

Could also be an ignition timing/advance issue.

Imho, it is really hard to be too rich with a shovel carb unless your way out there. On the other hand shovels are very picky on timing. retarded will make them buck or run hot and to advanced will make them ping and detonate like a bitch. I may be wrong but i have used every degree wheel,timing light window and other assorted timing super tools.
the only one that works for me is "seat of the pants" adjustment while listening and feeling how the engine sounds and pulls. Every cam,carb,pipe and ignition is different. Don't have a dyno,it would be cool though"probably would never learn how to operate it". I Have had shovels engines i have built and tuned, dynoed by customers for fun with little or no adjustments. Evo's and twinkies are a completely different story.

Now to really start a STORM! Dual plugs do not increase power or ease of starting. Porting heads on a shovel is a "splitting hair proposition" they already flow more air than most stroke engines can handle.A shovel will blow up and cannot handle rpm above 7000 rpm. Any stroke above 4 1/2" will cause accelerated piston wear due to piston-foot- speed. Only run straight weight 60 oil. LOL! fwiw.

RW

[Heretic]

I am going to agree with some of that, and disagree with another part....I do agree that seat of the pants timing is often the best....I will also agree that porting is best left to pros, with very expensive equipment, like flow benches.....

dual plugs not giving more power?...come on, does anyone really believe that? if this were true, you would never ever see a top fuel dragster engine with more than 8 plugs.......

I will admit I have heard this theory before though....usually not from someone with dual plug heads, but I have heard it......but of course, I have also heard how flat heads were the best engines harley ever built. In both cases it is a subject of opinion, with little concern for the physics that demonstrate otherwise.

[junior]

rw- i usually defer to you on shovel matters, but i gotta disagree about the dual plugging as well. i don't fool with them a lot, but i've seen how the dome of even a stock piston blocks the chamber considerably in +/- 15 degrees or so either side of TDC. this is why i'd think they went to a bathtub/squish chamber design on evos and up.

you're still the man though....

j

[Bigshovel]

I like dual plugged Shovels to be able to run more advance without detonation but that is the only advantage as far as I can see. It only contributes to a more complete burn on the power stroke.......just what I think.

[jazda]

I like dual plugged Shovels to be able to run more advance without detonation but that is the only advantage as far as I can see. It only contributes to a more complete burn on the power stroke.......just what I think.

.......hmmmmmmmmm............. this thread is turnin' into some pretty kinky stuff......

[GzrGldGeo]

.......hmmmmmmmmm............. this thread is turnin' into some pretty kinky stuff......

Only in your mind!