383 in M1008...No Power!

[Efituned]

A little history about the truck. I bought it a year ago with 18k miles in great running condition. I got tired of driving 45mph in the truck and needed an engine that could handle more revs with out changing rear end gears.

I got the engine from a friend that used it in a mud truck powered by propane. There is nothing special about the engine other than a Comp Cam 270h with roller rockers. I installed a Edelbrock 1406.

The engine cranks and idles perfect, but has no power under load. For instance if you try to power brake the truck with the pedal to the floor I will not spin the tires.

I did a cranking compression test and got 165psi on all cylinders. I replaced the distributor and I have tried about every different ignition timing position. I have another friend with a cucv and a worn out 350 that will smoke the tires and has great power.

What could be the problem?

 

[Keith_J]

Mixture is probably too lean. If it isn't blowing black smoke during these low power periods, it is probably lean.

Up to you to find the proper jet size.

 

[73m819]

Sounds like 45/55 is a LOT faster going down the road travel speed then 0

 

[ODdave]

Now this sounds stupid but........ You did drain the diesel fuel right.........

 

[Bob H]

Did you change the torque convertor?
probably gonna need at least a 2000 rpm

 

[Efituned]

Mixture is probably too lean. If it isn't blowing black smoke during these low power periods, it is probably lean.

Up to you to find the proper jet size.

I got a little black smoke under a load.

Sounds like 45/55 is a LOT faster going down the road travel speed then 0

It goes down the road just fine, have pulled anything with it yet. Transmission shifts points are normal from 1-2, then goes into 3 really soon.

Now this sounds stupid but........ You did drain the diesel fuel right.........

I used a electric pump and got most if not all of the diesel out.

Did you change the torque convertor?
probably gonna need at least a 2000 rpm

As far as I know the torque converter is stock. According to the specs on the cam, it will work good with a stock converter.

So far, asking friends around town, i have got that I need a higher stall converter around 1800-2200rpm or there is something wrong with the carb. I am going to check fuel pressure tomorrow and take to a guy that is a pro with carbs and see what happens.

 

[jw4x4]

Is it the same carb that was used when powered by propane?

 

[ODdave]

The trans is gonna be out of wack for a gas engine. Your going to need to change the governer out as well as the convertor.

 

[ODdave]

Is it the same carb that was used when powered by propane?

........propane is not supplied through a carb.......

 

[Bob H]

The stock TC from a 6.2 is gonna kick in before 1,000 with a SBC
either get a Holeshot 2000 or a TC from a SBC powered vehicle.

 

[jw4x4]

........propane is not supplied through a carb.......

Uhhh.....Propane is most certainly supplied thru a carb. Rock crawler rigs FREQUENTLY do it. It allows the engine to remain running at any angle. Just got to slightly modify the existing carb. Several companies manufacture and sell kits. I know a guy that owns a propane company and just about everything he owns is converted to propane.

 

[Bob H]

Is it the same carb that was used when powered by propane?

The OP stated that he installed an Edelbrock carb.

 

[porkysplace]

Uhhh.....Propane is most certainly supplied thru a carb. Rock crawler rigs FREQUENTLY do it. It allows the engine to remain running at any angle. Just got to slightly modify the existing carb. Several companies manufacture and sell kits. I know a guy that owns a propane company and just about everything he owns is converted to propane.

On my gas/propane generator the propane feeds into the intake manifold under the carb , it has a seperate regulator to meter the propane .

 

[jw4x4]

From all the input it seems to be a torque converter issue anyway.

 

[Efituned]

Sorry for the confusion, but I meant stock converter for a 350. It's defiantly not the 6.2 converter.

I don't see how it could be the converter when a stock 350 has more power than my 383. I could understand if it had a crazy cam that needed a higher stall for its power band. According to comp cams I can use a stock gas converter for a 350. I would think that the 383 has about the same power as a stock 383 from low rpm or really any rpm.

 

[Cucvnut]

how does a stock 350 make more power than a stroker motor that if built right makes 400 hp easy...my stock 350 made 210 hp...

 

[tm america]

Did you check the firing order?Bad mix of gas-diesel fuel..?Weak spark or bad cap and rotor?Issues felt under heavy load are ussually spark related... but if you can't figure it out just swap in a hemi and you will be burning the tires up

 

[Bob H]

A 383's gonna have more torque than a 350 because of the longer stroke.
If your rocker arm ratio is bigger than 1.5 that could put it past the limits of a stock TC
Did you put a new or used carb on? If used / not freshly rebuilt, then that is probably the issue.
Oh and if your rear brakes are good you won't spin the tires by "Power Braking"

 

[Efituned]

The carb is used, fairly new, but in unknown condition. I know all ignition is good. I will know the condition of the carb tomorrow.

 

[Cucvnut]

double post ?