440 Issues

[Chryco Psycho]

I tend to agree with Moper
your compression should be fine with 2355 pistons
 A looser converter will still help 2400 ish should work well
why you have the problem with pinging os a good question which is why I was pointing towards Spark plugs , lean jetting etc 

[440Charger]

Well I got the new correct spacer installed with gaskets on both sides.  Made a nice drivability difference and we were able to up the timing a degree or two, and the tires chirp in 1st now.  The vacuum leak theory was correct!
 

I'm thinking now were either running lean with the 750cfm carb or need higher octane fuel.  We put the timing to what we think was 36(ish) and it ran great but pinged like crazy under heavy load.  I'll know more on Tuesday.

[MEK-Dangerfield]

Just look at your plugs to see if you are running lean. That tells all. 

  Mike

[moper]

Slow down the centrifical advance with the spring kit MSD includes wiht the distributor. Go one step slower, than another,  until the pinging calms down. You dont have to change total, just delay the advance a little until the engine can deal with things. I have to do that a lot on cars that have mild gearing and tight convertors.

[440Charger]

Just look at your plugs to see if you are running lean. That tells all. 

  Mike

I finally took the car up tonight to that guy who builds performance engines.  He took out a spark plug and immediately said we're running lean.  The plug was almost pure white in the center.  So we started rejetting the Demon until we were about 10 sizes higher than what we started at...and we also found the initial jets to be a size or two smaller than the documentation claimed was preinstalled.

We replaced the plugs with colder ones.  Gapped at 45.  AC Delco's I think.  We checked the plugs after increasing the jets sizes (about 4 iterations) and after each run he said we were still running lean...and that's after 10 size increase.  And that's where we left it.  He recommended a high volume electric fuel pump, as we're currently running a stock mechanical pump.  Also, he recommended we replace our 5/8 inch lines with 3/4 inch.  He also recommended an Edlebrock Performer dual plane to replace the M1 dual plane.  He told us the same thing you guys did, which was that the M1 is a reproduction of the stock 440 intake, but aluminum.

After the jetting, the engine sounds more meaty and has more power (we test drove after every change).  It really affected the idle but I think I can tune that out.  He also recommended a 2800 to 3000 stall, like you guys did I think.

Any opinions on what this guy told us?

Thanks,
- Doug

[chevyconvert]

5/8'' to 3/4'' fuel lines?

[Chryco Psycho]

I hope he meant 5/16 - 3/8" lines
 I have had similar problems with Demons , they seem to need huge jets or you need to put in smaller air bleeds to get them to respond

[440Charger]

I hope he meant 5/16 - 3/8" lines
 I have had similar problems with Demons , they seem to need huge jets or you need to put in smaller air bleeds to get them to respond

Oops, yeah, those lines lol.  I dont' know anything about fuel line sizes so it's probably what you said.

So you've had this problem with Demon's also.  This guy recommened a holley (can't remember the size) to replace it.  He's been consistant on that.  But damn, we just got the Demon and really like it.  I dont' understand why upping the 750 by 10 jet sizes would keep us lean.  Maybe we need an 850?

[Chryco Psycho]

I always use at least an 850 on 440s but i doubt that is causing it to run lean , i assume you ahve the floats set up properly ?

[440Charger]

Yes, the float levels are centered on both front and back.

We're thinking it's fuel pump at this point.  We installed a temporary fuel pressure gauge and it was 7lbs of pressure at idle, but he had me hold the brakes and hit the gas and it dropped to 6lbs at about 2500 rpm.  I don't have a gauge inside the car for fuel pressure so we did the best we could.

[MEK-Dangerfield]

That's plenty of fuel pressure, so that isn't your problem. 

  Mike

[440Charger]

Thanks Mike, good info.  But even more frustrating for me.  I just don't understand how we could be running so lean as he told us...he kept pulling a plug and seeing it white, I saw it too.  After all the jetting, we still got ping at 34 degrees advance.

If it's not the jets or fuel pump, then what could it be.  I'm at a total loss here.

[Chryco Psycho]

I would not put it past Demon to have a restiction in the emusion tubes behind the jets so increasing the jet size is not increasing fuel flow internally in the carb 

[440Charger]

You honestly think they'd block jet changes?   

The jet changes made a difference, no doubt, just not enough.  There is something else going on here.

[Chryco Psycho]

it wouldn`t be intentional just a casting or production flaw