tuning issue?

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twayne24365

twayne24365

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ive been out driving my dart for a few days now getting things worked out, the one thing I haven't got yet. from a stop or a slight roll in 1st if you hit it, it takes off great and runs very strong, but once you hit 5k the motor seems like it just comes to life, the best way to describe it is like you hit the button on a sneaky Pete n2o setup.

is this familiar to anyone? is there a cause?or just the combination?
 
tell us your combo, what carb, cam,tranc,gears.........
 
.030 over 383
10.4:1
Mopar 557 cam installed at 106
street dominator intake 1" open spacer
750 mighty demon
firecore distributor locked at 36*
2" headers
727 converter flash about 3800ish
4.56 gears with spool
255 Mt drag radial
 
have you checked the movement of the carb linkage...full throttle...adjust accelerator pumps?

timing?....
 
Yeah because your timing is locked. 36 advance works really well at higher rpm, wot. You could gain some driveabilty/starting ability by using a mechanical advance distributor. After that, you can either install a wideband o2 and tune, or read plugs and use the vacuum gauge.
 
Tony, I have been working in the carb linkage. I have one of the billet throttle cable brackets and the problem is the cable is level with the lever on the carb. it gets full throttle but it pulls it straight back and it hits a bind point, instead of pulling slightly down, I'll mill the cable mount do give it a little more angle.
as to the timing it is locked at 36, I've tried up to 42* and it runs better at 36, I'm amazed at how easy it starts, cold or hot always fires on the first crank.
but it's a firecore with the screws that hold the advance plate so I can always "unlock" it ad try that.
plugs definitely are a little fat, I'm going to get a new set and drop a few jet sizes. jetting is stock at 77/85
 
lean out the primary and lose the spacer.
 
you might try a # 72 jet . Powervalve ? what is idle vac ? cranking pressure? my 383 is close to your combo.
 
power valve only in front, 6.5, haven't checked vacuum orc cranking compression
 
try the #72 jet without the spacer. read the plugs. I found 72 too rich on my combo with 750 on dominator. i'm testing a 70 now with 6.5 powervalve. its real close. almost forgot 35 pump shooter
 
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my recommendation on jet size is based for sea level, as I'm at 2300 ft
 
ok, I also was going to try the bigger squirters, it's got 31s in it now but I'll grab some 35s from my buddy,
got a set of plugs to put in today too so I will report back!
 
You're going to plug the Power Valve? If so, NOT a good idea on a street car for sure.
 
well the 750 mighty demon has a PC in the primary but no provisions for one in the secondaries
 
You only need bigger squirters if it launches, bogs..., then takes off again. You may have to big of a squirter.
Is this a stick shift car or if auto what stall?
twayne24365 said:
well the 750 mighty demon has a PC in the primary but no provisions for one in the secondaries
Click to expand...

Yup, I just didn't want you to take it out. Its there for streetability. and it's keeped in in most race engs as well. Make sure it is a good one. has not been blown from a back fire or something like that.
 
good luck with the dp, for street use I'm using the 3310. also I replaced the 557 with the 528. 155 # cranking pressure and 10" vac at 900 rpm @ 2300 ft
 
yea Pv is a 6.5 and is in good shape, auto flashes to about 3800, no bog at all, launches good just really comes on hard about 5k
 
Could use more converter. 3800 flash would be good for a 440 with that cam, but I feel the little 383 would benefit from a looser converter.
 
forphorty said:
Could use more converter. 3800 flash would be good for a 440 with that cam, but I feel the little 383 would benefit from a looser converter.
Click to expand...
I agree!
changed plugs and went for a 10 min drive, then made a wot pass and pulled in the driveway, here is #1 plug
5650.jpeg
5646.jpeg
5646.jpeg
 
What is your total time at? look like you could drop it a couple of degrees........or you need a cooler plug. What compression are you running?

Looks good. i wouldn't jet it any lower.
 
^timing is locked at 36.
looking at the ground strap it could go a step or two colder, I got a set of NGK race plugs r5670-7 which is 2 colder so ill try those tomorrow
 
Cold racing plugs will foul easier, if you're just putting around town. There designed to take the heat from the plug and put it in the cooling system. When you not making lots of heat(lead footing it) they may carbon up.

If it was me i would drop it 2 degrees (34). When you're at the track, make a run, bump it back to 36 and make another run, see if you MPH changes. If you get a better mph then think about going one step colder plug, for the 36* timing.
If the heat mark was all the way down to the ground strap weld or base ring, i would say get a colder plug now. To HOT......but it's not.
I bet around town driving it will run better with a couple degrees less with it locked out.........
For the street you probably should unlock it and just have a fast advance curve.
 
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