engine breaking up at low end

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JohnnyJet

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360 crate motor ...390 hp version. single plane with proform 750 carb. Car runs like crap til 3000 rpm, Im thinkin carb issue. anyone have any experience with this motor? Do I have to much carb? Any help appreciated. also anyone on Long Island know of a good Dyno tuner
 
I'd start by pulling all the plugs and checking to see if one of them has been miss firing. 1 might be black and rest brown around the electrode. Check all your wires to make sure that they're making good contact. Pull the distributor cap and look for carbon tracking on the inside. Are you getting black smoke out the exhaust at low RPM, if so primary side is to rich which you'll also see by looking at the spark plugs, they'll all be black. It could even be a problem with the ignition coil but these usually crap out at high RPM.

It could also be that that single plane intake is fighting with your cam in which case a 1 inch 4 hold carb spacer might clean up the bottom end, it worked on my BB.

Terry
 
ok ive narrowed it down plug in# 2 cylinder is balck as coal, all others are good, I changed carb to holley 770cfm stree avenger and changed plugs to champion rc12yc. gonna chnage power valve to 5.5 and jets in primaries to 74 from 72, Im close, hope this works, suggest away.............
 
I would compression test that cylinder.
Then I would test that wire depending on the result and also look at the float setting/needle seat.

1st thing though, what is timing set at?
 
thats a whole nother prob. I did it witha vacuum gauge as I could never get the line on the balancer to show. spun the dist. 180 degreees and the car wouldnt start.
 
ignition problem \\ check the distributor cap on the inside {center contact}
Where the rotor rides
Sometimes the contact will be burnt away and you will only notice a problem at high rpm :salut:
 
JohnnyJet said:
thats a whole nother prob. I did it witha vacuum gauge as I could never get the line on the balancer to show. spun the dist. 180 degreees and the car wouldnt start.
Click to expand...

well you got to find tdc with a stop or long skinny screw driver though the spark plug hole and look for a line on the balancer to be in line with the timing cover 0*
mark the balancer line with a white paint pen or white out if you have to.
 
I did all that and when it came to timing the car the line was out of sight. Im goin under the hood again today......im close
 
JohnnyJet said:
Yup.
Click to expand...
I am on my second Mopar Crate in about 7000 miles the first deronated the #8 piston in aout 5000 miles and the second is running like crap in about 2000 miles. The major problem is with the mopar cams they start to work about 3000 rpm, sorta gives that turbo feel. The best way to tune the engine is a new set of spark plugs, warm the engine set the idle at 2600 rpm (above 3000 with MSD or similiar after market box), set total timing, set idle speed and check timing for futurer reference. Initial timing is not important as long as the engine fires properly and shuts off without dieseling.
 
Ive got no dieseling. pinging popping farting or belching. timing is ok. Ill be back later to detail what if anything got fixed. maybe this thing needs a chevy motor??? im sorry i said that
 
WOW! Got it, changed primary jets to 74s and PV to 5.5. Changed coil and also changed plugs. It worked car idles at 950rpm pulls all the way through 4200 rpm and still had more. Thanks for the suggestions. Im still baffled about the tinming marks on the balancer but it runs so good I dont care
 
360 crate engine should come with 70 and later timing chain cover...

360 cast crank balancer were not available until at least 70 or 71 since that is the first year of the engine..

balancer outer ring could have slipped...
 
somethin is messed up. car is runnin like a champ. dont know what it could be because at TDC the 0 line is on the 0 mark on the block. unless im doing it wrong. I set the timing light at 33 and i got no line at all at 2800-3000 rpm.
 
Oh, gawd; just like my 340 gremlin. Won't idle under 20 Degrees at 800 rpm. 30 vac. At 30 degrees, better; 20 vac.
The cam seems to be purple, or close.
Centered.
I think this is what the engine want's; Gonna try to pull mech advance down in the dist. Oh, I tried normal timing light, and an advanced; difference of 10 degrees; don't trust either of them.
 
JohnnyJet said:
ok ive narrowed it down plug in# 2 cylinder is balck as coal, all others are good, I changed carb to holley 770cfm stree avenger and changed plugs to champion rc12yc. gonna chnage power valve to 5.5 and jets in primaries to 74 from 72, Im close, hope this works, suggest away.............
Click to expand...

only do one thing at a time!!
 
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