360 performance help

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tekslk

tekslk

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67 barracuda with a 360 auto, have been driving it for about 3 years with no problems, you could wind it up to 6500 with no problems but now it goes to 5000 and feels like valve float, just doesn't want to go further. Any sugestions?
 
secondaries do open, probably 3500 miles on rebuilt motor. Im thinking possible a week valve spring, or broken one? Doesn't matter if I take it slow or fast just stops at 5000
 
My 460 did that but it was the secondarys not opening. It just stopped at 4000 like a wall hit it.

Have you pulled the plugs, see whats going on? Possible low fuel pressure?
 
Lack of fuel would be my first place to check, sounds like it's starving. You don't mention any misfire, so that should rule out valve float, ignition timing could be, but I'd start with fuel, low pressure, plugged filter, low float level. In my experience 6500 is pretty high for a stock 360, has the engine been built for higher rpm? Mine previous one would fall flat after about 5500, partly due to cam profile and cylinder heads.
 
comp cam with 478 lift double valve springs, holley 870 street avenger. When it hits the 5000 and goes dead if I up shift to second its fine till I get to 5000 again. Electronic ignition, mopar performance distributor. timing at 20 initial 35 all in around 28oo rpms
 
Exhaust plugged up ? muffler baffle came loose and blocked the outlet.
Put a vacuum gauge on it and see if it drops low at 5000
 
It shuts off even when not into the secondaries, Im gonna pull valve covers tomorrow I have a sneaky suspicion springs are worn or broke.
 
@Prorac2 little Valiant just did something similar. They ended up swapping another ignition box on and it solved it.
 
No I didn't, also if it makes any difference I use the GM stuff and no longer have a ballast resistor and Chrysler box.
 
Check the mechanical advance on the distrib, needs to be lube once a year. Easy check, take the cap off and see if you can twist the rotor ccw and if it returns to the same spot.
 
well you should check the fuel pump make sure it's got pressure. You should I have a friend rev It Up with one of the plugs wires pulled loose real quick and see if you get spark over that RPM that way you'll know if that GM module is bad. Lastly I guess would be the springs... in order of what's easiest to check.
The Springs should be around a 115 psi seat @1.7 or something like that. There might be 2 versions. I had a set that was 140 seat 471 rate long ago, still have the box.
If you have the 115 seat.. ugh I'd put them in at 1.68/ to get a decent 120-125
 
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Is that a solid or hydraulic cam? You could be collapsing a lifter if hyd. Is there an aftermarket tach in the car? Sometimes they have a rev limiter in the tach.
 
Rig a fuel pressure gauge up on it so you can see it while revving up. That'll answer that question.

As above, tach's can sometimes kill the ignition. Usually not RPM related but you never know with electronics.
 
Well I had different springs so I changed them out, turned out that didn't fix it. Had a used gm module from a friend put it on and it works great again. I never saw that with the gm module before they either worked or didn't but at least it is fixed.
 
I almost guarantee it’s the ignition control unit like @RustyRatRod said I had the exact same problem with my my 318 and I just replaced it with a old used icu and I wound it out to 6000 rpm.
 
Prorac2 said:
I almost guarantee it’s the ignition control unit like @RustyRatRod said I had the exact same problem with my my 318 and I just replaced it with a old used icu and I wound it out to 6000 rpm.
Click to expand...
Guess I gotta carry a extra just like a ballast resistor.
 
If needed I have some nors Kem four pin modules tested. asking $35 for them shipped.
 
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