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Username Post: Stalling under any load?        (Topic#349834)
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
02-26-18 08:49 AM - Post#2725659    

Well, the saga continues. I'm here to bother you nice people again. So, I've replaced my cam with a mechanical flat tappet cam. It is .544 @291 on the intake side and .553 @295 on the exhaust with a 102 LSA. I got it to idle at about 950-1000 RPM and it sounds great. Idles all day long. UNTIL the electric fan comes on. The fan puts enough drag on this thing to kill it. I put it in gear, it dies. I can't put any load on the motor at all or it craps the bed. I'm at a loss for what is going on.

"8 cylinders of why the f&@% not" - me


 




Shepherd 
Frequent Contributor
Posts: 1423

Loc: Lake George, NY
Reg: 11-11-15
02-26-18 09:24 AM - Post#2725663    
    In response to Junkyardwarrior

This is a new problem? 102 lsa is pretty aggressive, what is your idle vacuum?



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
02-26-18 09:33 AM - Post#2725665    
    In response to Shepherd

Yeah it never did this before. When I had the old cam in it did develop an issue of just trying to die pulling up to stop lights, but that was only occasional. I'm not sure what the idle vacuum is right now. I gotta get my gauge on it tonight and see what it is reading. It revs good and sounds amazing, just refuses any load.

"8 cylinders of why the f&@% not" - me


 
Shepherd 
Frequent Contributor
Posts: 1423

Loc: Lake George, NY
Reg: 11-11-15
02-26-18 10:07 AM - Post#2725669    
    In response to Junkyardwarrior

This can be caused by carb issues, or at the extreme a bad torque convertor, that has little or no stall speed, but that wouldn't account for the alternator load stalling the engine in neutral.



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
02-26-18 10:13 AM - Post#2725670    
    In response to Shepherd

I was thinking carb as well since it is still set at the tuning for the old cam, I was just running out of daylight to mess with it yesterday. The stall on the converter is advertised at 3k. I've foot braked the car to 2800 before so I don't believe it to be the issue. It's a pretty extreme change in setups so maybe it just needs more idle fuel for the severe lack of vacuum?

"8 cylinders of why the f&@% not" - me


 
IgnitionMan 
Valued Contributor
Posts: 3412

Reg: 04-15-05
02-26-18 10:17 AM - Post#2725671    
    In response to Shepherd

What exact alternator is in use, what pulley diameter?

What ignition system, and what system voltage @ idle AND about 3K?



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
02-26-18 10:25 AM - Post#2725672    
    In response to IgnitionMan

Just a good ol standard alternator. Nothing special. Same one that's been on the car for the past 2+ years. Summit CDI Ignition box, MSD pro billet dizzy, MSD Blaster 2 coil. With the fan off the voltage read 13.8 at idle and 14.2 on the throttle (couldn't see the tach from the outside so not sure exactly what RPM that was at) only thing different from 2 weeks ago is the cam and lifters.

"8 cylinders of why the f&@% not" - me


 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
02-26-18 10:26 AM - Post#2725673    
    In response to IgnitionMan

Oh and the pulley sizes are all stock 70's pickup. Giant lower pulley and whatever autozone put on the alternator before selling it to me.

"8 cylinders of why the f&@% not" - me


 
Shepherd 
Frequent Contributor
Posts: 1423

Loc: Lake George, NY
Reg: 11-11-15
02-26-18 10:41 AM - Post#2725677    
    In response to Junkyardwarrior

Still sounds like basic tuning for the 102 lsa cam is out of whack, barring a major component issue in the ignition system. 102 lsa cams, for the most part are designed for maximum high rpm power. Do you know what the intake center line spec is? Not that this is the base problem, but in a street driven sbc, I would have chosen a 110-112 lsa cam can with maybe a 108 intake cl, this still would need decent gearing and the convertor you have.



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
02-26-18 01:38 PM - Post#2725695    
    In response to Shepherd

Not sure on the centerline honestly. I'll have to check the card when I'm back at the car. Duration at 50 is 252 in 255 ex. It's a Summit CT106. I believe I should be good on the gears with the 4.11's I have.

"8 cylinders of why the f&@% not" - me


 
Shepherd 
Frequent Contributor
Posts: 1423

Loc: Lake George, NY
Reg: 11-11-15
02-26-18 02:36 PM - Post#2725701    
    In response to Junkyardwarrior

Based on duration figures, your idle vacuum is going to be quite low. That alone changes all your tuning, especially referring to the carb.



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
02-26-18 02:44 PM - Post#2725705    
    In response to Shepherd

Yeah I figured as much. I'll have to get the vacuum gauge on it tonight to see what it's making. Make sure that the power valve is the correct size and probably bump up the fuel. A lot. Might go ahead and throw some larger jets at it too since I have significantly more lift.

"8 cylinders of why the f&@% not" - me


 
IgnitionMan 
Valued Contributor
Posts: 3412

Reg: 04-15-05
02-26-18 04:17 PM - Post#2725718    
    In response to Junkyardwarrior

"MSD Blaster 2 coil", BINGO. What country of origin is it, sticker on bottom should have that info. Clue, Mexico and China are the two outta 3 that are the serious problems. I strongly suggest taking it off the car, and finding a partrs store with an off vehicle run tester, and let it run to get it to operating temperature.

If possible, swap in even a used stock GM coil, even one for points, and see if it still does it. Don't buy a new coil to do this borrow one if you don't have one sitting around.

"Stock alternator", YES, but, which one, stock with remote regulator, 12SI, CS series, and what is the voltage output @ idle and about 3K RPM's?????



 
Rick_L 
Honored Member
Posts: 27446
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
02-26-18 07:09 PM - Post#2725746    
    In response to IgnitionMan

Have you tried more ignition timing? I think you'll need a lot of advance for this cam.

A cam with 106° or less lobe center angle is going to have really crappy low rpm performance, and a narrow power band. Usually this kind of cam timing is used in a race only engine that has some kind of limited cylinder head rule. It is not really suitable for the street, or with "good" cylinder heads.



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
03-01-18 08:11 AM - Post#2726095    
    In response to Rick_L

Ok, so believe it or not, it does rain in the desert sometimes, so I didn't get back to the car until last night. Local spot here checked out the coil (sticker on the bottom is MIA) and it's perfectly fine. I changed the springs in my distributor from the heavy to a mid and a soft (last cam did not like advance until it was up and going) Reset ignition timing to 36* overall, put bigger jets in the carb, and reset the valve lash. Seems to have solved the problem. Fan on and in gear she stayed running and made a nice pull around the block. Also, internal regulated alternator, 13.8 at idle 14.2 at elevated throttle position. Standard 3 wire.

"8 cylinders of why the f&@% not" - me


 
Shepherd 
Frequent Contributor
Posts: 1423

Loc: Lake George, NY
Reg: 11-11-15
03-01-18 08:37 AM - Post#2726100    
    In response to Junkyardwarrior

Good news!! Wonder what was the root problem.



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
03-01-18 09:15 AM - Post#2726107    
    In response to Shepherd

I'm thinking it to be most likely the timing and carb tuning combined. It was a lot easier to start after I reset the timing and it idled a lot easier with the carb jetted and adjusted. Where it was set before I adjusted the timing, I went to start the car up and it made a very nice fireball out the carburetor. I had to get it started, keep it running, and then bump the timing and it seems much happier.

"8 cylinders of why the f&@% not" - me


 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
03-02-18 08:50 PM - Post#2726284    
    In response to Shepherd

Ok, so something went horribly wrong when I went to get it home. It overheated. Bad. And then lost all oil pressure. I managed to limp it home after it cooled off a bit, fired it up today for a short run and cold idle it had 50 lbs oil pressure and sounded fine. I'm at a loss for this one. At first I thought maybe it spun a cam bearing but then the cold fire the pressure was great so I got nothin.

"8 cylinders of why the f&@% not" - me


 




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