Weird...cam problem maybe?

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JR

JR

Pissed off senior member.
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This morning when I was going to work my truck warmed up just fine but as soon as I backed out of the driveway it started to run like it had a broken valve spring. I didn't have time to mess with it in the dark before work (after I scraped all the ice off the windows) so I just drove it to work without getting on it. During my first 15 min break I went out, checked all the plugs, wires, cap, rotor, pulled the valve cover, checked all the springs (inners and outers, I'm running dual springs) checked the lash and everything is right were it was the last time I checked when it was running fine. At lunch I put the cover back on and checked the carb, rechecked the plug wires and still found nothing. Pulling all the plug wires one by one while the truck was running also had the normal effect. Each wire when held close to the plug or to a ground had a very strong spark (Accell HEI unit with a MSD Blaster 2 coil).

I buttoned her back up and at 2:30 went home. She was still running rough and under powered until half way home (9 1/2 miles) when I was on a steep hill and had to pass a flatbed hauling a backhoe. I just figured to hell with it, if she dies she dies, dropped into 2nd (A745 3 on the tree/3.55) and floored it. There was the expected cloud of smoke and she took off! At the top of the hill she was running normal just like nothing ever happened.

I let it cool off and I just wend out, fired her up and drove around the block with no issue at all.

What the F?

I am pretty sure that I don't have a bent valve that hung open, I checked and double checked all the springs/keepers while it was running and nothing was hanging open or busted, oil pressure is right were it has always been, the bottom end has all new bearings and all the cylinders when checked after I got home were with in 3 lbs of pressure form each other.

The cam is a Delta Cams regrind. I have been buying cams from them for years and years and years and years and never had a problem. This is however the first slant cam I bought from them. Here are the specs off the box...

RV 254 S Mech. Grind

Specs INT EXH

Duration Deg. 254 254
Valve lift .435 .435
Valve Lash .012 .012

The valve lash I called bullshit on after running it for a while, it runs best at around .008 to .009 but is still pretty loud (even for a mech. cam). I took car of most of the noise by installing the double springs that were on another slant I had in the garage.

I thought I read over on .org that there is no problem with the profile of Deltas cam but the issue is with the actual lobe patterns. The lobes were patterned after a Hyd. cam lobe. If this is the case could I just slap on a later Hyd. head and dro in a set of Hyd. lifters? The cam runs great in my truck and I would love to keep it unless the Hyd. lobes and Mech. lifters are causing the problems but I thought there were others on .org (Reed is one I can remember off the top of my head) that had the same cam in a daily driver.

Or is the cam even an issue? I am pretty brain dead at the moment after New Years weekend.

Other info...

Head is ported and gasket matched with stock valves.
Offy intake also hogged out a little and matched to the head.
Carb is off a Buick and is a 400 cfm AFB with electric choke.

This pic is when I had the POS Holley on it. ANd yes the cheap/crappy plastic fuel filter has been changed
100_5975.jpg
 
Could it be something as simple as a bit of water in the gas that passed? Putting Hydraulic lifters in a non-hydraulic block is never a good idea. They will be starved for oil and won't pump up. The use of a hydraulic styled lobe with a mechanical tappet may (key word) have drawbacks such as not spinning the tappet to decrease wear or effecting the shape of horsepower and torque curves. But the engine will still run smooth. Call it a hiccup, and forget it until/if it returns. Given your checks, I don't see any cam problems here.
 
'64 Cuda said:
Maybe some moisture in the distributor cap?
Click to expand...

Maybe, I thought about that. It has been pretty cold and icy the last few days and I didn't start the truck over the weekend but this is Seattle and with all the rain I have never had a problem with moisture under the cap.
 
Is it cold enough that the carb could have been icing up. Grab a little bottle of that methanol that you dump in the fuel tank next time.
 
It's been in the low to mid 30's the last few days and into the 20's at night. It's supposed to be in the 40's this week.
 
My vote is for a fouled spark plug that you fixed with your "Italian Tune-up" to pass the truck.
 
LOL, Well you know there is that whole Dodge/Fiat thing and we all know what Fiat stands for! :cheers:
 
I,d go the ethenol in the tank,with temps dropping.Maybe some water freezing up in your gas..to line.JMO happens alot up here with all gas engines.Crappy gas!
 
I like the carbon on the plugs idea too. If it smoked when you showered down on it that's carbon on the back sides of the intake valves right there. Romp on it some more. Better yet, get a small cup of water and run it through the carb while keepin it runnin. that will clean it right out. Or more nitrous.
 
What about a chunk of carbon caught in one of the valves? Also check
for carbon tracks on the sides of the spark plugs. Could be something
very simple.
 
demon seed said:
Is it cold enough that the carb could have been icing up. Grab a little bottle of that methanol that you dump in the fuel tank next time.
Click to expand...


You're KIDDING, right!!!????

He lives in the Renton WA area. Let's see, wintertime in Worshington, and high humidity, rainy weather..................

Ladies and gents, we have PRIME icing conditions!!!!

For the record, it doesn't have to be all that cold to cause icing in a carb. There used to be a woman around here who had a 250? Chivvy with headers and aftermarket manifold, no carb heat of any kind, and the damn thing would puke and barf up into the '50's
 
With my current set up the heater starts blowing warm in about 3 mins. The truck warms up faster and runs better in the cold than any 1 or 2 bbl stock set up I have had.
4 more years and we get to move out of this cold wet shithole! :cheers:
 
67Dart273 said:
You're KIDDING, right!!!????

He lives in the Renton WA area. Let's see, wintertime in Worshington, and high humidity, rainy weather..................

Ladies and gents, we have PRIME icing conditions!!!!

For the record, it doesn't have to be all that cold to cause icing in a carb. There used to be a woman around here who had a 250? Chivvy with headers and aftermarket manifold, no carb heat of any kind, and the damn thing would puke and barf up into the '50's
Click to expand...

Oh,thank you! :salute: I once had a corvair that had an aftermarket "center 4 barrel" that had no carb heat whatsoever, and that sucker would ice up big time! The fuel would just puddle up in the manifold and it would act VERY cold-blooded and backfire back thru the carb on takeoff.

But...did you determine which cylinders (if any) were not firing? Or was the engine just generally running crappy? (no particular cylinders dead)
 
The first thing that comes to mind is you might have had some bacon caught in one of the valves holding it open or the spark plugs were bacon fouled.
Seriously, i do think it was carb icing due to some crappy gas, and i also have had the plugs foul a lot on my /6 when i ran into some lousy gas mainly on #6 for some reason.
Maybe it's because it's the farthest cyl from the carb.
 
No, carb icing can and will always happen if the conditions are right, nothing to do with bad gas. It's that pressure drop when you're cruising along (air @ atmospheric pressure then into the intake manifold's vacuum) That's why I decided not to buy an Edelbrock "Air Gap" intake manifold. Gets too cold at my place in the winter months.

But you should still run your bacon on "lean"......:D
 
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