Need help with engine

tell us about your motor, what carburetor, what ignition, what camshaft etc etc etc

I had something similar happen twice on mine. The first time was caused by the timing chain jumping a tooth, and the second time was from the perforated tubes in the mufflers being plugged (back when there was lead in the gas).

Check the initial timing. If it's off by quite a bit, then it's a chain.

When I had the muffler problem, I pulled the engine cover and air cleaner and went for a drive. At around 3 grand I kicked in the secondaries. The engine was unresponsive. Upon looking in the rear view mirror, I noticed kind of a "mist" hanging above the carb. I went home and removed the mufflers at the headers. Went for another spin. What a difference!! It was like I just added 150 hp! Guess I hadn't paid much attention to the gradual decline in hp over time.

Engine specs: 351C bored .030 over. Keith Black Pistons, Com Cams 280 magnum cam (.530 lift, 234 at .050 duration), Summit ready to run distributor with vacuum advance (same as Mallory), Parker Funnel Web intake, and Mighty Demon 650 carb. Exhaust is a Mind Train exhaust system.

So does the motor idle as well as ever or has the idle worsened?

when it runs out of power at 3000 rpm does it "buck" or "lurch"?

did you do any work on the car at all immediately prior to the problem showing up?

does the problem show up accelerating on level ground, or when going up hill?

if it shows up on level ground, does it occur sooner (lower rpm) if you're going up hill?

Hi George, The car seems to idle fine. I do have a slight problem with the carb linkage sticking every once in a while and the idle will be at about 1500 rpm until I goose the throttle, then it will settle back down to about 800 rpm. This has always been there since I switched to the Demon carb. When you get up about 3000 rpm, the engine "feels" like it just isn't either getting enough gas or the electrical system is unable to ignite the gas. It just doesn't have any power. Since I live in Michigan, all our roads are flat, there are no hills to put additional load on the engine. The lack of power does seem to be very consistent and always occurs at about 3000 rpm. This is true whether I am on a back road or cruising down the freeway. I have often wondered if somehow the timing chain may have jumped a tooth. I keep ruling this out only because the motor only has about 3000 miles on it since I rebuilt it and I am using a Summit double roller chain. I guess I find it hard to believe that I could have stretch the chain already. However, I suppose it is possible. Do you think that I should pull the timing cover and look at the chain? Thanks for your input.

I would suggest that you check the initial ignition timing before pulling the timing cover. If it's off by quite a bit, then you need to find the cause. Since your timing chain only has 3k miles on it, it should not have stretched enough to cause it to jump, but it could have a manufacturing defect. The outer ring of the harmonic balancer could have slipped. Also check total timing.

When the problem occurs, does the engine just seem to go "flat"? Does it surge, sputter, or miss? Can you get more than 3k rpm?

Do you have a rev limiter on your ignition? If so, this might be causing the rpm to be limited to your 3k number.

Have you tried a known "good" carburetor? When I was shoppping for a replacement carb Chuck Nyutten was recommended. He specializes in turning Holleys. I asked him if he would tune my Demon. He politely refused - "They work great at WOT but a coffee can works great at WOT. I can tune it, turn the engine off, come back after lunch and it will be out of tune".

On any motor I've ever seen a timing chain slip, the result has been very rough idling or not idling at all, because the slipping of the timing chain drastically retards the cam & ignition.

I assume nobody has stufffed potatoes in your exhaust system, or that some furry creature hasn't made a home in same.

Fuel starvation is accompanied by lurching, you're not reporting that.

So here's where I would look for problems ...

>>if the carb has been removed recently, just prior to the problem showing up, look for the secondaries hitting the intake manifold & therefore not opening.

>>the ignition is not getting full 12 VDC power. So first make sure the battery has 13 to 14 volts when the motor is running. If it does, bypass the entire wiring harness of the car between the battery & ignition. To do this acquire a long piece of 12 gage wire with alligator clips on both ends, connect one end to the battery & connect the other end to the ignition module and/or coil (if the coil has a ballast resistor make sure to leave the ballast resistor in the circiuit). Afterwards give the car a test drive. Just remember, in order to turn the motor off afterwards you'll have to pop the hood and pull the wire off the battery.

>>a lifter has spewed its innards. The only way to determine this is to pop the intake manifold, luckily that's a fairly easy job with a Cleveland. I've seen this happen more than once over the years. Craziest thing, sometimes all 16 push rods remain in place in their lifters, but there will be lifter parts laying in the lifter valley. The result, all of the valves are being actuated, but one of them, the one in which the lifter has spewed its guts, is not being opened very far at all. Sometimes the pushrod of the bad lifter will just be laying loose, so your motor has one valve thats not being opened at all. The symptoms you describe are exactly how a motor will run when this happens, although the RPM where the motor flattens out may vary.

>>this is the frightening possibility, you have one valve in your motor slowly loosing its head, therefore its not seating fully. If a valve head drops in a running motor, the motor will be an almost total write off. You'll salvage one head, a few connecting rods & pistons, and maybe, just maybe, the crank. The block will be damaged beyond repair, a head will be damaged beyond repair, connecting rods will be bent & not repairable, a piston will be seriously beaten up, cracked, holed and otherwise abused. Kinda like my bank account after a divorce.

Thanks everyone for the suggestions. It looks like I am going to pull some stuff apart if for no other reason than to give me some piece of mind. Unfortunatly, I am running stock valves and they always have worried me that they will break. Hmmmmm, maybe now would be a good time to add some aluminum heads......

quote:

Originally posted by panteraufo:
Thanks everyone for the suggestions. It looks like I am going to pull some stuff apart if for no other reason than to give me some piece of mind. Unfortunatly, I am running stock valves and they always have worried me that they will break. Hmmmmm, maybe now would be a good time to add some aluminum heads......

and an MSD, and upgraded exhaust, and might as well yank the engine, and add a stroker kit, and hey why not spruce up the engine bay?, and,and,and..........!!!

The engine in my Longchamp has done the same, impossible to get above 3000 rpm. For me it started when I added an Ignition Box. I've tried both a Summit box and a MSD 6A. Same result, impossible to get it above 3000 rpm. When I remove the box and just use normal ignition, the problem is gone.

...........

George,

Shouldn't that be "Waytek #75302"?

John

Be sure the timing pointer is in the correct location and check the timing. Maybe your offf one tooth on your timing ? Try rotating the distributor and see if anything improves above 3000 rpm.

Try putting a pressure guage on the fuel line and bring the car up to 3000 and see what the pressure reads ? Maybe a blocked fuel filter..... dont assume that because its new its no plugged up ... my friends mustang did the same exact thing.

Ron

Ron