Jeep Strokers

I would suspect your exhaust valves are opening to soon.
That might allow low compression and combustion flame front to travel into the exhaust system.
Timing marks might be off, it does happen.
Confirm compression numbers with another gauge.
Can get them on fleabay fairly cheep.
To confirm piston is at the top of travel, use a chopstick or similar.Prepare to mark stick it at tdc and bdc and center between.
Remove sparkplug put stick in and rotate engine till piston is at max travel up, check timing mark at the crank, should be at tdc. and check distributor rotor position. should be at or near #1 cylinder contact. might have to go around twice to get to the compression stroke.
They must line up. if they dont your timing marks are off.

You can pull the valve cover off and check the valve timing.
You can watch the valves open and close as you rotate the engine.Best if all spark plugs are out.
I think the exhaust valve for #1 cylinder should be opening near bottom dead center.Watch the chopstick marks.
I think it might be opening like halfway in its trave down which would put a fair amount of unused flame into the exhaust.
That would be another indicator your timing is off.
M

Well, I guess I'll leave the newer manifold on until it's time to get smogged again. SilverXJ, I think you are right. The exhaust starts to glow before the engine has a chance to fully warm up, so the problem is in both closed and open loop mode. The power is great in the upper rpm, suggesting retarded timing. I put compressed air into the cylinders with the valves closed and did not hear any air coming out of the exhaust or intake. I checked the valve lash and the valves should be closing all the way. If the cam timing is retarded then it makes sense to me that the engine would pump unburned air/fuel into the exhaust that would be read as lean by the O2 sensor because the sensor only detects the O2, and if the mixture is unburned then it will have plenty of O2 in it. The cat glows a little too, and the pipe between the manifold and cat does not glow--so I guess this means that there is fuel burning in the manifold and cat? I checked the compression over and over, warm and cold, throttle body open and closed. What is weird is that no matter what I get about 89 psi on all cylinders--I thought the throttle position would affect this more, but I guess not. I hooked the compression tester up to my air compressor and it read 120psi at what my compressor reads to be 130, so the tester is not off by enough for the compression to actually be normal. This makes me think the valves are closing too late on the compression stroke. I put a pair of tweezers in the spark plug hole and actual TDC is at least really close to the TDC mark on the damper, so I'm assuming the damper is the right one (it's new) which would point to the cam or timing set. I did not expect that the timing could be this off, so I think there is a defect in the cam or timing set. I guess it's time to track down a degree wheel to index the cam and see if that helps...or I could just use the timing marks on the chain and go for 4 degrees advanced since I cannot find a degree wheel locally for the life of me.

Tequilamike, I just saw your post (didn't see the second page). I think you and SilverXJ are both on the right track. I need to degree that cam...ugh, I had an extra unused clevite timing set I just sold on ebay, could have compared timing with that.

I had to refresh myself on how a 4-stroke cycles. The exhaust valve closes when the piston is at TDC, then the intake opens as the piston goes down, then it closes at BDC, then the piston goes to TDC, ignites, and the exhaust opens around BDC...so unless I am mistaken, the exhaust valve should close well before the air/fuel goes into the cylinder even if the timing is a bit off. I guess this disproves my theory and goes with what Tequilamike suggested, that the exhaust is opening too soon. Unburned air/fuel going out the exhaust would require too much overlap ground into the cam, or an exhaust valve not seating, right?

Billygoat wrote:I had to refresh myself on how a 4-stroke cycles. The exhaust valve closes when the piston is at TDC, then the intake opens as the piston goes down, then it closes at BDC, then the piston goes to TDC, ignites, and the exhaust opens around BDC...so unless I am mistaken, the exhaust valve should close well before the air/fuel goes into the cylinder even if the timing is a bit off. I guess this disproves my theory and goes with what Tequilamike suggested, that the exhaust is opening too soon. Unburned air/fuel going out the exhaust would require too much overlap ground into the cam, or an exhaust valve not seating, right?

There is usually overlap in the valves, so both intake and exhaust will be open somewhat at TDC (of the exhaust stroke)

Printed a degree wheel from the internet and timed it with my dial indicator on the push-rod end of the rocker about 10 times. The cam timing is exactly 6.5* degrees retarded for both intake and exhaust. How do I adjust it 6.5*? Each tooth is about 17* isn't it?

hrm... if you don't have an adjustable timing set you could try moving the crank gear a single tooth. I believe you should move it a single tooth counter clockwise. Move both the crank and gear while keeping the cam gear static. Basically you want it to be off a tooth when you install it.

It's the cloyes double roller so it is adjustable +- 4*. I advanced it a tooth and it was 8 degrees more advanced than the cam specs, so I set the cloyes to 4 deg retarded and then advanced it a tooth and right now it is 4 degrees advanced over the cam specs (intake is at max lift at 103 ATDC and exhaust is at max lift at 121 BTDC). My other option is to set the cloyes to 4 deg advanced which would put it at 2.5 retarded compared to the cam specs. I'm thinking advanced would be better--anyone think that 4* advanced over the cam specs will be a problem?

Its hard to say without knowing all the cam specs. How does your timing chain adjust? Does it have the offset shims for the cam gear or is the crank gear notched?

You can use an offset crank key to change the timing a few degrees. Might get you dead on when combining with the timing set position change.
Be careful when determining the point of max lift, it will dwell there for a few degrees. You should measure down from max lift a few thou (on both sides of the max lift), note the position on the degree wheel, and pick the midpoint of the two readings... that's your center.

x2, you don't want to measure anything at max lift other than max lift. Its probably best to use the center line method when degreeing a cam in. Same thing with finding TDC. You want to go a few thou to either side (the same) and then see where the degree wheel is at and adjust the pointed until both degree when readings are the same.

The offset crank key is a good idea.

This thread may help you: http://www.jeepstrokers.com/forum/viewt ... f=5&t=2920

Very useful link--it's nice to know which woodruff keys I can use to fine-tune the cam timing. I've done nearly everything I can for this motor except getting the cam timing just right...no leaks anywhere, distributor is indexed perfectly, all electronics are functional. I tested the vacuum and it's low...around 13 at idle, up to 23 when I let off the throttle. I'm sure that getting the cam timing at factory specs would help, but I talked to Crane Cams and they said that a 4* advance won't cause my problems. Two things are coming to mind right now: I need a piggyback ECU like the one from Split Second, or the cam is defective. It makes sense that custom fuel and ignition maps would help out, but there are plenty of people running strokers with stock ECU's and no glowing manifolds. The fact that the cam was 6.5* retarded when set to the factory timing marks makes me think the cam might just be defective, which really would explain everything...low compression, low vacuum, glowing exhaust...So, if it were you, would you drop the money on the FTC1-019B tuner by split second or swap out the cam, lifters, and pushrods? Price is slightly less to do the cam, but it takes a lot longer. Also I could pull the head to inspect the pistons and valves, but that means buying another Mopar high performance head gasket, intake/exhaust manifold, and new head bolts (originals were already reused once)...

Edit: I mean new intake/exhaust manifold gasket and not manifolds...and I imagine I would just reuse the pushrods. Still though, this is just weird.

I seriously doubt your cam is defective and all this talk of moving it a couple degrees back and forth is not germaine to your problem.

You need to put an air fuel gauge on it and see if it is running lean. You need to shoot it with a temp gun and see what EGT's really are. Or kill two birds with one stone and take it to a shop and have them put it on a scope and watch your ignition timing through the entire RPM range and make sure it is not retarding while they watch the Air Fuel Ratio.

I personally look at cam timing events in addition to intake centerline to be sure I got the right grind. Cams being ground other than "straight up" to the pin is nothing new and once they are corrected in the engine through cam keys, offset pin bushings, or the timing set, the cam and crank do not care where the timing marks are stamped on the timing set.

Just to be doubly sure though, could you post the grind # and the intake opening and closing events as they appear on your cam card vs. your degree wheel readings?