Stumped

[whistlin']

89 2.5 T1. Quite awhile back the camshaft broke. Replaced with 94 TBI cam and worked fine but wouldn't rev past 5200 rpm. Today it was nice out so we put in an 86 turbo cam, same results. I have tried the cam at center timing and one tooth either way. When advancing it just brings the problem to a lower rpm.
This is strictly rpm related, does it regardless of the boost. Have tried known good map, tps, coil, hep. It sounds to me like the valves are floating, loading up the exhaust with unburned fuel. Fuel pressure is right on the money.
This car also has the PT lifters. Car ran great before the cam broke, hate to stick the stock lifters back in if I don't have to. Any help would be appreciated.

[overlordsshadow]

Did you do a full timing reset or did you just tie the belt back? I'm pretty sure my timing is off a bit at the top since when im around 5300 the car will bog right out in 1-3.

[whistlin']

I tied the belt back but made sure it was TDC when done, also checked ignition timing with light. I've checked cam timing and ignition timing multiple times and in several different configurations trying to get it to run right.
It really acts like the valves are floating, the unburned fuel in the exhaust causes backfiring.

[mpgmike]

Which came first the chicken or the egg? It could be possible that you have a siezed guide in the head and the additional drag snapped the cam. Changing the cam didn't get rid of the problem that caused the first one to fail.

Another consideration is where the cam snapped. I have a head here that I won't use because it snapped between cyl #1's intake and exhaust valves. The pull of the timing belt caused the one journal to oblong and oval. Did you look for stuff like this when you installed the new cam?

Mike

[GLHSKEN]

Not related, but an 86 turbo cam is a slider, not a roller follower... You need to run the correct followers.

[whistlin']

Not related, but an 86 turbo cam is a slider, not a roller follower... You need to run the correct followers.

Actually quite related:( . I feel like a dumb arse, not thinking about the different profile between the slider and roller cam. Going to a roller out of a 90 TBI got rid of the valve floating symptoms(popping and dumping fuel in exhaust). Still falls on it's face about 5,200 rpm. I'm going to line up a turbo cam and see if that makes a difference.


Which came first the chicken or the egg? It could be possible that you have a siezed guide in the head and the additional drag snapped the cam. Changing the cam didn't get rid of the problem that caused the first one to fail.

Another consideration is where the cam snapped. I have a head here that I won't use because it snapped between cyl #1's intake and exhaust valves. The pull of the timing belt caused the one journal to oblong and oval. Did you look for stuff like this when you installed the new cam?The other cam broke last fall, couldn't see any problems. He(my son) has driven it all winter with the TBI cam and no problems other than rpm limitation.
http://pic17.picturetrail.com/VOL846/881681/8484178/214865420.jpg