1st differential install - what went wrong? Long and some dumb questions.

sleeperstang · 05-06-2003, 11:37 AM

So this Sunday....

I finally got my engine ('68 spec 302 w/Xtreme Comp Cams XE256H) all set and ran it for a half hour. Ran somewhat smooth, but with some slight surging (mostly evident through exhaust). I figured it was part of the break-in, so then I come home yesterday (Monday) and go to turn on the engine. It's running the same for about 15-20 mins when all of a sudden I hear 3 metal pings, and it's clear it's from metal contact. I take off the driver side valve cover and tell my brother to crank the engine.

One of the #5 cylinder head valves is stuck about 1/4 of the way through (haven't determined if it's an exhaust or intake valve yet, and I'm at work). I bought this engine as a long block from a machine shop. Before any work on the engine was performed (installation of parts) I called the shop and asked if all bolts and springs on the heads had been set to spec and they assured it had.

When spec'ing out my engine I made sure by calling Comp Cams if this cam would have any problems with clearance of any sort as far as valve to piston, and they said there wouldn't be any, so that part of the equation is clear is not the problem.

I call the machine shop guy this morning to let him know what happened with the engine. He states that what probably happened is that due to the higher lift on the cam, it probably requires stiffer springs (engine had been built to stock specs including spring stiffness). He says that they probably just have to install stiffer springs and fix the valve and the engine should run fine.

My concern now is the following: Obviously if the valve is stuck, and I tried pulling it closed but it didn't budge, it's bent, so this would suggest that it's collided with the piston. I would say that the engine was running at 2000 rpm, so would this collision cause any damage to the piston?

I asked the machine shop guy the same question and he stated no, but I want to be sure that he is right so that I don't feel like I might be getting cheated with a bad piston when I go to drop off my car to get fixed.

Thanks in advance for any replies!!!

05-06-2003, 11:37 AM	#1
sleeperstang Registered Member Join Date: Jun 2001 Location: Lynwood, CA, U.S.A. Posts: 82	Rebuilt Engine Problems So this Sunday.... I finally got my engine ('68 spec 302 w/Xtreme Comp Cams XE256H) all set and ran it for a half hour. Ran somewhat smooth, but with some slight surging (mostly evident through exhaust). I figured it was part of the break-in, so then I come home yesterday (Monday) and go to turn on the engine. It's running the same for about 15-20 mins when all of a sudden I hear 3 metal pings, and it's clear it's from metal contact. I take off the driver side valve cover and tell my brother to crank the engine. One of the #5 cylinder head valves is stuck about 1/4 of the way through (haven't determined if it's an exhaust or intake valve yet, and I'm at work). I bought this engine as a long block from a machine shop. Before any work on the engine was performed (installation of parts) I called the shop and asked if all bolts and springs on the heads had been set to spec and they assured it had. When spec'ing out my engine I made sure by calling Comp Cams if this cam would have any problems with clearance of any sort as far as valve to piston, and they said there wouldn't be any, so that part of the equation is clear is not the problem. I call the machine shop guy this morning to let him know what happened with the engine. He states that what probably happened is that due to the higher lift on the cam, it probably requires stiffer springs (engine had been built to stock specs including spring stiffness). He says that they probably just have to install stiffer springs and fix the valve and the engine should run fine. My concern now is the following: Obviously if the valve is stuck, and I tried pulling it closed but it didn't budge, it's bent, so this would suggest that it's collided with the piston. I would say that the engine was running at 2000 rpm, so would this collision cause any damage to the piston? I asked the machine shop guy the same question and he stated no, but I want to be sure that he is right so that I don't feel like I might be getting cheated with a bad piston when I go to drop off my car to get fixed. Thanks in advance for any replies!!! __________________ 65 Mustang Coupe...Comp Cams 262 Xtreme Energy, T-5 conversion, Romac Balancer, 620 Front Springs-4.5 Mid-eye rear springs.......work in progress