[Cougar_is_Grr8]

If you have read my posts you know I just got my cat roadworthy enough to get registered and drive-able. Yesterday, after the vehicle inspection, I restarted her and she was pretty hot and popping from the carb. After the DMV (about 30-45 minutes) she started hot but as I drove she would peak and then drop off again, all the while the popping continued. I figured the 103 degree heat had something to do with it. I let her sit overnight and just now restarted her. Still getting the popping.

I had planned on doing a flush and fill this weekend and maybe replace the thermostat.

What do you guys think?

 

[1969XR7Vert]

Intake valve not sealing? Check the firing order against the wires too. Check the cap for carbon tracks. Or, a wiped intake cam lobe could also cause this.

 

[Cougar_is_Grr8]

I also had the thought that I might not have tightened down the distributor enough and she slipped around a bit.

 

[Bad69cat]

Recheck the timing, make sure your choke isn't closing on you for some reason too....I know if I forget to open mine up when shes hot, it will sputter. Have you done a compression check on it? Wouldn't hurt. Make sure your wires are good and not arcing somewhere (especially the coil) you can fire it up in the dark and watch for that.

 

[Cougar_is_Grr8]

Wires are new, no arcing at all and I checked timing and it sounds like it is in the right spot. I adjusted it until I got the weakest pops.. but they are still there. The sound is definitively coming out of the carb.

 

[ahunt191]

It really sounds like your intake valves are not closing/sealing. A compression test would tell you if this is the case. Has this engine had a valve job?

If you find that your compression is low and you decide to get a valve job, IMO it is a really good idea to move to an adjustable valve train. Things wear out and don't fit like they did when your car was new. Having the ability to adjust your rockers rather than using shims or custom length push rods makes life a lot easier. Plus, if you are already having a valve job performed, it isn't that much more expensive to have your machinist mill the pedestals down and tap your heads for screw in studs.

If you want to move to an adjustable valve train without machining your heads, Crane Cams make a kit for that.
http://www.summitracing.com/parts/CRN-36655-16/

 

[Cougar_is_Grr8]

I would think that no altering the heads would be a good move so if I ever had a total restore done it wouldn't effect the originality of the driveline.

Any idea of what costs I should expect?

 

[ahunt191]

I understand and appreciate your desire to keep everything original. The positive stop system works well if everything is new. It was implemented to improve productivity at the factory. When things like valves and valve seats start to wear, non-adjustable systems are not ideal. Rather than messing with shims or custom pushrods, I prefer an adjustable system. If you get the Crane system, you can always go back to the original positive locking system.

The cost of a valve job depends on how much you want to do yourself. If you remove and installed the heads and take them directly to a machine shop, you can save money. If you disassemble and reassemble your heads, keeping track of where things went, you can save money. If you lap your valves yourself, you can save money. You get the idea. The only thing can't do on your own is replace the exhaust seats with hardened seats, if the heads are original, and grind your valves and cut your seats. With new valve stem seals and springs, I estimate it will cost you between $100 and $400 depending on how much work you do yourself. If you just take your car into your mechanic, I have heard of people getting quotes of over $1000. BTW, don't get the cheap umbrella style valve stem seals. Get the better quality positive locking seals.

Anyway, all this talk about valve jobs and adjustable valve trains is pointless if you have good compression.