Any 225 gurus out there?

Hi guys, thanks for the response.

I've got an odd-fire here, I take it to be the original motor but there's no prooving that in any way that I know. The issue is backfiring in the intake (from the no. 6 cylinder only) above a particular rpm (rpm is variable, depending on whether the motor is cold or hot and also on ambient temperature). I couldn't decide if it was an intake valve hanging up (or a lifter stuck) or if it was a head gasket- after much monkeying I've decided on the head gasket. It's still possible that it's either a valve or lifter, once I get that head off I'll know for sure and will be able to deal with it.

If anyone has any information concerning a typical problem this motor has, it's very welcome and appreciated- so far I've addressed the carb, distributor (including checking the top bearing, cleaning the cap and rotor in case of crossfiring), new plug wires (before the issue came about, but long enough before that I don't suspect the new wires), checked for induction between wires (with the suspect cyl. plug unhooked and the wire hooked to another plug to produce the spark necessary to still cause the inductance), checked for arcing between wires.. rotated the distributor 120deg. and switched the plug wires back to where they oughta be (to see if the dist. cam had an issue).. No compression test necessary to know I've got two cyl. with low comp., put compressed air to the no. 6 cyl to listen for leakage in the intake and no. 4 but I can't hold the motor in one spot (auto trans) so that didn't help a lot..

I think the distributor you describe is the HEI, which is on the 'to get' list- I've got the breaker point dist. Interestingly, it's not possible to have a consistent dwell, due to the staggered firing, but it seems to not affect things much..

To tell a bit more about this Jeepster, it's a '69 with about 55K on the odometer. I don't know about the mileage, it might be 155K, but the motor is strong and has virtually no blowby. It's got the Turbo 400, I think someone tightened that up before it came to me as it shifts very crisp- before I put the 16" tires on it'd occasionally chirp a tire when getting second gear. Factory air too- but the hoses are bad, someday I'll address that. Overall it's a good machine. Needs a bit of body work, but that doesn't bother me much.

Hanging a dual exhaust under this was a real pain- I didn't want to alter anything important and there really wasn't a lot of available places to mount stuff. I ended up hanging the mufflers outboard of the frame rails, behind the rocker panels. There is 3/8" shims between the trans. crossmember and frame so I pulled one of them from each side and welded a bracket (to the shim) to come up under the floor pan to hang the mufflers. Bit of flex pipe on each side mated the pipe from the stock manifolds to the mufflers, little motor breathes well and sounds nice.

If anyone's not clear on the odd-fire/even-fire issue this guy describes it very well-

John

Well, ,you seem tohave the whole odd- even-fire thing under control. The rest is basic detective work. Once you get the head off, you'll know. My guess is a bent valve stem or a sticky lifter.