260 question - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

jtmarten · 07-07-2004, 19:35

Hi
I have a '64 Falcon 'Vert with a 260. Had a couple of bad guides and decided to upgrade the heads instead of repairing the 260 heads. I have a 351W block I'm going to build for it eventually, so I went with '69 4V 351W heads. Also installed a new Power Plus Cyclone intake and new 1.6 roller-tips. (had 1.6 roller-tips on 260 heads with screw-in-studs but had to go to the rail type). The problem: Now I get a constant backfire through the carb. I've checked the firing order repeatedly and its correct, timing adjustments don't help. Restabbed the dist 180 with no luck. At idle its just a small pop, pop, pop. I'm wondering if it could be the intake not sealed properly? Had a similar problem with an aluminum intake on the 350 (yuk) in my boat.
Any help is greatly appreciated!
Jeff

svo347 · 07-07-2004, 19:47

Im guessing your right with the intake leak, spray some carb cleaner around the area if the idle revs increase you have a leak.

Racer · 07-07-2004, 23:33

I didnt think "big" valve 351 heads would fit with the small 260 bore. Are you sure you don't have valve to bore clearance problems?

jtmarten · 07-09-2004, 21:16

Well, got the intake gaskets changed out tonight. Used FelPro's this time, last time I got a complete kit (was cheaper - for a reason

). Won't be doing that again! She's now running with no backfiring! I am getting some noise I don't like though. First I thought it was intake valves contacting the bore, but I'm not hearing it with the stethoscope on either side and no backfiring, etc., so I'm hoping its just something that is still not bolted down thats making the noise. Next week I'll have time to finish putting her back together and hopefully go for a cruise.
Jeff

jtmarten · 07-11-2004, 16:43

Well, she's running great now! Noise was the belt, which was just hanging there, but making enough contact with one of the pulleys to make a small screeching noise, kinda like bearings running dry. Just have to readjust a couple of rockers that are still a touch too loose and she'll be ready for a cruise!
Have a good one!
Jeff