Sick motor and even sicker owner.

Spanish Dave · Feb 24, 2004

I have just installed the engine in my 65 289 after rebuilding it .... new pistons, cam, timing gear, lifters, valve springs, pushrods, oil pump, bearings, flywheel, clutch etc. I thought I'd done a real good job ... until it came to start up time. The car started, ran for about 30 seconds, then backfired. I shut it down then tried again ... ran for 5 secs. then backfired with flames coming out of the carb (holley 650) I had nothing to put the flames out with, so I just wacked the carb several times on the top with my Mustang wiring diagram ... this eventually put the flames out!!
Then I called a pal of mine who came round and we checked everything we could .... the timing, firing order, changed the plugs, dist.cap, spark plug leads to no avail. Then we removed all the leads one at a time from the cap and tried to start it after each time ... car still backfired every time. We have pretty well eliminated electrical problems and now seem to think the cam timing may be a tooth off. Any ideas what the fault could be before I wheel the whole thing into the ocean

mustang70 · Feb 24, 2004

Check your float level. You carb might be dumping too much fuel into the motor at idle. And that can cause it to sputter and die.

stangman67 · Feb 24, 2004

sounds like an intake valve might be cranked down alittle too much, i had this happen and burnt a lobe.

Spanish Dave · Feb 25, 2004

I have just checked and re-adjusted the rockers ... all was Ok except 3 were just a little loose. I have taken the front cover off to check the cam timing and that is ok too. When the car was running the backfire was quite regular as if it was just one cylinder .... if that means anything.

19stang67 · Feb 25, 2004

the only time i have seen that is when the distributor was off a couple of teeth. Try pulling the distirbutor, rotating engine to TDC on #1 and reinstall.

Spanish Dave · Feb 25, 2004

Thanks for the reply 19stang67 .... the distributor was initially off, but we rectified that and still have this problem.

94CobraPace · Feb 25, 2004

Sounds like a timing issue. Might try to retard the timing and\or advance to see if it helps.

jesserose17 · Feb 25, 2004

I assume the points gap has been checked... Some people assume that the firing order in the dist cap is clockwise... it's really counterclockwise. You might want to double check that.

Spanish Dave · Feb 25, 2004

thanks for the replies

Yes we have checked the points gap and the timing (set @ 6 degrees BTDC) Also the firing order is OK and we have changed the distributor, leads and plugs.
I remember reading on this forum about backfires affecting the power valve on Holley carbs ..... what are the symptoms of a *blown* power valve??

Pakrat · Feb 25, 2004

My thoughts exactly. I was just about to ask what you had under your distributor cap, new electric or old school points. I was still running dual points and if the gap is even off by the tinyest bit, you will get a backfire. In fact, I had such a time trying to get it right once that I had to close one set for the day so I could drive it and went back to fixing it the following weekend. Now I finally run pertronix but have kept the dualpoints and condenser as a back up.

Pakrat · Feb 25, 2004

Wait a sec, 6 degrees? That's textbook and OK if you have rebuilt your engine to stock specs, but it would actually probably like a little more. I only slightly modded my 302 to include a 4v carb and intake, new headers with dual exhaust and a mild CAM upgrade, and I ended up closer to 12 at the end of the day. What you should do is try advancing it just a tad and see what happens. The best way to find your cars specific timing (since they all are different) is to keep advancing it slightly until she starts to ping, then back off a tad and wherever that is will likely be where you car is happiest.

Spanish Dave · Feb 25, 2004

Thanks for the reply Pakrat
The car is not stock .... it has 351w heads ... a comp cams 280H cam with comp cams lifters and comp cams roller tip 1.7 rockers .... headers (tri-y or similars) ... holley 650 with vac secondaries on a weiand stealth intake ... the exhaust is dual with a H pipe ... I will try advancing as to your specs. and see what happens.

Pakrat · Feb 25, 2004

Can't wait to hear how you make out. I'm betting that's it. FYI, if you got most of your specs out of a text book for a 289, then you may want to experiment with several things to see if the overall running condition improves once you stop the backfires. For example, you can probably gap your plugs a little more, like say .045 as opposed to .036 or even increase the point gap more than a .020. One thing you could do for reference points is say compare the stock specs on a 351 vs. the 289, note the differences and split them to start, then increase or decrease as necessary.

Good luck.

Spanish Dave · Feb 28, 2004

Well ... I got the thing running today The problem was the rocker arm nuts were not going far enough on the studs (screw in) to engage the locking bit ... this was happening on several which were working loose and causing vales to not open when they should leading to backfires etc. As a quick fix I have turned the nuts over so the locking bits are at the bottom and now sit really firm. I am just ordering some longer studs ... I only wish that Comp Cams had specified longer studs with the roller tip rockers I bought, then the problem would not have occured in the first place.
BTW I did change the timing to 12 before as you suggested Pakrat ... thanks for the tips.
Next problem is the clutch .. I will post a new thread for this.

Pakrat · Feb 28, 2004

Glad to hear it, congrats!

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