I started the topic because it morphed from an earlier one re correct spark plugs and has had me chasing a backfire in my KR.
So in summary:
Engine starts, idles and cruises fine but it backfires when accelerating harder than just cruising.
Car was running fine until i had it stored in a workshop for 3 years slowly getting some work done when it developed a backfire once it was started.
Had the carby rebuilt
Changed points, condenser and coil, set timing, checked number of spark plugs and they're fine no sign of wear or fouling and the problem is still there.
Could be a vacuum leak causing engine to run to lean
Tilt away was fixed by changing the relay but now the relay is working but the tilt away wont tilt back so I'm thinking there's a vacuum problem in the system which could be related back to the backfire.
A couple of guys on the forum have offered some assistance which is much appreciated, thanks Shelbydoug and 1967 eight barrel
So this is the current position, I'm going to chase down a vacuum leak as my next step,
If anyone else has had a similar issue your feedback would be appreciated by me and also to assist for anyone else who may experience the same issue in the future.
Ross
Easy stuff first. Change your cap and rotor. Solved my problem.
Cap and rotor changed also
Sorry forgot to mention that.
Bring it in. I'll fix it for free. :D
Come to Australia I'll put you up for free ;)
Quote from: GT350AUS on April 16, 2019, 08:38:54 PM
Come to Australia I'll put you up for free ;)
Let me get my Google driving instructions.
Cool
I'll have cold beer waiting for you.
Ross
Timing or carb issue is about all that's left. Would have to be a big vacuum leak....
At this point, after installing a vacuum gauge, I'd disconnect the vacuum cannister for the tilt column and plug the hoses. Run the car. See if the problem goes away.
I would go back to the carb. Just because it was rebuilt doesn't mean it was rebuilt correctly. Get a new or proven carb, put it on and try it before you do anything else. I suspect that is where your problem is.
Does the car have Thermactor System? If so, it could be the backfire valve.
Another problem causing this can be the float level in the carb.
Texas Swede
No thermactor system fitted. It was removed before my time.
Float level is set correctly.
Thanks for your suggestions.
Go back to the basics, your missing something, it is a very simple system
Quote from: PR on April 17, 2019, 10:44:53 PM
Go back to the basics, your missing something, it is a very simple system
Yep I agree...its probably staring at me but I can't see the forest because of the trees....LOL
Once I get it sorted I'll post back on the forum.
I realize a stumble is different from a backfire, but I would still take another look at things that can cause both:
Carb, fuel filter, bad fuel, fouled spark plug(s), bad ignition wire(s).
You wrote that you checked a number of spark plugs. I'd check and replace them all. Yes, it's a pain, but the one plug you don't check or change will always be the bad one.
Nobody has mentioned flat cam lobe yet??
(exhaust lobe)
Don't think so because it runs fine from cold start to cruising. Problem comes up when under harder acceleration. Flat cam lobe would be evident from start up.
Others should be aware that 68s have a different vacuum footprint then other years and potential for weird vacuum issues as a result.
Backfire is gone!!!
Problem was timing and point gap.
Once checked, found the harmonic balancer has moved on the rubber so the standard readings are useless.
Starts up fine. Runs perfect. Accelerates hard and no backfire or pinging.
Pulls hard as a Jet.... a Cobra Jet!!!!!!
A great Easter present for me.
Now all i need to do is drive it before winter hits here in Australia.
Thanks to all you guys for your suggestions.
Quote from: GT350AUS on April 18, 2019, 05:45:32 AM
Don't think so because it runs fine from cold start to cruising. Problem comes up when under harder acceleration. Flat cam lobe would be evident from start up.
My experience with a flat lobe is it starts and idles fine, revs fine, when you drive it, give it gas and put a load on it, it feels like a miss fire , or runs like crap....no back firing in my experience.
Post 7. Timing 😁
Yep you were right but timing marks gave the wrong reading and point gap had to be reduced from standard due to movement in the dizzy shaft.
All in all a great result and good info for anyone else chasing a difficult to diagnose problem.
That's the benefit of this forum.....
Quote from: GT350AUS on April 19, 2019, 11:24:01 PM
Yep you were right but timing marks gave the wrong reading and point gap had to be reduced from standard due to movement in the dizzy shaft.
All in all a great result and good info for anyone else chasing a difficult to diagnose problem.
That's the benefit of this forum.....
Now all you have to do is go out and buy a new balancer and dizzy :)
Quote from: GT350AUS on April 19, 2019, 11:24:01 PM
Yep you were right but timing marks gave the wrong reading and point gap had to be reduced from standard due to movement in the dizzy shaft.
All in all a great result and good info for anyone else chasing a difficult to diagnose problem.
That's the benefit of this forum.....
Thanks for sharing the cause and outcome, especially since this is not on the shortlist for most!
So the root cause is a rotten elastomer strip that allowed the outer damper ring to slip? I have seen it a couple times. I didn't think about points as most of us have got away from them. Especially those with dual points. I'm glad you have it sorted and can enjoy it before it gets put away for the season.
-Keith
Spot on Keith.
Starts first kick every time nw and I can enjoy the drive before the weather turns sour.
Thanks again
Ross
I'm glad you're not dealing with my issue. Machinist that don't know their way around an FE and the common core shift issues.
It's an expensive proposition to do right.
-Keith
I would like to know how you determine slippage of the outer ring ? Was it crooked or other distinguishing factor?
This is a common occurrence these days on Fords which largely have un-bonded rings.
I haven't looked at any in a while but I seem to remember that the Clevelands have a cut notch in the ring that is keyed to the crank key.
There are a few exceptions. My Boss 351 for instance has a bonded ring. That probably is because of the expected higher rpm use and the greater mass of the ring.
The 427 Fords are similar but not as massive as the Boss balancers. I can't remember the exact weight right now but the ring is two inches thick. That's in most cases twice as thick as a 4v balancer and considerably thicker then my 67s ring.
The plus of this is that they are all "re-buildable" and bondable. If you are building an engine now with a used balancer it would be highly advisable to send them out to have rebuilt for high performance use.
The 427 and 428PI weigh in at about 18 lbs. Both have an incorporated single groove pulley. The PI has the beveled edges and timing marks where the 427 damper simply has small v groove on the front edge of the pulley. They are about 7 X 2.2" and is massive. To my recollection they weigh more a Boss 351 damper.
The are the heaviest harmonic damper I have seen. Interestingly enough I was surprised that it wasn't chosen for use on the CJ nor the SCJ. Both wound up with the thinner FE damper and the SCJ wound up with the small counterweight in place of the spacer.
-Keith
Quote from: 1967 eight barrel on April 27, 2019, 08:24:03 AM
The 427 and 428PI weigh in at about 18 lbs. Both have an incorporated single groove pulley. The PI has the beveled edges and timing marks where the 427 damper simply has small v groove on the front edge of the pulley. They are about 7 X 2.2" and is massive. To my recollection they weigh more a Boss 351 damper.
The are the heaviest harmonic damper I have seen. Interestingly enough I was surprised that it wasn't chosen for use on the CJ nor the SCJ. Both wound up with the thinner FE damper and the SCJ wound up with the small counterweight in place of the spacer.
-Keith
I have both here. The PI and the Boss 351. I did weigh the Boss dampener, but don't remember what it was.
It is definitely thicker then the PI. Since the PI incorporates the pulley, I have to think that it is part of the mass calculation?
The PI is still on the shelf in the shop. The Boss is on the car. So I can't do a side by side for you.
In the case of the Cleveland, the stock 4v balancer is only good to about 5,000-5,500 rpm's. The engine will turn more then that but that block in particular reacts adversely to harmonics and during it's racing days typically would crack through the #2 main bulkhead, then up into the cylinder wall.
The thick balancer is really a necessity for the Cleveland. In the day, it was successful at adding much durability for "high-performance" use.
Interestingly enough, my 67 427 side oiler block failed in exactly the same way as a "raced" Cleveland would. The #2 main cracked (sawtoothed bad). The engine builder said I twisted the block due to a high rpm inbalance. He's the one that balanced it so what do I know right?
Simply put, 427 Ford blocks are junk. The best ones are the hydraulic blocks with the square cylinders. That doesn't mean they are good. Just better.
They really are just the evolution of the 352.
Ford tried to fix the block weakness with the cross bolts and when they were just a couple of hundred bucks new as a service part, that was sufficient. NASCAR engines only lasted one race. If you were lucky. Then you threw it away and put a new one in it.
The problem is block flex. Sideoilers were just lip service and originally made for the Cam'ers. Oiling is not really the issue here. The problem is you can't make a donkey into a race horse champion.
One difference is that in the case of the Cleveland, the iron crank is the way to go rather then steel. It flexes more and as such absorbs more of the harmonics.
All a steel crank does is pass through more harmonics to the block and give you one or two more rebuilds on the crank because the harder crank doesn't let the bearings embed themselves as much in the races.
All things aren't equal between the engines though. They just have some similarities. For one thing they are balanced differently.
The 351C NASCAR or Austalian blocks have noticeably thicker bulkheads but the cylinders are still thin cast and many have "core shift" and if they have are useless for racing use. Those they actually put into trucks in Australia.
But I think that, yes, the Boss balancer is up there in weight also. 18 pounds sounds about right.
I just measured and weighed my PI balancer.
The ring is 1-1/2" thick. It weighs 18 pounds with the bolt on pulley. It weighs 8 pounds without it.
The Boss balancer ring is 2" thick.
It's very difficult to find a production balancer thicker then the Boss balancer. I don't know of any.
Many people confuse the 4v Cleveland balancer with the Boss. The 4v is 1" thick. That's the one that the ring spins on. It's not bonded to the hub like the Boss balancer is.
I may have one of those here? If I do I'll take a pic and show you the difference. I may have junked that one though? Not sure?
I can say that I can see where the PI's have the timing marks worn off. My front anti-sway bar has a definite mark in it where it rubbed on the balancer.
I've seen starter rings on flywheels "machined down" where they rubbed against the inside of the bell house also. I don't have a picture of that but do remember the sparks after I put a new ring on the flywheel.
Who exactly was in charge of engineering these things? Was it some sort of work release program? Florida's gonna' let them vote now? :o
Quote from: 1967 eight barrel on April 27, 2019, 08:24:03 AM
The 427 and 428PI weigh in at about 18 lbs. Both have an incorporated single groove pulley. The PI has the beveled edges and timing marks where the 427 damper simply has small v groove on the front edge of the pulley. They are about 7 X 2.2" and is massive. To my recollection they weigh more a Boss 351 damper.
The are the heaviest harmonic damper I have seen. Interestingly enough I was surprised that it wasn't chosen for use on the CJ nor the SCJ. Both wound up with the thinner FE damper and the SCJ wound up with the small counterweight in place of the spacer.
-Keith
The 64/65 427 balancer is a C4AE and the 66/67 427 balancer is the C6AE unit. They are identified with the characteristics that you mentioned. A slight revision is in order because the 428 Super Cobra Jet balancer was also a larger diameter one. It is different then the standard 428CJ/390 balancer . It is similar to the 427 balancer but without the made in pulley.