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Ford 1500 Kent Pre-Cross Flow Mystery

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Chevron56

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In a recent vintage race my 1500 Kent pre-crossflow engine suddenly dropped from firing on four cylinders to two. Cylinders one and four are firing, two and three are not. Over a period of several days I have tried the following:

- Replaced the entire ignition system incl. distributor body, points, condenser, coil, high tension and low tension wires and spark plugs.
- Replaced the head gasket.
- Performed compression and leak-down tests with all reading within acceptable limits.
- Verified cam timing.
- Verified valve operation, lift and lash.
- checked intake valve stem seals.
- Tested an alternate intake manifold / carburetor system.

None of these actions has any effect on getting cylinders two and three to fire.

Does anyone on this forum have any additional input or theories to help resolve this issue?

Thank you
 
Oh heck... My gut reaction was that it might be a carburetion issue but you covered that. Have to ponder this. Throw your question in the racing forum as well, just in case. A Ford Kent engine has lots of applications so someone else probably has experienced this.
 
Have you put a timing light pickup on wires 2 and 3 to SEE if they're sending electrons?

From what you describe, you have compression. The induction wasn't described but I'd assume (bad, but logical) the fuel is sent thru two carbs feeding two cylinders each... no way they wouldn't feed the middle cylinders if the end ones are being fed. All that's left is a flinky iggy system someplace.
 
I'm curious... you didn't mention what evidence there is that the problem is limited specifically to #2 and #3 cylinders. That might give us a clue.

You mentioned changing the distributor body, points and condenser... did that also include the distributor cap and rotor?

Cheers,

David
 
I've used an induction timing light to check all four cylinders and they are all timed correctly. I am using a single sidedraft Weber and the same runner that goes to cylinder one (which works) also feeds cylinder two, the same relationship between three and four.
 
I've changed complete ignition systems - two different caps, points, wires and rotors on my Lucas distributor and a completely different system of components on my Mallory dual point distributor. I can confirm that #2 and #3 are the problem by pulling off individual spark plug wires while running. Pulling off either #1 or #4 will kill the engine. Pulling off #2 or #3 causes no change, in fact I can pull #2 and #3 at the same time without affecting the running of the engine.
 
Are the #2 & #3 plugs wet after the engine runs with all spark plug cables connected?

When you put it all back together with the alternate ignition parts, did you run the plug wires for the correct firing order, 1-2-4-3 (distributor turns CCW), not the usual 1-3-4-2 order that is so common for other four bangers including Lotus twinks? That'd do it for sure. Just swap the cables on #2 & #3 plugs to see if they are in the wrong order :yesnod:

Cheers,

David
 
Well, with one single side-draught it ain't carburation. Gotta be an iggy issue.

Changing out th' diz should rule out shaft "wobble"... have you tried juxtaposing wires to fire in the traditional 1-3-4-2 order?

I know, I know... Just grabbin' at straws here. Th' thing ain't in front of me!
 
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Different cams can have different firing order. 351W fords, for one, stick one of those cams in a 302....but, if you didn't change cams, this mystery occurred without you changing any wires, or ignition bits...then it's else where.
Tell me, just to humour me, if the car ran perfectly one day, two cylinders the next, and you touched nothing?

Now. Vacuum gauge.
Plug one in, run it, Does it bounce to beat the band?

Valve guide slipped.
Intake valve guide shot.
Broken valve spring.
Flat cam.

I have seen engines that will idle, no power, wrong (too short) valve springs.
If you have something, may not even be 2&3, applying pressure to the inlet, it will kill the fuel flow.
So, you may have an inlet on 1 or 4 killing vacuum by pushing some pressure back into the plenum...compression may be fine.
I'd do a vacuum gauge test first, followed by a manual operation of the valves to see if a spring is broken.
Engines can do odd things at running speed they won't do at idle.

Dave
 
Yes - the engine was running perfectly and then suddenly dropped to running on two cylinders during a session. I have checked the valve guides and seals and also measured valve lift (at the rocker) and all are the same, seemingly ruling out a flat cam lobe.

My first response was it has to be ignition but having changed every ignition component more than once I'm turning my attention to fuel flow. Thanks for your suggestions.
 
Are you getting any "clacking" when you are running the engine? could be sticking intake valves (which I have seen too much lately) :frown:
BillM
 
I re-iterate. Vacuum gauge. Sticking valves or broken springs will show up right now on a vacuum gauge.
Quit in the middle of a session sure looks like broken part.
I would not imagine a valve to guide sticking issue would happen while running....unless the guide came loose from the head and shifted, or lack of lubrication galled it.

Cam lift all within spec you stated. Good. Eliminates that issue.
Spring tension.
Check them all......use your thumb if you have to...same thumb, cam away from lifter, you have a broken spring, you'll find it with thumb pressure.
 
Thinking about this. You pulled the head and replaced the head gasket.
While off, did you pull all the valves? Lay them out in order? Set the springs out in order, and at least visually check along the top for one or more way out of height with the others?
Did you check for cracked or broken springs?
Did you look at the back of the valves for large carbon buildups and clean them if present?
Did you check the guides with the mating valve for looseness or tightness?
Did you visually inspect the seat and valve faces for proper mating?

Just thinking, is all.
 
TOCs on to something! You replaced the head gasket and all looked good? Then replaced the electrics. Get the vacuum check and then do a manual spring check. Also, check for a warped intake manifold ( I doubt, since it happened during event ) seen clearance and leaks between middle cylinders from manifold. But, check the vacuum as TOC suggested and it will immediately tell you where to close in. Vacuum gauges are a real plus and old school at tracks.
 
Any update as to where you are in finding problem?
 
I can’t think of anything to try that you haven’t tried already.
Have you had any luck figuring out the mystery yet?
Just interested.

Derek K
Another 62 Lotus Super Seven S2
 
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