V8 only firing on every second cylinder? Any Ideas

Could it be excessive play in the dizzy shaft causing the points not to open enough and charge the coil. Guessing not due to the fact its missing on the same four cylinders.

I have had this before and it was a broken cam shaft !

frank_grimys, seriously mate, it may look like 1 barrel feeds left bank and the other feeds the right. But honestly it doesnt, unless your v8 is some sort of a 1 of the kind special. I been building and racing V8's since the mid 60's, and EVERY stock and aftermarket dual plane manifold, whether for 2 barrel, 4 barrel or multicarb, that Ive ever come across has been the same. The runners form 2 seperate overlaying H patterns feeding 2 cyls from each bank from each barrel.
A V-8 engine fires a cylinder every 90 degrees of crank rotation, and the induction cycle of any given cylinder will greatly overlap the induction cycle of the next cylinder in the firing order. The two-plane design isolates each side of the manifold and connects the cylinders in a sequence in which each isolated plenum is connected to every other cylinder in the firing order. Plumbed as such, each side "sees" only every other firing pulse. Rather than having overlapping intake pulses coming into the plenum every 90 degrees as with a single-plane, each side of a dual-plane gets a much cleaner induction pulse every 180 degrees of crank rotation. That's why a dual-plane intake is often referred to as a 180-degree manifold. With the induction pulses coming into the carb every 180 degrees (or actually only one-half of the carb in a divided plenum two-plane), the induction pulse seen at the carb is greatly enhanced, especially at low air speed.

I said that was going to be replaced today.I did, and ffffaaaaarrrrrrr out, sorted out a lot of issues, jumping over small ripples this morning.Went to go out again though and the coil started to short straight to earth, so unsure how as I've rewired it all, looked up the model number apparently it's not internally resisted like repco said it was, so off to repco to get a new one, the proper one this time and then more fun unless the wind picks up much more, flat bottomed boat so not overly fun in times of choppy conditions

yes, I checked and you are correct, I was wrong in assuming each side fed one bank, but since the problem made itself more known under heat, and and load it pointed more to spark, which it was.Searched more thoroughly on the net and rotors shorting to earth under heat is a common fault for the distributor in this modelhttp://www.vord.net/cars/mgb_mods/engine/engine-trouble.htm

Great, Im glad your sorted, they can be a total pain in the arse to find some of these faults.

yup your on to it with your open mind. happens on a lot of older v8s.

hi, how old is the fuel, if older than a month throw out, do not keep or use else where, the stuff the sell today is s**t it does not have a life span as the old leaded fuel had, when they changed back in 1998, the stuff has that much additives to keep it alive, do you remmember the little squirt they sold at garages (dont not use) was full of kerosene, we used to love the stuff we would sell 50 spark plugs near every hour, the stuff would soot up the plugs people would remove clean put back in and wham all the same problems as before,the fuel comes from asia cheap as chips is a 87 octane level then they boost it to 98 for the travel and by the time it go here was 91 octane an we go bang it in and drive, fresh fuel should be used in 3wkstime,the lawn mover guys love it you fill up once every two months and atleast buy a plug every few months try a fresh set of plugs and fresh fuel (just for incase you wonder i am a mechanic by trade, fitter turner, fitter engineer, fitter welder,as well, done auto motive sales for 4yrs repco, and now im a painter decorator by trade,done it since i was a tot (family owns a firm and that is where we hung out during school holidays)cos i like my weekends off, hate smelling like an oily rag all the time, and working on cold steel in the middle of winter with the wind and rain coming in and cookin my a** of in summer in a bake bean tin, and they dont train you any more, not like the old boys of the sixtes + where you done every thing in shop, now you just un bolt it and send to the specalist an bolt it back on just like a wrecker does ask a mechanic to shim a diff today and he looks side ways at you, oh the good old days some of the boys who trained me built steam engines then work on trains planes and ships try fixing them not near anywhere, you would find a piece of number 8 wire and build yourself a new part

sweet glad ya got it sorted. rotors are often misdiagnosed or overlooked. The right coil and you will be away!

I'm glad it is sorted.

Well done bigfatmat1 !(post 28!).

So where and when do we all turn up for an outing on the lake!

Only seats two, squeeze three in maybe, but can't be too heavy, as it affects performance, have to be heavy enough to stop porpoising.And there are manylakes, if you ever see someone in a 13ft jetboat doing hamilton turns around the place ask if they're me and if it is I'll take you for a blat.