345 V8 diagnosis and engine tech

Stoopid spark plug engines! I'm a diesel guy from way back, if it's pumping fuel and it's got compression the bugger will run. Seems like if an african on the serengeti sneezes then a petrol engine the other side of the world gets a cold and won't run. Timing wrong - won't run. Air fuel mix wrong - won't run, spark weak - won't run. compression a bit ordinary - won't run. It's a friday - won't run.

So my 345 has all new ignition system, and the carb has been rebuilt. We did the carb because it was gutless, and you could see black unburnt fuel coming out the exhaust and at times it simply wouldn't even free rev.

So after putting the carb back on we couldn't even get it to start with basic carb settings. Did a compression test and got between 85-90 on all pots with a wet test returning the same. So i'd say that compression or lack thereof is more likely the issue rather than fuel metering. Sound about right to you guys? I figure if it couldn't get compression it probably didn't have enough vacuum to keep the power valve closed which meant it would have been dumping a crap load of fuel in at all times hence the black smoke, lack of balls and 52l/100.

Sooooo, my thoughts are that with the wet and dry tests being similar that would indicate the rings are fine and it's more likely the valves right? What's a valve or head job on these buggers worth? We don't really want to go spending a motza on it as it's destined for an engine swap later on, we just want it running for now.

thoughts?

You might be right on the valves but my experience is that one or two will go before the others and you would not get 80 to 90 across all cylinders. Try your compression gauge on a known healthy motor and see what it says.

Good idea pete, thanks

Do 345's have timing chains? Could've jumped a couple of teeth.

My Dad's 302 ZH Fairlane ran a tooth retarded for years before finally jumping another one. Went like a rocket after we fixed it.

I've also had a single good backfire take out one of those Holley power valves. Would only start and run on full throttle.

Jarrod.

asw120 wrote: Do 345's have timing chains? Could've jumped a couple of teeth.

My Dad's 302 ZH Fairlane ran a tooth retarded for years before finally jumping another one. Went like a rocket after we fixed it.

I've also had a single good backfire take out one of those Holley power valves. Would only start and run on full throttle.

Jarrod.

Hmm, no idea on the timing.
When it did run it backfired both directions regularly, but the power valve was fine when we pulled the carb down.

I stand correcting, but I would think way - out valve timing would give you low compression readings.

80 to 90 is awfully low, especially wet. (assuming your lifters are OK - been there with really bad bearings once in a Holden 186)

I've found generally anything under 75 - 80 won't fire at normal cranking speed. Can you temporarily rig 24 volts up to the starter?
That would at least get you running with low compression, then you could check other things.

Also - could it be flooding due to grit in the needle and seat? Another common, but easy one. At least you can check the float level on those while they're running.

Jarrod.

I find it amazing that people are suggesting the timing has skipped, just seems so unpossible for the chain to be that loose as to jump a tooth :ohmy:

How would you check? rocker cover off and watch #8 valves at TDC on the crank?

I dont think it has jumped a tooth and wouldnt worry about the compression either at this stage back to basics
REMEMBER IT RAN A BIT BEFORE YOU FIDDLED so a fare chance something you have done

pull a plug wind it over with your thumb on the spark plug hole does it feel like fairly good compression
does it dump fuel when open the carb as in turn the accelerate around ??? if so dump some fuel in with a few pumps then wind over
if it doesnt dump any fuel maybe that will let you know where to start looking
Do you have good spark have you wound it over with a plug hooked up just resting on the head or rocker cover ??
Should have a good spark if your not sure just grab hold of it (yes Im serious you girly men) it will soon tell you if the spark is good or not

As for timing pull the rocker cover off what ever side number one is and wind the motor over by hand and make sure the valves are still in the correct position when at TDC on the spark side of things as well maybe the dizzy is 180 degrees as about if you have had it out

Sorry if I sound rude or am been to simple not my intention as I dont know what you have checked or havent

Paul

In the past, I have checked it by the "rough" method:

Get either #8 (don't know why IH did that), or it's opposing number at TDC as marked on the crank. I don't remember what a 345 has for this, but let's assume it doesn't slip, like it can on a Holden red motor. Whichever one is at TDC firing position will have both valves shut hard, on the other at TDC, they should both be "rocking" as you rock the crank back and forth.

I'd think a 345 would easily outlast a timing chain, if a 302 Ford does. On dad's Ford, the timing chain was hanging under the crank gear, barely touching the teeth. The plastic coated cam gear teeth don't help, as the plastic breaks up. Car engines tend to have this (AMC / Jeep 360 also comes to mind). I don't know if IH used them. A 350 Chev truck motor I stripped once did not. Hy-vo chains don't last forever, either. Not sure if IH used that, roller, or gears (which can strip - another story!)

I expect you will get more potential answers tonight after people get home from work (I'm at home recuperating).

Blocked muffler also comes to mind, but I don't know how that would affect your compression readings.

I would love a bit of education, myself on this as I keep an eye out for a cheap ACCO.

Best of luck, Jarrod.

Spark is good, I found out the hard way. I'll have a look at the valve timing at some point.

I've got my eyes on a late model diesel and there's a Gen4 Gm sitting in the shed as well. It's starting to look like more and more obvious what way to go