JMG2

im officially offering a case of beer or bottle of choice to whoever helps solve this overheting issue.

JMG2

the holly efi doesnt controll mechanical distributor, which is what i have. only thin it gets from the distributor is tach out signal.

JMG2

looking at the motor, I notice that the lower rad hose looks a bit old, and doesn't have a spring in it. Wonder if it's sucking close at higher rpms-- would certainly explain why it's overheating at higher rpms, regardless of the speed. Doesn't explain though why this wasn't happening before...

New hose on order..

SDVette

I had a high RPM cooling problem last year.
It turned out to be a bad radiator cap..
The old one had a slight leak and the system could not pressurize.

Easy to try.... good luck.

Faslane

No such thing as EFI without timing control, has anyone told you about getting a small cap HEI (it would have been the original dizzy in the 88 motor. Injectors running on just a TPS is a carburetor. No telling whats coming out those injectors. Call holley, goggle it.

JMG2

ok, so to clarrify what I said previously, of course the holley efi can control timing, but I'm not using it to do so. It also works with non-computer controlled mechanical advance distributors and when it does (as in my case), it only gets a tach out signal (this is not something I jury rigged, it's specifically designed to work with non computer-controlled distributors-).

saying that an efi working on tps is "just a carburetor" is wildly inaccurate. I can think of a million differences-- the pressurized fuel alone is a huge difference for off-roading (high off camber moves will very easily stall a carb, not so with the efi). That alone was the primary reason I bought it, to be honest... IO got tired of stalling the carb on a highly off camber, up hill move (even though I have a properly tuned off road carb, they still cant touch fi in this area). One of the most popular install bases for the EFI and others such as EZ EFI is for offroaders, specifically for this reason. o2 sensor alone gives it far more advantages over a carb. Have you looked at these seriously? Many, many people use them with mechanical advance distros. I agree you're not getting the most out of it if you do, but calling it a carb unless it controls timing is a gross oversimplification. Fair, it's not as efficient over a wide range of RPMs as an efi that is controlling timing, but if it is nothing more than a carb .. well, I'd love to see the carbs you're running :-)

Especially in my case, where I only use the truck for a very, very narrow band of rpms. I was considering replacing the mechanical distro with a computer controlled one, but its not a "must have" upgrade, properly tuned the one I have works fine for my application, which is almost exclusively low-rpm crawling.


Anyway, this isn't a thread about whether I should get a computer controlled distro. I think I have the timing finally dialed in, but it didn't really help the overheating... I have a few more things I can try before I start making offerings to the car gods for inspiration.

kingwoodvette

Install that new lower radiator hose yet?

I once installed one of the GM throttle bodies on a Jeep 6 without any spark control and I agree with all of the above. Not any noticeable increase in power, but that thing would run hanging from its front bumper!

GTOguy

It sounds like you mainly off-road, so you are moving at slow speed. The tight engine compartment of your Jeep might be contributing to the heat issue. Some vents could be helpful, as well as an auxiliary electric fan, to be used on the trail. I 4 wheel in an '83 Toyota Hilux 4x4, and that carb is no fun on steep inclines. My '05 Tundra does MUCH better, as did my '94 4Runner. The short wheelbase and lifted and locked '83 is the champ on rough rocky narrow stuff, though!

JMG2

ARRRRGGGGHHHH..
installed new lower rad hose. No difference. Anyone got anything for me? I'm ready to sell this thing and get a wrangler ...


I have hood louvers. I'm also running a rad made by novak conversions-- they special build for Cherokee 350 conversions (never would have guessed there was that many out there ...). No room for any more fans, already running 3x spall 9" super duty fans. At low speeds, zero overheating issues, it's just when I increase the rpms. I don't need a lot-- even climbing an access road for about 1/2 mile at 5 miles an hour was enough to ramp the temps up.

tuxnharley

Here's one more thought. While it sounds like you've got the radiator capacity and air flow issues covered, I'm starting to wonder about the coolant flow as a possible issue.

You apparently are overheating during low speed low rpm high load conditions. I wonder if your water pump is just turning too slowly to move enough coolant through the radiator so as to make adequate heat transfer from the heat load generated by the engine in those conditions?

If it were me my next step would be to try a high capacity water pump and/or a larger diameter pulley.

Don Julio anejo, por favor!

GTOguy

Another thing, what is the condition of the engine? Has it been bored oversize a bunch? Are the cylinder walls thin? Does it have a bunch of blow-by so that the combustion super-heats the engine oil? Are there any vanes left on the water pump? High RPM=higher heat in most engines, but if it's going into the stratosphere, there's an issue for sure....possible leaking head gaskets, etc. Perhaps a leak down test and a block test on the engine are in order.

JMG2

I was thinking the same thing.. I did put in a brand new "heavy duty" water pump from advanced auto (store brand), but maybe a weiland and see if that makes a difference.

bone stock, not bored. water pump brand new.
I think you've hit the next step, if novak does send me a new rad, and that doesn't work, I'll have to have to heads tested.

Faslane

If you swapped to a serp system for a truck (like for a TBI engine) you need a reverse rotaion pump to spin it the proper direction? This issue has got me a couple of times.

Faslane

mid 80s and back

63 340HP

The answer is yes.

30 degrees total mechanical advance can cause overheating.

Usually when it does, the problems are a combination of timing and fuel delivery.


If you achieved a stable 30 degrees, at what rpm did it stop increasing advance?

Where did the idle advance end up with 30 degrees total mechanical advance?

Where did the idle speed advance move to with the vacuum can hooked to manifold vacuum?


What is stopping you from adjusting the mechanical advance to 34 or 36 degrees?


What is the idle vacuum & A/F mixture, and at crawl speed?

JMG2

yup-- it's a serpentine belt, and I'm using a counter clockwise pump.

JMG2

Right around 2700 rpm

Initial timing is at 10 degrees.

I didn't try that --- at 2700 or so, shouldn't advance from vacuum be negligible? Regardless, I'll try it.

my timing tab only indicates two more a total of 12 degrees of advance. I could just dial in 4 more degres on the timing gun and advance 12 degrees at idle (which would give me a total of 16 degrees initial timing). I also stopped at 10 degrees because it's very difficult to hear pinging -- the exhaust on this truck is absurdly loud.

idle a/f is 13.3, cruise (crawl) is at 13.3 also, WOT is 13.1. I intentionally kept it a little on the rich side.


Anyway, I'll try adding more timing, but I guess I just had a gut feeling that 16 degrees initial timing was a little on the steep side.

GTOguy

Odd you can't get more than 30 degrees of advance out of that distributor. How big is the limit bushing in the mechanical advance? I would be inclined to stab another distributor in there and re-check. If I got the timing curve where it needed to be and it still overheated off of idle, my next check would be with a block checker for a leaking/cracked head or block. It's amazing how fast combustion chamber heat will heat up coolant. 2000-2500 degrees turns 180 degree water into 280 degree water real quick.........

JMG2

I'm sure I can get 36 degrees on it if I add another 6 degrees of initial timing - but I'm already at 10 degrees initial, which seems a bit hig h for me.

I believe it's an MSD distributor with whatever bushing in it that it came with.. I could obviously easily change that out for a smaller bushing... only reason I'm a little hesitatnt to do it is that while I understand mechanical distributors at a high level, it's not something I have a ton of experience with. where would I even buy smaller bushings?

JMG2

ok, well,5 getting 35 degrees of total timing wasn't too bad-- I'm at 14 degrees initial timing, and just sitting a little above 35 degrees of total timing with no knocks at 3000 rpm. I'll wait for this thing to cool down, tighten down the distributor, and take it for a ride.