Sorry, you'd already mentioned Tim's pistons in the 'cooling a 400' thread, and I'd forgotten.

Those pistons would increase the compression from 8 point something to 9 point something thus requiring less total timing.

I just read that thread again, and in it, you mentioned adjusting the timing until you got pinging, then backing it off etc.

It sounds like you know the sound of pinging, and how to adjust the timing.

You have enough info already to dial in the timing.

You also mentioned that you got the correct t/stat, and that a 20 mile drive was trouble free.

I've attached pictures so that you can double check, but I'm sure your t/stat is 100%.

Thinking out loud :

When the engine was built, were the coolant drain plugs removed prior to a thorough engine clean ?

If not, and there was crap in the block, that crap could now be in the radiator.

Does the overheating occur in slow town traffic ? (Sounds like it doesn't when you're cruising along.)

Was the cam run in correctly ?

I'm starting to think that you're not hearing pinging, but lifters or something as you previously mentioned.

Attach a vacuum gauge to the engine and post up the reading and needle behaviour.

Cranking pressures per cylinder could also be useful.

 

I forgot to upload the t/stat pics

 

You asked what pressure the radiator cap should be. 13lbs.

How often do you drive the truck, and how many miles have you done since the rebuild ?

When did the knocking noise start ?

I'm beginning to think that your cooling system and ignition timing are not the problem.

That said, if you run the truck at idle for say 15 minutes, does the temp stay constant at the +/- t/stat rating ?

Did you get the Champion shroud with the dual 12'' fans ?

 

Here's the thermostat I'm using: http://www.tmeyerinc.com/product/high-flo-thermostat/
I don't drive the truck very often; i'd guess less than 100 miles on the rebuilt engine. As for engine break-in, I used rotella 15/40 and a zinc additive. I ran the engine, varying rpm's from just above idle to about 3000, for a total of a couple hours. Was only able to run it for about 30 minutes at a time, due to the motor getting hot(before I changed to the TMeyer stat). Could hear a slight tick in the valvetrain ever since I first started it. After this, I changed the oil to 10W-40, which is what was run in this motor since new.
Engine temp seems to hold in the 180-190 range when idling, but if it ever tops 200, it continues to rise until I shut it off & let it cool off a while. The last time, it got up to 240, I waited about 20 minutes for my trailer to show up, & by the time I restarted it to load, it had already cooled back to 200.
I am running the champion shroud with their dual fans.
Not sure about possible contamination in the block, but it should have been flushed & hot tanked. I know when I got it back as a long block, it looked like it had been completely cleaned up. I was planning on draining the entire cooling system, pulling the radiator & water pump for thourough inspection, & flushing the radiator & block.

 

On the timing issue: Just to clarify - retarded timing can cause overheating & too much advance causes pinging?

I think my initial timing of 14* is right for the engine, but was just wondering if the mechanical advance on my HEI distributor might be wrong. Anyone know how much mechanical advance was built into the stock one?

 

wow, quoting myself..in the same thread......

 

And you can rev your engine up too say 3500rpm and use a dial back timing light to see exactly what YOUR distributor is advancing too. Total timing is more important than base timing, I meen both matter but too much total timing is worse than too little base timing.

 

Dial back type timing light is handy, but isn't really necessary so long as the damper has marks out to 40° or 50°. Flourescent timing tape does that nicely and is super easy to read. Jegs and Summit sells it reasonable. Since he has an overheating problem we want to eliminate retarded timing as a possible cause.

 

I'll have to check - think my damper is only marked to 20*

 

Yes that t/stat is correct, and yes to too much retarded timing causing overheating and too much advanced timing causing pinging.

When running in your cam, the lower rpm range of ''just above idle'' might have damaged your cam !!
The lowest rpm should have been more like 2,000 rpm.

We've gone from pinging to knocking to ticking. Which one is it ?

Idling steady at 180-190* implies the fans are doing their job. But, when EXACTLY does it creep up and continue to rise ?

If the block was in fact cleaned, and you have a new radiator etc, you don't need to do a thorough inspection.

100 miles in a year is nothing, and isn't doing your engine any favours. Drive it more !

The engine is still not run in.

You asked about the heater hose routing.

They should go from the block fitting, next to the t/stat, out to the heater, and return from the heater to the driver side fitting on the water pump.

 

If I could ever get all these issues figured out, I would drive it more! It's nice enough driving around town with the addition of power steering & the auto, but the 4.56 gears don't do me any favors with highway driving. In retrospect, I'm starting to think I should've just went with a rebuild of my Y-Block instead of the motor/trans swap! Hopefully I'll have time this weekend to check out the timing. Now that the weather's getting nice, I've been busy with lawn & landscaping chores on the weekends.

 

Run it till it gets hot. Then put your hand in and feel the radiator core all over, don't worry about the tanks. If you feel any cool spots in the core then I'd say it needs rodded out.

 

It's a brand new champion aluminium radiator. I have less than 100 total miles on this engine since install. I filled with dex-cool - any reason that would be a problem? I just don't see how the radiator could be plugging up. I'm still hoping it's a timing issue. Going to try to check that out this weekend.

 

Well, for starters, I don't think running Rotella 15W 40 (post # 19) for a break in oil did your engine any good.....fresh rebuild, close berrin tolerances, etc and all. You could be hearing a lifter failure due to a wiped cam lobe. Not sayin' fer sure, but it's possible.

As for overheating.....isn't Dexcool a GM product? Or specifically made for newer GM vehicles? I seem to remember (years back) lawsuits against GM for using/recommending Dexcool.....that it turned to sludge after a while causing overheating.... I don't know for sure. I s'pose I could look it up....but then anyone could look it up, too..................Me? I would have (and still do) use the Prestone green mixed 50/50 with (shoot, I'm getting old - can't remember the type of water) ...........distilled, yessuh, that's it....distilled water.

Look at your block, specifically, the core plugs.....are they new? If so, I would guess your builder(s) took 'em out when they tanked the block. If not, well, you still might have goobers in the block water passages.

Timing, if retarded, would be a cause of overheating also.....seems like that isn't the case, but who knows now....?

 

I was having same overheating issues with your same set up ( champion radiator and their dual Chinese fan and american made shroud ) and my temperature will go as high as 230*. What solved my problem was getting rid of the champion fans and replacing them with dual Spal Electric Fans 30103202 from Summit racing. Upper fan gets activated by a 185* Thermo-switch and second one by a 200* . Now the newly rebuilt 400 runs @ 185* all day long. It was my engine builder that asked me to get rid of the champion fans and I'm glad I did. My $0.02