Hubnut
1/2 ton status
Is it possible the serpetine belt is installed incorrectly resulting in no coolant flow? Just an observation.
CK5
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TBI Running Hot
- Thread starter pseudomike
- Start date
pseudomike
1/2 ton status
Ok, I am not 100% what solved this but the problem seems to be solved or working for the time being.
I drove the truck to work again yesterday w/o changing the chip running a stant 160 thermostat (with a hole drilled in it) and an oem replacement water pump. Truck ran great on the way to work, but on the way home I took the highway and it overheated once again and blew the radiator cap. As a former boy scout I brought along a 5 gallon can of water and tools to pull the thermostat out (I'm running an o-ring style neck for fast thermostat changes at this point). So on the side of the highway I yanked the thermostat and refilled it with 100% water and drove it home...ran under 100 degress and no heat naturally.
When I got home I pulled the OEM water pump back out and re-installed the high flow Edelbrock unit. Being that I had no clue what the coolant ratio was I decided to flush the system with the garden hose once again to get everything out (no thermostat installed). Once I was back to 100% water I installed a new Delco 170 deg stat and plugged an ECM with the factory chip in place of mine. I took the truck for a ride, ran like crap of course zero balls under 1/2 throttle almost stalling at a stop. I beat on it pretty good and what do you know coolant operation just as it should be. So I pulled over, plugged the chipped ECM back in and went back to running it pretty hard up and down the highway...I figured for sure it would overheat but no avail...ran steady at 170 deg. At this point I'm a little confused and assumed that the stat simply must have gotten to temp with the old ecm and stayed open? So I drove home, let the truck cool for a couple hours, took it for another beater run and still runing 170 deg. Hmmm. So I drove it home again, drained the radiator, filled it with coolant this time (I think I've lost about $100 worth of coolant through the rad cap in the last week) and let it sit until this morning to drive it to work...boy scout supplies in the cab waitong for the worst. Well, truck warmed up to 170 on the freeway and stayed there. Let it cool for 4 hrs, drove it around at lunch still 170 deg. So for now it seems that it is functioning normally with the high flow pump, a 170 stat w/no hole drilled in it. THis is the first time I've had this luck as it usually burries the gage right out until the stat opens. Anyhow, we'll se what the ride home brings but I did want to give you guys an update. I don't know if I flushed air/crap out of it or what the deal is. THis isn't the first time I've flushed it so it doesn't really make much sense unles I got like 8 bad thermostats in a row (seems to defy statistics if that the case). I'll watch it for a couple days and re-post if it changes.
I drove the truck to work again yesterday w/o changing the chip running a stant 160 thermostat (with a hole drilled in it) and an oem replacement water pump. Truck ran great on the way to work, but on the way home I took the highway and it overheated once again and blew the radiator cap. As a former boy scout I brought along a 5 gallon can of water and tools to pull the thermostat out (I'm running an o-ring style neck for fast thermostat changes at this point). So on the side of the highway I yanked the thermostat and refilled it with 100% water and drove it home...ran under 100 degress and no heat naturally.
When I got home I pulled the OEM water pump back out and re-installed the high flow Edelbrock unit. Being that I had no clue what the coolant ratio was I decided to flush the system with the garden hose once again to get everything out (no thermostat installed). Once I was back to 100% water I installed a new Delco 170 deg stat and plugged an ECM with the factory chip in place of mine. I took the truck for a ride, ran like crap of course zero balls under 1/2 throttle almost stalling at a stop. I beat on it pretty good and what do you know coolant operation just as it should be. So I pulled over, plugged the chipped ECM back in and went back to running it pretty hard up and down the highway...I figured for sure it would overheat but no avail...ran steady at 170 deg. At this point I'm a little confused and assumed that the stat simply must have gotten to temp with the old ecm and stayed open? So I drove home, let the truck cool for a couple hours, took it for another beater run and still runing 170 deg. Hmmm. So I drove it home again, drained the radiator, filled it with coolant this time (I think I've lost about $100 worth of coolant through the rad cap in the last week) and let it sit until this morning to drive it to work...boy scout supplies in the cab waitong for the worst. Well, truck warmed up to 170 on the freeway and stayed there. Let it cool for 4 hrs, drove it around at lunch still 170 deg. So for now it seems that it is functioning normally with the high flow pump, a 170 stat w/no hole drilled in it. THis is the first time I've had this luck as it usually burries the gage right out until the stat opens. Anyhow, we'll se what the ride home brings but I did want to give you guys an update. I don't know if I flushed air/crap out of it or what the deal is. THis isn't the first time I've flushed it so it doesn't really make much sense unles I got like 8 bad thermostats in a row (seems to defy statistics if that the case). I'll watch it for a couple days and re-post if it changes.
pseudomike
1/2 ton status
Well, one more update. Truck once again got hot. I think I am getting to a point where I understand it though. This morning, when it was cold I let it warm up and no problems. Leaving work today I just hopped in it and went and it go to about 245deg before the stat opened and ran fine there after at 170deg. I'm thinking the water is not circulating or heating up in the thermostat area quickly hence the delayed opening. This well could be an issue with the coolant superheating in head/cylinder area. I really don't know a sufficient way to test that. Anyhow, what I am thinking about doing is moving the outlet to the heater core from the rear of the engine to a port up by the thermostat housing which should..in theory...get water circulating around the thermostat quicker. I realize this is probably no different than drilling a hole in the thermostat but it should tell me whether or not it is an issue with the water not heating around the thermostat quick enough. There is obviously some underlying reason for this behavior like cylinder walls that have been bored too far or a core shift but there is really little I can do about that at this stage in the game. I do have a 383 I was putting together so hopefully this one lasts until I gather all the parts for the build. I did see that jegs or pace performance was running a deal on the GMPP 383 4 bolt main block which is a new block, standard bore walls with OE siamesed hatching. I think it would make a good base with no worries of core shifts, or thin walled cylinders. If anyone has some nice aluminum heads (64cc or so) they want to part with so I can run up in the 10:1 range drop me a PM.
That block isn't filled with concrete or something is it?
Only thing I can think of that would affect water flow internally is an obstruction somewhere that changes the flow patters, or as mentioned, too thin cylinder walls.
Only thing I can think of that would affect water flow internally is an obstruction somewhere that changes the flow patters, or as mentioned, too thin cylinder walls.
pseudomike
1/2 ton status
The only thing that I can think of..other than thin cylinder walls is that it has incorrect or incorrectly installed intake manifold gaskets. I know marine application gaskets are different, perhaps others are as well.
Somewhere on the engine there is probably a tag from Jasper that says what the bore and crank sizes are. See if you can find a tag and see what it says. From everything you've done i think it is a block that is either bored too far oversize and has thin cylinder walls OR there is a bunch of core shift in the block and there are thin spots in some or all of the cylinders. Like you said, there is nothing you can do about it especially since you've had this engine for awhile now. I would seriously start gathering parts for your 383 build and do something quick while this engine is at least still running.
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Could always run a restrictor and see if you can't get it close to where it needs to be. Or drill holes in yours until it stops acting up at all. 
Or just run it without a thermostat at all...at least localized heating would be potentially less.
Or just run it without a thermostat at all...at least localized heating would be potentially less.
I know on my intake manifold gaskets the back water hole had a small hole in the gasket ( as some kind of restrictor ) not like the front water jacket hole. Does that make sense?
Can anybody tell me why that is like that. Thanks
Tarey
Can anybody tell me why that is like that. Thanks
Tarey
SUBFAN
1/2 ton status
I would try a second mechanical temp. gauge and see what that does for you....
In all GM SBC engines from 1955-1986 there is no water passage crossover in the back of the intake and those gaskets just have the same size water opening at each end of the gasket. Starting in 1987 when TBI was introduced the intake manifold design was changed and now there is a rear water crossover passage and that passage is connected to another passage that is running from the rear of the intake up to the front of the intake. The 1987 and later gaskets have a metal restrictor plate with a small hole in it to control the amount of water flow. Not sure why GM decided to do that other than possibly trying to keep the throttle blades from "icing" like they did with the TPI set-up running a water passage around the throttle plates. Apparently this was a problem with TPI (TPI started in 1985) and GM possibly carried the design over to TBI when it was introduced in 1987.
Is there really a water passage that runs all the way front to back on those intakes? The intakes are heated, but I thought it was with exhaust...
My take on the restrictions in the intake is pretty simple: where is your Heater core tapped into the motor? Do you really want full flow/pressure from your water pump going through your heater core all the time? Last time I looked, it seemed like the rear passage wasn't there for anything but the heater. (or to also balance/exchange heat from head to head?)
I'll look at one of my spare intakes sometime today...
From what I've seen the carbed intakes didn't have crossovers in the rear. My Vortec TPI base does...I'm not sure if all stock TPI bases did or not(my base is the SDPC part of course), I know at least some did. I suspect it had to do with more even cylinder cooling as compression climbed.
Water pump fitting is *typically* an outlet, so there is little to no pressure there. GM uses the water pump fitting on the block side of the water pump because pressure from expansion and the water pump is high enough to force the hottest coolant in the motor through the core with no "active" pump on those lines.
Water pump fitting is *typically* an outlet, so there is little to no pressure there. GM uses the water pump fitting on the block side of the water pump because pressure from expansion and the water pump is high enough to force the hottest coolant in the motor through the core with no "active" pump on those lines.
Is it running fine now? I would still like to see timing specs (even if it's just at idle) for the "TBI Chips" chip. It just seems that you are having EXACTLY the same problem that I just had. I think your motor (bore size and cyl thickness) might be just fine, but even with no core shift you can't argue the fact that they're thinner than stock now...
The cyl wall itself disapates heat, and keeps the coolant from seeing short bursts of intense heat... go thinner and can't disapate the same amount of heat as well...
I'm SURE the overheating in my motor was caused by the chip (or having my motor bored depending on how you look at it). The advance and fuel curve on the chip I had were creating some serious heat (why do you think the instrucions say to run a 160 thermostat instead of the 190 degree?). Now, that chip I had might work O.K. for a standard bore block with thicker walls using a 160 thermostat... But with thinner walls more heat is transfered to the coolant FASTER. By the time the 160 thermostat sarts to open, the temps at the cyl walls are rising out of control, starts to overheat, blow your radiator, and THEN whatever coolant is still cool in the system rushes in to take care of things...
Didn't you say the temps on your gauge would Surge? Too Hot - then back down - too hot - then back down? The problem may not be that the thermostat is not working, but that it just can't open fast enough. You have put all your old "Bad" thermostats into a pot on the stove with a thermometer to verify that they were not opening right? Mine seemed to work fine... untill they were in my engine.
The idea of a restrictor in place of the thermostat intrigues me, but would take a lot of trial and error, and still might not allow my motor to heat up fast enough in the snow...(well maybe not my motor)
THE ONLY THING that changed MY cooling issues was dumping that chip.
Turns out the chip I have was called the "stage one chip". Stage one for a stock motor (with thicker cyl walls). Was your chip a custom burn? It might have to be...
I would still like to see some timing specs.
pseudomike
1/2 ton status
I don't know where the timing is running but it somewhere more advanced than I can set my gun which is 25deg at idle. The chip is custom. It is setup to run the larger cam w/1.6 rockers, larger caprice interceptor injectors, bored throttle body, and higher fuel pressure. I think it may be a "stage 2" but my memory fails me there. Brian originally sent me a chip that required premium gas and the truck definitely hauled ass but I had him swap it out for a milder 87 octane safe chip. I did find a plate on the motor and it says it is bored 40 over with 10 over journals. In my opinion 40 over is way to far (I can't imagine where they even found the pistons?), I would be hesitant at 30. I know the only way to check is sonic test but even then, what is acceptable for a number? I question things like who came up with this "ok" range for cylinder wall thickness. Not to mention what is ok for a stock street motor may not be ok for a worked motor running an aggressive spark curve. Either way, with '87 octane the truck does not ping even when running hot. L05 heads are 76cc so there is a lot of room for detonation and pinging so even if the curve is more agressive than stock it still isn't beyond the limit of where the motor should run safely. With this in mind I think the 40 over is probably a huge factor, and running a cooler chip would probably alleviate some problems, but it is an issue either way and changing the chip out is going to do nothing more than delay something that is certain to become an issue somewhere down the road. I am disappointed in the Jasper quality on this one. They have a good name, they should know better. Onward with the stroker, I'll build my own engines from now on. Oh yeah, and I'll be sure to fill this one with concrete before using it as an anchor for you Dorian.
I know some SBCs get bored .060" over. I don't think anyone bores them less than 0.030" over. Try checking timing with the plug by the steering column disconnected just to make sure the distributor is clocked right. Idle and low-load timing can be pretty high, but has nothing to do with WOT or high-load timing. In other words, 25 degrees at idle doesn't really tell you anything about what the advance is at WOT.
pseudomike
1/2 ton status
I'm fairly sure later model SBC, unless it's a bowtie block or something are limited to around .030" over ...and less than that for anything considered performance. I know you can bore the older blocks to .060" over something like pre 197X. The 197X -1985ish blocks are good to .040" over. Anything 85 on .030" is about the limit and .020" over for anything with a performance build. Following the good old saying they don't build thing like they used to.
.040 over is not a big deal as long as there is no problem with core shift.
My block is an '89 and it is .060 over. NO problems with overheating at all... even with the stock 190 degree thermostat it runs about 212 all day long. Idle, freeway, 600rpm, 4700rpm, rain, shine, sleet, snow, blah blah blah, still right around 212 degrees. Put the TBI chip back in and presto! running hot, then ok, then hot... I'm not running a cam that's not too much different from stock, so I can get away with the stock chip for the moment... needs some tweaking but hopefully it can wait untill I can try it myself.
I would hace prefered my current block to have cleared .030, but it was a roller block, and it was free. Nothing wrong with going .060 over as long as there's no core shift, and you understand you won't be rebuilding the block anymore... also wouldn't try pushing the compression too high at this point...
I still have a couple motors, so not too worried about it.
My block is an '89 and it is .060 over. NO problems with overheating at all... even with the stock 190 degree thermostat it runs about 212 all day long. Idle, freeway, 600rpm, 4700rpm, rain, shine, sleet, snow, blah blah blah, still right around 212 degrees. Put the TBI chip back in and presto! running hot, then ok, then hot... I'm not running a cam that's not too much different from stock, so I can get away with the stock chip for the moment... needs some tweaking but hopefully it can wait untill I can try it myself.
I would hace prefered my current block to have cleared .030, but it was a roller block, and it was free. Nothing wrong with going .060 over as long as there's no core shift, and you understand you won't be rebuilding the block anymore... also wouldn't try pushing the compression too high at this point...
I still have a couple motors, so not too worried about it.
My machinist claims all the blocks started being cast in Mexico around '86 and that's when the quality declined (not suprised) Bottom line is if there is too much core shift don't bore the block - doesn't matter what year it was made. He also say's "why don't you just build a ford", but he's still a good guy.
pseudomike
1/2 ton status
Either way you have a block .060" over that overheats with a chip. If that thing isn't detonating and pinging it certainly shouldn't be overheating unless it has a blower or something. Chipped or not, the real problem is thin cylinder walls or something along those lines. If my machinist put together a motor that acted this way I'd find a new machinist...especially if he was a ford guy. I'm not going to argue what each year block can be bored out to. Those are guidelines I was told, reaffirmed with a google search and the total consensus is nothing is 100% without sonic testing. Mine's coming out, I know where you can get another block that overheats for free.
SBC's will go .040" without any issues, it's when you start taking them to .060" and beyond that you COULD have troubles. Of course as i've said before if there is core shift then all bets are off.
Sonic testing a block you really want to see at least .100" thick walls in all locations and especially on the thrust side. Once you start getting thinner than that or are going to run the piss out of the engine then you will start having heat issues and or a blown out cylinder wall.
Sonic testing a block you really want to see at least .100" thick walls in all locations and especially on the thrust side. Once you start getting thinner than that or are going to run the piss out of the engine then you will start having heat issues and or a blown out cylinder wall.
