Sorry gang, I've been off line...just got back on to check my thread...wow, I knew I could count on you guys to pitch in. Tom, I haven't called you yet as I am trying to get more information from my builder that I don't have. I've talked to John, but I am not the party with the MSD ignition. Sorry, I am not mechanically inclined so there are so many questions you guys posed, that I can't answer. Except to say this is a new build, with all new parts except the block which was treated, etc. from a very reputable machine shop. Because, as many of you pointed out, it could be a hundred things, we are treating them one at a time, with the simplest fixes first. I too feel like there is too much friction, but my builder thinks it's an air flow issue. He has built several 427's, including his own L-71, and has never had this type of overheating problem. He's concerned that possibly the ProComp aluminum heads might have water passage issues...anyone heard of this? Anyway, it's very frustrating at this point...putting in a new 180 thermo today (from the 160) to see if keeping the coolant in the rad longer will help. Let's hope it's something that simple. And thanks again for all the comments...feel free to keep them coming. Nick

 

The reason I said what I did in post #28 is that I have seen that situation occur. A mysteriously hot engine with low power was found to contain internal problems when examined. Your engine builder (unless he is a personal friend of yours) will not own the problem, unless he is forced to, of course.

If you exhaust all of the usual fixes, and the problem still presents, then the unthinkable will be the reality. I agree that 27 degrees initial timing at idle (about 10 static plus about 17 vacuum) will lower your exhaust temp and engine temp...............but a healthy engine should NOT overtemp simply as a result of insufficient idle spark advance.

Two more "band aid" fixes that you can try would be to richen the idle mixture, and, if you have a flat tappet camshaft, use Mobil 1 15W-50 racing synthetic motor oil. It will significantly lower engine friction, oil temp, and coolant temp. It has more than 1300 ppm zinc dialkyldithiophosphate (ZDDP) which is safe for flat tappets.

I have 3/4 "street" filled my 327 engine block's coolant passages with Hard Blok and have absolutely no cooling problems. True, the heads rather than the lower block being plugged would constitute a different situation. If that were the case, I would expect the engine to detonate itself to death before cooling issues became apparent.

 

I have seen this problem many times over the last 15 years. Guys mixing up parts, installing the wrong piston or rings, and/or trying to "out do" the general by reducing clearences. I often hear guys say "man that baby is tight" and my response is...Too bad.

It really will. Since JohnZ has brought this to everyone attention many years ago, I have help solve over a hundred over heating issues by just correcting the VA system.

The other ideas (band-aids) you suggested are good ones and I sometimes will throw those out there too. Many times the solution isn't just one thing but if you can drop 5-10* doing three or four things can fix it.

In this case I think we have a bigger problem and it could be as you suggested a motor problem. With 2500 cfm fan it is absolutely NOT an air flow problem as that is three times what the stock system provided at idle. I would dump the flex fan, as that is simply redundant and provides no benefit.

One possible cause for sever overheating is a blown core. Due to extremely high pressures in the coolant, typically a heat gasket problem, you can balloon the cooling tubes in the radiator. When this happens the flat tubes try to go round and the cooling fins get crushed. Almost no air can get through the core and no cooling will be the result. Check the air flow across the radiator by placing a sheet of paper on the front of the core. It should pull it up there like a vacuum cleaner. You should be able to slide a zip tie right through the core in multiple places, if you can't, then this condition may exist. It's not easy to spot this because when the fin crushes, it does it in a very consistant pattern and it's not real obvious unless you know what you are looking for. Below are pictures of good fin and crushed fin for reference.

 

That's another "internet myth". The thermostat is wide open at operating temperature, and the coolant flow rate is constant throughout the system; it's a closed system - the coolant can't be "fast" in one part of it and "slow" in another part of it. The only time the thermostat will affect the system is if it's defective and doesn't open all the way.

 

Quote:65tripleblack
If you exhaust all of the usual fixes, and the problem still presents, then the unthinkable will be the reality. I agree that 27 degrees initial timing at idle (about 10 static plus about 17 vacuum) will lower your exhaust temp and engine temp...............but a healthy engine should NOT overtemp simply as a result of insufficient idle spark advance.

I have looked around the net at various sites and find no mention of timing making more than a 10 to 15 degree increase. I do wonder if a combination of lean mixture andtiming problems may result in a 1+1=3 situation. The "once it gets hot, it stays hot" mode may be the oil getting up to a temperature that keeps it from doing any cooling.

 

Most if not all sixties vintage Chevrolet engines, whether they be SBC or BBC, specify 8-12 degrees distributor vacuum advance. You might be confused because 8-12 distributor degrees equals 16-24 crankshaft degrees.

If an engine is "hot rodded", meaning it is blueprinted to the point that static compression ratio is maxed out relative to the cam timing (ie: inlet valve closing point), then it might not tolerate anything more than a few crankshaft degrees vacuum advance.............perhaps none at all, while operated on ordinary HIGH QUALITY BRAND NAME 93 PON fuel.

Yes, enriching the fuel mixture (only up to a point) will add power, while slightly lowering EGT, which will, in turn, lower coolant and oil temps slightly. Best power is usually produced with A/F ratios between 12.5:1 and 13.5:1, with longer duration camshafts producing best power closer to the richer end of the range. Max power drops off faster as you vary to leaner settings than it does as you move to settings richer than this ideal range

Again, concerning the OP, these are "band aid" fixes since if the engine is tuned as it was delivered, and the cooling system components are relatively new and working as designed, then coolant should NOT overtemp unless there is an internal friction problem somewhere.

 

Nick,

Unless the current thermostat has failed, changing stats is not going to have any effect. The thermostat only controls the MINIMUM operating temperature of the engine.

I may have missed it in the preceding 3 pages, but I am wondering what kind of distributor you have in the car.


Nick

 

:

OK, here's the latest. I drove down to my engine builders this am, after changing the thermo back to the 160. The temp the whole way was 205. At his shop, we pulled the aux fan off and just left the flex fan on. I had him read John Z's article and he gave it some serious thought so decided to set up at 19 degree initial w/o va, and 35 degrees at idle. We are at 4800 feet here so he thought a little more initial would help. One the drive back (20 miles), the temp never got above 160 while moving, 185 stop and go and it's a 85 degree day. No pinging either. So once again, John Z show's us why he's da man. More testing to follow, but I think we are on the right track...finally. Thanks again to all those who gave me all that great input to hash over; we went over every comment to see how it might apply to this build. In the end, after all the trials and tribulations, it WAS just a vacuum issue, not a engine issue. Nick

 

Nick,
Good to hear. Now we can race for pinks.

Dave

 

Dave, I've followed your build...we wouldn't be racing for pinks...my face would be shameful red after taking you on...remember, at my age I'm a pacer not a racer...on the other hand, at least mine's running...you going up to HAN Tahoe this weekend or HAN Reno the next? I'm doing both...it will test this cooling system fix big time...later, Nick

 

Yeah, I'll bet you're a happy camper now. I have about 200 miles on mine and the doors are on now. Just have to put the windows in this weekend and make sure the AC is right before I hit Reno next week. There is still a lot of stuff I want to do, and/or redo as I'm not happy with a few things, but that's normal for me. Hope to see you next week.

Dave

 

So, if you had a California calibration '66-'67 AIR car that called for 4* ATDC timing at idle instead of your 19* BTDC timing, what would you do?

The California cars ran okay with that timing. Hell, you're talking about 39* difference in timing at idle between what you now have and what was spec'd for the California engines.. Gimme a break!

I think the only thing you fixed is getting the auxillary fan out of the airstream. Or something.

 

That is my point, exactly.
If a woman has a black eye and covers it with makeup, she still has a black eye.
Everybody touts this timing band-aid as a panacea. It is good, sound advice, but must not be substituted as a "fix" for an underlying problem!

 

Joe,

This is known as a "mob rule" fix.

 

MikeM, don't have an answer for you other than I'm glad it's not a California car. It's been a mystery that's for sure. I agree that taking the fan out helped, but for the life of me can't figure out why...if you are pulling an additional 2500 cfm of air through the rad, why wouldn't that help cool it down? Anyway, if this is a band aid fix, it's the best band aid fix we tried...sometimes a different perspecttive as to what works is not just a band aid, but an actual fix to an underlying problem that just wasn't diagnosed. For me, it was a miracle...I can actually drive my car again...it runs much cooler, it runs faster, it has better response...not sure how that is a bad thing, but I'm grateful for the heads up. Nick

 

This is the kind of thing that frustrates me about forums the most. When something works as JohnZ and myself suggested you would think that would put the issue to bed and we all could all move on to other stuff. But no, the controversy continues and readers of this thread learn nothing.

I don't know why the OP set up so much timing but the normal would have been about 8* and the advance would add about 15* for a total of 23*. Your California car would be -4 + 15 =11 for a total of 12* difference. My guess (maybe JohnZ can confirm) is the California motors had different cams and carbs to allow for this lower advance.

The ONLY way that fan had anything to do with the problem is if it was actually pushing instead of pulling but I highly doubt that was the case. I never want to see people do two things at the same time for just this reason and IMO he removed the wrong fan. I would have dumped the flex fan and kept the 2300cfm electric which is a much better system.

If anyone does not believe the Vacuum advance can cause this problem simply plug the vacuum hose and let the car idle for a 1/2 hour. Your temperature will rise 20-30 degrees over the stat setting. Many people have called me wanting to buy a new radiator and I told them they didn't need one. After fixing the VA they called back and said I was right, it fixed the problem. This didn't happen once or twice but at least 100 times over the last ten years. Isn't that enough proof to make you believe?

 

IMO he removed the wrong fan. I would have dumped the flex fan and kept the 2300cfm electric which is a much better system.


I can attest to that!

 

this forum im sure has provided great info to those who really need it at times, both john and tom are correct that if you are running a vac. dizzy, and the can ruptures or the vacuum supply is cut off you will most likely increase coolant temps due to too low timing , however no one should infer from this that a vac. dizzy is solely required,or that there are no other options.....if an all mechanical map is properly set, along with enough initial timing, you will have a cool running mill, if it overheats, the problem is elsewhere....,

 

But how often do you think vacuum adv distributors are replaced with purely mechanical distributors without adjusting the timing to compensate for the lack of VA?
I would bet a lot of them get swapped out and are just timed to the book value for the original VA dizzy. Mr DeWitts anecdotal evidence seems to support this.

DT

 

Interesting thing happened to me this afternoon. I've had my hotrod for sale and today I got a call from someone who wanted to take a ride in it. I had just installed a new starter in it yesterday and was fiddling with some odds and ends, checking the timing, changing the oil etc. So off I go to give the check ride and the thing is running about 20 degrees hot. I just blow it off since it's hot outside and the AC is on full blast so I figure no problem and it's hesitating a bit on the throttle too. I give the guy a ride and hope he doesn't notice the temp gauge and the stumble. He doesn't notice and says come over tomorrow and I will have the $. GREAT!
So back to the shop I go, expecting to find something bigtime wrong and won't be able to sell the car. I open the hood and take a temp gun reading, sure enough 210 degrees. I look down onto the intake and what do I find??
THE VACUUM LINE TO THE CARB IS UNPLUGGED! Dewitt rad, SPAL fan. Plugged it back together and within a couple blocks we're back to 180 degrees. Simply amazing. Guess Tom/John Z. are right after all.