I have been battling a cooling issue with my recently finished roadster since last summer that I cannot figure out. Here's the details: 32 Roadster with .030 over 327, flat tops, 268 Comp cam, double hump heads and rochester FI unit. I know the mixture is correct, set with air/fuel meter and timing is correct. Walker Cobra radiator, zip riser, flowcooler high flow pump, 17" flex fan, currently no shroud. T5 with .63 OD and 4:10 gear. Have a brand new SW mechanical gauge and checked in boiling water to confirm working OK. Without a thermostat in the system and 50/50 mix last summer in 105 deg Texas heat I could not get the temp above 140 and maybe up to 150 when idling. Wanted to get the temp up to at least 180 so put a stock 180 deg thermostat in. Immediatly started having problems. Currently have a 170 Deg balanced high flow type thermostate in the system and checked it on stove and it is opening correctly. Here is what happens. As long as I am in 4th gear and turing around 2200 RPM everything is fine, temp is around 170/180. Go to 5th and RPM's drop to 1700 at 70MPH and temp starts climbing immediatly and keeps climbing to 240 withing a couple of minutes. Go back to 4th and temp drops right down to 180. Also having issues at idle, temp climbs to 230 or so quickly. This was yesterday in 60 deg weather. I tried changing to a stock pump with a cast iron impeller but it did no good. I know a shroud would help at idle but do not see where it makes any difference at 70 MPH. I have bled the Zip riser and raised the front of the car etc trying to make sure there is no air in system. I feel it is a water flow issue as it only gets hotter when the RPM's are down. Because it cools too good without the thermostat, how is the thermostat affecting the system? Any ideas would be appreciated.
Sounds like a nice setup. I'd definitely only focus on the change (Thermostat) that produced the ill effect. The flow w/ the thermostat sounds severly restricted. In general the exchange of heat (radiator, water passages) require turbulent flow for efficient exchange. A laminar flow will have thermal stratas. The larger the temperature delta, the more BTU's are exchanged. If you have changed nothing else it sounds like your 180* is either upside down or is restricted from opening adequately
You have a air flow problem. How far is your fan from the radiator? Should be no more than two inches. What do you have in front of Radiator?? Type of grille? Do you have a license plate in front??? Put shroud on force air through radiator. Just my two cents. Ol Radiatorman
Since it cools better with more RPM's. Is it possible to redo your pulley sizes to get some more speed in the water pump?
The flex fan is no good IMO i would take that off it could be straightening out and whe it does that it doesnt pull the air through it creates a neg affect. What do you have for pulleys. Are you running a moon tank or A/C?? you could gut the guts out of a old t-stat and restrict the water if that helps its flowing to fast,or it could be to slow just some things to try
"Without a thermostat in the system and 50/50 mix last summer in 105 deg Texas heat I could not get the temp above 140 and maybe up to 150 when idling." Seems like plenty of cooling before the 180* thermostat
Take out the thermostat and run it through all your drills, if it comes up fine on the higher temp end, try a cooler thermostat. Or you can try drilling holes in the thermostat plate to allow additional water to circulate. At higher temps it will help if this is your issue but it may take a little longer to warm up. You could also run it without a thermostat at all, just take the time to warm the car correctly. How many row is the core you have? 3 or 4? Before forking out on a new radiator I would experiment with shrouds and fan combos, even consider an electric fan if it can be hidden? My Father owned two radiator shops for as long as I can remember, he is now a rep for some radiator company (no idea who!?). That's where I get my radiator guff from. Edit, it's all pretty good advice up there, you will just have to work through it untill you find a solution. Doc.
Cars can be funny things. Sometimes what should work doesn't and vice versa. If you've tried all those things you mentioned and you're still having problems, I'd take the thermostat back out.
I'm a strong believer in fan shrouds. I am running a Zips riser in my coupe. I have not had any cooling issues but have had problems with trapped air in the system. I recently realized I had no bypass connected, got that fixed and things are better now.
I had a funny heat problem with a car I traded for recently. On the freeway, she ran at 180 until I slowed for traffic. The temp rose to 210 and stayed there, even when traffic cleared. The radiator was a 3 row so I had it flushed. Same problem continued. I had a flex fan with a shroud. It pulled a lot of air at idle and 2000 rpm. So I went with a 4 row triple pass radiator and a 160 thermostat. At idle, she ran at 160 but heated up to 185 driving around. Now this car was a relatively new build for the Long Beach Motorama in 2010. What I should have done was check the mechanical advance. It was frozen. I popped a new distributor in and now she runs at 140, no matter what. Yeah, I know it's too cool, but I'm adding A/C. I will check again once the A/C is on.
I strongly suggest a shroud and the by-pass hose from the head ( between #6 and #8 cylinders ) I also drill a pair of 1/16ths holes in the outer edge of the themostat. I also use GM vent number 10070107 to bleed the air out. It really helps getting ALL the air out and quickly. This vent is also easier to use than the screw that comes from ZIPS.
Wayne, I have the very same problem on my coupe. Almost the same set up as well. I just cant get the temp under control at idol or in traffic. When i get on the high way all is well. Please share if you find anything. i have been dealing with mine for a while now. Good luck to you.
I would go with shroud, air turbulance could be preventing proper air flow thru radiator. I have seen these issues before on cars with tilt front ends and stand alone radiators, the air flow is more of a tornado and takes path of least resistance and for all effect bypasses radiator core. Always run a thermostat. I also like water bypass at extreme rear of intake manifold either to thermostat riser assembly or just side to side (cyl 7 to cyl 8), IIRC kits for dirt track cars available thru Speedway Motors.
From the sound of it, the car did ok (well better.....) without the thermostat - meaning a shroud or anything additional is not necessary. If you want some confirmation on that, pull that thermostat out and make sure the engine runs too cold again. As someone else said, I'd say the thermostat you have in the car right now has something to do with it.....maybe try just a standard 180 deg thermostat?
You need more pump speed, if going down the road with rpm up it cools, same speed but in 5th gear it overheats, it aint the fan or radiator. Change the pulley to speed it up at least 20%. This will also help idling temp. Good luck.
How much advance are you getting at 1700 rpm ? How much do you have at 2200 ? Does your distributor have vac adv ? What is your actual compression ratio ? My thinking is that the timing is retarded due to the low rpm. Also, your cruising rpm doesn't seem right. 4.10's should be turning way more than 2200 at 70mph.
I was thinking the same thing but why did it over cool without the t-stat if the pump is turning too slow ??
Are you sure you don't have a water pump intended for serpentine belt setup? They are availiable in short configuration, too, so it is possible to get it wrong. The serpentine pumps are kind of mirror like the V-belt pumps: Both pump the water in the same direction, but while doing that, the serpentine pump goes in opposite direction than the V-belt pump. If you use a serpentine pump in a V-belt setup (or vice versa) the impeller will turn backwards with poor pumping performance as a result.
The general rule of thumb is if your engine cools at highway speed and not at idle or low speed there is an airflow problem. Once up to cruising speed there should be enough air to cool the radiator unless the hot air can't get out of the engine compt. which in your case shouldn't be an issue. Also the thicker the radiator,the more air has to go through it to reach the flow tubes on the engine side of the radiator. Like previously stated ck your advance on the distributor. I know I had a flow cooler water pump with a Ron Davis radiator and a stock thermostat with holes drilled in it and water barely trickled out the tubes,changed and put a medium sized restrictor in instead of the thermo and the coolant really flowed through the tubes. Problem solved. Different angles to look at and check !!!
Thanks for everyone's responses, see below: FastRoadster: The fan is only about 1/2" from the radiator at the bottom. Nothing blocking the radiator, no AC or trans cooler etc. Since it cools better with more RPM's. Is it possible to redo your pulley sizes to get some more speed in the water pump? Water pump pulley is pretty much all that would fit, would have to increase lower pulley diameter if I can find one larger. How many row is the core you have? 3 or 4? 3 core I'm a strong believer in fan shrouds. I am running a Zips riser in my coupe. I have not had any cooling issues but have had problems with trapped air in the system. I recently realized I had no bypass connected, got that fixed and things are better now. Bypass connected to lower drain hole in block as I have early heads and no tapped hole in head. Seems like plenty of cooling before the 180* thermostat Agreed, this is what I do not understand I strongly suggest a shroud and the by-pass hose from the head ( between #6 and #8 cylinders ) I also drill a pair of 1/16ths holes in the outer edge of the themostat. I also use GM vent number 10070107 to bleed the air out. It really helps getting ALL the air out and quickly. This vent is also easier to use than the screw that comes from ZIPS. Deuce Roadster, I am using the GM vent per one of your earlier post. Plan to add a shroud. I have the latest design Zip riser, at first had one of the early cast iron ones and though that might have been the problem so went to the later design with no change. Please share if you find anything. i have been dealing with mine for a while now. Good luck to you. <!-- / message --><!-- sig --> JimP: Will do From the sound of it, the car did ok (well better.....) without the thermostat - meaning a shroud or anything additional is not necessary. If you want some confirmation on that, pull that thermostat out and make sure the engine runs too cold again. As someone else said, I'd say the thermostat you have in the car right now has something to do with it.....maybe try just a standard 180 deg thermostat? I have tried three different thermostats with the same results. I have taken the thermostat out completely a couple of times and could not get above 140 Deg. How much advance are you getting at 1700 rpm ? How much do you have at 2200 ? Does your distributor have vac adv ? What is your actual compression ratio ? My thinking is that the timing is retarded due to the low rpm. Also, your cruising rpm doesn't seem right. 4.10's should be turning way more than 2200 at 70mph. Ray-Jay Going to recheck timing and advance. I had to replace the vac advance because the old one in the FI dist was bad. I discovered there are a number of different ones that pull in at different vac levels. It was working OK when I last checked. May be acting different under load. Agreed the RPM's are low. When I put the car together I thought the OD in the 5 speed was .78 and it is actually a .63 ratio. By my calculations I should be around 2000 RPM's at 70 but tach is reading 1700 to 1800??? I know I had a flow cooler water pump with a Ron Davis radiator and a stock thermostat with holes drilled in it and water barely trickled out the tubes,changed and put a medium sized restrictor in instead of the thermo and the coolant really flowed through the tubes. Problem solved. Different angles to look at and check !!! Bingo, this is what I theorize is happening. Can you run just a restrictor with decent results, IE cool the same in 105 Deg or 60 Deg weather? Thanks Wayne <!-- / message --><!-- attachments -->
If it is doing OK without the thermostat and warms up with one ... you are having a coolant flow problem. The small hole in the block ( where the water pump bolts up ) and the small hole in the water pump allows coolant to move ( flow ) all the time ... no matter what the thermostat position. ZIPS do not have this feature That is WHY I always drill a pair of small holes in the outer edge of the thermostat. I also also only use Robert Shaw hi-flow thermostats.
I haven't read thru all the responses but a shroud is an integral part of a properly operating cooling system.
I used to pit on a lot of dirt track cars , all SBC, some of the 'wing nut' driver owners would think taking out the therm would make 'em run cooler , nope, removing the thermostat only makes the things worse , we took some phenolic washers , (similar to those behind door handles and the spring) and put in place of the therm. this restricted the flow and forced water to the rear of the engine , I'm sure racing shops have the restrictor washers . We also used products like 'Wetter water' which is an additive that makes it run 10-30 * cooler , but a close fitting shroud and a straight steel fan was what worked best , Needing restriction is especially important on flathead V8s , and if one water pump goes out on a flattie , just change both,
You and I have basically the same engine although I have a automatic transmission,,,I also have a zips riser and have a 180 degree thermostat and never run hot,, my question,did you follow the zips recommendation and use the pulleys they suggest? HRP
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