Higher running temps after 2.79 to 3.80 swap

I'm running a 25 inch tire with 3.5's in my 9 inch. I put in an aftermarket 23 tooth speedo gear. Now I'm about 98.5% accurate. The pitch is a little different, but should still be good for about 25K miles. Clink on link and scroll down the the Ford gears. Use the calculator there too.
http://www.transmissioncenter.net/speedometer_calibration_______va.htm

The 16 pound cap is very high. I've destroyed 2 radiators (smaller 2 core style) with 14 pound caps. Now I run the 7 pound cap on the larger 3 core radiator and it doesn't spew much at all, although a little does puke out in the summer when it gets over 210. Freeway driving makes it always run hotter than city driving. Probably all the extra rpm/friction with the engine running at 3K at 60mph.

PS: Has anyone made that AOD crossmember yet? LOL!

 

Oops, I guess it's been long enough since I looked that I was a tooth off on the aftermarket gear. At the time I guess I needed 22, because I remember it was in between the Ford gear and the Steeda gear. I need to calculate now, but I'm sure I need more than 23 with this output shaft that's in my C4.

 

I calculated by following my wife in her car with correct mileage, comparing her 30, 40, 50, 60, and 70 mph to my speedo, and found that for instance, 70 REAL mph appeared as 95 mph on my speedo. That is pretty much a 25% difference. So I added 25% to my current 18 tooth gear, and went to the local Ford dealer. The largest they had was 21 teeth, which was a little over half-way to what I thought I needed, and got me a little over half-way to correct. Now, rather than 25mph difference at 70, I have a 12 mph difference. I still think I need the 23 tooth gear.

I sent an e-mail to the site that Comet155 gave me and will see if they agree that the 23 teeth will be close enough for my setup.

Thanks for the website info.

 

With the new gears, the engine is reving higher like your speedo shows, the car thinks it's going faster then it is, but the air flow is only for the old engine speed. You may be over reving the water pump causing cavatation. You may need to ad a plate behind the impellers. Flow-Kooler. I went to summit for info: http://store.summitracing.com/default.asp?target=/egnsearch.asp&N=400299

Here is Flowkoolers home site:http://www.flowkooler.com/

I'm running one on my street rod and it made a heck of a difference.

 

This may help with the "new gear speed-o" questions.
http://bbs.hardcore50.com/calc/?mode=speederr

 

When I go to flow kooler, am I looking at buying a complet aftermarket water cooler, or just a plate? I seemed to only find entire water pumps. If I have to do that, wouldn't I be better off going to an electric water pump? How are they in reliability and functionality?

 

By reading the description, the "plate" is built into the pump to prevent cavitation. Correct?

I am currently using a stock replacement from Hi-Lo, piece of junk right out of the package. I may swap, depending on feedback from you guys.

I will take my chances and drive to work today. I drove about 45 minutes yesterday, highway and around town and never got above 200, even after sitting a couple times. Work is highway all the way, no stops for 30 miles. I will come home early, so outside temps should be cool both ways. IT is 69 now and probably 75-80 on the ride home. Should be ok.

 

I forgot to tell you, I also went with a high volume water pump (chrome). I did it for looks at the time. I was never having a overheating problem with the stock water pump. Just thought if I'm going chrome, why not go high volume & no cavitation. Didn't want to have to pull it again (just in case it overheated). Always thinking ahead & remembering the saying "Do It Right The First Time". That saying, saves alot of headaches....

 

Buy the entire pump, not just the plate. They will also recomend a T-Stat. Hi volume is not the issue, cavatation at higher rpm is.

 

I'm not too sure about what I've been reading here. Although I'm not running 3.80s, I swapped from 3.00 to 3.55 gears and there was absolutely no increase in operating temperature. Not even one degree. I suspect that something else is causing the high-temp condition in question.

By the way, I also changed the speedo gear (can't remember what it is now, but I think it's a 21-tooth). Original was a 19-tooth. My speedo reads about 4mph faster than what the car is actually going (according to Police radar), however my truck ('81 F-350) also reads 4mph faster than what the radar says, and it's bone stock.

 

I tend to agree with T.L.

My rpm's going up increased temp because I have a problem with my cooling system. Could be just the added heat from the tranny causing it in your case, but it isn't with mine. I've gone through everything, it has to be a restriction in my block, rust, corrosion or something. Bottom line, if I keep it under 70, she's fine. 70 or over, temp just keeps going up. That is the primary reason for my rebuild. Aside from that, its a solid engine.

Keep in mind, if your radiator was stopped up, odds are some crud is still in your engine unless thoroughly flushed (btw, flushing didn't seem to help mine, it will be vatted and gone through completely) and may have stopped or slowed down flow through the radiator.

 

I drove the Mav to work yesterday, at about 65mph, which is right around 3000 RPMs. It started at 180 and stayed there for about 5 miles, then went up about 5 degrees for each 5 miles. When I got to work, about 40 miles, 35 being open highway, then 5 of country back roads with a couple of lights and a 4 way stop, I was up to 220.

Drove home with the heat of the afternoon, and same thing, Up to 220. With the trans cooler on it, it heats up slower and doesn't go to 230.

Is 3000 rpm "high RPMs" that would cause cavitation? If so, will the flow-kool pump fix me?

Also, should I go back to the 160 degree thermostat, or keep the 140 in there? I did drop back to the 13 lb cap, since I was afraid the 16lb cap would build pressures that this old system was not meant to handle.

I am almost to the point of taking the battery to the trunk and putting in a supersized aluminum radiator that goes at least 3 inches further on each side, and maybe thicker, with an electric fan. I am not sure if messing with the stock radiator is worth the hassle. And eventually, if I really get into some HPs, I will need the larger cooling area anyway.

 

The engine wear is more severe with cooler t'stats, I'd go back to at least 180 since you drive it somewhat regularly. if it were a strip only car, I'd leave it as is.

Another thing worth noting, now that I think about it, my car's temp steadily rises at 70mph even with overdrive, only turning about 2000rpms. The engine load probably has more to do with it in my case than the actual rpm. It would still be caused by insufficient cooling.

 

If everything is flushed out right and your water pump is working it sounds to me like possibly some performace mods and the Texas heat is starting to get the best of your Mav. I am not sure what other modifications you have done like cam, headers, etc but many of those things can start adding more heat with the higher RPMs. I myself have been fighting a heat problem and have determined its due to the fact that I am high performace and we have a limited cramped engine bay that will not flow air. That's my problem airflow my breaking point was when I added my headers not only do they throw off more heat but they prevent the air from moving thru the engine bay as easily, after the headers with the combination of everything else the factory radiator really had a battle. I am currrently running a Griffin Rad and a flow kooler pump and I do fine moving actually run right at the thermostat 180 but when I sit I shoot up to 210 -220 in 5-10 minutes in the summer heat. I had a pusher fan on the old factory radiator and it looks like I need to put it on this one for when I sit idling to assist the regular fan. I also opened up my Grabber scoops to try to create a heat escape and maybe a little fresh air when moving.

Your car is probabaly running the 423 standard radiator. I did use that one for awhile but I started to outdo it. A 353 will fit in your car. Its a heavy duty ac version radiator from earlier models but it will bolt into your 74 as I stepped up to this radiator. This one helped me it has much larger tanks and three rows instead of the 2 that the 423 has, but I still was fighting heat on hot days. So I stepped up to a Griffin alum radiator. They build one that will bolt in our cars. I have not yet got to test this in 95+ degrees but when in motion it really seems to cool compared to where I was with the factory version but like I mentioned I am still going to have to add a pusher fan for when in traffic or forced to wait.

The 353 may help you if you can find one cheap?? I don't know if you have a fan shroud but according to autokrafters their should is similar to factory and fits all years 71 - 77 so hopefully that would not be a problem if you change radiators

There are other variables. What kinda of fan do you have? If it is factory its not a six cylinder four blade? You do have a fan shroud, if not even an aftermarket one is better than nothing? The tranny cooler is a good idea! Your not running too lean or over advanced on the timing? How far is the fan from the radiator, have you changed that? I would step back up to at least a 160, the 140 is basically like having no thermostat in there.

Just trying to help

 

Got a part number on the Griffin bolt in?