Scott333

As part of a complete frame-off restoration, the radiator is definitely one of many items that will need to be replaced. DeWitts seems to be the obvious choice for function, quality, fit and correct appearance, and since Tom is having a sale for us here on the Corvette Forum, it has moved up my timetable to investigate this subject.

The car is a '67 4-spd coupe with the L79 small-block, and has a "factory" A/C that was taken from a donor '67 Corvette that was being parted out back around 1978. The A/C was installed by an engineer and lifetime employee of GM (my Dad), and I think all of the proper additions/changes/upgrades necessary to make the car appear and function the same as one equipped with A/C on the assembly line are in place.

For the engine rebuild, after doing a great deal of forum archive research in the last week or so, I am now leaning toward the high-revving LT1 or 30-30 cam option similar to what Ghostrider20, SWCDuke and others have discussed extensively in the archives. I only mention that here because I’m not sure if it would affect radiator choice or not.


The stock factory correct replacement radiator on the DeWitts website is P/N 941 (http://www.dewitts.com/pages/productdetail.asp?ProdID=2)

But they also have another option, the same 941 model with a 16" electric fan attached, P/N SP020 (http://www.dewitts.com/pages/product...asp?ProdID=257)


If I understand correctly, the "stock" radiator has a 4,600 BTU rating, while the electric fan assisted radiator has a 5,500 BTU rating.


Question(s):

1. Will the electric fan assisted radiator fit under the stock fan shroud, and will I still be able to use the OE engine fan (and is that the proper method of installation for this electric fan option)?

2. Does the electric fan in this set-up run constantly, or only when needed (i.e., is it thermostat controlled)?

3. Wouldn't having the electric fan (and the associated fan-housing) between the radiator and the engine fan reduce the "normal" cooling capacity of the originally designed OE system (with or without the electric fan running)?

4. Is the electric fan assisted radiator even necessary for my application, as a daily-driver in Ohio?

I need to be able to use the A/C in the city when necessary (e.g., on the way to work, wearing business clothes) without worrying about overheating (either the car or me ). My previous experience is with a '69 Corvette that had overheating problems, and I would really like to eliminate overheating as an issue this time around.

Thanks for any and all advice,

Scott


P.S. Should the expansion tank normally be replaced when the radiator is replaced? Reasons? Pros and Cons?

Tampa Jerry

I have a 68 small block with factory air and a 66 small block with Vintage Air. Both cars have DeWitts alum. radiators. I use a 180' thermostat with a functional clutch fans and full seals on the shrouds. Neither car runs hot at any time. On the 66 I added a push fan on the front of the condenser for added protection. My black/black coupe stays cool here in Florida even in midday sun in the summer. If the engine is set up correctly, timing, carb, no vacuum leaks, good clutch fan, seals etc., you should have no problems with a Dewitts rad. alone. I think the dual fans may be overkill. If you go that route, you should go up to at least a 100 amp. alt. Jerry

Powershift

Scott:

I have a 1967 327/350 HP factory air convertible and live in New Orleans, so I am familiar with air conditioning and hot weather.

My recommendation would be to purchase a DeWitt correct aluminum radiator only, and forget the auxiliary fans. Make certain that you have the correct fan or a 7-blade GM replacement, a good, working thermostatic clutch, the proper radiator shroud and seals for a factory AC car, and a working/correct vacuum advance. Then you should be all set.

I would NOT recommend an LT-1 or 30-30 cam however, if you want the air conditioning. Stay with the stock 327/350 HP hydraulic cam. Even then, you will have to jack up the curb idle to keep the car and air conditioning running properly during stop and go traffic (particularly in the summer). I have to run 1000 RPM with the air off, which provides about 800 RPM with the air on. The 350 HP cam get a bit ragged below about 700-750 RPM. A 30-30 or LT-1 cam will be worse. There is a reason why only a few of these solid lifter engines were ordered with air conditioning.

If you want the bigger cam, go for it......but AC performance and driver satisfaction will suffer.

Larry

wmf62

you can get an electric idle control solenoid, that cycles with the a/c clutch, that mounts on the carb and provides a stop for the carb linkage in order to raise the idle speed when the a/c cycles on.

but, a 1000 rpm idle is not an unreasonable idle speed in order to keep the engine from stalling. before i installed a idle soleonid, i used to set the idle on my FI engine at 1000 in order to compensate for the rpm drop when the a/c is on... BUT, setting the idle speed too high can cause engine 'run-on/diesel' when the engine is turned off...

Bill

JohnZ

You don't need anything other than the properly-functioning stock components; the only difference in the cooling system between A/C and non-A/C cars was the added rubber seals between the radiator and support and between the top of the support and the hood. Get the DeWitts restoration radiator.

Powershift

John:

The 1967 factory AC cars also had a radiator shroud (lower) ring in addition to the items/seals you mentioned. The AIM shows the part number, but my copy is too blurry to read correctly....but for the small blocks the last three numbers are 424. My car has this ring.

Suggest Scott333 refer to the air conditioning section of the AIM for all of the various components used/required for factory air to avoid missing any. Excellent info.

Larry

tentuna

I have a 66 L79 with A/C stock cooling system, Dewitt's stock replacement radiator and it runs 180 degrees constant.

Scott333

Thanks Jerry, from your comments and others below, it sounds like the DeWitts radiator by itself should be plenty



I plan on all new or reconditioned parts, so it sounds like I should be okay without the electric fan. I thought I read somewhere that the fan for the A/C cars was a 5-blade, so I'll have to check that to be sure. The 7-blade fan makes more sense though...



I read in the archives about the solenoid solution Bill mentions below, so I'm hoping that will work.

As for the LT1 or 30-30 cam engine rebuild, I'm still trying to figure out what to do engine-wise. I'm converting the engine to run on pump-gas, and the lower compression ratio is going to cost some horsepower. I would like to get the rear wheel hp and torque back up to the 280-300 range, and the LT1 or 30-30 cam seemed like the way to do it while maintaining an original appearance and mostly OEM parts (pocket-porting the heads, 2.5" rams horn manifolds, etc.). Most of the time I like to drive with the windows down and the A/C off, even when it's really hot out (I'm a hot weather person, not a cold weather person). I mostly use the A/C when I'm over-dressed for hot weather (mostly work or church). I don't expect to use the A/C a lot, but it's nice to have when you need it



Thanks Bill, that's what I'm going to try

Scott333

Thanks John



I'm sure my Dad used one when he installed the A/C, and I'm sure we'll need one when we begin putting the car back together I will have to remember to look up the lower ring on the fan shroud, I hope it's not too expensive if I have to replace it... but it probably is, everything else on the car is!



180° with the A/C on would be great.

Scott333

Does anyone have any thoughts about the surge tank? Is that something that never needs to be replaced as long as it looks okay cosmetically, or is it a good idea to replace the expansion tank too when the radiator is replaced?

stingrayl76

No need to replace the expansion tank if it's not leaking and the condition meets with your approval.

Dave

Powershift

Scott:

Agree with STINGRAYL76 that if the expansion tank looks good, re-use it. No need to replace just because its old.

My comment on the radiator fan was to use the correct 1967 5-blade fan (with diameter of 17 1/8 inch) OR the GM replacement that has 7 blades. Original/correct 1967 fans are sometimes difficult to obtain, but Paragon and others sell the 7-blade AC fan. My car lost the original fan somewhere during its life and now has the GM 7-blade fan installed. I think that many folks installed these to try to improve engine cooling. The GM parts book also shows the 7-blade fan as the service replacement for AC cars. Your choice.

If you go with the solid-lifter cam, keep in mind that the air conditioning compressor clutch pully for these engines was larger diameter to help keep from overspeeding the compressor at 6000+ RPM. Not that you would do that . So if you change cams, also check diameters on the various pulleys. Alternator may be the same situation.

Larry

Scott333

Thanks Dave, that's good news. I would like to keep original parts and refurbish them when that is practical. Is there a recommended process for thoroughly cleaning the inside the surge tank? The outside is in good shape and should clean up very nicely. I believe it's original, and I'm glad to be able to keep it


Good news about the surge tank, and it seems like the 7-blade fan should move more air, and it should also be easier to find



Uh-oh... if I have an engine capable of safely revving past 6,000rpm, chances are very good that I will do that... if I had a Magic 8 ball, it would say "all signs point to yes"...

I have a lot more research to do on the engine rebuild before making any final decisions, and I appreciate the heads-up on potential flaws in my plan. I'll start a new Thread on rebuilding the L79 after I've done more homework.

Thanks again,

Scott

KC John

I want to mention (someone might have already and I missed it) that a 16" Spal fan is loud as heck. If you had to go electric for any reason the dual 11" fans are a much better choice because they are not as loud.

Nev Williams

I recently went thru the cam choice flip flop choice process and decided on the Comp Cams version of the L79 cam.
http://www.compcams.com/Cam_Spec/Cam...?csid=110&sb=2
So far very pleased.
Fuel down this part of the world is an issue so I wanted to keep compression ratio sane. With 62cc Trickflo heads & KB Hyper Flattop +.040" pistons, this gives me 9.8:1 static.
The engine has that nice distinct lope of L79 cam, idles happily at 750 rpm and goes like gangbusters when I "lean on it" - though at present engine is still fairly new, so I'm having to restrain myself a bit!!! On the odd excursion around 5000rpm though, the motor is extremely strong and sounds and feels as though it is just clearing it's throat for a real good howl.

stingrayl76

Scott,

The alternator should be a 55 amp #1100694 with a pulley diameter of 3 3/8" with a 1/2" groove.

If you are planning to use the stock A/C compressor, the diameter of the pulley for the 350 HP engine is 5 3/4". If you are planning to rev higher than 6000 rpm, I would use the 365 HP pulley which has a diameter of 6 3/8".

Dave

Scott333

Thanks for the cam info Nev, it sounds like you're having fun. It's good to know that Chevy's finest production from 1966 is still running strong and screaming across New Zealand 42 years later

ghostrider20

Dewitts Radiator and be Done with it for the next 35 years.

Scott333

I will check on the alternator and I have added the 365hp A/C pulley to my treasure-hunt list. I wouldn't have figured that out until I did some kind of damage, and then posted a Thread here asking what caused the problem.

Thank you Dave, very much appreciated

0Tom@Dewitt

John,

You can't put duals on a midyear radiator, they just won't fit. But you can replace the HP 16" (2360 cfm) with a curved blade 16 (2000 cfm) which is much quieter and they have the exact same bolt pattern.