1966-67 HCS Radiator cap question

[66hcs-conv]

Our '66, 289, 2 bbl has the nasty habit of spitting up a little coolant while it is driven, and parking it in the garage.

The radiator is filled just over the fins.

Just guessing I need another radiator cap, but how do I detrmine what # cap to buy?

It has a 13 # cap on now. The car probably hasn't been driven more that 2,000 miles with that cap, but it is 7-8 years old.

What # cap should I be getting?

thanks, dave

 

[stangfan]

Pretty sure these cars usually have 13lb. (or 13#) caps. Maybe have your cap tested to see if it is correct. All my classic Mustangs have had 13lb. caps.

 

[robert campbell]

13 pound cap. You can install a coolant recovery system. What thermostat are you running? Sounds like your car runs a bit hot.

 

[66hcs-conv]

I had the engine rebuilt a while back, but I've only driven 800 miles since the rebuild.

Using a heat gun directed at the top inlet for the radiator, I get 190 degrees, after a 2 hour drive. I put a 3.5 inch shroud on the radiator, and I am using a 160 t-stat. The fan blade is a fixed 6 blade fan & it is 1/2 way into the shroud.

I did put a recovery tank on, but still using the standard radiator cap. So the coolant goes into the tank, and not on the driveway, or garage floor.

It does run cooler than it first did after the rebuild, but continue's to spit up a little coolant. *When I got back from the 2 hour drive, I had about a quart of coolant in the recovery tank - doesn't seem normal to me.

I think the advance is more than the manual calls for. The engine is not pinging, but maybe pulling the advance back a few degrees will help it run cooler ????

thanks, dave

 

[robert campbell]

Retarding the timing will make it run hotter, perform worse, and use more gas. Try advancing the timing 2 to 4 degrees. If you get a light ping pulling a hill, but it goes away if you floor it, there are adjustable vacuum advance pods for your distributor to cure this anomoly.

Have you tested your vacuum advance to see that the advance plate moves and it holds vacuum? If it is bad, it will cause a car to run hot and perform poorly. Is your vacuum advance pod a single line or a dual line style? The dual line style is for emission control and tricky to work with. I recommend removal of this type, unless your car is a concurs class show car. Put it on the shelf and install a single line type.

Rob

 

[66hcs-conv]

Distributor is a single line type. Last summer when I was having trouble getting it to run right (vacuum leak), I tested the vacuum advance, and it holds vacuum real good, and the plate does move under vacuum.

The engine doesn't ping under any loads.

thanks, Dave

 

[66hcs-conv]

Update

Took old radiator cap to O'Reilly's, tested it, and it would just barely get to 13 lbs, but it would not hold pressure. Pressure would immediately fall off, and within 15 seconds it would fall to 5-7 lbs. The guy tried 3 different testers using my old cap, and they all did the same. Their testers did hold pressure with a new cap.

Got another cap, but not a pleasant day for a drive.

Thanks, Dave

 

[robert campbell]

I would find a nice day and test it. Note the advance now and then advance it ahead 2 degrees at a time. When it starts to ping bring it back just enough to stop it.

More advance equals, more power, better mileage, and less heat. People worry about advance, high compression older engines, and today's gas. In my experience today's 92 octane gas functions almost identically to old 99 to 101 premium in the past. Todays gas is carp next to the old stuff in performance, but it does not ping any easier. Just burns with less energy that the good old stuff.

I run Val's 1967 289 Weber engine with 18 degrees advance of initial timing with 38 total at 3,000 RPM. It is a 13 to 1 compression motor and it does not even hint of pinging.

I could start a new thread on the subject of today's gas, old engines, timing, and hardened valve seats.

Rob

 

[franklinair]

My small blocks really like the 100LL Avgas (when you operate a small airport)

Neil

 

[robert campbell]

Dad,
You are killing me!!! Can you pipe over some of that gas!! My cars would LOVE AV gas!!

Your son Rob

 

[p51]

Couple of other suggestions/comments...

(1) Has the cooling system been "burped"? If there are any air pockets in the cooling system (aside from the top of the radiator) they can expand after the engine heats up and you get coolant regurgitation.

(2) Are there any leaks in the cooling system? The way to check is with a vacuum/pressure pump (eg like a mityvac) hooked up to the radiator. Pressurize to just over 13# (don't go too high, you don't want to blow any gaskets) and see if it holds pressure.

Its important that there is no air bubbles or leaks in the system as either of these can allow for local hot spots in the engine.

On the topic of advance/retard timing, as Rob said, the more advance the cooler the engine runs. I use a disti with vac advance canister on it and hook it to manifold (not ported) vacuum which gives it lots of advance at idle when there is no load. Seems to idle nice and cool with less gas usage.

 

[robert campbell]

Couple of other suggestions/comments...

(1) Has the cooling system been "burped"? If there are any air pockets in the cooling system (aside from the top of the radiator) they can expand after the engine heats up and you get coolant regurgitation.

(2) Are there any leaks in the cooling system? The way to check is with a vacuum/pressure pump (eg like a mityvac) hooked up to the radiator. Pressurize to just over 13# (don't go too high, you don't want to blow any gaskets) and see if it holds pressure.

Its important that there is no air bubbles or leaks in the system as either of these can allow for local hot spots in the engine.

On the topic of advance/retard timing, as Rob said, the more advance the cooler the engine runs. I use a disti with vac advance canister on it and hook it to manifold (not ported) vacuum which gives it lots of advance at idle when there is no load. Seems to idle nice and cool with less gas usage.

All engines react differently, but in my experience ported vacuum is the way to go with as much initial as you can dial in! If you use a constant vacuum source it does bring in a lot of advance at idle. Sometimes way to much! Vacuum advance pods range from 11 to 15 degrees of advance and at idle you have near full vacuum which means the vacuum advance is all the way in.

As you step on the gas, the vacuum reduces and the advance goes away and actually can cause a flat spot. Especially if under a bit of hard acceleration. If you go to zero vacuum just as you leave the stop sign or light, all of the vacuum advance is gone and the motor just lost nearly 13 degrees of advance.

When using ported vacuum the engine receives additional advance under nearly all but the hardest of acceleration. It is not drawn it at all at idle and as you open the throttle plates the engine is fed additional advance to compensate for the need as you accelerate. And with 12 or so degrees of initial advance dialed in, it never drops below that.

If you introduce bigger cams and such, it gets more complicated. But for near stock engines, I prefer to use ported vacuum.

But other engine tuners have had luck with constant vacuum.

Rob

 

[66hcs-conv]

I checked the timing & it is 12-13 degrees advanced. I left it alone until I get to road test the car.

I put on the new radiator cap, and had the engine running for 5-7 minutes.

The temp gauge just barely moved into the normal range. Where before the gauge would be at least 1/2 way. The temp in the garage was around 60 with the overhead door open, so it wasn't very warm.

I am hopeful that the new rad cap will help the engine run cooler. But the weather here is supposed to be in the 50's and rainy for the next week, so I am probably not going to able able to drive the car - rats!

Neil - what is the price of the AV gas? Do you deliver?

THANKS for all your help.
Dave

 

[p51]

All engines react differently, but in my experience ported vacuum is the way to go with as much initial as you can dial in! If you use a constant vacuum source it does bring in a lot of advance at idle. Sometimes way to much! Vacuum advance pods range from 11 to 15 degrees of advance and at idle you have near full vacuum which means the vacuum advance is all the way in.

As you step on the gas, the vacuum reduces and the advance goes away and actually can cause a flat spot. Especially if under a bit of hard acceleration. If you go to zero vacuum just as you leave the stop sign or light, all of the vacuum advance is gone and the motor just lost nearly 13 degrees of advance.

When using ported vacuum the engine receives additional advance under nearly all but the hardest of acceleration. It is not drawn it at all at idle and as you open the throttle plates the engine is fed additional advance to compensate for the need as you accelerate. And with 12 or so degrees of initial advance dialed in, it never drops below that.

If you introduce bigger cams and such, it gets more complicated. But for near stock engines, I prefer to use ported vacuum.

But other engine tuners have had luck with constant vacuum.

Rob

This is one of those almost "religious" arguments that I refuse to get pulled into. I've seen way too much back-n-forth on this. It's sorta like the Catholics and Protestants in N Ireland :wink:

The best writeup I've seen on the subject is the following by an ex GM engineer - yeah, I know, a Cheby guy...

http://www.camaros.org/pdf/timing101.pdf

 

[robert campbell]

You and I have been here before.

I will liken myself to a Southern Baptist!! But the facts are compelling. Time your car a 6 degrees BTDC, induce 15 degrees of vacuum advance at idle, and when you step on the gas, advance leaves the engine.

Time an engine at 12 degrees initial BTDC, use ported vacuum, and as you step on the gas you go forward to at least 18 or 20 degrees under light acceleration. Easy math for me. Mo advance is better as you transition from the idle circuit to the low speed circuit, bust the power valve at 6.5 inches of vacuum and smoke that "cheby" next to you. Slam it down off the light and you at least have 12 degrees of timing as you wait for the centrifugal to spin in. Again, easy math.

A motor with 6 degrees of initial timing with non-ported vacuum will be right a 6 degrees BTDC under heavy acceleration as you leave the stop sign. Bog....... Until the centrifugal spins in. Again, why Ford engineers set the cars up with ported vacuum. In every engine back in the day. And so did Cheby engineers. I work on them to and they respond the exact same way.

Rob

 

[p51]

You and I have been here before.

I will liken myself to a Southern Baptist!! But the facts are compelling. Time your car a 6 degrees BTDC, induce 15 degrees of vacuum advance at idle, and when you step on the gas, advance leaves the engine.

Time an engine at 12 degrees initial BTDC, use ported vacuum, and as you step on the gas you go forward to at least 18 or 20 degrees under light acceleration. Easy math for me. Mo advance is better as you transition from the idle circuit to the low speed circuit, bust the power valve at 6.5 inches of vacuum and smoke that "cheby" next to you. Slam it down off the light and you at least have 12 degrees of timing as you wait for the centrifugal to spin in. Again, easy math.

A motor with 6 degrees of initial timing with non-ported vacuum will be right a 6 degrees BTDC under heavy acceleration as you leave the stop sign. Bog....... Until the centrifugal spins in. Again, why Ford engineers set the cars up with ported vacuum. In every engine back in the day. And so did Cheby engineers. I work on them to and they respond the exact same way.

Rob

Got it. Thanks.

I'm more of a Calvinist