Diputado

Hey folks, picked up my current '65 about 2 years ago (see engine specs below in signature line), and it had some real overheating issues and hot-start problems. the PO who built it told me that he never could figure out why. He said he even pulled the heads to make sure the head gaskets were on right. Anyway...I put in a 4-row aluminum radiator, fan shroud, 160 deg. thermostat, and a Flowkooler pump AND a new high-torque TuffStuff ministarter and at least got rid of most of the starting issues. But, engine still tends to get hot (>190) if sitting in traffic for more than 5 minutes (daytime temp. here is always 85-90 F), and I've always noticed that when it gets to that temperature, it seems to rev slower. Lately, hot-start issues have also returned. Stop for gas, and you have to wait about 20 minutes for it to crank over easily. Starting to worry that the PO didn't properly clearance those forged pistons. Thoughts...ideas....???

Starfury

First off, >190 isn't a problem. Less than 190 is too cold, and can result in excessive quench in the chambers and carbon deposits. The engine is supposed to run at ~205-215F. With a proper 192/195 thermostat, this is usually where it stays. Once it gets above 225, start to worry. My car runs at 205-210 during 105F summers here.

As for the hot start issues, is this an issue with the starter not turning over? Or is it an issue where the starter turns but the engine won't fire?

67mustang302

Running warmer at a stop is a fan/shroud issue, and yeah, you don't need to worry about overheating until you get upwards of 230* (unless you get detonation before then).

It could be a tuning issue, wrong timing or fuel ratio. It could be a clearance issue as well, but there's really no way to know for sure other than tearing it down and inspecting (or by process of elimination with everything else).

What battery do you have and how old is it?

Mark Hone

You can start by putting a 180* thermostat back in. (it slows the water down and allows for better heat transfer). You can try some water wetter if you want. Your engine is bored .040 over, so you can expect some heating problems along with a cam, a 600cfm carb and big pistons. Mark

69mach1377

In addition to all the above; What kind of shape are your battery cables in?

Diputado

Thanks to all for these comments. As for battery and cables...both are fairly new and good shape. When engine is cold it spins over quick and fires right up. Over 190 degrees and it's "ruuump...ruuump....ruuump", and then it might start. I usually just plan on sitting wherever I am when I stop for at least 20-30 minutes. Fill up with gas...buy a beer and sit in the shade for a while. Coolant mix is about 60:40 water/coolant with a bottle of Redline water wetter thrown in for good measure. I think fan is maybe just a little too far into the shroud, though, and plan to use a shorter spacer to pull it back about 1/2" and see if that helps.

Timing and fuel mix....when I first got the car, I thought about that and adjusted the timing up slightly. This helped some. Problem is...the PO who built the engine didn't put a timing pointer on it. Said he timed it "by ear". So I'm left doing much the same. I set the idle mix using the instructions that came with the Holley carb. Aimed for an intake vacuum of about 14-15" at idle. Throttle response is good....up to about 200 degrees, when it seems slightly less "crisp".

More info...engine only has about 5,000 miles on it. If....IF...the forged pistons are indeed a little "tight"...any chance this will "break-in" more with a few more miles??

67mustang302

Your timing is probably way the **** off. Put a timing pointer on it and fix your timing (which is probably really high atm).

If the pistons are too tight they'll eventually "wear in"...by ****ing up the pistons and cylinder walls and ruining cylinder seal. Or they'll seize.

Probably timing though.

Starfury

+1

Hard starts with varying temps and no timing pointer; timing issue is the simplest explanation (occam's razor).

Diputado

Good points! Yeah..can't figure why the PO didn't put on a timing pointer. Actually, kicking myself now for not doing so last year when I changed the water pump..duh!

Anyway...planning on a heads/cam swap early next year anyway, so I'll also put on a new timing cover AND pointer then. If anything, current timing might be a little low. When I first got the car and noticed this issue, a friend (who is an actual mechanic!) recommended backing off the timing. Well, I did only slightly (about 1/8" counterclockwise turn of dist. base). Had to advance it back again right away because in less than 5 miles the engine would overheat to the point of shutting down/dieseling!

So...another question...when I pull the heads, how can I tell if the piston clearance is the problem WITHOUT tearing everything completely down? With .040 over forged pistons, what exactly should the cylinder diameter be? I can easily measure that with the pistons in. Any particular upper cylinder wear patterns,etc. after 5,000 miles that might also indicate such a problem?

67mustang302

1/8 of a turn on the distributor is ****ing HUGE for timing. That's literally a change in timing of 90*.

If the pistons are too tight you'll know, when you pull the heads the cylinders you can see will be all scuffed and scored. So if it has vertical scuff marks, it's too tight. Proper clearance with proper lubrication and across the entire life of the engine there should be very little to almost no visible vertical marks, and often the cross hatch on the cylinder is still faintly visible. Unless it was built using ****ty old ring technology with cast iron $10 rings, then it'll have more wear.