65silververt

I just installed a heat shield on my fathers 427 66. This car has had serious heat soak and percolation issues which ended up filling two cylinders exactly one year ago and causing a bent rod. I installed an aluminum intake, ditched the heat riser, and used intake gaskets with cross over block off plates, but the problem still persisted, although not as bad. Hopefully this will be the end of the issue.

I had to trim a small piece of the shield off to provide clearance for the choke arm. without trimming the throttle linkage would have only opened about 80 percent of the way. Took 3 minutes with the dremel tool



I used thinner gaskets than what came with the shield. There was a 1/4" thick gasket included, but this car is lacking in hood clearance, so i used thin paper gaskets.



Im pleasantly surprised that the shield is not very visible.

tbarb

Beautiful car! Take a look at your AIM for that engine, I think the heater hoses are routed incorrectly where they come out of the heater core. The lower hose should go behind the upper hose then up/over as it goes forward, this gets it away from the hot exhaust manifold. The upper hose connects to the "T" and the "T" should be at a 45* angle so the hose points lower as it comes off the "T" moving forward.

Also, check the ignition timing and make sure the vacuum advance is pulled full at idle and total idle timing is 25*+-.

65silververt

Here is the shield I purchased just in case anybody needs one.

http://www.summitracing.com/parts/oer-3969835/overview/

65silververt

Well, that didn't work either. Carburetor bowls are at 145 degrees and 140 degrees and the rear, which is the hotter of the two, percolated a small amount of fuel out after shut down. It probably would have been worse if I had left the air cleaner on. HOWEVER, the fuel bowls are now 20 degrees cooler than they previously were without the shield.
Car is running right at 180 degrees while cruising, with a max temp of 195 degrees when idling at a stop light. Temps confirmed with an IR gun to make sure the temp sending unit is functioning properly and not giving erroneous readings.

Y0GI

That is a large volume of gasoline to percolate!

Have you checked your carburetor needles, seats and floats?

Yogi

65silververt

Everything has been checked. The original holley did the same thing. In addition, I actually have the floats set a bit below half point hoping that would help.

Y0GI

OK.

Good luck with the HS.

Yogi

tbarb

Get as much timing in that engine as it will take without detonation, (ping). I don't know if that engine has a ported vacuum advance or not but connect it to full manifold advance and get a vacuum control that allows full advance below the idle vacuum so it's pulled full at idle speed.

65silververt

Thanks Yogi! I appreciate the reply and I hope you did not think I was being rude with the previous post.
I just went back out and checked the car again and it has sucked the carburetor completely dry. I guess I am going to start over from point A and hope I can find something in the carburetor that is causing the issue!

65silververt

Thanks!

I have it set at 35 degrees advanced at 3200rpm and the vacuum advance is connected to full manifold vacuum. I guess it is just the nature of the big block, but this damn engine stays hot for the longest time after shut down. The aluminum intake is at about 220 on the runners after shut down. The car does run at normal operating range as mentioned. We had some minor issues with the coolant temp going above 200 a few years ago, so I installed a new dewitts aluminum radiator in place of the copper core unit.

Y0GI

Thanks, but I didn't think that you were the least bit rude.

I really find this baffling! I've never heard of a carb that would boil the bowls dry! Really strange!

Good luck!

Yogi

mrg

[QUOTE=65silververt;1589616251]Th The aluminum intake is at about 220 on the runners after shut down. The car does run at normal operating range as mentioned. /QUOTE]

I akso had a similar problem, though on SB engine. Moderately warm days is when the problem manifested itself. Intake runners would run between 210-230 degrees. Without throttle manipulation the engine would tend to stall at idle. Not always but sometimes when starting out from a stop, up to about 1800 rpm the engine would run rough and sometimes buck. Fuel percolation was suspected.

The stock cast iron manifold was changed out for an aluminum EPS. Fuel injection heat passage block-off gaskets were used. Intake runners now running nominal 150 degrees. Carb is an AFB. Float bowl body also shows 150 degrees on the IR gun. ..

The manifold change out was done only recently. I've only been able to run one warm day (85*) test, so far.

Compared to before, engine behaves much better now. Idle/low rpm performance is much improved. I'd still like to do more testing on even hotter days to verify.

It sounds like you've done about everything that can be done to address your continuing problem. The Holley float bowls showing 140 degrees on the IR gun seems reasonable. What's surprising is the intake manifold running 220 degrees after heat passage being blocked off. Quite a mismatch between the two. .

For all that's been done so far, maybe add a sheet metal hot oil separator under the intake manifold (if not one already in place) might be a consideration?

Just wanted to share my experience.
John

rene-paul

IMHO, I fought this with my 63 base eng roadster. Two types of heat we are fighting, conductive and convectional. You MAY have the conductive heat solved but the convectional heat is still there. I wrapped my fuel line from pump to carb with a slit lengthwise rubber fuel hose and wrapped that with a heavy foil [airplane speed tape].
When I fabbed my heat shield I extended it as far forward and around the water outlet.
You may want to extend yours and put a vertical piece to further block the outlet. I also extended mine to the sides. I do not recall if you blocked the heat riser passage. I also do not latch my hood. A 63 does not have open side louvers. You may want to try that.
It is a step by step process. Keep plugging.
Brgds,
Rene

6T5RUSH

65silververt,

Just reviewed what you've done to mitigate your heat soaking. I can see the installed heat shield under your carb. Just an observation but if that shield could have been shaped to cover over the center ports on of your carb, that might further deflect the heat soaking going on. Realize yours is a big block and you've got the '66 big block hood to help ventilate the engine.

Here's a pic of my small block (I have a big block 65/66 hood that helps too) with the Mr. Gasket aluminum shield. Again, my carb's a Holley but you'll notice it does extend out on either side to deflect the heat. I also have the cross over passages sealed with epoxy.


Shield extends out on the pass side.


Still can see it but I think it is a clean looking approach.

This is the Mr. Gasket shield I used:


This is the # I'm using on my small block.


Besides the #3710, Mr. Gasket makes these as well.

Here's proof this works well on my small block...there's a 60 degree difference between the thermostat housing and the front fuel bowl.





Just thought this might be helpful as installing this type of shield is not a big deal to do.

Good luck!

Jim
In God We Trust!

Tom Austin

I bought the Holley "generic" shield a few years ago and trimmed it to fit my '66 L79 . . . haven't had an issue since I installed it - works great and you can't even see it when the air cleaner is on.

Tom

tbarb

35* timing at 3200 is fine provided there is approx 25-30* idle timing. Giving the engine lots of initial with a correctly calibrated vacuum advance will greatly reduce the heat rejected to the cooling system. The heat will be used to push the piston, the limiting factor is detonation. The more you reduce engine coolant temps the less heat soak. The coolant may be 180 but the cast is hot.

The ethonal fuel is not helping anyone though, that's what is different.

65silververt

Thanks for all the advice! As soon as I have more time to tinker with the car, I will report back. This has to be resolved or something bad is going to happen again. Soaking the cylinders with gas after every drive isn't going to help the longevity of the engine. While this engine has some aftermarket parts, it is a numbers matching 427/390hp and it would be devastating if anything were to happen to the block.

DansYellow66

This sounds like a very puzzling case. Sounds like you are trying all the right things - surprised you aren't getting better results. One thing I found out some time ago is not to completely trust IR temp guns. Apparently they are calibrated to read correctly on a flat, black surface. An aluminum or light colored surface will read much lower (which I assume to mean lower than the real temperature). So the temps you are reading on the intake and possibly the aluminum colored thermostat housing may actually be on the low side. You can Google this subject and find a lot of information on line. I think this is why everyone who had their headers ceramic coated with silver thought they were dramatically lowering their under hood temperatures by measuring the header temp with an IR gun. Actually the gun is just reading incorrectly and low.

Sooo - depending on where you are taking your temperatures (with an IR gun) you may be running hotter than you are aware of. But if you are reading the radiator hose then probably not. Hope you find a solution.

65silververt

Excellent points and very true of reflective surfaces from my experience, but the radiator and radiator hoses(flat black surfaces) actually read right at 180 after shut down, which is lower than that of the bronze temp sending unit which reads about 185-190

TCracingCA

First you defeated the dual benefit of that heat shield by getting rid of the designed thicker gasket! have you taken some playdo and stuck it on top of the aircleaner to see how close you actually are? Or did you have the gaskets on and it hit?
Two if you are thinking that you still have to play with your timing and advances, you are probably still screwed up! I don't like the book tuners to a spec, but like the tuners that tune to the actual engine! what are you seeing as soot out of you exhaust? What are your plugs looking like when you check them?
I would bet you have some internal carb leak that emptied a bowl, I find it hard to believe the entire volume boiled off/revapped off! Is the float filling to the proper level?
I have seen many a fuel line run too close to a heat source or even laying across one!
I just insulate mine anyways.
I would need to go back and read more to get a judgement on your cooling system.
How is your oil drain back. is too much being throw in the upper engine and maybe hitting in an excessive volume the underside of an unshilded intake manifold.
I could probably keep going on ten more!
My computer keyboard is acting liike i spilled water or something in it. Maybe it is just getting hot and acting up!


T