Here's the deal. I just installed a 427/435 motor in a friends 67 vette. He had it built by Chicago Corvette 15 years ago with numbers matching parts. It sat in his garage for all this time. He had it pickeled and in a dry place. It fired up on the first try and has 80psi of oil pressure when cold. After about two hours of running it was evedent the rockers weren't oiling enough. Turns out it had the wrong lifters in it. Changed to Comp cams lifters and problem seem ok now. But the thing runs at 230 degress. New 4 core radiator,no combustion gases in water (checked with analyzer) timming right on at 8 degress initial and a total of 35 degress. New stock 7 blade fan clutch and fan shroud. And a 160 degree high flow thermostst. Any ideas? Thanks
Mark

Is it a thermal or non thermal clutch for the fan?
Non thermal is the one you want.How about an air pocket? are both heater hoses warm? If one of them is cold,you have an air pocket..I'd give it more base timing too.

Do you see the coolent circulating in the radiator when it is above the thermostat temp?

Do you have a radiator shroud?

Do you have a collapsed hose anywhere?

Does turning on the heater fan affect the temp?

JIM

12-15 base, limit the mechanical then to 35 total, else it might ping.

You drove the car and got 230 degrees, or just sitting and idling???

Pull a plug and see what the mixture reads like. Might be it's lean. Set the float on the center carb.

The clutch fan is thermal which was stock and it's a brand new reproduction unit for the vette. Yes, the fluid is circulating through the radiator very well. It pours out the tubes about half way between the tube and the side of the radiator at idle. Idle temp sits at 210 and it runs 230 down the road with an outside ambient temp of 90 degress. I have the timming at 8 degress initial because if you remember the 435 uses manifold vacuum at idle. I have bumped it up to 12 with no change in temp. All three carbs were rebuilt just prior to firing the engine by Dave Lange one of the industries best and are using stock jetting. Plug reading shows perfect mixture.Chris, why do you think the non thermal clutch is the one to use? I have always used the thermal type with good luck. Maybe your correct.
Mark

Mark,the thermal only works when the motor needs it.I've always run the non-thermal..alway had good luck with cars that ran hot switching over to one.The non thermal disengages at higher RPM's/highway use.

My first set of guages threw me off. I changed almost everything untill I figured out that the cheap Summit guage I had read at 230 when a SW read at 185.

Are you sure the temperature guage is accurate? calibrated?

Sender in head or intake?

Don't know if it will affect much, but a 160-degree stat seems really low...

I have thought of the thermostst and am going to change it to a 180 but in the past with big blocks I rarely use a thermostat at all being in the desert heat and all. I'm getting the reading from the stock guage and I double checked the temp reading using an infra red gun. They match and if you shut it off it will push a little fluid past a 15lb radiator cap indicating it really is hot. I'm using a mix of about 20 percent coolant and the rest water with a bottle of water wetter as well. This is a tuff one for sure.

It's only low if the engine runs at 160 Tony, Mark's buddy's doesn't.

If it does this at highway speeds its a airflow issue. ( or in my case, when the level is low).

I wonder if the 'stock' timing curve lets the engine see all the advance at your highway rpm ( whenit gets hot). Assume vacuum advance is operational.

Good point I'll look at the advance again.

Does the thermal fan actually ever lock up? Big Block Vettes always run very hot. 210 at idle with 90deg outside is normal. Despite what is claimed about not needing a fan at speed with the screwball radiator layout the fan must work at freeway speeds or the engine will overheat.

Mike, I agree. My 72 Chevelle SS 402 overheated until I replaced the old fan clutch with a thermal new one. Now it runs at 190 with the A/C on in 110 degree weather. Same scenario with my daughters 73 Camaro we built last summer. Couldn't get it to cool until I replaced the flex fan with a clutch fan and a seven blade fan. On both cars I can hear the clutch come in during cruise. I can't hear that on the Vette. It's a replacement reproduction part and I just don't trust it in fact I just got back from the auto parts store and bought another one to try. I have always been able to cool down a car with a shroud and a good fan clutch. We will see what happens! Thanks
Mark

Originally posted by 1966_L78:
Don't know if it will affect much, but a 160-degree stat seems really low... I completely agree. The lower temp thermostat lets water move out of the engine sooner, however it also has the effect of forcing water back out of the raditor faster, possibly not allowing the raditor to cool as efficiently. I changed from a 180 to a 195 in a 85 Monte Carlo and dropped my normal operating temp from almost 220 to just over 200 on very hot muggy summer days.

Interesting, I've never heard that.

Well, your not going to believe what I found!

I did replace the fan clutch last night and the temp dropped by 10 degress but still ran at 220 on a cool night. I was walking around the car and noticed the left side exhaust was putting a lot more out the tail pipe than the right side was. Mind you it's a completely new exhaust system from the manifolds back. So I traced the problem forward to a stuck heat riser valve. It's a new unit but a lousey reproduction I guess. It is now missing the butterfly valve and the car runs at 190 down the road. Perfect!! The exhaust gas from the right side was running through the intake as it should when cold but after warm up it was simply super heating the manifold and the coolant. Always turns out to be something simple and as I always say it's always the last repair that works.

Thanks guys for all you help. You all had some good ideas. I will just add this fix to my memory bank for the next time!
Mark

Mark,glad it all worked out graemlins/thumbsup.gif

Weld that ***damn thing open will ya! graemlins/clonk.gif

Heat riser valves on a 435hp motor! You Vette guys slay me! If your buddy piloted a certain heavier 67 Velle with a 435 hp clone in it, he'd crap himself I should think!

Nitrous!? No,

Let that beautiful lil 427 BREATHE!

Ok, sorry for the digs! Good thing! And no effort wasted on that new clutch. Where you're at, 10 degrees is important I should think.

Tell him to run 'er up to 7 a few times to get it good and loose! :cool:

Check your belt tension.... ;)

Thanks 427. I hear ya about the stock riser but he wanted to keep it completly stock and if you remove the riser the exhaust pipe moves to far up and hits the floor board. Go figure. I guess that's why some people call the owners(not me) fibergl*******s! Thanks for you help.
Mark

Mary,just an FYI,there is a spacer available that is the same dimensions as the heat riser valve..

WOW, good catch. thats one to file away in the back of the ole' thinker for sure.

Bob

or you could remove the plate from the heat riser, and keep the block and spring.

Mark, just feel that with 1125 cfm on tap up top, anything you can do to let it breathe 'out the back' is worth it's weight in gold. Anyway, glad it fixed and hope all those little 2 bbl throats wide open gives your friend a thrill!

Yah, I'm with Brian. 'Disarm' the repo crap, use it for looks only. Now you know why. I had a friend mig the thing open, or so he said.

Hmmm. I may have to try a slightly warmer thermostat in the truck to see if I can get it to run a little cooler. Easy enough to try it out, I seem to have about a 100 thermostats lying around anymore!