68/69 427 owners
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From: Cape Cod, Mass.
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68/69 427 owners
How warm are your 68/69 427 cars running in the summer? Mine runs about 185 around town but with sustained highway on an 80 plus degree day my 68 427/390 will see close to 210 (not alarming but not where I'd like to see it). I have confirmed the gauge with an IR gun and eliminated all the normal suspects except the old, original style big block copper/brass radiator. I am leaning towards an aluminum Dewitt's but wanted to know what you guys are running for temps before I take the plunge. I know his aluminum radiators lowered the temps in my small blocks by 25 degrees.
Would love to hear from original big block owners like Wally to see how warm they ran when new.
Thanks
Would love to hear from original big block owners like Wally to see how warm they ran when new.
Thanks
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Ol' Red ran a bunch warmer on the highway(210*) than in town with stop and go traffic. And I have the L-88 radiator with no fan clutch and a shroud that's modified from about 3 different ones. I found out that airflow was the problem. I removed the front license plate and bracket and it runs 185-190* now.
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Joined: May 2006
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From: Dayton, Ohio
Ol' Red ran a bunch warmer on the highway(210*) than in town with stop and go traffic. And I have the L-88 radiator with no fan clutch and a shroud that's modified from about 3 different ones. I found out that airflow was the problem. I removed the front license plate and bracket and it runs 185-190* now.
Scoop in some more air. 
Race Director
Joined: May 2006
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From: Dayton, Ohio
Have you tested your temp with the lights up ?
Here's an old post with a couple scoop ideas.
Here's an old post with a couple scoop ideas.
Here is what I did om my 78:
The air scoop is made from a Rubbermaid dust pan..very flexible/forgiving...you use existing valance bolts for attaching...but only works on later versions with valance center opening...this knocked 4-5 degrees off temps at Hwy speeds above 65 mph...
This pic shows my spoiler "extension".(before scoop)..made it from garden edging my wife had...this gives me 4" total depth,very flexible/forgiving...and I attached it to my stock spoiler...
These two combinations work good for me...less air under vette...and more to the rad...
I might add that that spoiler from Vancor looks good and would be very functional on vettes with center valance openings like my 78...don't think it would work well on my 69,as there is no center opening in valance..just one each side...so I run with no front plate and removed the headlight sheilds for more air to rad on the 69...
Rich
The air scoop is made from a Rubbermaid dust pan..very flexible/forgiving...you use existing valance bolts for attaching...but only works on later versions with valance center opening...this knocked 4-5 degrees off temps at Hwy speeds above 65 mph...
This pic shows my spoiler "extension".(before scoop)..made it from garden edging my wife had...this gives me 4" total depth,very flexible/forgiving...and I attached it to my stock spoiler...
These two combinations work good for me...less air under vette...and more to the rad...
I might add that that spoiler from Vancor looks good and would be very functional on vettes with center valance openings like my 78...don't think it would work well on my 69,as there is no center opening in valance..just one each side...so I run with no front plate and removed the headlight sheilds for more air to rad on the 69...
Rich
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From: Cape Cod, Mass.
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That probably would help some but I hate to lose my "RAT 427" vanity plate up front.
I never really drive the car at night, but I suppose there would be a bit more airflow with the lights up. I would really like to maintain the stock appearance of the front air dam.
I never really drive the car at night, but I suppose there would be a bit more airflow with the lights up. I would really like to maintain the stock appearance of the front air dam.
Last edited by capevettes; Jul 17, 2011 at 12:58 PM.
Melting Slicks
Joined: Mar 2007
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From: Frederick Maryland
My '69 427/435 generally runs around 180 degrees...in idling traffic maybe about 200. It takes a real hot and humid day before it goes over 200. I was in a parade once with it in that kind of heat and it went over 220...plus I could smell the clutch burning. No more parades after that experience.
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From: Dayton, Ohio
My '69 427/435 generally runs around 180 degrees...in idling traffic maybe about 200. It takes a real hot and humid day before it goes over 200. I was in a parade once with it in that kind of heat and it went over 220...plus I could smell the clutch burning. No more parades after that experience.
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From: Cape Cod, Mass.
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My '69 427/435 generally runs around 180 degrees...in idling traffic maybe about 200. It takes a real hot and humid day before it goes over 200. I was in a parade once with it in that kind of heat and it went over 220...plus I could smell the clutch burning. No more parades after that experience.
Burning Brakes
Joined: Apr 2007
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From: Pinecrest FL
2015 C3 of the Year Finalist
My 69 427/390 4 speed has factory AC.
I just re-cored my original harrison radiator. I replaced all of the shroud seals, etc to maximize cooling. My cooling system is totally stock. In heavy traffic with 90 plus degree Miami heat I am pegged at about 215.
My 63 327 with a be cool radiator runs at about 190 in the same conditions.
I just re-cored my original harrison radiator. I replaced all of the shroud seals, etc to maximize cooling. My cooling system is totally stock. In heavy traffic with 90 plus degree Miami heat I am pegged at about 215.
My 63 327 with a be cool radiator runs at about 190 in the same conditions.
Melting Slicks
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From: Frederick Maryland
Race Director
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From: Taylor Michigan
Stock radiator {copper}, head lite shields in place, 180 thermostat, 15 lb radiator cap........ at approximately 200 miles while under warranty a dealer installed L88 short block replaced the OE L71 .....there has never been any overheating problems with the car at speed or idling....with no problems I rarely looked at the dash gauges other than that fast moving gas gauge towards empty......But I do not have any temperature problems with my BB Camaros either, one of which is a factory air, T400, L-72 which I will use later today for a local cruise.......a 67 L-78 car and another 68 with a LS-7
by the way its going to be in the mid 90`s today and for the rest of the week including through the Telegraph Cruise ....
by the way its going to be in the mid 90`s today and for the rest of the week including through the Telegraph Cruise ....
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Thanks for the replies My temps aren't so high that it's a problem. I would just like to see it run 180 or so on the highway. I may get an aluminum Dewitt's at Carlisle. Maybe Tom will run a show special.
My temps aren't so high that it's a problem. I would just like to see it run 180 or so on the highway. I may get an aluminum Dewitt's at Carlisle. Maybe Tom will run a show special.
Drifting
Joined: Oct 2005
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From: East London/SW Essex UK
My stock 427/390 ran at temperatures yours runs at - I flushed block out thoroughly - new water pump - water wetter - sealed rad surround - stock viscous fan and shroud - dropped license plate down to get more air through - used plastic billboard sheet cut to shape to make sure ALL air drawn through rad ONLY come in from the font intake - it then ran at 185/190 or so. Then came the 489/528 hp lump - time to invest in DeWitts radiator - now 180 degrees all day, even in heavy traffic 185 is maximum and will hold 90 mph continuously on a hot summer day 
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My stock 427/390 ran at temperatures yours runs at - I flushed block out thoroughly - new water pump - water wetter - sealed rad surround - stock viscous fan and shroud - dropped license plate down to get more air through - used plastic billboard sheet cut to shape to make sure ALL air drawn through rad ONLY come in from the font intake - it then ran at 185/190 or so. Then came the 489/528 hp lump - time to invest in DeWitts radiator - now 180 degrees all day, even in heavy traffic 185 is maximum and will hold 90 mph continuously on a hot summer day
Drifting
Joined: Oct 2005
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From: East London/SW Essex UK
Sounds like you went through alot of the things I have to get temps down. I have done the flush, the Water Wetter, vacuum advance/can is correct, timing, seals around the shroud, new clutch fan, etc, etc. I am determined to keep it stock. Looks like a Dewitt's for the big block. Both of my small block cars were running about 210 until I got the Dewitt's for them. They both run 180 all day long no matter how hot it is out. Just didn't want to buy a 3rd one
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Safety Car
Joined: Oct 1999
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From: NorCal
I'll chip in. 427/400 with A/C, 4speed. I run a DeWitt rad, no front plate, 3 inch chin spoiler, single electric fan with adjustable on/off controller, headlight covers in place, and a mega seal job around the radiator and support.
With A/C running on a max heat day (100 degrees plus), It's fine on the Hiway running 180 - 185, but it'll warm up in traffic or any other stop-and-go usage. I'm going to add the dual SPAL fans and that should do it.
The two (well, three) best things I did were: remove plate, add spoiler and the aluminum radiator. It all matters, but those were the most important, especially the spoiler. I made mine out of black conveyor belt. It has a nice satin finish and flexes nicely if it hits something, but it's stiff enough to resist the force of the airflow at speed.
With A/C running on a max heat day (100 degrees plus), It's fine on the Hiway running 180 - 185, but it'll warm up in traffic or any other stop-and-go usage. I'm going to add the dual SPAL fans and that should do it.
The two (well, three) best things I did were: remove plate, add spoiler and the aluminum radiator. It all matters, but those were the most important, especially the spoiler. I made mine out of black conveyor belt. It has a nice satin finish and flexes nicely if it hits something, but it's stiff enough to resist the force of the airflow at speed.
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From: Cape Cod, Mass.
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Thanks Wrencher
Any other big block guys out there?
Any other big block guys out there?
