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Old 12-06-2005, 02:06 PM
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ivanvel ivanvel is offline
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Question 429 thermostat and carb questions

Hey everybody i have a couple question as to what thermostat to use. I put a 195 degree thermostat on there now but some people around here told me that with a high compresion engine (about 11.0:1) it is better to run it cooler.. is this true? what are you guys thoughts on this?

As for the engine setup:

I have a 429 cobra jet bored .030 over, 11:1 compression forged aluminum flat top pistons, ARP rod bolts, comp extreme energy 274/286 - .562/.565, DOOE-R Cobra Jet heads w/3angle valve job, harland sharp roller rockers, Trick flow pushrods, comp cams double springs, full msd ignition and distributor, weiand stealth intake, and a holley 600 double pumper.

And for the carb quesion; I bought a holley carb from someone who told me it was a 750 double pumper, it runs great but seems to hold back at around 5300 rpms. So i looked at the casting numbers on the carb to see exactly which model it was and it turned out to be #4776 which is actually a 600 cfm! I bought a cheap holley 750 vaccum secondaries from the auto parts store and it reved up past 5300 to like 6200, but ran way worse all across the rpms. So i took it back. Any recomedations on carbs? I was looking at 750 Mighty demon mechanical secondaries or the holley #4779 750 double pumper... oh yeah the elevation here is around 5600 ft. Please help me with any ideas on this.

thanks, Ivan
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Old 12-09-2005, 12:16 PM
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C'mon somebody's gotta have something to say.....
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Old 12-09-2005, 01:02 PM
RTM RTM is offline
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The stat you have should be fine. The tolerances of the motor are design for a motor at that operating temp anyways.

As for the carb those heads could use some CFM. I would say the 750 needed rebuilt or tuned if it wasn't running right. If you have an auto I would run a vacuum carb and a DP with a manual set up. This could very depending on what the motor is in and used for.

If this cam 274/286 - .562/.565 is 224/236@.050 then I would say the cam should have been bigger with those heads. The SCJ/CJ heads have very large ports as you more than likely already know and they breath very well at higher rpm's and the cam to me just seems a bit on the small side for those heads. That's just my opinion and it may mean nothing.

What is the motor installed in and what is it used for? What is the max rpm of the cam?
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Old 12-09-2005, 02:35 PM
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The engine is installed in a 78 f-250 4x4, its got about 8 inches of lift, a manual transmission, 3.53 (or 3.51) gears, and for right now 35" mud terrains, i plan to put on 38" boggers in the spring... I use it just as a play truck, cruise it once in a while and take it to some mud bog events in the summer
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Old 12-09-2005, 03:19 PM
BBF250 BBF250 is offline
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Use a 180 degree

Use a 180 degree. It is the best compromise between decrease wear, efficiency, and parts longevity.
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Old 12-09-2005, 03:19 PM
 
 
 
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