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350 Chevy overheats when started

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Nov 21, 2018, 8:10 AM

Post #1 of 4 (353 views)
350 Chevy overheats when started Sign In

Street Rod: 400in. chevy small block. Starting cold, engine temp climbs to 240ish, after short time drops back to normal running temp. Car has new radiator, thermostat. Any help on why?

Hammer Time
Ultimate Carjunky / Moderator
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Nov 21, 2018, 11:31 AM

Post #2 of 4 (346 views)
Re: 350 Chevy overheats when started Sign In

Was the thermostat replaced for this issue of was it before this happened?


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 21, 2018, 11:31 AM

Post #3 of 4 (344 views)
Re: 350 Chevy overheats when started Sign In

Custom set up so can do educated guesses only really: Make sure fan is strong and stays strong when needed apparently only first warmup? Odd? Maybe it's fooling you how full coolant is? Also thermostat could be slow then when warm behaves should be so easy try a real good one my favorite is going to be the marine type see if I can post a link or pic of one later. First name of them was "Robert Shaw" fits exactly almost can't stick. Works and fits exactly.
On that make sure this holds pressure and does use a pressure cap now. Your call Stant also sole thru Napa sells a 703-1444 7Lb one is good for boiling point of 233F antifreeze mix adds a few more degrees if that will do it's less stress on hoses but must never fluctuate when open or it's boiling toss it fast for 15. FYI you add to boiling point 3F / Lb. of pressure so you know and it needs to stay liquid.
Electric or clutch type fan and how set up IDK. You may have chosen something that just isn't fast enough to pull strong air thru?
Don't overdo the % of antifreeze? It's true it's lousy at transferring heat takes some "tweeking" to lower it to set to -20F even -10F is a pill to get exact but really helps heat exchange if engine is working hard and still always use antifreeze or that's your trouble soon or already.
So do some test feeling for temps from stone cold. T-stat housing and upper hose should stay cool/cold till t-stat opens then upper hose warms up. Feel outside of radiator for temp as you know it flows losing heat to cool on lower hose.

Whacko other usually a warm engine thing and high speed: Put a spring inside lower hose? Why - they came with them so lower hose, suction of water pump before pressure wouldn't suck it shut! If a bend too harsh it would also help. Stainless best not sold new that I know of was factory to re-use to next hose things.

Can use springs from a broken irrigation pop up sprinkler head stretch one out if you suspect that at all I'll make those still!
Touch, feel, observe and are locations of items such that anything isn't right for just your time you notice this alter to fix as you see fit,


Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 21, 2018, 11:58 AM

Post #4 of 4 (336 views)
Re: 350 Chevy overheats when started Sign In

See if a pic shows of type of thermostat I mean - a must for performance IMO...….

If not pic came from Amazon at this link here...……
>;spf=1542826137759 <
Again why. Higher flow and faster response. N/A for marine it chops debris like sea-weed, Tom

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