My Hertz has a 302 currently in it and I have seen the small rubber hose on the engine block. This engine builder says that it is a worthless hose and if you block it with a penny, a 302 will run 10 degrees cooler. Any truth to this or is it voodoo magic?
https://www.youtube.com/shorts/iUhiB_fn2jM
I think you should try it. 🙂
Maybe try a nickle that should run even cooler
Small hose is called "coolant bypass hose" and it lets coolant flow through the engine when thermostat is closed , in all my years in automotive repair business I have never heard anything about blocking it to make engine run cooler but try it and let us know how you make out ???
Tall tale, I'd say he just does not want to be bothered with replacing/installing it.
Yeah, that's going to be a hard pass. Ford engineers back in the day were not stupid. I always like doing a deep dive to check the merits of any statement. Just like I did back in 2020. To block the passage sounds neither safe nor effective. I'll listen to opposing ideas but does not mean I will fall into the trap. Thanks for the info. Going to leave as is.
Hmmm. So blocking off the bypass hose is an improvement in their thought.
Meanwhile, if no coolant is moving, what is prevent "hotspots" inside the block and heads?
Yes, the purpose for the small "By-pass" hose is to provide a coolant passage during the period of the closed thermostat which blocks the pathway to the radiator and otherwise coolant motion as a whole. And the provision for "this" coolant circulation is important in order to achieve a proper "warm-up" process and to avoid localized heating differentials of the castings. :)
But unfortunately this execution, that of bypassing the closed thermostat at the intake manifold (the hot & high pressure side exit) and just routeing the coolant back into the water pump (cool & low pressure side inlet) is one of simplicity, and unfortunately remains unchecked (with the exception of just being a smaller passage) even after the thermostat does open, which itself is still intended to provide a sum of flow resistance for the purpose of providing a pressure increase (above the radiator cap value) within the engine proper, and therefore the by-pass "is" at this point actually defeating the intentioned efforts. :o
So, in racing applications where a thermostat is "not" going to be utilized (but there are other engineering aspects that must be considered), it "is" best to eliminate the bypass routing. But since for street driven applications I would consider it a mistake to not be utilizing a thermostat, the bypass "is" necessary; therefore the "penny" (or nickle) idea, though has merit (though poor execution ::) ) , this shouldn't be considered here. ;)
If you'll review the design effort in the 335 series engines, one will witness where Ford engineers acknowledged this previous executions' shortcomings, this where the thermostat is just proving the feature of open or closed (with certain sum of modulation), but now acts with a "shuttle-valve" feature providing greater directional control and efficiency, pertaining to this subject. :)
Scott.
Quote from: pbf777 on October 07, 2026, 01:36:37 PMIf you'll review the design effort in the 335 series engines, one will witness where Ford engineers acknowledged this previous executions' shortcomings
They didn't get it right on the 32 valve SVT engines either.
https://www.motortrend.com/how-to/1412-how-to-install-the-cobra-engineering-cylinder-head-cooling-mod
Quote from: 98SVT - was 06GT on October 07, 2026, 05:20:07 PMThey didn't get it right on the 32 valve SVT engines either.
https://www.motortrend.com/how-to/1412-how-to-install-the-cobra-engineering-cylinder-head-cooling-mod
It's too bad, that in the desperation to bring what might appear to be revelations, that the media prints/posts these quaint sort of stories, being presented as a matter of fact, which are garnered from a vendor looking to promote a product, but that may not have actually had any real testing with clinical conclusions vindicating it's actual worth! ::)
I'll first say that no coolant flow path in any internal combustion engine has proven to be ideal, and that this particular cylinder head does present a rather complicated coolant flow path so it wouldn't be unexpected to anticipate challenges. But, if we will perhaps refer to the considerations made by the manufacturer, with "real" engineers and actual product testing, though admittedly they don't "always" get it right, then we might in this aftermarket product environment ask ourselves: what might we be defeating with our bright idea? ???
Hint: This engine is still basically a "front-to-back & back-to-front" coolant path system and in this instance the engineering incorporated a "flow restriction" in the original plumbing configuration, the "story" says: it's "optional", so how much flow rerouting are we actually facilitating; and then this so as to "not" defeat the coolant flow intention across the cylinder heads ("back-to-front") as we plumb this short-cut from the back of the cylinder heads directly back to the water pump! And is this sum now not going to be passing through the heat exchanger (radiator) and since it's by-passing the thermostat restriction we're losing pressure, so aren't we actually "defeating" the cooling system in more ways than one? :-\
Then, as what actually has been "established" to be the biggest issue that initiated the more commonly encountered failures associated with cylinders #7 & 8, was that the P.C.V. system was of poor execution, in a number of ways, and resulted in excessive concentrations of oil carry-over (low octane!) into those two cylinders causing detonation (heat!). And just like the "ad" stated: the harder you ran it, the bigger the problem! :o
And then it would seem, Ford acknowledged this fact with the "AIR/OIL SEPARATOR KIT(s)" developed for specific models in production and then made available through Ford Performance as an aftermarket enhancement product. ;)
Remember, just because you saw it in a magazine, or more so these days, on the internet, doesn't make it true! ::)
Scott.
Quote from: pbf777 on October 07, 2026, 07:21:38 PMRemember, just because you saw it in a magazine, or more so these days, on the internet, doesn't make it true! ::)
If you are just putting around town you'll never have a problem. Lean on it for an hour or so at a track day and you may have some problems.
BTW: The Road Runner Boss 302 had similar problems. This one had sensors to detect the problem that the Terminator didn't have and put it into limp home mode before damage was done.
High Cylinder Head / Engine Temperature: Hard track driving can push cylinder head temperatures past 250°F or lower oil/coolant pressures, causing the Powertrain Control Module (PCM) to pull power or force limp mode to protect the Roadrunner V8.
Quote from: 98SVT - was 06GT on October 07, 2026, 08:32:30 PMQuote from: pbf777 on October 07, 2026, 07:21:38 PMRemember, just because you saw it in a magazine, or more so these days, on the internet, doesn't make it true! ::)
If you are just putting around town you'll never have a problem. Lean on it for an hour or so at a track day and you may have some problems.
BTW: The Road Runner Boss 302 had similar problems. This one had sensors to detect the problem that the Terminator didn't have and put it into limp home mode before damage was done.
High Cylinder Head / Engine Temperature: Hard track driving can push cylinder head temperatures past 250°F or lower oil/coolant pressures, causing the Powertrain Control Module (PCM) to pull power or force limp mode to protect the Roadrunner V8.
In the Tail of the Dragon with the Laguna Boss, the cylinder head temperature got up to 219-220 degrees. It was mostly third gear through the Tail and sometimes fourth. I kept an eye on the cylinder head temps. They seemed to go down some when I turned the heat on in the car.
Quote from: 98SVT - was 06GT on October 07, 2026, 08:32:30 PMIf you are just putting around town you'll never have a problem. Lean on it for an hour or so at a track day and you may have some problems.
No doubt! After all, if one is to be honest, these powertrains 'were' engineered for "putting around town", O.K., with "intermittent" spirited driving occasions sure. And I'd venture to say that most American "production" vehicles are probably reasonably capable of utilizing a range of 75-100% of their capability, for say . . . . 25-30% of the time, modulated intermittently, within each hour period of operation; after that . . . . So, if you do choose to "track" the car, know that you 'are' (if your any good! ::) ) probably going to be pushing the vehicle beyond it's intended environmental application and melees very well may materialize. :)
What was the famous line, . . . . "A man's got to know his [cars'] limitations" (Harry Callahan); but then isn't that what "track-prepping" a car is sorta about? ::)
Quote from: deathsled on October 07, 2026, 10:10:34 PMThey [cylinder head temps] seemed to go down some when I turned the heat on in the car.
Yes, as that sum of heated coolant that 'was' by-passing the engine radiator (heat-exchanger) is now utilizing the HVAC system's "heater-core" (heat-exchanger) with the fan on and ducting open, i.e. "air motion", before it's being injected back into the low-pressure, cool-side of the water pump. ;)
Kinda relevant to the initial posters' subject of inquiry, "by-passes" . . . . hmm? ::)
Scott.