Convert Gen I SBC to Reverse Flow Cooling

[Indycars]

Wondering what was involved in converting a Gen I SBC to reverse
flow cooling. It certainly can't be as easy changing the water pump.
The thermostat would have to change, what else would change?
Does someone make a conversion kit ?

How much is to be gained.....for example maybe a full point in the
compression ratio before detonation, what else ???

 

[grumpyvette]

Chevy reversed the flow direction in the LT1-LT4 engines to direct the cooler coolant from the radiator into the heads first, before in flowed into the block in an effort to reduce cylinder head temps because high cylinder head temps tend to increase the potential for detonation with lower octane fuels, and most modern cars run at higher average temps and have restricted air flow rates thru the radiators,
keep in mind an LT1 or LT4 production engine made well under 400hp in factory form, needed to pass emission testing and was designed to operate for years mostly spinning well below 5000rpm the vortec head design took the basic LT1 intake port and used it in a standard flow head design, reverse flow was a band-aid cure for a problem that better heads and a larger cooling system can easily over come. the direction of coolant flow is not nearly as important as keeping a rather consistent and controlled low coolant temp, in the cylinder heads coolant passages, if you have an aftermarket high capacity multi core aluminum radiator, and a high flow water pump and several other mods that maintain consistent coolant temps the direction of coolant flow is not critical, what is critical is moving the coolant under pressure at a fairly fast rate of flow thru the heads so the coolant can absorb and transport heat out of the heads to be dispersed in the radiator to air flow.
if coolant is not moving rapidly thru the heads steam pockets can form reducing the coolants ability to extract heat.
Ive tested dozens of engine combos, and for awhile that deal of running extra coolant ports at the rear of the intake and several more between the center exhaust ports, and the result is that, If you have aluminum heads and you use thermal barrier coating on the combustion chamber and pistons,and if you have a fully functional high volume water pump and a radiator capable of dissipating much more engine heat from the coolant than the engine produces, rather rapidly and your using a surface tension destroying additive in the coolant like purple ice or water wetter and a fully functioning oil and transmission fluid cooler with auxiliary fans and with a t-stat that keeps the trans fluid at 180F and the oil at 215F-220F the potential gains of reversing the coolant flow are minimal at best.
the effort required simply is wasted in my opinion ,time and money best spent else-ware, if you've maximized the cooling capacity and maximized the heat transfer rates.
the object is to remove heat from the heads to reduce the potential for detonation, and to increase cylinder pressure, a correctly designed cooling system can do both.

some chevy race intakes have rear coolant ports to allow rapid coolant extraction from both ends of the cylinder heads

using a surface tension destroying additive in the coolant like purple ice or water wetter can significantly reduce or prevent this, which is one of the reasons the 400 chevy has extra steam holes in the heads and gaskets.
pumping cooler coolant that has a higher capacity to absorb heat also reduces cylinder head temps as does increased oil flow thru the valve train if your using an oil cooler that maintains consistently lower 215F oil temps

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[Indycars]

I was pretty sure it would not be as easy as it might sound on the surface, but
I wasn't sure just how complicated it would get. I'm kinda surprised no one makes
a kit for this purpose though.

The coolant passage exiting the intake manifold at the rear, would you run two
separate 3/4" lines back to the radiator directly ???

 

[grumpyvette]

http://www.streetrodstuff.com/Products/1749/

http://www.nookandtranny.com/Info_LT1.html

the twin rear manifold ports are usually run to a thermostat spacer like this, one above, routed so hot coolant leaves the heads at both ends of both heads and is directed back into the radiator with four barb 3/4" hose fittings (two in the rear of the intake manifold feeding hot coolant from the rear of the intake directly too the two barb fittings screwed into in the t-stat adapter spacer) and twin short sections of 3/4" heater hose

if you do research youll find that they redesigned the standard flow heads and now they can make 600-700 plus hp with a standard flow direction cylinder head on a sbc engine

http://www.brodix.com/media/media.php

http://www.trickflow.com/articles/18degree_hp/

http://www.airflowresearch.com/articles ... 5/A-P1.htm

 

[busterrm]

Hey grumpy,
What would it do if you ran the hoses and fitting on one of those manifolds to recirculate the coolant back to the radiator, would it cool better?

 

[grumpyvette]

Hey grumpy,
What would it do if you ran the hoses and fitting on one of those manifolds to recirculate the coolant back to the radiator, would it cool better?

IF your running the rear coolant port hoses to the radiator t-stat spacer, you ARE running it directly back to the radiator if those rear manifold coolant ports have fittings and hoses routed to the spacer under the t-stat, all water flows out or the t-stat spacer and upper radiator hose directly into the upper radiator

keep in mind the openings in the head gasket restrict coolant flow till all the area around the cylinder walls are full and only then does the coolant flow up into the heads coolant passages and back to the radiator, the holes are designed to restrict coolant flow so its more or less equalized as it moves up into the heads and back to the radiator, if the holes in the head gasket were not slightly restrictive the front cylinders would be much more effectively cooled as coolant would take the fastest and easiest route of least resistance, having a restrictive head gasket makes all coolant flow paths roughly equal in the crappy diagram below the blue shows the head gasket

some intakes don,t require the adapter as theres already 4 ports designed for the coolant re-routing modification , like the edelbrock #2925

AND you can,t go the other direction and use a standard GENI block on a GENII engine like the LT1 either,
the standard 350 gen I block is NOT directly interchangeable with the GEN II (LT! LT4) due to reverse coolant flow, a totally different water pump, coolant passages and ignition, and head ports for coolant, yes if you have a good deal of money and time you can get parts modified, but its far easier to stick to the original block,head design and original block and coolant routing

the lt1 heads will bolt on, too a standard sbc block, BUT the coolant passages are not an exact match, and theres no coolant ports in the LT1 heads too feed coolant too the intake manifold and radiator

http://h-body.org/people/projects/building_lt1/lt1 info.html

READ THE LINKS AND SUB LINKS

http://www.enginebuildermag.com/1999/09/rebuilding-the-chevrolet-lt1-engine-2/

http://garage.grumpysperformance.com/index.php?threads/lt1-cooling-info.2538/

http://garage.grumpysperformance.co...nvert-gen-i-sbc-to-reverse-flow-cooling.6099/

http://garage.grumpysperformance.co...-engine-parts-differences-useful-links.13141/

LT1 HEADS

theres no coolant flowing through the LT1/LT4 intake manifold, so you can,t bolt the standard SBC intake too the LT1 heads and get coolant flow back too the radiator, you can,t bolt an LT1 water pump too an earlier first gen SBC as the block and way the pump is driven is totally different, the LT1 water pump is driven bye a camshaft splined drive
on an LT1 coolant enters and exits the block through the water pump passages and the blocks not interchangeable with the more common first gen 1955-1991 SBC
http://www.chevyhardcore.com/news/r...s-changing-your-small-block-worth-the-effort/

LT1 water pump

Last edited: A moment ago

 

[busterrm]

So what your saying is that its not of any real purpose on a gen I small block chevy? What do you do with those ports, just plug them off? If you drill the 1/8 holes in the Tstat like I have read in some of your posts wouldn't the coolant just keep circulating?

 

[grumpyvette]

with todays much improved cylinder head designs I don,t see reverse flow cooling as any big advantage, even the racers have tried it and found the standard flow works fine in a well designed system.
yes the holes drilled in the t-stat flange does allow REDUCED coolant flow rates all the time but it also prevents several problems, and while it takes a minute longer for the engine to reach operating temps, it also tends to significantly reduce temp swings, I personally don,t see any down side unless your concerned with maximizing emission testing and limiting the testing to the first 5-7 minutes it takes an engine to reach full operational temps, simply because a standard t-stat is supposed to spend most of its time partly of fully open once an engines up to temp.

 

[busterrm]

Well, what I really meant was what would it do if you just used standard cooling and piped those ports at rear of a manifold to the spacer under the t stat, with the t stat drilled? Would it hurt or help any?

 

[grumpyvette]

I can,t imaging it would hurt cooling a bit, but I doubt it would provide a great deal of improvement on a basically stock engine run below 5000rpm most of the time either