Manifold Water Fittings/Thatch Mod

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I want to do the Thatch mod, and am thinking the hose fittings (1/2" & 5/8") on the manifold need to be reversed to keep the same water flow to the muffler.

Just not looking forward to removing fittings that have been fusing into the manifold for (possibly) decades.

Any input on experiences with this greatly appreciated.

Thanks much

[JOHN COOKSON]

I don't know what your set up is but when I did mine the brass parts came loose or unthreaded from the steel real easily. I just traded the two brass fittings around at either end of the manifold.
Steel to steel parts were totally fused forever.

TRUE GRIT

[sastanley]

go for it!

I like my thatch mod..it makes sense to me. I am running at least 5/8" hose everywhere on the motor now (you'll see the electric antifreeze pump to side plate is 3/4"..running from the 'wrong side' under the alternator..that size matches the pump fitting.) My fittings are cast where ever possible to get smooth bends and more flow..the square fittings to me seem to inhibit water flow as compared to the smoother cast fittings.

Also....make sure you have Permatex (Don Moyer likes #3, as do I) on hand to seal the threads. In a pinch, teflon tape will do, but I've all but eliminated it from the boat.

Usually a large adjustable wrench works well on removing plumbing fittings from the manifold/water pump/t-stat housing, etc. on the engine.



here is a 2nd pic from the other angle, showing the fittings better, maybe.

[hanleyclifford]

Just to be on the safe side have a 1/2" NPT tap ready with the 23/32" drill bit. The modification is important enough to risk the breakage. And like Shawn said go for the smooth plumbing fittings and step up to 5/8" hose wherever possible.

[sastanley]

To clarify Hanley's post...I have 'upgraded' my side plate to 1/2" NPT. It is a lot bigger than the stock side-plate fitting, which I think is 3/8" NPT, but I do not remember for sure.

I completely understand and agree with real engineers that the smallest hole in the loop is the constrictor, so I've tried to keep "upping" the sizes around the loop to maximize flow.

This post is a mix of raw & fresh water cooling discussion. I have a Johnson electric pump circulating the antifreeze. However, in another thread on this forum, this week, I made comments about changing out the Oberdorfer 202m3 with a Moyer 502 pump on the raw water side of my heat exchanger. Now, the engine is running 15-20°F cooler...still with 3/8"NPT fittings in the raw water side...the additional volume of water flow of the Moyer pump itself made a huge difference. - as evidenced by my raw water strainer that was about visually 60% full with the Oberdorfer, to totally flooded (100%+) with the Moyer pump...

If anyone was ever thinking about the Moyer 502 pump and wondering if it was worth the expense, it moves LOTS of water.

[hanleyclifford]

+1 on the MM 502. I have two; one is for a spare. I am completely out of the Oberdorfer business and I will ship what I have anywhere in the continental US upon receipt of $100. The MM 502, like the Oberdorfer uses 3/8" NPT ports; this is the constricting point in the system. However, the pump is of such strength and quality it can move coolant way faster than an A4 could ever need. The key as Shawn mentioned is to make the rest of the system smooth and "pump friendly". To achieve maximum flow and velocity I have gone to some fairly wild extremes because there are other considerations such as elimination of "dead" spots and uniform flow thru the water jacket. Dead spots allow crud to accumulate and ultimately lead to "hot spots" especially at the base of the sleeves.

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Disimilar metals = go for it

All good news, Gents! Thanks.
Will definitely be switching to cast fittings since reading some other threads regarding improved flow.

Current config is 5/8 thru-hull (rwc) to pump and at manifold outlet; 1/2 at pump to t-fitting to therm house to manifold inlet.

I don't have the bypass valve to give preferential flow to the block. Maybe keeping the 1/2" hose sections in the loop would help (?) or is that N/A with this mod?

Hanley, thanks for the tip on which tools to have at the ready, should the fix be needed.

This job just move up to the top of the list

[sastanley]

It looks like you have a cast fitting already at the bottom of the manifold, so there is one less to buy. The square machined fitting in the other end of the manifold is one you'd like to get away from.

I'll second a 1/2" NPT fitting in the side plate. I did that to mine as well, and since I am FWC, I totally eliminated the bypass, which I copied from someone else here..maybe Micah (msauntry), if I remember correctly.

If you'd like, I'll send you my Moyer bypass kit, since I am not using it anymore. - It won't be fire engine red though..you'll have to paint it to match.

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Thanks for the offer!

I'll take you up on that!

No prob on the color. The cap on the spray paint (ford red) looked a bit more traditional, brick reddish, than the product, but oh well. So she's not as fast as she looks.