The Tom Thatch Modification

[hanleyclifford]

This engineering idea has been rolling around in the brain for some time. Here is the change executed on my engine using a few items from the "possibles" bag. A more complete visual can be seen on my album.

[thatch]

Hanley,
I am flattered and humbled that you would tie this minor modification to me. I personally feel that the input from some seasoned pro's like you, N. Dutton, Dave Neptune, Latt 64 and many other contributors has done an imeasureable amount of good toward lengthening the life span of these unique engines. Shortly after buying an A4 powered sailboat a couple of years ago, and after doing some research, it became apparant that there was no suitable replacement engine (other than deisel) that would suit our needs nearly as well. I even went so far as to check things like "rod ratio" and "horsepower per cu.in." compared to other popular power plants, and soon realized why our little 30 H.P. gems were so prized. The patience and comradery displayed on this site is also a testament to the efforts by many toward the common goal of prolonging the legend of our "little beasties".
Thank's, Tom
P.S. Please forgive the ommision of mentioning the great photographic contributions by many and of course for the Moyer "family" for providing us with this gathering place.

[hanleyclifford]

For some of the original thinking on this idea go to the thread "another thought on coolant flow".

[lat 64]

I'm just a hack. My base is in car stuff. The product of a mis-spent youth.
I'm really a new A-4 owner (10-2008). I have only one to show for my experience, but they have to run on the same physics—fire, air and Jurasic hi-test.
Also it's kinda cold and dark up here so I post a lot. You see, I'm just too much of a loose canon to have a Facebook page. Now that'd be bad for everybody

Keep thinkin' outside the box all,
Russ

[thatch]

Russ,
I participate on one website, this one, because of the importance of the subject matter, (the A4) and because of the sincere, grass roots mentality of most of the participants. You're a perfect fit to the cause, so please don't underestimate your importance here.
Sincerely, Tom

[Baltimore Sailor]

I'm a bit confused. Could this mod be used on a raw water cooled engine as well? Or is it a design for FWC engines only?

[Dave Neptune]

Hanley, did you run and shoot with the I/R gun and notice any additional cooling at the "U" spot? Tom same inquiry to you also.
I have been wanting to turn mine around mostly because I check and clean out the manifold exit every year or two. It is just easier access at the front end.
I'd really like to know if anyone has played with a differant cam profile. I can't help but think (a personl weakness) that since so many of us are using the A-4's power at a much lower RPM range than it is rated for that a differant cam for the direct drives may have a bit of an advantage. Or perhaps has anyone tried to advance the existing cam a bit?

Dave Neptune

[hanleyclifford]

Originally Posted by Baltimore Sailor

I'm a bit confused. Could this mod be used on a raw water cooled engine as well? Or is it a design for FWC engines only?

I think Dave is still running raw water, and he is considering the modification.

[hanleyclifford]

Dave - I love the way you west coast guys think. I guess you could advance the cam one tooth and see what happens. Or we could get Iskendarien to cook up (a re-grind?) something for us. I still dream about rollers on the mains and rods but I may be getting senile! Regards, Hanley

[Dave Neptune]

Baltimore, yes my A-4 is raw water cooled and going on it's 41st year.

Tom, I don't know how many teeth are on the A-4s cam drive assembly, actually can't remember. Going a whole tooth would be a bunch. Is either gear mounted ar are they all fixed? Perhaps Isky could regrind a stock cam to a lesser duration and have it open about 2~3 degrees sooner.

Over the years Isky has made a few custom cams for me and they worked great. There is a lot of knowledge in their shop to draw on. I still like the idea of a roller cam on a flathead. I know a few who have redone their 32 roadsters and pulled the SSB Chevy's out and put back in the flatheads with roller cams. Yes they did sacrafice a bit of power compared with the SSB Chevy but they lost a lot of weight in the total drive line~~ie smaller trans and rear ends. They look awesome with the Strombergs and polished Copper heads.

Dave Neptune

[ILikeRust]

For those of us just tuning in and having not a clue what the hell you guys are on about - could you expand a bit as to what the mod is and why it's a good thing?

And while you're at it, type slowly and use small words for us slow types.

[Baltimore Sailor]

Let me see if I can explain it right, so that I'll know if I have a grip on the concept.

Rather than take the outlet from the thermostat to the forward (next to the thermostat) inlet on the manifold, you run the line down to the aft fitting, then run an outlet from the forward fitting to the injection point. The thinking behind this mod is that the vast majority of A4s tilt toward the aft, so that cooling water introduced at the forward inlet just runs "downhill" to the aft inlet. By introducing the coolant at the rear of the manifold it's forced to fill "uphill" before it can exit to the muffler.

Is that right?

[hanleyclifford]

Exactly right.

[hanleyclifford]

I made an hour long test run today with the TTM in place and discovered something unexpected. Even though I have been FWC for many years and recently did a thorough cleaning of the manifold including removal of both freeze/expansion plugs, I noticed a significant amount of crud in the strainer as soon as I started up. The strainer had been almost clear. FWIW.

[sastanley]

Tom , there was a Kaminsky modification a while back that I think is now standard practice on the reversing gears from Moyer...why not have a modification to the cooling system called the "Thatch cooling modification" if it proves effective!?!?!

I just pulled some of my cooling lines today (still RWC for the moment) and the aft manifold area was nasty and clogged...even if you stay RWC, having this 'flushing' forward and not resting and settling in the aft end of the manifold seems an improvement to me.

It is backyard innovators bucking the standards that keep these motors running.

(psst. Lat64, I am only at Lat 38 and I don't have a Facebook either..it is a social engineering scam!!!!)

[hanleyclifford]

Shawn - You make a good point here. The RWC group can get a big benefit from this modification. It's like back flushing and driving the chips and crud out the exhaust pipe.

[sastanley]

Hanley, I took my cooling lines apart (I may start a new thread over in the off topic area for fun) to do some 'spring cleaning' and painting of the engine compartment today, so I got to thinking...even if I don't actually get my FWC system installed this spring, I am still considering sending the outflow from the late model head t-stat housing into the back of the manifold and then the forward manifold port would now be the exit to the exhaust system injection point.

Regardless, I will be shifting to cast pieces wherever possible based on Tom's flow analysis of the improvement that said pieces provide. When I pulled my aft manifold fitting today I immediately said to myself, "why did I ever allow that restriction in the system??" - it is funny the continuing education one receives from this great site. - The threads in the aft manifold fitting are 1/2" NPT if I recall, but the silly fitting squished down so far on the hose barbs that it was probably 3/8" or less ID of water actually flowing thru the hose.. - I put it in a ziploc, labeled it and noted, "replace with better flowing fitting ASAP!"

[hanleyclifford]

The funny thing about those boxy brass fittings is that they do work if kept clean but in the real world that just does not happen.

[Baltimore Sailor]

Consider how the cooling lines now cross over the engine, perhaps we could call the mod "The Thatch Weave"?

/ducksandruns

[sastanley]

Hanley, in this case it was a straight thru barb, but the barb's ID was quite skinny (& clogged), despite the manifold hole being 1/2" NPT...the stuff in the manifold came out with a shop vac, but I am sure it was inhibiting water flow that far away from the pump..not much pressure there I figure.

Here is a pic of the fitting (clamps hanging on the fitting, before I put the hose on) - I am going to replace it with a cast 90 elbow I picked up at my local hardware store for about $5. I got parts for both ends of the manifold for less than $20..I still need to re-read thru Tom's thread to design the side plate improvements. My brain doesn't stay on one task very long, so I make lots of little trips to the hardware store and have lots of small orders from McMaster Carr.

I also noticed some sizeable chunks come off the manifold in the area between the cooling water fitting and the exhaust flange...I hope I can get the FWC assembled to stop the decay before it is too late..it is already an MMI replacement..I assume from lack of care the original failed long ago as well.

P.S.> Hanley, I've been meaning to ask you, what is the turnbuckle attached to in your picture and where does the other end go?!?!?

[hanleyclifford]

Originally Posted by Baltimore Sailor

Consider how the cooling lines now cross over the engine, perhaps we could call the mod "The Thatch Weave"?

/ducksandruns

If we can adapt this for maneuvers at sea we might get hired by the brass at the Pentagon. Who says people with A4 gas engines are backward?

[hanleyclifford]

Shawn - The turnbuckle is to adjust the hot section "headstay".

[sastanley]

Wow...great idea! I worry a little bit about the 10+ lbs of iron hanging off those two little bolts.

[Dave Neptune]

Hanley, I too wondered from the angle what the heck. The new angle certainly eleminate alot of head scratching.
Thanx for another bald spot.

Dave Neptune

[thatch]

All,
After my posts on saturday I disconnected my computer to do some home painting. I did not expect so many questions to crop up but will try to address the ones that have not been delt with.
Balti,
The concept of having the water enter at the lowest point of any accessory and exiting at the highest point should hold true for components of raw water or fresh water cooling systems. This concept just tries to eliminate as many air pockets as possible.
Dave N.
Recently there has been some photographic evidence showing bearing damage on the lower main bearing shell, toward the center of the A4's in question. I personally had misdiagnosed this condition as "acid erosion" but have come to believe that the problem was caused by crankshaft flexing caused by "lugging". Because of this, I have come to the conclusion that trying to add any more horsepower to the basic design would be unwise.... On the subject of the hot spot on our manifolds, since there is an un-waterjackted section on the manifold at the #1 exhaust valve, no change in the cooling systen should "cure" this condition.
Shawn and Lat64,
IMHO, real men don't need facebook.
Sincerely, Tom Thatcher (Thatch)