PDA

View Full Version : Holman and Moody manifolds



Trebor
09-04-2007, 10:02 AM
Holman and Moody manifolds

I have rebuilt a new motor after the first one blew up. Now the new one is blown as well. After a slow run and a at 3500rpm the motor ran well. As I took the throttle down the motor heated up instantly. Im running a 351 Windsor with all H&M manifolds and H&M water intake. The out drive is a Volvo pinta 250. Can any one let me know if they have seen these taps on the manifolds before? All marinas around me say they have never seen this.

I am wondering if this is the source of my heat problem. Water runs out the back of the boat. through the red hoses. and also comes out the exhaust.

BigGrizzly
09-04-2007, 10:46 AM
I have seen them and don't use them. They were to keep temps of the manifolds and engine warmer They are adjustable for over the side water They don't use this system much anymore. Let me guess you dropped the exhaust valve both times and the engine runs hot when trimmed in the third hole. Put a transom on it. Thoes manifolds crack inside and the gasket between the log and riser leaks and you ingest water! I chased my tail o this on on our 16, without engine blow ups, but the Corsican wasn't so lucky. Noe they are gone and life is good. The crack did them in finally on both boats.

Trebor
09-04-2007, 11:36 AM
Thanks BigG.

I have the valves "taps" in the off position. The manifolds are not cracked and have new gaskets on both sides. What do you mean by put a transom on it? My #4 piston keep burning up on me.

MOP
09-04-2007, 11:56 AM
I think Randy was speaking of a transom water pickup, curious what firing order are you using. Reason I ask is I seem to remember a similar issue due to the firing order, #4 two times in a row means something is whacked out.

Phil

MOP
09-04-2007, 12:10 PM
Added note riser taps are far from unique, in fact they are very prevalent on large marine diesels they are used to control back pressure. There have been a few discussions on other sites about where to dump excess water pressure, more then once the exhaust was brought up each and every time it was a big NO due to the added back pressure. I have seen with my own eyes an engine surveyor open closed taps and the tach rise 20-30 rpm at WOT on a big Hatt MY.

Phil

Trebor
09-04-2007, 12:14 PM
Firing order is correct. 1-3-7-2-6-5-4-8 Ford 351W. Also running MSD.

First time I nuked the engine! Second time not full throttle. Motor was new and just out to work it in. Engine got hot when I came down off the throttle. 4000rpm back to 3000rpm. Blew head gasket and milked the oil. Cant seem to keep it cooled. On land the motor runs like hell. But in the water seemed to feel like the first time I blew the motor???

Trebor
09-04-2007, 12:18 PM
Should I have these taps open or closed?

I dont see how these can heat the motor? They are after the water temp. and seem to flow as would the exhust flow.

Sweet little 16
09-04-2007, 02:09 PM
what is your source of water? the drive leg or a transom or hull pick up??? a true holman moody crank driven cross over???

Trebor
09-04-2007, 02:56 PM
Water comes from the bottom of the outdrive. Volvo 250. To a water pump on the front of the motor. Manual off the front of the crank. Then splits into two. and goes in the block. Comes up into a Performer intake manifold through a water temp. or small by pass hole. Into the H&M manifolds and out the exhaust or out the taps and red hoses if opened.

I do know that there is no leaks on the motor side. And does not seem to be on the outdrive side. When started on land we bypassed the outdrive and attached hose directly to the hose going through outdrive hull mount. Did not have good water attached to the bottom of the outdrive.

f_inscreenname
09-04-2007, 05:14 PM
I cant see much use for it unless you are trying to create less exhaust back pressure and even if you are I can only see picking up a couple HP at best from it.
I mean I could even see if the motor was getting to hot and they were trying to pump more water through it but I cant see the 250 outdrive being able to keep up with the demand and if the outdrive is just a "pick up" again I cant see it keeping up. My 351 never had a heating issue. For that matter if you put a 140* thermostat it would run at 140*. They are cooler motors by nature. There must be something wrong.
Post a picture of your cooling system if you can. I thought mine was right when I bought my boat but couldn't figure out why it kept blowing freeze plugs (sometimes) at WOT when I put a thermostat in it. Lucky or unlucky I blew one in front of a marina and while waiting for the wife to come pick me up I'm BS'ing in their shop and what is sitting there? My same motor but with one tiny extra hose.

As for #4........Hummm
I used to kill 302's on average, 2 a season for years. When I moved to a 351W and was never happier (until I wrecked the boat). So I am not sure why you are killing them. But #4 is in the back where water likes to go to from a bad manifold. Have you had them pressure tested? What about the water valves, have you left them open for a run (sorry if you couldn't before it blew)?

Sweet little 16
09-05-2007, 06:28 AM
the 351 w in our 16 runs about 180 in cool water and 185 in warm water and peaks in hot weather after a hard run at around 195 then drops right back to 180-185 and old timer said a warmer motor makes a little more HP the 16 has run this way for a LONG time

Trebor
09-05-2007, 07:41 AM
The water valves where open the time she first blew. and the second time. The marinas have never seen this on a boat. The taps where actually zip tied open when I got the boat and I've never taken them off until now. I cant see them being the problem, but I need to look at all my options now. Im a little tired of blown motors. New 351 was built sound. I think that it should have ran for ever as well, I was not beating on it. The temp was around 120* at 4000rpm she started to rise a little but no where near 195* as I came down off the throttle she jumped to 240* and that was the end of it. We ran her hard on land with out the outdrive and no problems.

Do you think my 250 outdrive is starving the motor? Anyone hear run this same set up? and have some comments? I will take pics of outdrive. Motor is pulled now.

As I run not to increase temp. I think the taps should be left in the open posion not closed. Can anyone tell me good way to pressure test manifolds?

DON N.
09-05-2007, 07:54 AM
The Manifolds Could Be Cracked On The Inside .

DON N.
09-05-2007, 08:04 AM
I Think One Of Those Didgal Heat Scan Guns Would Find Hot Spots In The Exhaust Manifolds If They Are Leaking Internally.

BigGrizzly
09-05-2007, 10:19 AM
I did mean a transom water pickup. Mine doesn't like the lower unit only at high speed. The water pump you have is a H&M with a hydraulic spider rubber cupling in the pump which rides on a steel (EEK) PLATE) it can rust like mine and corode where water just doesn't pump. I changed mine and put a brass plat on mine to repair it then I spaced it out and put the whole pump in place. also that pump will pump with only 0ne vane inplace at low speeds but will over heat up stairs.

Ted Guldemond
09-05-2007, 01:22 PM
I have a somewhat similar situation with the 351W in my GT-21. Runs 160-180 by electric gauge below 3000 rpm. Higher rpm and the temp will start to creep up. When I back down temp will go up slightly then slowly come back down. I've checked the crank driven pump, heat exchanger, sea strainer, connecting hoses,thermostat, manifolds and riser cooling passages! My best guess is as others have stated, probably marginal water flow through the volvo I/O. This year I added an oil cooler which helped significantly. Now temp doesn't creep up unless running near or at WOT. One other thought on chronic overheating. My older brother has a 1965 Ford Galaxie with a freshly rebuilt 390, new radiator, termostat, etc. Took it to the Woodward Dream cruise last summer and nothing but overheating problems. The old time Ford guys said that was typical for that car/engine combo. Turns out my brother replaced the stock ford carb with a nice new Barry Grant 4 barrel. He inadvertently failed to plug a small vacuum port at the carb base. Once plugged no more over heating. I assume the vacuum leak caused an excessive lean condition leading to the over heating?

mphatc
09-05-2007, 08:11 PM
Overheating and H&M manifolds . .
These aluminum manifolds may very well be semi corroded shut and the cooling system is not flowing adequetley . . . I had mine apart 3 years ago, and found the inards clear, but around the connection passages from the log to the risers they were restricted.

A crank driven water pump on the 351 should deliver water to a H&M steel crossover that feeds the block through the timing cover . . and the steel mounting plate by H&M . . then coolant exits through the Tstat and should split to each exhaust manifold.
Is this what you have?

I never experienced overheating in my 302 . .but more a lack of heat, as my water pick up is through the Bravo I to the stock pump with a silicone impeller. I suspect that this set up lewaves me with too much water flow , and pressure , forcing water thru the bypass . .

Ultimately my H&M logs failied in a big way with internal cracks that caused my engine to suck water in through the xhaust ports and tulip the glowing soft intake valves after a long full throttle run . .

IMO, get a new set of manifolds . . .

Mario

tiger lily
09-06-2007, 01:20 AM
mine are pluged , no hoses, im wondering originally if my boat had that setup, my boat as i am told originally was a h&m engine setup, is the water shallow, or real sea weeding where you run?? alot of times when i run through the smallest amount of sea weeds that are under the surface my boat will over heat, and it will keep climbing while i fall off plane, ive burried my temp gauge a time or two, it will start climbing slowly, by the time i fall off plane and get it in reverse, ill be at 220+ , wrap the throttle in reverse, and go wot open throttle back on plane and it will fall very quickly back to normal temp

Trebor
09-06-2007, 08:37 AM
BigG, my water pump is like that. I took it apart last night. I have the brass fitting already installed. Water pump is clean spider rubber is in great shape. She is defiantly pulling water from the outdrive.

We tested the water flow out the back, and found some bubbles and a small leak through the knuckle of the outdrive. This could be a source of air. Air sucks more than water. I have some pics to show what I mean. Water comes out of the "L" off the outdrive into the boat. Just under that first bracket its leaking small amounts of water.. Did I find the problem or is this just a new thing to fix?

Thanks for all your comments and helping me on this!

BigGrizzly
09-06-2007, 09:20 AM
You guys just reminded me of something. the water intake runs through the center steering shaft. My 250 leaked so bad that at high speed it sucked too much air so the transom pickup was a must. Also at certain boat attitudes the drive holes don't pick up enough water over 50 mph. I hated to get rid of the H&M but it was the best thing I did.

gcarter
09-06-2007, 09:46 AM
You know your not the only one with Volvo overheat problems. Here's an example; http://www.donzi.net/forums/showthread.php?t=50138

Trebor
09-06-2007, 10:55 AM
If I install a transom water pickup, Do I need to remove the motor mount pump? Or can I run two pumps? Is a transom water pickup electric or manual?

gcarter
09-06-2007, 04:22 PM
The ideal setup is; transom pickup, shut off valve, strainer, existing raw water pump. I think it is best to disconnect the water supply from the drive, remove the hose from the drive to the gimbal, and, finally, fabricate a plate to fit the two bolts on the inside to seal the inside water fixture.

f_inscreenname
09-06-2007, 09:44 PM
I am still using the same cooling system from my Mopar small block on my 454 Big block (Volvo drive). Sits at 160*. The only difference between mine and your cooling system is mine has a "through hull pick up".