question for engine builders? hardblock
 

The guy building my shortblock is primarily a drag race engine builder, Flame away, but he has done some boat motors and has been more then willing to follow manufacturer directions on raw water cooled motor. He had to bore the block to 4.565 to clear the cylinders and I already ordered custom pistons. He said if it was a drag motor he would fill the block, has anyone tried this on a marine application? He did not suggest it, he just brought it up, but said he had no experience with it on a marine application. I know it would make the block heavier, but beside that are there any other problems. I run a crossover with no thermostat so I dont think heat would be an issue, actually it may help. Any thoughts or opinions would be helpful. Even thought about doing a partial fill to stablize what are boarder line cylinders walls.

I would not use it it will not cool very good but I guess it all depends how far he fills it.

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From what know, filling is done in certain parts of a DRAG engine to allow circulation to only go to certain areas so that the engine can generate heat faster so it doesn't need to warm up as long, it also lessens the burden on water circulation because drag motors normally run electric water pumps or underdriven pumps to save HP. The block isn't totally full, it just reduces the coolant holding capacity and block certain areas deemed less necessary.

NOT something I would EVER consider in any motor designed to last more than 10 seconds total between rebuilds!

Drag race engines take every HP shortcut known to man. If it makes more power, they'll do it. I once raced at Mission raceway in Canada with no power steering, alternator or water-pump belts, and I even plugged my brake booster vacum for one run... DUMB idea, you try stopping a 470hp El-Camino at the end of 1/4 mile on manual brakes!!! (rookie mistake).

As others have said... bad idea on marine apps. On drag motors back in the day, they primarily used the block fill to stabilize the cylinder walls due to extreme bore sizes. Nowadays, we have much thicker casting blocks and hard-fill is not used much at all anymore, especially in the mega HP motors.

They do not stategicaly fill certain parts of the block, They fill it from the bottom up on one side with the deck level, then when it dried fill the other side. It is not filled full, the top of the deck is where the heat is generated and that is where the water is left to circulate. He builds a lot of very competitive drag motors and says it is common place for him to fill blocks, even on new dart blocks. He said that they even do it on some dirt track motors and they stay cool just fine, a lot longer then 10 sec run. It is not done to decrease cooling capacity, it is done to add torsional rigidity to block and support the cylinders. I am not saying this is a good idea and neither is the builder, It just came up that if it was a drag motor that is what he would do, I just wanted to have some opinions from poeple that know out of sheer curiousity.

I way there the other day and he was working on a 565 for some girl running in the 7s with a door slammer, new dart block and fill. Like I said, I dont know much about it, I was intrigued because I have problems with the motor staying too cool because I dont run it that hard, and lack of thermostat.

I hear ya on the drag motors, although I am surprised to hear people still doing that especially to Dart blocks... but I've heard far more stranger things. LOL.

Keep in mind though, heat is also tranferred throughout the block which is why the water passages go that deep in the block.... to pull heat out. So I still say it's a no go for marine, but ultimately it's your choice.

I dont feel like being the guinea pig at this time, I was just curious what others thought, or if anyone had tried it.

:evilb: I don't blame ya on that!!! Too much work pulling these things out.

tx,

I just filled a 400 Chevy block this AM. It is a drag race application, but I do know of guys using filled blocks in circle track applications. You only fill the block up to the bottom of the water pump inlet holes so there is still plenty of circulation. Not sure how it would work in a Marine application though. Drag race engines are not an issue, they only run 8 seconds at a time :) Oil temps generally go up a little on the round track engines. I do know of guys running filled blocks on the street also without any issues.

I would have to sonic test the bores first to see how thick they are, then make the decision.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Yes I have.I have a mark 4 block which I had dropped a valve in and cracked a cylinder.I had a sleeve installed in that cylinder.It is bored .100" over(4.350) and I run a Lunati 4 1/4 " stroke crank for a total of 505 cu.in.'s. I filled the block about half way up with Moroso Block Hard as you described earlier one side at a time on a engine stand with the cylinders turned straight up and down.The machine shop recommended it to add stability to the block.These blocks are thin at the bottom of the cylinder between the cylinder and the camshaft area.I've been running this engine in my boat now for 8 years without a single problem.It runs at about 148-150 degrees with a 140 degree thermostat. I think before it might have run like 143-145 degrees.So it runs about 5 degrees hotter now which is not enough to cause any problems.

I think it's apples and oranges gentilmen. Drag racing engines and marine engines run nothing alike. Maybe a circle track car, MAYBE. I think you answered your own question when you said filling is for a tortional value increase. Drag cars flex when under a tremendous load thus pulling the block apart and twisting. I've seen the sidewalls pulled out where the engine mounts bolt up. Also they can get away with less coolant due to the shortened run times. I don't think that a marine engine is under the extreem side loads a drag car is and the run time are quite longer needing as much coolant flow as possible. My opinion is it's no good and doesn't compare or apply.

Thanks Jim, that is what I needed to know. I am using a gm block, and at the bore I am at it is pretty thin at the bottom of the cylinders. My builder was just not sure if it had been done on a marine application. He likes the Moroso product also.

I wouldn't recommend to do it if you have a good block.I only did it because it was a patched up block.However I guess I got lucky beings I haven't had any problems with it.

My block is fine, just at the large end of what is a acceptable bore for the block.

TX,
My only issue with the Moroso product was the fact that they wanted you to wait 14 days before doing any machining. I also did not feel that it mixed very well compared to the Hard Block brand. With the hard block, you can actually fill the block after machining if you want because it does not expand or "move" around as it sets up. Its been quite a while since I tried the Moroso, so the formulation may have changed but it used to move around quite a bit for a long while.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

You might want to go over on performanceboats.com and post the question. I have seen a number of the jet boaters comment on filled blocks. Perhaps they were drag race applications only, but they might be on lake applications.

I would not run a filled block in a reg boat app, not enough cooling in the lower portion of the block after running extended periods of time...fine in drag racing....both car and boat..as only run short times...Rob

Many marine engines are running around with a mud and sediment packed block. Pull the heads off a and look down in the block of a boat that has been run in river or muddy bottom lakes. There will always be a cerain amout of crud in there and depending upon the depth it could have a change in cooling.

Here is another example of why drag race guys have problems building marine enignes that live. If your builder does not specialize in marine engines it is best to go somewhere else. So many things are not the same such as cam grind, cooling, tolerances, valve train, fuel system to name a few.

He is just assembling the shortblock from parts that I picked or had from a previous engine built by a marine builder, so cam grinds and such are not a problem. As far as clearances go you can read on the box for raw water cooled engine. The fuel and cooling system are up to me, and thanks to this site should be fine. And from what I have read filling the block is not completely a terrible option. My builder did not recommended the fill, if you read all the post you will see that.