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Discussion Starter · #1 ·
A friend of mine raised an interesting point today...

We were discussing the use of grout to give greater rigidity to cylinder walls that have been reduced in thickness by boring. He expressed the view that he wasn't sure it did anything.

I will add here, by the way, that we are talking about partial fills, not complete 'drag race only' complete block filling. This is for road race use, where a race might last 15 minutes and more.

Anyway, he said that he'd asked various 'experts' about it and put this question:

"Every block I ever saw split a bore split it from the top down. Why would you fill the bottom of the water jacket when it's the top that needs it?"

He claimed nobody ever had an answer for him.

His suggestion was that water jacket holes could be bored through the grout, but it does leave the question about whether the top of the bore... the hottest part... might lack sufficient cooling.

What do you guys think?
 

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I would not use building construction grout, concrete or cement, etc. While the real thing is expensive (compared to just using grout), it has iron in it to mimic the expansion/contraction of the block itself- something worth considering, because if the filler delaminates from the inside surfaces, all you then have is a heavy, OEM-strength block.

In cases where a lot of clearancing is needed at the pan rail (like if using a 4" stroke or a big stroke and aluminum rods), block filler can prevent coolant leakage from the water jackets.

The block should be agitated during the fill to prevent air pockets from being trapped. Rocking the block and wailing on it w/a big rubber mallet can help 'burp' it.

Another consideration if the block filler is being used to help with the rigidity of the block, is to tap as many holes for steel screw-in plugs as you can. This will mean all the welch plugs, possibly the center lifter valley oil drain-back holes and the unneeded deck holes.

HERE'S the maker of one type of block filler.
 

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block

Filling blocks are done for different reasons.

The filler does 2 things, strengthens the bores, and also helps stop the ring, or harmonics.

A partial fill may be done just to help absorb the harmonics. It’s been my finings that blocks split due to detonation not heat. So if you can rock the bottom of the block and help take the ring out it will add to the life of the engine.

I personally would never do a full fill on anything but a drag engine. If you have a road race engine that needs a full fill to fit the application then I think you need an aftermarket block to build from.

Keith
 

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Discussion Starter · #6 ·
Originally posted by cobalt327
I would not use building construction grout, concrete or cement, etc. While the real thing is expensive (compared to just using grout), it has iron in it to mimic the expansion/contraction of the block itself.....
Sorry, I used 'grout' as a generic term, I would never have dreamed of using anything other than the right stuff. Way too chancy and not getting the job done at all!

.....In cases where a lot of clearancing is needed at the pan rail (like if using a 4" stroke or a big stroke and aluminum rods), block filler can prevent coolant leakage from the water jackets.....
Not an issue with us. The rules in the class preclude stroking, but allow boring without resorting to sleeves (except in the case of a repair).

.....The block should be agitated during the fill to prevent air pockets from being trapped. Rocking the block and wailing on it with a big rubber mallet can help 'burp' it.

Another consideration if the block filler is being used to help with the rigidity of the block, is to tap as many holes for steel screw-in plugs as you can. This will mean all the welch plugs, possibly the center lifter valley oil drain-back holes and the unneeded deck holes.
Good information, thanks. But I don't think I correctly understand the bit about tapping holes. Do you mean screw in plugs instead of the regular welch plugs on the outside of the block? And certainly I don't know what you mean here about the valley drain back holes. These need plugging?

HERE'S the maker of one type of block filler.
Looked at their site, they do give what seems to be good information about it. They claim good heat dissipation, so perhaps it would be okay for use at the top of the cylinders too?

This is my question, as asked at the beginning of the thread. Would it be practical to use the grout (yeah... hardblok or similar) in that top inch or so of the block, providing waterways through it just as they are through the top of the block?

Here's another thing we're thinking about...



As we're working up to do a major development job on one of these engines, my nephew has sectioned a head across various lines to see what he can find and where he might well improve porting, how much he can mill away and that sort of stuff.

Now here we have another question. The water jacket in the head goes higher than the outlets, which are slightly higher than the inlet ports (painted in yellow, water areas are painted in blue). This pic has been turned to the correct 45º angle and the white line goes across approximately at the level of the top of the water outlet port.

So there is water above that level, which may (or may not, of course) mean that air (and steam) pockets can develop in that area with no prospect of dispersing.

Would it be a good idea to fill this area of the water jacket too?
 

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Discussion Starter · #7 ·
Originally posted by k-star
Filling blocks are done for different reasons.

The filler does two things, strengthens the bores, and also helps stop the ring, or harmonics.

A partial fill may be done just to help absorb the harmonics. It’s been my finings that blocks split due to detonation not heat. So if you can rock the bottom of the block and help take the ring out it will add to the life of the engine.

I personally would never do a full fill on anything but a drag engine. If you have a road race engine that needs a full fill to fit the application then I think you need an aftermarket block to build from.
Thanks Keith, again a tip (about detonation) that may not have been obvious to all...

We can't go to an aftermarket block. Again we have specific rules, the block and head castings must be as produced for that model car. We can then modify them by grinding, milling, boring etc, but they have to have started out as a regular factory item.

And I'll ask you too, as I asked cobalt, what do you think of filling the top inch or so with the water jackets allowed for?
 

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Ray Bell said:
Sorry, I used 'grout' as a generic term
Gotcha!

Do you mean screw in plugs instead of the regular welch plugs on the outside of the block? And certainly I don't know what you mean here about the valley drain back holes. These need plugging?
The welch plugs can be tapped and fitted w/solid plugs. Not necessarily a necessity, but is an option:




As for the valley oil drain holes, they, too, can be threaded and either stand-offs or plugs used. This might stiffen the lifter valley some, but the MAIN benefit is to keep oil from draining back onto the crank- reducing windage:



If you are still wanting to have water circulate, the block's deck can be stiffened by judicious use of plugs that will pass coolant where necessary. The passages are smaller and correctly placed, not the ragged holes that are as-cast.

I've not found an image showing this in detail just now, but the gist of it is the passages are rounded, then drilled/tapped and the plugs are then milled flat when the deck is surfaced. In cases where the block is going to be fully blueprinted, this can be done w/weld.

perhaps it would be okay for use at the top of the cylinders too?

This is my question, as asked at the beginning of the thread. Would it be practical to use the grout (yeah... hardblok or similar) in that top inch or so of the block, providing waterways through it just as they are through the top of the block?
As in, tip the block so that you can grout just the top inch or so? If that's the case, it should help- I think- but I've not heard of this. That does not mean it isn't used, though- just that I have no knowledge of it.

Otherwise, the ability for the coolant to do a decent job might be compromised somewhat- unless you were just wanting to make the cooling system be mainly effective in cooling the heads.

Even though the 'grout' is supposed to conduct heat, I'm thinking it could be lacking when it comes to actually conducting well enough to trust it to cool the engine effectively. It is an interesting idea, none the less.

...there is water above that level, which may (or may not, of course) mean that air (and steam) pockets can develop in that area with no prospect of dispersing.

Would it be a good idea to fill this area of the water jacket too?
I believe as long as there is good coolant flow and good pressure in the cooling system, that void will not affect the engine- instead, under operating conditions, it should fill with coolant. But I have no actual proof of this- in that case, you may well be on to something! ;)
 

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If you fill the top of the block around the cylinders, it will overheat. It would really be no different than filling the block completely, because the top of each cylinder is where all the heat is. All you can do for road race use is a partial fill of the lower water jackets to stabilize things. The top 1-1/2" of cylinder wall needs to have water around it.

Don't try to fill the top of the head either. The best plan here would be to tap holes there and run small(3/8-5/8") water lines to the main water outlet area on the block or intake, at the thermostat area.
 

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Discussion Starter · #11 ·
Okay, so it's bottoms of the cylinders only...

Now, about the top corner of the head, it's not an important cooling area, surely? So if it's not, why not fill it and eliminate the need for any bleeding?

I'm just looking for the answers, you see. I've had a bit to do with engines with bleed lines on them and they can lead to problems.
 
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