Too blockfill or not too blockfill

Imo Apita

Imo Apita

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Feb 28, 2009
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I'm a little sidetracked on my engine project due to funds but I went to see a local machine shop the other day.
030 to 060 over is the same price about $300 including hot tanking,freeze plugs and cam bearings, ready to assemble.
I was planning on going 030 over for a 383 stroker.
So I'm thinking why stop at 030?
David Vizard recommends half block fill for 060 in one of his books and claims the water temps will remain reasonable as most of the cooling takes place in the top of the block anyway.
Machine shop guy says no, the oil temps will get too high if you do even a half fill.
Opinions, recommendations pls.
 
Don't punch it to .060 if it's good at .030, no need to and thinner walls are not better walls. If you feel like it, fill to the freeze plugs w/ the deck level on the side you're filling (so that the block rock sets level/perpendicular to the bore) and have the block bored & honed after and poissiby align honed. The curing block rock will distort the case.

The oil temp won't get too high, that's BS. If anything it will allow you to run a slightly lower coolant temp without the oil temp suffing, being to low to boil out water. Just do it! If you are worried about the oil temp you can always run a thermostatically controlled oil cooler or heat exchanger sandwich adapter like on many GM cars.
 
For a street engine/daily driver type, I'd be concerned about wall thickness with a .060 overbore more than the heat. That's why I only went .030 on my BB. Hydrostatic testing showed the cylinder walls would be too thin for reliability on the street. That being said, if the cooling system is built for the engine, it should be able to dissapaite the additional heat of the .060 overbore and not sacrifice the oil temp right?
 
The oil temp is a result of the block fill, with that the coolant only cools the top part of the cylinder bore and the head, not the bottom part where the bulk of the oil is scraped off. In this way it has an effect on oil temp but it's not a bad effect at all, if you use it to your advantage.
 
Have you block sonic tested for cylinder wall thickness and from what I have seen there are not many blocks I would use at .060 and be dependable.

And its a good Idea to have your block torque plate honed using a good hone as those cylinders will really distort at .060
 
Thanks guys, the block is a '74 4 bolt.
Since there's no substitute for cubic inches and the price is the same I got thinking about the 060. The thin walls would be supported by the half block fill.
But I'm not looking for the oil temps to hit the roof.
I'm still thinking about the piston oil cooling jets, that in it self would heat up the oil a little more. Since this is still a no-budget build are 060 pistons that much more expensive then 030'ies?
The machine shop seems to be pretty busy with local racing motors he had a swamp racer in the shop when I went there :lol:
So what would be the vote:
030 and no block fill,
060 with block fill?
The target: a no-budget tire shredding torque motor
 
I know my way around an engine and this seems to be an area I do not understand. How much stress is there in the bottom of the cylinders? At bottom dead center the cylinder pressure greatly reduced because 30-40% of the endergy has been converted to mechanical push on the piston. Also the pressure is approaching atmospheric (depending on cam and exhaust opening etc). The real bang and energy use has already taken place at top dead center. If you could fill the top of the block that would make a difference in power. The cylinder wall deflects at the top when the peak cylinder pressure is reach and decreases as the piston travels down the cylinder. I saw graphic chart once that was a measure of cylinder deflection in the cooling jacket directly against the water side of the cylinder wall. Almost all the deflection was within 1/2" of the top (on the way up and on the way down).

Notice how hot rod blocks all tout a .6" thick deck etc? Not just to hold the heads flat but to keep the top of the bore round.

Why fill the bottom unless the block is not very strong at all? Educate me please.

My vote is .030 no fill with the information I have now.
 
I'd go 30 over no fill. This gives you some room to bore bigger later, thicker block has to be stronger and I think may run a bit cooler at +30 then at +60 to boot. We have drag raced with filled blocks for years. Still cracked cylinder walls above the grout line. We had a problem BB filled to just below the head bolts s.o.b still cracked on us. It was an alki motor so temperature was not an issue but I don't think it would have been runnable on gas as it would have been too hot to quick
 
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