maximum bore size

delray

Member
i know this might be a loaded question,
what would be a maximum bore size you could go with on a aluminum block and still have good wall thickness or i should say a good safe wall thickness before running into problems. for example : cooling,strength...etc...
having any you guys got into this area when trying to bore a cyclinder to it's max.
 
Most aluminum blocks have lined or coated cylinders. You have not stated what engine, your question is very vague and impossible to answer.
 
no really specified engine that i am talking about. i was assuming that most aluminum blocks where just solid cast aluminum and then bored to size. i didn't know there was a liner in them. unless you are talking about a iron sleeve for example?
some of the engines i am talking about would be a briggs animal,honda gx200,clones,briggs flathead,tecumseh flathead, those types of 4cycle engines.
sorry about the open question kart43. maybe this will help little........thanks
 
Most industrial engines will be slleeved, some of the cheap consumer engines are not. The Honda GX series are, Briggs animal are, some Briggs flatheads are not, Clones of the GX series are and their liners vary in thickness. Some will speak up that have more experience, some have bored and resleaved up to almost 3".
 
ok kart 43, so most of them are sleeve. so at that point a machine shop would have to determine a safe boring size to sleeve a engine ,if it uses one.
i was just wondering what a save bore size would be on all aluminum bore engines before it gets to thin of a wall? for example 1/8 inch...less?
also when you say coatings early. are you referring to plating the cylinder wall. another example : nikasil plating.
thanks.......
 
You could take a aluminum flathead out to .174 over.
How long it would last is something else.
Steel sleeve at .030 seems pretty thin.
 
Max Bore

Info from Dave at LA Sleeve, I talked to a year ago for my Skidoo/Rotax 2 Stroke Big Bore, you need a Minimum 2mm / 0.07873992" Cylinder Wall whether it's a Steel/Iron or Nikasiled. They make Aluminium Sleeves.

Figure out your Engine of Choice Head/Cylinder Bolt Pattern. Like my Skidoo/Rotax use's a (4) Bolt(8mm Studs) 100mm Bolt Circle. 8mm Studs/Bolts usually use a 9mm Hole for Clearance, 82mm is the Max I could use. But I have seen people use 82.5mm. Most Stock Skidoo Sleeves can be overbored 2mm.

Here is an Example of a 110mm (4) Bolt Pattern, and a Stock 72mm Bore. Center to Bolt Holes = 101mm -4mm = 97mm Max Bore!
 

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