Problem #0, OK, I'm a newbee... shade tree mechanic on a good day ...but I'm trying to do this right, so here goes.
Story: I'm helping a friend do a '77 FJ-40 rebuild and have got a 2F 214020 block and a 60032 head - which I'm guessing was a 2F open. (By the number 60031 = "open", but looks to me like what I think of as what a bathtub head would describe. Seems to have newer oil holes - like crossover, does either F or 2F.) It's a racetrack style combustion area, much smaller than piston top - with straight walls on the sides.
Rig got rolled and disassembled, but was supposed to be "in great shape", low mileage and all original motor. We pulled the pan and dropped a bearing to check... bad rod, check a main... what babbit? Not checking out per info given, so we pulled the head and found bad ring groove and eliptical cylinder walls, so we jerked the motor, had it punched 20, decked the block, shorted the rods and ponied up for new pistons. Rebuilt the cam with an RV grind.
Cyl head turned out to be toast (crack - had been overheated and was having water added - so that makes sense) but a really nice guy (Rodney) was nice enough to find us a used head for real reasonable - so we're back in business.
Head was milled apparently .020". Heading for swapping the valve guides to use unleaded. Know I'll have to watch the oil hole alignment...
Now the trick is to get it together right...
(Could be sooooo much fun if we could get it back together.)
So, back to being sure the piston does not have a very bad day -- pretty much everything by way of piston to head clearance geometry has changed so the old handy/dandy guess and grind seems risky...
Which gets us to the issue. Pistons stop just short of the deck, maybe .012" - .014" inch with light oil on the rod bearing (don't know if that was typical - seems reasonable). Gasket seems to be .050" uncompressed (but wrong gasket and I have to get another measure -- will adjust for difference). Fitting the domed (doomed?) piston to the head by hand, leaves about .060 - .070 (hard to measure without gauge blocks which I don't have).
Right now I figure I'd better remove at least .020" dead min from the edges of the head for about 1 inch of each cylinder - minimum.
Problem #1 is: During assembly the head freeplay on the bolts would about have to be able to move a little ways and if it did, smack... pistion and head could have a meeting of the minds, oh say just about TDC, and create a REAL bad day for the owner.
I could use a little paint but then I'd have to torque the head gasket multiple times (for each piston - i.e. until they clear) and, as I understand it, that's way not cool (for leaks). It's also way not cool for hot - it's not going to set in until it's hot... (right?) so the actual clearance measurement won't be right anyway.
Problem #2 is, I have no idea how much I need to remove to avoid detonation on regular petrol (probably back to 9.5:1? - however much that takes, i.e. depending on what it is now, 10.5:1?).
Fortunately, problem # 2 should makes lots and lots of space... meaning problem # 1 is NO PROBLEM unless the piston isn't centered??? Bad thought... (Where's Superman's calibrated xray vision when you need it?)
Checking the FAQ, all I've seen so far is bathtub head is no go on a 2F... So I'm asking first, and if this is a "can be fixed", and if so, then I'm planning on melting a (big )candle into a ("big") yogurt container, remove and inverte it then fill it with plaster of paris... then use the cast to check the actual clearance (i.e. from maybe three bolt holes).
Problem #3 is, I don't know how much the gasket will compress, head will slide, hot/cold cycles will change clearances, etc. and how much compression needs to be dropped. (10:1 would be 10% of cylinder volume - 9.5:1 would be the end volume difference more.)
What I'm thinking about doing is removing quite a bit - maybe .100" or so (to make the combustion chanber flow better) and then grind out for volume - to avoid 10:1. Sounds like a serious amount of grinding - per cylinder. Depending on what's under all that metal...
(Note: Oil hit $100 a barrel today and was predicted to hit $120/barrel. At 42 gal/barrel the $126/barrel is $3/gal without refining or tax. Plus refining, delivery, tax and gas station profit, we're probably talking $5 to $6/gal regular eventually. Seems like premium is an economic no go... Makes a BJ-70 look real nice!!!)
Anyway, moving from 10:1 to 9.5:1 would be 3.7 cc more space - wow. To 9:1 would be 7.8cc - that's huge. Wow, wow, wow - don't want to "drill" down to discover water or oil!!! Soft grinding 6x cyl's?
Other than melting wax and measuring the CC,'s how do I figure out where the compression is... (Not competition, no turbo, not a lead foot customer... though we are all boys at heart.)
Any suggestions from the vastly experienced set???
(Maybe this would be a good thread for the FAQ???)
Thanks!
Story: I'm helping a friend do a '77 FJ-40 rebuild and have got a 2F 214020 block and a 60032 head - which I'm guessing was a 2F open. (By the number 60031 = "open", but looks to me like what I think of as what a bathtub head would describe. Seems to have newer oil holes - like crossover, does either F or 2F.) It's a racetrack style combustion area, much smaller than piston top - with straight walls on the sides.
Rig got rolled and disassembled, but was supposed to be "in great shape", low mileage and all original motor. We pulled the pan and dropped a bearing to check... bad rod, check a main... what babbit? Not checking out per info given, so we pulled the head and found bad ring groove and eliptical cylinder walls, so we jerked the motor, had it punched 20, decked the block, shorted the rods and ponied up for new pistons. Rebuilt the cam with an RV grind.
Cyl head turned out to be toast (crack - had been overheated and was having water added - so that makes sense) but a really nice guy (Rodney) was nice enough to find us a used head for real reasonable - so we're back in business.
Head was milled apparently .020". Heading for swapping the valve guides to use unleaded. Know I'll have to watch the oil hole alignment...
Now the trick is to get it together right...
(Could be sooooo much fun if we could get it back together.)
So, back to being sure the piston does not have a very bad day -- pretty much everything by way of piston to head clearance geometry has changed so the old handy/dandy guess and grind seems risky...
Which gets us to the issue. Pistons stop just short of the deck, maybe .012" - .014" inch with light oil on the rod bearing (don't know if that was typical - seems reasonable). Gasket seems to be .050" uncompressed (but wrong gasket and I have to get another measure -- will adjust for difference). Fitting the domed (doomed?) piston to the head by hand, leaves about .060 - .070 (hard to measure without gauge blocks which I don't have).
Right now I figure I'd better remove at least .020" dead min from the edges of the head for about 1 inch of each cylinder - minimum.
Problem #1 is: During assembly the head freeplay on the bolts would about have to be able to move a little ways and if it did, smack... pistion and head could have a meeting of the minds, oh say just about TDC, and create a REAL bad day for the owner.
I could use a little paint but then I'd have to torque the head gasket multiple times (for each piston - i.e. until they clear) and, as I understand it, that's way not cool (for leaks). It's also way not cool for hot - it's not going to set in until it's hot... (right?) so the actual clearance measurement won't be right anyway.
Problem #2 is, I have no idea how much I need to remove to avoid detonation on regular petrol (probably back to 9.5:1? - however much that takes, i.e. depending on what it is now, 10.5:1?).
Fortunately, problem # 2 should makes lots and lots of space... meaning problem # 1 is NO PROBLEM unless the piston isn't centered??? Bad thought... (Where's Superman's calibrated xray vision when you need it?)
Checking the FAQ, all I've seen so far is bathtub head is no go on a 2F... So I'm asking first, and if this is a "can be fixed", and if so, then I'm planning on melting a (big )candle into a ("big") yogurt container, remove and inverte it then fill it with plaster of paris... then use the cast to check the actual clearance (i.e. from maybe three bolt holes).
Problem #3 is, I don't know how much the gasket will compress, head will slide, hot/cold cycles will change clearances, etc. and how much compression needs to be dropped. (10:1 would be 10% of cylinder volume - 9.5:1 would be the end volume difference more.)
What I'm thinking about doing is removing quite a bit - maybe .100" or so (to make the combustion chanber flow better) and then grind out for volume - to avoid 10:1. Sounds like a serious amount of grinding - per cylinder. Depending on what's under all that metal...
(Note: Oil hit $100 a barrel today and was predicted to hit $120/barrel. At 42 gal/barrel the $126/barrel is $3/gal without refining or tax. Plus refining, delivery, tax and gas station profit, we're probably talking $5 to $6/gal regular eventually. Seems like premium is an economic no go... Makes a BJ-70 look real nice!!!)
Anyway, moving from 10:1 to 9.5:1 would be 3.7 cc more space - wow. To 9:1 would be 7.8cc - that's huge. Wow, wow, wow - don't want to "drill" down to discover water or oil!!! Soft grinding 6x cyl's?
Other than melting wax and measuring the CC,'s how do I figure out where the compression is... (Not competition, no turbo, not a lead foot customer... though we are all boys at heart.)
Any suggestions from the vastly experienced set???
(Maybe this would be a good thread for the FAQ???)
Thanks!
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