the codes D6DE indicate that this block is a 250 , not a 200 like i was told ,correct?
All Small Six 200 head onto 170
- Thread starter Johns62
- Start date
This relates to all small sixes
Milling the head to the earlier specs will reduce the chamber volume and increase the effective compression ratio. In case you are not aware, the static compression ratio is the ratio between the maximum and minimum cylinder volume when the piston is at the bottom and top of its stroke. Milling the head reduces chamber (and therefore total cylinder) volume. Reducing the cylinder volume creates a higher compression ratio. Higher compression ratios are beneficial for engines - because the engine can extract more energy from the combustion process due to better thermal efficiency.
Taking it one step further - an engine has two compression ratios -- a static compression ratio and dynamic compression ratio. The static compression ratio is what you measure when you cc' the combustion chambers, calculate the gasket and deck height volumes, figure in dome or dish volume, valve reliefs, etc., therefore the static compression ratio is a fixed number. But valve timing (which is determined by the camshaft) must be taken into consideration, because the camshaft determines the points at which valves open and close (and the length of time they stay open), and that impacts actual cylinder pressure (cylinder pressure is generated during the compression cycle, after the intake valve has closed and before the exhaust opens). Within practical limits, an early intake closing and late exhaust opening will maintain the highest cylinder pressure. So, valve timing (including LSA) must be used to calculate the dynamic compression ratio, because the dynamic compression ratio is what your engine actually "sees".
Depending on how much the head is milled, the resulting increase in compression may (or may not) trigger the need to use higher octane fuel, again - depending on the dynamic compression ratio. This is true because (assuming the same cam is used) (1) a higher compression ratio will increase cylinder pressure and (2) lower octane fuel is more likely to auto-ignite (spontaneously combust) under higher cylinder pressure (than higher octane fuel).
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thanks, i have a photo of the water pump bolt holes ,thats what tipped me off. sorry i will have to get my son to help attach the photo
the t5 is in my ranchero with the 170, which is a runner. the 200/250? is the donor. which was a candidate to go in my 62 wagon or (maybe the ranchero ). are you suggesting the "250" could bolt up to the t5?
'the codes D6DE indicate that this block is a 250 , not a 200 like i was told ,correct?'
all 1976 or so 250's will have the starter BELOW the bottom of block and all 76 or so 200's will be ABOVE the bottom of block. 250's use V8 bellhouse/starter configuration. ALL 250's Water Pump will have 4 bolts and all 200's have 3.
.
170/200 starter location
.
250 starter location
'are you suggesting the "250" could bolt up to the t5?'
The 250 with the OEM - SBF manual 'Toploader' bellhouse will accept an adapter plate to 'bolt on' a T5. Bolting a 250 in an early 'Roundbody' like a 62 is a whole other involved thread ...
61 Comet 250/T5 Tri-Power
.
63 170/T5
.
74 Maverick/Comet 250/T5 Vortech V2 Supercharged.
( I never learned to drive an automatic )
have fun
all 1976 or so 250's will have the starter BELOW the bottom of block and all 76 or so 200's will be ABOVE the bottom of block. 250's use V8 bellhouse/starter configuration. ALL 250's Water Pump will have 4 bolts and all 200's have 3.
.
170/200 starter location
.
250 starter location
'are you suggesting the "250" could bolt up to the t5?'
The 250 with the OEM - SBF manual 'Toploader' bellhouse will accept an adapter plate to 'bolt on' a T5. Bolting a 250 in an early 'Roundbody' like a 62 is a whole other involved thread ...
61 Comet 250/T5 Tri-Power
.
63 170/T5
.
74 Maverick/Comet 250/T5 Vortech V2 Supercharged.
( I never learned to drive an automatic )
have fun
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thanks, i have a photo of the water pump bolt holes ,thats what tipped me off. sorry i will have to get my son to help attach the phot
OK I misunderstood when you stated you have a T5 on your Ranchero.
sorry about the size of the pics. i have decided to sell the block and head , ive listed it as a250 unless i am proved wrong and its a 200. i think for my abilities i am better off sticking with the 170 and just add a few extras and dress it up as best i can.
as stated U can do anything w/anything (they leave out "for any $"). Adaptors R pretty easy here but every town has several machine shops (we got an ol Bridgeport in the shop) as the industrial revolution started here (I guess is Y).
The pad for rd draft tube is right up frnt drivers side, an embossment that comes up the block to the deck (stops paralell to head bottom surface) and flattens out there as a "pad' (wish bubs were here, could explain it beddah) way up frnt on that side, almost to frnt corner).
Water pump bolts'n deck hight can B the real give aways if U cant 'read' the bell area as SBF shape. This is Y the 4.1 is called "the odd ball".
"...add a few extras and dress it up..."
like to hear what that is~
for me, powerband is the expert on that (efi, turbo and MORE !)
-All hail to bubba/Robert-
The pad for rd draft tube is right up frnt drivers side, an embossment that comes up the block to the deck (stops paralell to head bottom surface) and flattens out there as a "pad' (wish bubs were here, could explain it beddah) way up frnt on that side, almost to frnt corner).
Water pump bolts'n deck hight can B the real give aways if U cant 'read' the bell area as SBF shape. This is Y the 4.1 is called "the odd ball".
"...add a few extras and dress it up..."
like to hear what that is~
for me, powerband is the expert on that (efi, turbo and MORE !)
-All hail to bubba/Robert-
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