hmmm... destroked cast crank project for Doc?????
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| 1964 170 crank, in a 1973 198 motor https://slantsix.org/forum/viewtopic.php?t=60923 |
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| Author: | Yaz79 [ Thu Mar 23, 2017 5:33 pm ] |
| Post subject: | 1964 170 crank, in a 1973 198 motor |
I have a very nice crank out of a 64 slant six 170 motor. I want to put that in my 1973 slant six motor to make it a stroker. can I get away with doing this thanks for the help Dave |
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| Author: | Dart270 [ Thu Mar 23, 2017 6:37 pm ] |
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That would be a "reverse stroker". The 170 has a 3.125" stroke and the 198 has a 3.625" stroke. You could do it but you would have a 170 cu in engine and you would need much longer connecting rods. Best wishes, Lou |
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| Author: | SlantSixDan [ Thu Mar 23, 2017 8:03 pm ] |
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In mulling this over, I find myself curious what connecting rod length would be required. The RG (198/225) block is an inch taller than the LG (170) block, so if we just drop a 170 crank and rods into an RG block, the pistons are going to be an inch too far below the deck -- that is, an inch plus the regular amount of negative deck height. That'll be an engine with super-low compression ratio. If it'll start at all, it won't have any octane requirement; it'll run on paint thinner, but it won't make any power to speak of. So we'd need connecting rods an inch longer than the 170 rods to compensate for the taller block. The 170 rods are 5.7" long. An inch longer than that is 6.7". Which is how long the 225 rods are. So could we just use 225 rods on the 170 crank…? For that matter, what gets in the way of a long-rod 170 (RG block, 170 crank, 198 rods, high-pinbore pistons)? Somebody smack this mental math around, please; I didn't get enough sleep last night so my ideas here could be dumb. (Also keep in mind that if this would work, it is going to result in a heavier-than-normal 170 engine that will not go in front of a '68 or later automatic transmission without a custom torque converter) |
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| Author: | Dart270 [ Fri Mar 24, 2017 4:03 am ] |
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You would need 7.2" rods to get a stock piston to the stock 225 piston-deck ht (0.5" lower piston at TDC with 1" smaller stroke than 225 in a 225 block). 7.35" would be a better rod length to get you close to zero deck. To use a shorter piston, 7.5-7.7" rods would work well... Lou |
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| Author: | Greg Ondayko [ Fri Mar 24, 2017 8:57 am ] |
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I wonder if the added rod weight would equal the weight savings afforded by the crank? Are 170 cranks lighter than 225 / 198 cranks? Greg |
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| Author: | SlantSixDan [ Fri Mar 24, 2017 9:41 am ] |
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Quote: You would need 7.2" rods to get a stock piston to the stock 225 piston-deck ht (0.5" lower piston at TDC with 1" smaller stroke than 225 in a 225 block).
Uhhhhhh…oh yeah.
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| Author: | Dart270 [ Fri Mar 24, 2017 10:25 am ] |
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170 cranks I have are about 67-68 lbs. 225 forged crank around 76 lbs if not an early one. IIRC, the 170 block is 15-20 lbs less than a 225/198 block too. Lou |
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| Author: | Greg Ondayko [ Fri Mar 24, 2017 11:01 am ] |
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hmmm... destroked cast crank project for Doc?????
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| Author: | Yaz79 [ Fri Mar 24, 2017 2:27 pm ] |
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Thanks everyone appreciate it |
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| Author: | Yaz79 [ Fri Mar 24, 2017 3:20 pm ] |
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OK one more question. The difference between a 198 and the super six are the connecting rods? 7.005 for the 198, 6.7 for the 225. Top Dead Center is .300 before top of black or is the piston pin on the super six move down to offset the difference? So they are both at the top of the block ??? Thanks again Dave |
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| Author: | Charrlie_S [ Fri Mar 24, 2017 4:32 pm ] |
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Quote: The RG (198/225) block is an inch taller than the LG (170) block,
This is a common misconception, but not correct. Yes the 225 has a one inch longer stroke, than the 170, but the deck is actually more then an inch higher. Don't have the exact number handy, but somewhere about 1.5 to 1.625 taller. Just tried to measure them, but had eye surgery, yesterday, and can't read the numbers any closer.
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| Author: | SlantSixDan [ Fri Mar 24, 2017 5:09 pm ] |
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Memo to myself: don't post stuff with numbers and math on three hours sleep. 
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| Author: | DusterIdiot [ Fri Mar 24, 2017 5:12 pm ] |
| Post subject: | Not really... |
Quote: OK one more question. the difference between a 198 snd the super six are the connecting rods 7.005 for the 198. 6.7 for the 225. Top Dead Center is .300 before top of black or is the piston pin on the super six move down to offset the difference ? So they are both at the top of the block ???
198 and 225... use the same pistons.198 uses longer rods and a unique crank to acheive the same compression ratio as the 225...but with a bit less displacement the 225 uses a crank with longer throws and shorter rods.... You can install a 198 crank in any 225 up to 1976 that came with a forged crank... in 1976 they changed to a cast crank with narrower bearings... The super six is a 2 barrel package that appeared in the late 70's on the 225 (cast crank version)... it can be used on other slants with a bit of work... This is not to be confused with the late 60's Super 225 emblem that appears on unsilenced air cleaners, those are 1 barrel setups... In our article section there is a number of "must reads" on blocks, the super six, and stroking the slant six... http://www.slantsix.org/articles/articles.htm |
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| Author: | SlantSixDan [ Fri Mar 24, 2017 5:58 pm ] |
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Trivial point of clarification: The '63-'69 "Super 225" (Plymouth) and "Charger 225" (Dodge) decals went on silenced air cleaners. The unsilenced cleaner was only on '62 170 engines, and din't get no steenkin' decal. |
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| Author: | DusterIdiot [ Fri Mar 24, 2017 6:45 pm ] |
| Post subject: | My bad... |
LOL... Dan's got it... that's my mistake... somewhere I still have one of the super 225 cans in a tote... |
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