has any one ever had the crank offset ground on an a20? i know sb chevy guys do this utilizing smaller rod journals from other engine designs to get more stroke. does anyone know of a honda w/ smaller rod journals? is there enough material on our stock crank to do something like this? since the price of a custom forged stroker crank would be outragous i thought maybe we could make this work
Is there even enough room in the crankcase to put a stroker crank? How much additional stroke are you expecting?
Dr_Snooz
"I like to take hammers, and just break stuff, just break stuff." - Beavis
1989 Honda Accord LX-i Coupe, 240k miles, MT swap, rear disc swap
Shop manual downloads available here: CLICK TO VIEW
i don't know if theres room in th crank case. i have alot more researching and alot of math to do but i know the sb 350s can get an extra 41ci by having the cranks ground down to the 2'' 327 rod journal. obviously an a20 will never get that much(only 4 cyl and much smaller bores) but every little bit helps w/ a four banger when it comes to making power. when paired w/ an overbore maybe .1 liters. and all of this depends on if i can find something with a smaller rod journal. i've never been any deeper in an a20 than taking the head off for a head gasket so this is all hypothetical. does anyone have any specs on the stock a20 crank?Originally Posted by Dr_Snooz
Last edited by 1813mdw; 02-24-2011 at 07:11 PM. Reason: t
Anything's possible but with a smaller rod journal you'll have a mission finding rods that will fit. That and the stock ones are nice and light and can take some punishment before they bend and break. The crank really needs all the strength it can have so grinding them down is not really a safe bet, you could do it by using oversize bearings and you could gain a little bit but you'd have to make sure the pistons don't go over the gasket if they do you may need to machine the crown a little bit or bore match the chambers to the block to avoid any contact. This would help in raising CR ratio up as well as a small CC increase. This engine is easily capable of some big numbers just requires some calculations on tuning the exhaust manifold and inlet manifold, as well as the right cam specs the lift on our engines is very conservative and with a big valve conversion like mine ideally we need around 12-13mm lift. My current engine is around the 200bhp mark and thats with a stock spec A20 with 9.4:1 CR ratio pistons, stock cast manifold, rubbish crush bent system and downpipe 2.25" main size collector is only 2", cam is 285 with 10mm lift. So when i get shot of exhaust and get decent manifold and 2.5" system mandrel bent, A18 prelude head with CR ratio of 11.5:1 maybe 12:1 if i skim it again, and a camshaft with extra 1.5-2mm lift I should easily be able to see around 240-250bhp without it being undriveable and totally unreliable. Although at the moment i have so much piston to bore clearance with the cold weather sounds like a diesel! lol! Pulling nicely to 8k even with dodgy exhaust and 285 degree cam.
D series have slightly smaller rod journals, but as the authority on engine builds (read: rjudgey) said the gains would be small and not worth it.
Think it depends on a few things really, if you were really struggling to get a good CR ratio would be worth it to bring it up a bit, but you'd be weakening the crank so making constant high rpm passes might cause it to break after a while, if it was an out and out race engine that was only gonna be used for a season or half a season then worth getting done. Whats your realistic goals for power and how many miles a year you planning on doing?
I just remembered this. You CANNOT grind down these cranks. They are hardened and any grinding will wreck the hardened finish on the crank journal. The only thing you can do is polish the journals.
Dr_Snooz
"I like to take hammers, and just break stuff, just break stuff." - Beavis
1989 Honda Accord LX-i Coupe, 240k miles, MT swap, rear disc swap
Shop manual downloads available here: CLICK TO VIEW
?
From a machining standpoint, this is absurd. Grinding is the process to use when turning or milling won't cut it in hardened or extremely tough material. I've also heard that you "shouldn't" grind A20 cranks because the journals have a nitride coating, and obviously grinding removes this. For one, nitriding only increases surface hardness marginally, as well our shop sends shit out for nitriding daily, so getting the coating put back on isn't hard.
Anyways, why not have the journals built up with alloy rod then ground farther from centerline back to stock spec? They build up camshafts all the time, and they are garbage material. The only problem with increasing the stroke is the already dismal rod ratio gets even worse.
Last edited by Ichiban; 02-25-2011 at 11:52 AM.
ICHIBAN!
"Now, even more better!"
Yep everything he said ^ above^ in a nut shell it can be done.
I'd look at your piston speeds with the different stroke ratios Hondas can get some pretty crazy speeds just stock. there's formulas for all this some place just gotta look.
wp
1988 Lxi owner since August 1995
336k miles running strong!
Now running E85.
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Anyone have access to a B16 crank? I read somewhere a while back about a few guys using A20 cranks in their B16s and achieving some awesome numbers. They kept spinning bearings though.
this seems like alot better aproach, Ichiban. the eventual plan is to have the head machined for oversized valves and a p&p. then forged rods and pistons w/ a small turbo that will spool quickly. i'm all about torque, so the bumped displacment would def help. i would need to find a way to lower the comp ratio, though. custom rods might be a must. on a related note; i found a machine shop with a machinist who is familiar w/ a20s and reasonable with prices last week
I was thinking these engines were already over square to begin with, I wouldn't mess with the crank, these are some of the toughest cranks Honda ever made, anything you do to them is going to change that. They are also forged, I wouldn't mess with a forged crank. There are other ways to increase power other then adding displacement, in Honda circles there are pretty large displacement anyway.
I was repeating what my machine shop told me when I took my crank in. I assumed it was correct. Sorry.
Dr_Snooz
"I like to take hammers, and just break stuff, just break stuff." - Beavis
1989 Honda Accord LX-i Coupe, 240k miles, MT swap, rear disc swap
Shop manual downloads available here: CLICK TO VIEW
I'm surprised you never questioned that seeing the plethora of -.010 rod and main sets out there for the A20. I hate it when shops tell people things that are fundamentally absurd because they are too stupid/poorly trained/poorly tooled up to do the job.
Fuck sakes, Honda ground them round, why can't anyone else?
ICHIBAN!
"Now, even more better!"
Hello everybody I am new in this thread.
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Thanks and Regards
Very useful thread.
stroke x 2 x redline revs and divide by 60 = piston speed in mm per second.
divide that by 1000 to get meters per second.
have read in articles by respected engine building gurus that 25 meters per second is about the limit before engines start to fail after short amounts of time.
i dont even think F1 and moto gp and superbikes exceed this by much if at all.
apparently longer rods and pistons with a smaller gudgeon to crown measurement will reap gains similar if not better than a stroker crank.
uh oh. more research and math lol. thank you for the info, hauntd
the new formula engines exceed that, but they are built with extremely high tech and very expensive alloys, once you get to that point you start using rocket scientists to help in your engine designs, some of the new stuff they do is mind blowing,
true, but they only have to last maybe 1000 km and half the time dont do that
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