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wc piston question

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Topic: wc piston question

Posted By: nborga87
Subject: wc piston question
Date Posted: 27 Jan 2015 at 2:16am

im sure this has been discussed on here before. i did a little searching but could nt quite find an answer to my question. If you use wc or wd pistons with a wd 45 crank, what kinda compression would that give you? what would the difference in compression be between flat tops and the dished pistons? has anyone done this type of setup with success if so which pistons did you use and what to you end up with for compression? thanks, nick

Replies:

Posted By: Zaddison
Date Posted: 27 Jan 2015 at 5:34am

Aftermarket 4.125 flat top pistons and a 45 crank came out to be right at 9:1 on my last motor build. Not sure on stock flat tops cause they are a hair shorter at least mine where. As far as dished pistons that's tuff because there's so many different ones out there 45,d17,170,175 and that's not even listing the aftermarket ones like m&w. so with a dished piston u could be any where from around 4:1 all the way to around 11:1. I would of rather ran dished pistons I think u have a little better combustion chamer with them but I couldn't find any m&w and most new after market dished are alittle over 6:1, which would be closer to a d17 motor. So I went with the overbore flat tops and had good luck. For the money u can't beat a 240 cubic inch motor.

Posted By: Charlie175
Date Posted: 27 Jan 2015 at 10:37am

my PSI went from 145 with stock D17 power crators to 210 with flat tops (4.125).

D17 motor.

Research as not all are made the same. I used Tisco HiComp

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Charlie

'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD

Posted By: Dipstick In
Date Posted: 28 Jan 2015 at 1:37am

Is 9:1 to high for regular gas?????????

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You don't really have to be smart if you know who is!

Posted By: DrAllis
Date Posted: 28 Jan 2015 at 6:58am

Try and use 89 octane(or better) if you can find it. Set your ignition timing to 25 degrees BTDC @ wide open throttle. If you have to run lesser octane, your timing may need to be 20 degrees BTDC to avoiding pinging.

Posted By: mattb
Date Posted: 28 Jan 2015 at 9:22am

mine likes e85 mixed in with pump gas

Posted By: DrAllis
Date Posted: 28 Jan 2015 at 10:28am

Too much octane rating for the compression gains you nothing. 89 is enough for 9 to 1 compression. 106 octane on 9 to 1 will probably yield less HP.

Posted By: nborga87
Date Posted: 29 Jan 2015 at 2:13am

ok cool that answers my question. now for another question i hear a lot of people talk about degreeing the stock cam. what are they degreeing it to? and will this help with low end torque?

Posted By: nborga87
Date Posted: 29 Jan 2015 at 3:11am

also do you have any idea which dished piston could give you 11:1?

Posted By: Zaddison
Date Posted: 29 Jan 2015 at 7:47am

Most people want u to degree it to 104 atdc. Yes it sould raise your compression alittle which should give you more tourqe. I think u can get 11:1 with m&w for a wc not some cheap knock off but uyou will hav to mill a little of them and they are hard to find.

Posted By: DrAllis
Date Posted: 29 Jan 2015 at 8:50am

M&W pistons for a WC-WD are numbered SP-46. If you use them with a WD-45 crankshaft, you'll need to remove about .150" to 170" off the tops, so they don't hit the cylinder head. I had an engine like this 30 years ago and when running a compression test it had 240 to 250 psi with a 175 camshaft timed to stock degrees. Absolutely had to use 100 plus octane fuel and set ignition timing at 18-20 degrees BTDC wide open throttle.

Posted By: mattb
Date Posted: 29 Jan 2015 at 9:04am

e85 makes more power its been proven several times I don't mix it straight

Posted By: mattb
Date Posted: 29 Jan 2015 at 9:10am

i cut .125 off the set i did it will start with stock starter but you have to have a pretty hot starter

Posted By: mattb
Date Posted: 29 Jan 2015 at 9:11am

i mean battery lol

Posted By: nborga87
Date Posted: 30 Jan 2015 at 2:41am

thanks for the replies guys