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preacherman

Bike spark plugs in ya engine

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What's the advantage of fitting bike spark plugs. You can buy adaptors to fit bike spark plugs into pintos,crossflows etc. Just wondered if anyone has done it and seen any benefit.

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Its for piston to plug clearance.

People running flat top or intrudor pistons sometimes have issues wih the earth electrode making contact if the plug screws-in and the electrode ends-up in the wrong position.

Bike plugs are smaller so electrode is smaller.

Its not for performance gains,

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Agree on the slight compression increase they create and also on them being used in higher compression engines with skimmed heads or pistons protruding to stop the electrode contacting the piston at TDC. 

DPR8EA-9 plugs with adapters will be around the £40 ish mark, but you will also have to factor in custom leads to fit, as your Pinto leads won't fit. 

If you are going to work out the compression ratios of your new engine build to suit your cam choice and you're also thinking of using bike plugs, then it might be worth getting your head CC'd with the adapters and plugs fitted so you get an accurate reading of your final build. 

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2 hours ago, dt36 said:

DPR8EA-9 plugs with adapters will be around the £40 ish mark, but you will also have to factor in custom leads to fit, as your Pinto leads won't fit. 

Why so? The ceramics of most plugs are pretty similar so the boots should fit ok and bike plugs can take the screw on contact nipples so that's covered as well. I had the reverse problem - wanted to fit bike COP's which don't use the big nipples and Zetec's only take one type of plug - taper thread and 'welded on' big nipples so had to change the COP's!

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5 hours ago, katana said:

Why so? 

I did a bit of research a while back as I was thinking of going down this route. 

From the reading I was doing it seemed that standard plug leads wouldn't fit. Maybe this is incorrect, but as I never followed up on buying these adapters and plugs, I never got to confirm this. 

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I’ve got smaller plugs and adaptors in 1 of my Pinto’s, got the plugs from Burtons, they look just like normal plugs with a thinner threaded bit.

the adaptors sit flush to the chamber walls, the plugs a little higher than standard plugs, top of plug where the lead sits is exactly the same as standard plugs.

i assume these plugs are just a different size of car plug.

bike plugs used to have a different lead fitting (screw or clip) which may be where the “leads won’t fit” statement but most are the same as cars now.

when I’m building an engine I do a chamber volume measurement using a pippet  but think the statement that fitting bike plugs and adaptors will increase compression enough to make 2 bhp is pure fantasy.

I also factor in 1cc for ring depth below piston top however you can change your compression value by using pie to more decimal places and then making excel display less decimal places in the final solution.

 

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1 hour ago, Snapper said:

i assume these plugs are just a different size of car plug. Why? Because you got them from Burton's?

bike plugs used to have (still do) a different lead fitting (screw or clip) which may be where the “leads won’t fit” statement but most are the same as cars now. Most certainly not!

when I’m building an engine I do a chamber volume measurement using a pipet  but think the statement that fitting bike plugs and adaptors will increase compression enough to make 2 bhp is pure fantasy. *

* - Have you done back to back dyno testing on the same day with an engine optimised for each plug type? If not, then your statement is incorrect in that you do not know that for a fact. My stated 2 hp gain was a potential possibility not fact, nor fantasy - if the CR increase made it knock, so having to reduce timing a degree, you could easily lose 2 or more hp!

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49 minutes ago, katana said:

* - Have you done back to back dyno testing on the same day with an engine optimised for each plug type? If not, then your statement is incorrect in that you do not know that for a fact. My stated 2 hp gain was a potential possibility not fact, nor fantasy - if the CR increase made it knock, so having to reduce timing a degree, you could easily lose 2 or more hp!

No have you?

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