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12G940 New Valves?

engine

Best Answer Moshtaraq , 09 March 2020 - 09:37 AM

The valves cleaned up real good by grinding and not much pitting. I'll get my machine shop to look at them and let them determine if I need inserts. I'm on a budget but want to make a healthy engine. Go to the full post


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#1 Moshtaraq

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Posted 08 March 2020 - 09:04 PM

Hi,

 

I'm currently building a 1275 i bought unseen (a bit stupid, I know). It has a 12G940 head with the following valve sizes:

inlet 35.6 single groove

exhaust 29.3 single groove

The seats need recutting because I can't grind them clean.

I was wondering If I need new valves as well if I get the seats recut? And if yes, can I use a size bigger than 29.3 on the exhaust? AHU1049 on Minispares looks kinda cheap compared to the C-AEG544 inlet valves I would go with, so I would like to have some race exhaust valves but they only come in bigger sizes.

 

some specs:

+60 bored (not my choice, was already +40 and it was a crap job)

I'm raising the CR to about 10.5:1

Evolution 1 cam

nural high compression pistons

CAM6232 crank

 

Thanks in advance!

Jens

 



#2 Earwax

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Posted 08 March 2020 - 11:18 PM

There is no real need to go bigger on the exhausts- except to clean them up.  Have a look at say Calver Special tuning cylinder heads ( 37 mm inlet x 29.5 mm exhaust) - even in race mode they flow plenty .  You may wish to get an unleaded insert. I like the CAEG544s as well.



#3 Moshtaraq

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Posted 09 March 2020 - 08:27 AM

Thanks Earwax,

My question was more about if I could get away with the C-AEG106 exhaust valves since they are 29.5 in stead of the 29.3's I have fitted. They're the only single groove ones I could find.

And more importantly if I need new valves with a valve seat recut?

 

Jens



#4 Turbo Phil

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Posted 09 March 2020 - 09:17 AM

Unless the valves are worn you don’t need to replace them just because you’re recutting the seats, though if the seats are badly worn you may find you’ll need to go up a valve size in order to be able to cut a decent fresh seat.
If the exhaust seats are bad it’s worth considering fitting hardened inserts for unleaded fuel.

Phil.

#5 Moshtaraq

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Posted 09 March 2020 - 09:37 AM   Best Answer

The valves cleaned up real good by grinding and not much pitting. I'll get my machine shop to look at them and let them determine if I need inserts. I'm on a budget but want to make a healthy engine.





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