FAQ  •  Register  •  Login

Alloy cylinder heads

Moderators: Curt!, Pa

<<

Galea

Posts: 41

Joined: Mon Aug 30, 2010 4:20 pm

Post Sat Feb 19, 2011 6:23 am

Alloy cylinder heads

I have 2 alloy cylinder heads for use on the 45 engine I am rebuilding. One of the head has a visibly deeper combustion chamber than the other. Is this normal or have I got two heads with different compression ratios? One head is marked with a 2 and F whilst the other has no such markings. Thanks, Joseph.
Head2.jpg
You do not have the required permissions to view the files attached to this post.
<<

helsingborg

Posts: 81

Joined: Tue Jan 29, 2008 8:08 pm

Post Sat Feb 19, 2011 9:14 pm

Re: Alloy cylinder heads

Maybe someone shaved one of them to fix a bad gasket surface; maybe the engine was put together with two different CR heads.
But...It doesn't matter if they were a matched set in the past or not. If they are visibly different (and I agree they are) you should correct this. First try to mesure how much water they can hold. If the difference is higher than 5% I think you should consider milling the bigger head so they can hold the same amount of liquid. Panic's 80 performance book has a very helpful table, but i'ts for BTSV, not the 45...maybe his 45 book has the same table...It will help you to determine how much to mill the heads. And try to find a good machinist, because those aluminum head fins will break easily in the wrong hands. Good luck!
<<

jib

Posts: 570

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Sun Feb 20, 2011 2:37 pm

Re: Alloy cylinder heads

used a burrette with parrafin to measure as it doesnt 'wet ' like water and less miniscus. and milling machine to do mine. used 3 engineers screw jacks and standard clamps to hold then level and secure to the bed
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
<<

Galea

Posts: 41

Joined: Mon Aug 30, 2010 4:20 pm

Post Thu Feb 24, 2011 9:39 am

Re: Alloy cylinder heads

Thanks for all your advice, scored another one through ebay. Seems ok in the photos, will measure the capacity when I receive it (will be some time though as its going to a friend in the US). Was not comfortable with milling the front one down as I don't think these were ever meant to be high-compression motors anyway!
<<

jib

Posts: 570

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Thu Feb 24, 2011 12:22 pm

Re: Alloy cylinder heads

running mine at about 6.5:1 , they made 6:1 harley ones and you can buy aftermarket 6:1 as well
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
<<

Galea

Posts: 41

Joined: Mon Aug 30, 2010 4:20 pm

Post Thu Feb 24, 2011 2:49 pm

Re: Alloy cylinder heads

Hello Jib, any idea what the heads marked 2 are in terms of compression ratio ... unless they have been milled down of course? Regards, Joseph.
<<

jib

Posts: 570

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Thu Feb 24, 2011 5:38 pm

Re: Alloy cylinder heads

joseph, show us a picture, dont think ive seen one with a 2 on it .
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
<<

Galea

Posts: 41

Joined: Mon Aug 30, 2010 4:20 pm

Post Fri Feb 25, 2011 12:39 am

Re: Alloy cylinder heads

From what I've read, the alloy heads were marked either 5 or 6. The 2 I'm referring to is visible on the top part of the second photograph I already posted showing the underside of the front head which I have. On the rear head I've just found on ebay, the seller's photos also show a 2 on the underside but only now I'm also noticing a 5 on the side which I think refers to the compression ratio.
You do not have the required permissions to view the files attached to this post.
<<

jib

Posts: 570

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Fri Feb 25, 2011 11:39 am

Re: Alloy cylinder heads

the 2 looks like a mold marker.
the 5 is a compression marker.

you will have to measure and probably adjust the combustion chamber volumes if using mismatched heads.
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
<<

Galea

Posts: 41

Joined: Mon Aug 30, 2010 4:20 pm

Post Fri Feb 25, 2011 2:29 pm

Re: Alloy cylinder heads

Thanks for the advice Jib, that's what I intend to do. Regards, Joseph.

Return to 45 Flatties

Who is online

Users browsing this forum: Bing [Bot] and 12 guests

Powered by phpBB © 2000, 2002, 2005, 2007, 2012 phpBB Group.