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Offline tony sawyer

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sohc f2 head
« on: December 11, 2012, 11:51:26 AM »
hi any problems with the f2 head on f1 or k barrels ,i take it i have to use f2 pistons or higher comp than stock  any other issuse rgds tony
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Offline madmtnmotors

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Re: sohc f2 head
« Reply #1 on: December 11, 2012, 12:23:46 PM »
Here's one post: http://forums.sohc4.net/index.php?topic=369.msg42059#msg42059

and there are numerous threads devoted to this, still filtering through the search results.

http://forums.sohc4.net/index.php?topic=17622.0;nowap
http://forums.sohc4.net/index.php?topic=49659.msg547619#msg547619



 The later F2 heads require the ability to address the exposed studs that happen to serve as oil returns on the earlier heads and cylinders. You either need to combine the F2 head with F2 cylinders (and the FOUR additional o-rings at the base of the cylinders) or the F2 head can be sleeved (AND sealed) at these stud locations to eliminate their exposure to the atmosphere in order to use the F2 head with earlier cylinders. I just spent two months chasing the source of the four hot oil fountains at the head because the P.O. left out the four o-rings at the base of the cylinders on my recently aquired F2/F3 (78 CB750F)
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                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
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                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: sohc f2 head
« Reply #2 on: December 11, 2012, 12:26:35 PM »
Yeah, it's pretty much as cases-up swap BUT if can be done otherwise BUT it ain't worth the trouble to do otherwise
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Offline tony sawyer

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Re: sohc f2 head
« Reply #3 on: December 11, 2012, 12:55:11 PM »
hi have  another  option of f2 head and barrels 836 or f1 head and barrels 836 both pistons 10.25
wot cam any prefrences
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Offline Sam Green Racing

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Re: sohc f2 head
« Reply #4 on: December 11, 2012, 01:17:36 PM »
I take it it's for the side car :-\ if so, depends on where you're racing.
Megacycle 125-70/75 for IOM, gives more top end.
Megacycle 125-60/65 or Dynoman DP295 for short circuits, lots of low down and mid range grunt with 836 pistons.

Sam. :)
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Offline Howell

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Re: sohc f2 head
« Reply #5 on: December 11, 2012, 01:18:15 PM »
Difference K and F2:
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Offline bear

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Re: sohc f2 head
« Reply #6 on: December 11, 2012, 05:12:10 PM »
We have found that the F2 head is the best option for us.
We use comp. S/S valves from an EVO8.
35mm in. and 30mm exh.
Some machining is required but nothing a good head man can't handle.
The Mega 125-70/75 is the go with the head mods mentioned above, it has good lift and short duration.
We set the timing with 5deg. more advance than suggested on the timing card, this brings the curve down to a more usable rev range for the chairs.
PM if you would like more details.

Cheers,
Brian
« Last Edit: December 11, 2012, 05:15:20 PM by bear »
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: sohc f2 head
« Reply #7 on: December 11, 2012, 08:02:17 PM »
If you have the complete F2 top end I'd go with that. The larger valves will breathe better.

Howell, great compilation of info! What is the source for that?
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Offline cbr954

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Re: sohc f2 head
« Reply #8 on: December 11, 2012, 08:07:07 PM »
Cycle X has that sheet up on there website but I think that is from Action Fours???  I am not sure of that though.
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Offline dragracer

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Re: sohc f2 head
« Reply #9 on: December 12, 2012, 06:14:42 AM »
Stupid question, whats an EVO8?????


Quote from: bear on December 11, 2012, 05:12:10 PM
We have found that the F2 head is the best option for us.
We use comp. S/S valves from an EVO8.
35mm in. and 30mm exh.
Some machining is required but nothing a good head man can't handle.
The Mega 125-70/75 is the go with the head mods mentioned above, it has good lift and short duration.
We set the timing with 5deg. more advance than suggested on the timing card, this brings the curve down to a more usable rev range for the chairs.
PM if you would like more details.

Cheers,
Brian
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Offline Tintop

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Re: sohc f2 head
« Reply #10 on: December 12, 2012, 07:21:44 AM »
My quess would be a Mitsubishi EVO.
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Offline johno

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Re: sohc f2 head
« Reply #11 on: December 12, 2012, 11:48:32 AM »
 Mitsubishi  it is , I used the same valves on the hi port head.
johno
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Offline dragracer

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Re: sohc f2 head
« Reply #12 on: December 12, 2012, 08:10:19 PM »
Quote from: johno on December 12, 2012, 11:48:32 AM
Mitsubishi  it is , I used the same valves on the hi port head.
johno

Can i assume that the stem size on the EVO valve is the same as stock F2 stems???
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Offline dragracer

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Re: sohc f2 head
« Reply #13 on: December 12, 2012, 08:52:06 PM »
I researched a few sites and confirmed the stem diameter is close. I have not measured the length of the stock F2 valve yet. Hopefully its a lot shorter than the EVO valve so theres room for a new keeper groove.

http://www.racecomponentsinc.com/Evolution-Evo_VII_IX_Intake_and_Exhaust_valves_1mm.html
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Offline johno

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Re: sohc f2 head
« Reply #14 on: December 14, 2012, 04:43:12 AM »
captain dragracer  :D

I will be back home on Monday, I'll take some pics of them and specs to fit etc and send to you if your interested. Stems a touch bigger but For the larger bore brigade they allow you to run an average port diam of around 31.5mm with good air velocity up from 30.6mm with a 34mm valve.    Still why worry ! just put evan bigger valves in and run a sprocket as big as the wheel ;D ;D ;D
 Begs the question! whats the biggest inlet valve anyone has run or heard of being run ?  ( apart from captain Ken at Cycle x new beast) ;)
johno
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: sohc f2 head
« Reply #15 on: December 14, 2012, 03:46:53 PM »
Have we told anyone the secret intake size of the NEW CycleX head?!?!
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Offline cbr954

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Re: sohc f2 head
« Reply #16 on: December 14, 2012, 05:21:18 PM »
website says 38mm intake  32mm exhaust.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: sohc f2 head
« Reply #17 on: December 14, 2012, 05:44:00 PM »
And it's true. Does it say the intake runners are set up for 40mm carbs?
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Offline dragracer

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Re: sohc f2 head
« Reply #18 on: December 14, 2012, 06:10:57 PM »
Heck, i even got to touch it in person. I'm still dreaming about that head!!
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Offline dragracer

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Re: sohc f2 head
« Reply #19 on: December 14, 2012, 06:18:15 PM »
Quote from: johno on December 14, 2012, 04:43:12 AM
captain dragracer  :D

I will be back home on Monday, I'll take some pics of them and specs to fit etc and send to you if your interested. Stems a touch bigger but For the larger bore brigade they allow you to run an average port diam of around 31.5mm with good air velocity up from 30.6mm with a 34mm valve.    Still why worry ! just put evan bigger valves in and run a sprocket as big as the wheel ;D ;D ;D
 Begs the question! whats the biggest inlet valve anyone has run or heard of being run ?  ( apart from captain Ken at Cycle x new beast) ;)
johno

Sir Johno.

I would be most honored if you would kindly share the information on using the EVO valves in an "F" head. My email address is; NEXTPLAIN@aol.com. I cannot afford to buy or duplicate one of those CycleX heads but if there is a chance to do some affordable mods to mine like the use of the larger EVO stainless valves, I will surely pursue that option to the best of my financial ability. The only drawback is the need for stiffer springs to keep those heavier valves from bouncing off the seat and the impact to my current cam tower set up. But then, CycleX already has a fix for that one too. 
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Offline MRieck

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Re: sohc f2 head
« Reply #20 on: December 15, 2012, 05:26:52 AM »
Not to be a buzzkill but those valves are real heavy. I have had the stock size F2 valves made up with 5mm stems (with the stock tulip)....they are still heavy. One problem I found was valve to valve clearance with a real big cam with a lot of overlap. Another problem was getting enough spring with Kibblewhite 5mm guides. That was for an LSR engine but drag racing is the same. If anything I'd go to a 36mm intake (changing the seat) and shrink the exhaust valve (changing the seat again). The F2 port could handle the 36 intake. But where do you get new F2 carb manifolds???????? ;D ;D ;D
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Offline dragracer

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Re: sohc f2 head
« Reply #21 on: December 15, 2012, 07:35:22 AM »
Die grinder????
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Offline dragracer

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Re: sohc f2 head
« Reply #22 on: December 15, 2012, 07:43:28 AM »
Mike,

I felt that weight would be a big issue so the correct seat pressure is extremely important. Finding the right springs could be an issue.  Good point on the valve to valve problem.

Lots to think about and experiment with at this point. It could be time to invest in some equipment and find a few old heads to play with.
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Offline MRieck

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Re: sohc f2 head
« Reply #23 on: December 15, 2012, 08:56:55 AM »
Quote from: dragracer on December 15, 2012, 07:35:22 AM
Die grinder????
Yes....that would work Frank. ;D ;D
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Offline MRieck

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Re: sohc f2 head
« Reply #24 on: December 15, 2012, 10:09:31 AM »
Quote from: dragracer on December 15, 2012, 07:43:28 AM
Mike,

I felt that weight would be a big issue so the correct seat pressure is extremely important. Finding the right springs could be an issue.  Good point on the valve to valve problem.

Lots to think about and experiment with at this point. It could be time to invest in some equipment and find a few old heads to play with.
I agree THOUGH you could use Ti. ;) ;D
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