Topic: sohc f2 head

[tony sawyer]

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

[madmtnmotors]

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)

[Jerry Rxman Griffin aka MuthaF'er]

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

[tony sawyer]

hi have  another  option of f2 head and barrels 836 or f1 head and barrels 836 both pistons 10.25
wot cam any prefrences

[Sam Green Racing]

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.

[Howell]

Difference K and F2:

[bear]

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

[Jerry Rxman Griffin aka MuthaF'er]

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?

[cbr954]

Cycle X has that sheet up on there website but I think that is from Action Fours???  I am not sure of that though.

[dragracer]

Stupid question, whats an EVO8??

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

[Tintop]

My quess would be a Mitsubishi EVO.

[johno]

 Mitsubishi  it is , I used the same valves on the hi port head.
johno

[dragracer]

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???

[dragracer]

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

[johno]

captain dragracer 

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
 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

[Jerry Rxman Griffin aka MuthaF'er]

Have we told anyone the secret intake size of the NEW CycleX head?!?!

[cbr954]

website says 38mm intake  32mm exhaust.

[Jerry Rxman Griffin aka MuthaF'er]

And it's true. Does it say the intake runners are set up for 40mm carbs?

[dragracer]

Heck, i even got to touch it in person. I'm still dreaming about that head!!

[dragracer]

captain dragracer 

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
 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. 

[MRieck]

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??

[dragracer]

Die grinder?

[dragracer]

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.

[MRieck]

Die grinder?

Yes....that would work Frank.

[MRieck]

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.

[bear]

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??

Horses for courses I suppose Mike. I wouldn't know one end of a drag racing motor from another. The head combination we use, is cost effective, works well for us and they usually give a service life of around 80 to 100 hours.

This will really get you tearing your hair out mate.We use the cast guides with these valves as well.

Never had an issue with valve clearance we haven't been able to sort with the cams we have run.
As for valve train weight, your right it's not the lightest set up in the world, but I'm not a great believer in reving the tit's off these old motors anyway.

A quick overview of the setup used in our road race chair.

Inlet;  evo8 S/S valve +1mm @35mm keeper grove needs to be machined, stem shortend, I use 6.5mm x1mm  lash caps but you could stellite I suppose. Std seat.

exhaust;  evo8 S/S valve std @30mm after .5mm machined off dia. the rest same as inlet.

Megacycle 125-70/75 cam. We run an Ivan Tighe monster in our B motor but I wouldn't wish that on anybody.

I think the spring pressure with Mega cam is around 60lb closed, 100lb open but I need to check.

We haven't stripped any cam tower bolts with this setup and we don't use the braced valve cover.

[dragracer]

What brand springs are you using??

[bear]

What brand springs are you using??

Don't remember Frank.
I'm up at my sister's for Crissy at the moment.
I will ring one of the boy's at home and get them to check.

Cheers,
Brian

[johno]

On the head I run with mitsi valves I used the old yoshi S&W springs base and retainers, worked fine.
johno

[johno]

Bolt some of those new fangled flat slides to this.
johno

[johno]

 

[johno]

   This what the 35 mitsi valves are in.   Port diam 32 mm

Ive just got home and its 11pm so its nighty night for tonight , I'l take some pics of the valve set  tomorrow night
ciao johno

[Bill/BentON Racing]

Real nice!    what's being bolted on them manifolds? Flatslides?  Sweet

[MRieck]

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??

Horses for courses I suppose Mike. I wouldn't know one end of a drag racing motor from another. The head combination we use, is cost effective, works well for us and they usually give a service life of around 80 to 100 hours.

This will really get you tearing your hair out mate.We use the cast guides with these valves as well.

Never had an issue with valve clearance we haven't been able to sort with the cams we have run.
As for valve train weight, your right it's not the lightest set up in the world, but I'm not a great believer in reving the tit's off these old motors anyway.

A quick overview of the setup used in our road race chair.

Inlet;  evo8 S/S valve +1mm @35mm keeper grove needs to be machined, stem shortend, I use 6.5mm x1mm  lash caps but you could stellite I suppose. Std seat.

exhaust;  evo8 S/S valve std @30mm after .5mm machined off dia. the rest same as inlet.

Megacycle 125-70/75 cam. We run an Ivan Tighe monster in our B motor but I wouldn't wish that on anybody.

I think the spring pressure with Mega cam is around 60lb closed, 100lb open but I need to check.

We haven't stripped any cam tower bolts with this setup and we don't use the braced valve cover.

I have no problem with iron guides as they last longer than any bronze guide. I think the old RC guides were  steel. The guy that does my valve jobs won't put bronze guides in a Harley head. On the other hand the bronze guides pulls heat out of the valve better which isn't a bad thing when you are racing.
 The valve to valve issue was with the Harmon "Super F" cam and the stock size F valves.  It ended up working but another problem I had nothing to do with kinda screwed the pooch.

[bear]

"Screwed the pooch"? ???Not shore what that means but it doesn't sound to good.

Cheers,
Brian

[Bill/BentON Racing]

Bear,you're RIGHT! Not good,ask the pooch!! Meams it was F'd up by someone/something else! Bill

[johno]

Pic of the Mitsubishi valves, not EV8 valves but mitsy valves never the less, they love this size of valve and use it in both petrol and diesel  engines  You can see the valve collet groove is machined for the good K collets,
Had a couple of comprimises to use the prefered cam,
Length of valve is slightly shorter at 99.2mm long  ( compare to stock 34mm is 101mm and say manly 33.5mm is longer 102.5mm long).

Had to Machine the inlet head down to 34.6mm and exhaust 30.5mm to get it all together.

S&W springs were free length 40mm, installed height 29.5mm @ 110 lb and at 21.5mm @205lb
ciao johno

[bear]

A bit more spring pressure than us mate.

Cheers,
Brian