Topic: cylinder heads compatibility

[mad mike]

  Hi,  Advice please,   building a race motor ,   Based on a K6 ..... unsure which heads i can use?..... I'm sure this question has been asked before, but i can't find an answer in the search iv'e done  ..... I have two different cylinder heads,  a 410 and a 392 .... intend to fit to a K6 cylinder, .... the 392 was the original to the K6 cylinder,  [so no problem]   ..... will the   410 head also fit without causing the oil leaks associated with an F2 head , when fitted to a K series cylinder ...... Is the 410 head o/e for the F1 motor         Thanking in advance.     Mike

[Jerry Rxman Griffin aka MuthaF'er]

The 410 head is originally from the F2/F3. Bigger valves and resulting bigger chambers and higher domed pistons to maintain compression. It can be used on the K6 but it would require more mods that I can tell you about. Probably a complete F2/F3 top end is the "easy" way to proceed. It can be used on the K6 with some tricks. The 392 head first appeared on the 75 F0.

[mad mike]

Thanks  Jerry,  .... best regards.   Mike.

[PeWe]

I have 392 head too. My K6 was delivered with a 300 head.

392 had valves with same type of keepers as the F2. Valves have a slim groove.

My 392 head got new guides and K valves with the longer keeper grooves.
Even aftermarket Kibblewhite make the keeper grooves irritating long.

Why not at least 1.5mm shorter leaving more valve lift without the keeper groove entering the seal causing severe oil consumption??

The stock guides had to be sunken rather much for the keeper groove to stay away from the valve stem seal causing huge oil consumption.
Different than the 300 head.

Here not enough for 10mm lift cam despite guide sunken. Running lash 9.80mm measured.
Fix guides once again even lower made clearance for 10-11mm lift.

CycleX has guides adapted for higher lifts.
Hopefully OK as is with K valves in 392 head.

Below 392 head, sunken stock guide, Kibblewhite 33.5/28.5mm valves. Only 9.6 mm clearance. OK for modest  cams with 0.360" lift

Head is fixed now getting another 1.5mm IN clearance, EX another 1mm.
Seal has just enough room on guides. Springs shimmed too.


K2 head with stock F2 in valves (has lash caps for lenght and durability), K kibblewhite 28mm ex .
Note the clearance between seal and F2 in valve keeper groove.

#
Here with keeper, lots of space. I do not know if guides are sunken.  That head got TI retainers after photos were taken.
Sit on my K6 engine now.

[Old Scrambler]

Mike.........the only issue with matting a 410 head to a 300 or 392 cylinder is the need to install 'pipes' around some of the stud journals to prevent air/dirt/water/oil from entering or escaping the motor. Pics are on the Cycle-X site under the F2 section.

I use Ferrea valves with 5.5mm stems originally for a Prelude motor. Their guides have the same OD as CB750 and are a bit shorter, even more so on the exhaust.........so I use all exhaust guides and have approximately 5.5mm of space between the bottoms of the 410 keepers and the top of the seals when at full valve-lift. Recommended lash is 5-thou.

[Jerry Rxman Griffin aka MuthaF'er]

PeWe, your 392 head must have been from a K8. I believe the K7 also used the earlier F0/F1 and earlier K keepers. That's when they played with the keepers (and the stronger F2/F3 springs??)

[scottly]

Jerry, I also recall that the K8 used the F2/3 style keepers, while the k7 392 was the same as the F0/F1.
IIRC, the 410 head had a 28cc chamber, the 392 had a 24cc chamber, and the 300 had a 20cc chamber?

[Jerry Rxman Griffin aka MuthaF'er]

Agree with the keepers but I couldn't say about the size of the chambers

[PeWe]

My 392 head with 392 upside down.
Chambers all 23.6cc. Ex valve has rather deep dome so volume could be slightly less.
Kibblewhite 33.5/28.5mm.
Head not decked, only refurbished surface.

I do not know which valves this head had. Bought an ugly project head with bad guides but good outside.
The feeling with this head was that the stock guides had to be sunken more "than normal".

When fixing it, thoughts about the long keeper groove entered our heads, mine and the mechanic.
Drilled dents for MLS rivets, usually hammered flat but need space in head and maybe block too.

392 head before refurbished and ported, new stock guides, kibblewhite valves and springs, APE retainers.

[mad mike]

  Thank you gentlemen for all your advice on the heads.  Greatly appreciated.   

[Don R]

 If we ever get a comprehensive list of 300/341/392 and 410 heads, and the ways they can be swapped it should be added to tips and tricks or FAQ's. 
 This is a popular question, like the early/late transmission swap.