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sssgtr
02-15-2003, 04:34 AM
I am about 85% complete in regards to the headwork i am doing on my KA24 SOHC head: welded in extra material into combustion chamber, matched ported intake side, polish exhaust ports, cleaned up general casting marks etc.
It is being sent off to the shop in 2 days to have the rest of the work done (3 angle valve job, new exhaust guides, 10 thou machined off gasket surface etc etc); my problem is, with the extra material welded into the combustion chamber, i don't want to remove too much material as i have set my sights on a CR of 9-9.2:1 as opposed to 8.6:1. From this photo, should i be worried about the bumps etc in where the extra material has been added? All the comb. chambers will be cc'd and evened out to within 0.5cc. Opinions, comments, criticisms?
http://board.performanceforums.com/gallery/data/500/534P1010043.jpg

inthewind
02-15-2003, 10:25 AM
my problem is, with the extra material welded into the combustion chamber, i don't want to remove too much material as i have set my sights on a CR of 9-9.2:1 as opposed to 8.6:1.


if you're only shooting for 9-9.2:1 compression, why didn't you just switch to flattop pistons? stock bore would give you 9.1:1 and a 0.02" overbore would give you 9.2:1. you're doing alot of work to gain a half a point in compression.



From this photo, should i be worried about the bumps etc in where the extra material has been added?


yes. leaving the material the way it is will affect how intake air and exhaust gases enter/exit the combustion chamber. i suggest taking it to someone who has some experience with cylinder head welding.

-demetrius

sssgtr
02-15-2003, 07:25 PM
I would have switched to flattops, but i'm not touching the bottom end at the moment (no cash to do so...)

As for the welding, a reputable cylinder head specialist welded in the additional material, and i'm cleaning it all up.
I must admit though after further work with different grit flap wheels, the chamber is MUCH smoother.
Let me also add after the additional grinding, all the chambers were cc'd again and matched exactly.

demcj: out of interest, have you had any such work done like this?

inthewind
02-15-2003, 07:36 PM
demcj: out of interest, have you had any such work done like this?


no. i had planned on using oversized flattop pistons and having the cylinder head welded to get 11:1 compression, but my 240 days are about over.

time to move on to other things.

-demetrius

sssgtr
02-15-2003, 07:43 PM
That's fair enough. I'm still a student (mech eng), so i've got a fairly tight budget. Would've considered an SR swap but haven't got the cash.

RedShred
02-15-2003, 09:15 PM
I dont know about reshaping the squeeze area if it is worth it, apart from removing casting junk... I had about 20,000 removed from the head and about 8,000 taken from the block from its last rebuild. I used forged alu dished pistons but they are .20 over. The machinist said I have about 9.5:1 or so. The Head has been port matched on intake side and polished on exhaust side with a 5 angle valve job. I had a Nissan HO cam installed as well.

As my injectors are leaking, I have no idea what impact octane ratings have right now....

Irie_eyes
02-16-2003, 04:45 AM
http://www.flex.com/~irieeyes/unshroud.jpg

That's what I see, only based on what I know.

sssgtr
02-16-2003, 08:32 PM
That's what i thought too. But if i remove too much, i have to even the rest out. Oh well, thems the breaks...

Q45tech
02-17-2003, 11:52 AM
What does static compression have to do with anything? Other than cranking!
It is the running [effective] compression that counts [a function of cams and filling and reversion coefficients].
Are you going to use tuliped stem valves? These can change the filling rate by 4-5% effectively changing the running CR by 4-5%. Just as an antiversion lip inside port can change thing by 3-4%.

ADAM HUTCHINSON
02-17-2003, 12:08 PM
i would work on your bowls..you can see that the lip between the bowl and the valve seat..this transition area must be smoothed out..that lip is not good...

IMO i would not have welded that area...who knows what that is going to do to the flame front since the sohc has an offset plug... i opted for flat top pistons....

adam

sssgtr
02-17-2003, 05:03 PM
I'm hoping (as it hasn't been done to my knowledge on a KA) that the extra material and the angle of the slope add to the quench area.
Adam: Everything has been blended accordingly after that photo was taken, several runs with different grit flapwheels (40,60,80,120) do wonders!

The head that is coming off the car will be cleaned up and left as is (except for the ports) IF this head is a dud in producing more power; when the bottom end is rebuilt i will use flattops and a std combustion chamber head.

ADAM HUTCHINSON
02-17-2003, 05:17 PM
get it flowed and tell me what you got.......i will then give you the stock flow rates...then you can see if it improved