4A-GE engine mix - question

[Bean]

IMHO as you need to remove the hotspots from the smallport anyway (else it's wasted with cams like yours) try to push head cc up to reach your desired CR.

BTW stock bigport DCR is ~8.2;~8.7 respectively for 9.4;10 :1 pistons. Mind you though at stock power final combustion pressure is less than on a tuned motor.

[Uzelac]

If that smallport can't be used it will be used for head work practice :/.
But, will try to see if we can find 2+ cc, I prefer smallport over bigport although i never drove AE86 with a smallport, opinion created on-line .

Bluetop I would not use in stock form, of course. At least i have a backup

[NoHachi]

Like I said, take the head to the machine shop, have them regrind the valve seats with a 3-5 angle job, 1mm sunk. Deshroud them yourself (smooth the newly created step) and you are done. 2.5cc gained.

+ that the 3-angle job is just about the biggest easy flow gain you will find in a 4AGE head. So money well spent.

[Uzelac]

Uhhh
My mechanic who doesn't have experience with 4AGE but is a professional engine builder doesn't like the idea of sinking valves. Beside, in that case i would need to get whole new shims set.
My head starts to hurt

[Bean]

Uzelac Wrote:Beside, in that case i would need to get whole new shims set.

true but not so difficult to get... anyway IMHO let him clean out the hot spots and equalize all chambers and see where you at.

[Uzelac]

Bean Bandit Wrote:true but not so difficult to get... anyway IMHO let him clean out the hot spots and equalize all chambers and see where you at.

Can be if you don't know what you have .
This head came with different springs and under bucket conversion, and the prevoius owner doesn't know the brand/part number. Think it is TRD, not sure.

[Project D]

whatever the brand, if you can mesure the size of the shim it's all good

[Uzelac]

Hmm.. this is Serbia, i'm not sure where to find a guy who can do shims in this precision and quality.
They are ~13mm wide and 3mm ±0.5mm thick.
Would standard SS be ok or these are made from some titanium/@#$@#$ stuff ?

[NoHachi]

What does the 4AG use? 6mm valve stems? You could even use Chevy stuff.

The valve job is the expensive bit, but imho you would be crazy not to do it if you are doing a rebuild.

I'm not a machinist, but I always believed that sinking valves to a certain degree was the 'normal' way to equalize chambers. Just make sure to blend them back in. You even gain a little piston crown clearance.

If the shims are MORE expensive then the 3-angle valve job, then my brother is coming over to Serbia next time with a miata head in his handluggage
Do they do 3 angle jobs? How much would they charge for the valve job and a head skim?

Edit: to be clear.. you can use valve-stem shims to set lash, and just leave the current ones in place.

[Bean]

Uzelac Wrote:Hmm.. this is Serbia, i'm not sure where to find a guy who can do shims in this precision and quality.
They are ~13mm wide and 3mm ±0.5mm thick.
Would standard SS be ok or these are made from some titanium/@#$@#$ stuff ?

You could order them from abroad. Maybe someone with a TRD kit can measure his, then you would know if they are the same or not
Better to measure exactly though as ~ doesn't exist in engineering