What headwork to be done on a street NA/future turbo

[CJCSum41]

Hey guys I blew my head gasket just before winter and I'm going to have to have the mating surface machined, will probably have them take off a couple thousandths to ensure straighteness and to bump the compression up a little bit but I was wondering what other things should I have them do to the head while it's off? For the next year/ year and a half I'll be running it N/A with a turbo setup in the far future.

Btw I will not be putting cams in this because at $625 that's $625 better spent towards a turbo setup in the future. I also have a 93 head and cams as well which is better suited for turbo anyway.

[mrturrari]

I would just have them check it out and make sure everything is in good shape. It might be a good idea to change the valve seals while you are in there too though. They will have to disassemble and clean everything if any machining is done anyway.

If you want to do a little work yourself, and you feel comfortable doing it, just clean up any casting flash in the ports while it is disassembled and match them to the intake manifold (not the gasket). You could also round out the short side radius near the valve seat if you are very careful not to nick it. Anything else like oversized valves or more extensive porting isn't really worth the effort with the stock cams. You gain a little bit more top end but not enough to justify the cost.

[CJCSum41]

So nothing like a 3-angle valve job or anything? Would you recommend while I have it apart to re-shim everything?

[mrturrari]

It should already be 3-angle from the factory so if you don't have to redo the valves you should be good. You should check the clearances when you put it back together but if you don't do anything to the seats and keep each valve, spring and shim in the same place (label them when you take it apart) then you will probably find they will be in spec.

[Drew]

is there any kind of compression calculator for the 5s? not trying to thread jack but im looking for about 11:1 for a 93 octane tune. Headwork is something im getting better at, but without having seen any pics of the ports, combustion chambers and valve seats, what area aside from the cams would need the most attention on the head?

thanks guys

[CJCSum41]

mrturrari- I think you may have posted a while back the amount the head could be shaved and how much it would affect the compression do you still have those numbers?

[mrturrari]

Sure here it is...

I used this calculator at Calculating Cubic Inch Displacement & Compression Ratio

Roughly, assuming the compression really is 9.5:1 from the factory and I measured the area of the combustion chamber correctly, when you plug in all the numbers for a stock 5sfe (87mm bore) you get this:

Shave .5mm or 0.020' - 9.8:1
Shave 1mm or 0.040" - 10.15:1
Shave 1.5mm or 0.060" - 10.5:1
Shave 2mm or 0.080" - 10.9:1
Shave 2.5mm or 0.100 - 11.3:1
Shave 3mm or 0.120" - 11.8:1
Shave 3.5mm or 0.140" - 12.3:1

[Drew]

wow again, great information. is there alot of material to work with on the 5s head? and this is all considering the block isnt decked right?


Fantastic information. You are a great help sir

-Drew

[mrturrari]

Yeah there is quite a bit to work with but the more you take off the closer your valves get to your pistons. Probably after you shave 1-2mm off you then have an interference motor. No big deal unless your timing belt breaks. And yes those numbers are assuming you haven't decked the block. If you have you just have to take into account the amount that was shaved and change the deck height in the formula.

No problem.

[Drew]

well im sure i will have more questions down the road. I'll shoot you a Pm, i have some questions about your cams.


-drew


p.s. vote to sticky the link for the compression calculator