HG bore size and cc?

[tig321]

I took some measurements of my bottom end this weekend. My 83.44mm (3.285in) ross pistons are poking out of the block 0.2032mm (.008in), will the 0.56mm (0.022in) clearance of a 84mm bore HG be fine? As long as its smaller it should be fine right. Also the combustion chamber cc'd out to 39.5cc (stock is 40cc) How much do you think the machine shop took off? Do I really need to know this anyway? Volume is the important thing to know right?
Thanks in advance

Are Titan headgaskets only available in 86mm bore? I cannot find it listed anywhere online.

 

[suprarich]

If I recall and with out looking in my note book, the stock head is 116mm or 4.566". If the machine shop does not know how much they took off the head then shame on them. You always mic the head before and after. If you had material removed from the head and increased the bore size, you should be installing a 2mm hg and not a 1.2 or 1.4. Titan headgaskets only come in one bore size.

 

[starscream5000]

There is also a 3mm MHG, but I doubt you'd need it unless you just want to have outrageous boost.

 

[tig321]

If I recall and with out looking in my note book, the stock head is 116mm or 4.566". If the machine shop does not know how much they took off the head then shame on them. You always mic the head before and after. If you had material removed from the head and increased the bore size, you should be installing a 2mm hg and not a 1.2 or 1.4. Titan headgaskets only come in one bore size.

I will take my head to work tomorrow and have one of the machinists mic it. It's a jdm head but I think the engine its from may have had a bhg once already.

I was under the impression that measuring your combustion chamber area and how much you pistons stick out was the more accurate way to determine your final compression ratio. My pistons and rods (eagle) are not stock
according to this comp ratio calc. http://www.csgnetwork.com/compcalc.html
entering my #'s
bore=83.439mm
stroke=91mm
HG bore=86 (I assume this is Titan's bore size)
cyl head volume=40cc ( I'm not confident in my 39.5# I had trouble getting all the air out, I have to recheck this)
piston dome vol= -19.3 (Ross piston)
piston deck clearance= .008"=0.2032mm

with a 1.4mm thick gasket I get 8.5 to 1
a 2mm gets me 8.12 to 1
I'm not really sure where I want it to be? I'd like to keep it close to stock I think, maybe a point or two more.

 

[suprarich]

Yes, that works fine as long as all your values are accurate. The reason I mentioned to mic the head was just to see how much material was removed. Then to keep the stock Comp. ratio, you simply add the missing value to a thicker head gasket. Was any material removed from the block? If not then it is common advice for a mhg install that the block and timing cover be milled true then improve the surface up to the required RA value for the given gasket. In the titans case that would be a RA of 50.

 

[tig321]

Yes, that works fine as long as all your values are accurate. The reason I mentioned to mic the head was just to see how much material was removed. Then to keep the stock Comp. ratio, you simply add the missing value to a thicker head gasket. Was any material removed from the block? If not then it is common advice for a mhg install that the block and timing cover be milled true then improve the surface up to the required RA value for the given gasket. In the titans case that would be a RA of 50.

I see what your saying. I will check how much has been machined from the head because I am curious. The bottom end has been decked also. When I asked how much, I was told "as little as possible" but not given a #. I'm very unhappy with that shop for many reasons.
They are expierianced (domestic) machinists but they think they know it all. I may know very little but when a customer say's something like "I want the main/rod bearings on the tighter side of the factory specs" Do you do that?, or do you just polish them. And when the customer comes to pick it up and inquires about the standard bearing size, and oil clearance you reply "they 'should' be fine, I only polished them a 'little' bit" I better stop here before I lose it:aigo: :runaway: :biglaugh:

Thanks for you help rich. So Titan hg's are 86mm bore correct? Thats likely who I'll go with... So you say you know who 'really' makes Titan's Hg's, eh... Care to end the debate.:icon_razz
Edit: It's cometic