2.0 Gte Head

[moodoo]

Folks,

Anyone know what the compression chamber volume is on a 2.0 head? Or have a head they could measure it on?

Also, I've measured very close to 103mm for the distance from the top to bottom gasket faces (i.e. from the head gasket face, to the rocker cover gasket face) on both a 1.9 and a 2.2 head. and got around 103mm. Anyone have a 2.0 head they could take a similar measurement from?

Am looking at buying a 2.0 head from a forum member, and it seems that his head measures 102.5 there, which I'm figuring means it's had a 0.5mm skim, if the measurements of the heads I have is correct.

Am trying to figure out what size of chamber I'll be left with, to see if my CR will be OK.

Thanks,

Fin

[mantadoc]

Piece of glass or perspex with small hole in

Smear machined face with grease or vaseline

With valves in head (obviously) inject water from a syringe that is labelled in CC until full. you now have your volume.

As these are sand cast no two combuston chambers are likely to be the same unless lucky so any skim for CR needs to be based on smallest or balance them with a die grinder / dremel etc.

[cam.in.head]

hi. had a similar problem to this a few years ago. a standard`` carburretor`` original unskimmed head would be around 102.8 to 103.0(compared to all the ones ive come accross).but a standard gte head is thinner anyway to give the higher cr ratio for injection.i have had a few heads done with unleaded valve seats at various local engine shops & most of them dont know or seem to care whatsoever about volumising each chamber.i had one head done where the valves were all sitting at very noticeable differing heights.when i asked if they were all the same volume due to this they looked puzzled & said it doesnt matter!!!.with regard to the amount i didnt make a record of the amounts but ended up equaling the volume in each chamber by taking a small amount of metal off around the sides of the chamber with a little grinder.making them the same as what the best(smallest) one was before it had been skimmed & had its inserts fitted.this resulted in a pretty stable idle speed & spot on compression readings.bear in mind also that the original gm head gaskets can be thicker/better quality than some aftermarket ones.

[cam.in.head]

also my two original unskimmed 2.2 heads are both 103.2 mm

[mantadoc]

i had one head done where the valves were all sitting at very noticeable differing heights.

The biggest single issue with this is the effect on valve spring length and clamping force.

really they should be level in the head but the way around is to assemble with a light narrow spring and measure the height from valve spring seat on head ro valve cap and then shim accordingly.

Only advantage of not doing it is the valve bounce rev limiter is more progressive but lower

[moodoo]

Thanks guys. (I should have said, my questions are in relation to looking at using a ported 2.0 head for a 2.2 engine, rather than a 2.2 head.)

cam.in.head - your numbers look spot on to what I've measured. I saw somewhere on opelgt.com that the 2.0 head has approx 51cc chambers, compared to 53cc-ish for a 2.2.

What you've said about the 2.0 being 'thinner' is interesting - I was presuming the 1.9, 2.0 and 2.2 might have all started with similar thickness heads, but if the 2.0 really is thinner, then the

102.5 number the current owner has measured might not mean it's been skimmed 0.5mm after all. My fear was that if it started at 51cc, and had a 0.5mm skim, and had bigger valves in, then

the chamber would end up not much more than 49cc, at which point CR would be in the region of 10.5.

Anyone have an unskimmed 2.0 head they could either measure the chamber on, or take a height measurement?

[lamchop77]

Moodoo

I wouldn't be bothering about this too much. Std manta engines are about 9.4/1 comp ratio as are the 2.2 motors. They are prob slightly less due to the bigger valve cut outs. Reducing your chamber by 2cc is prob going to increse the comp ratio by 0.3 ish so i would reckon you might just get to 10.0/1 if your lucky!!!! Bigger the comp ratio better the power!!!

At those sort of figures you should be fine on std pump fuel.

Chris

[moodoo]

Thanks Chris, that was the sort of reassuring thing I wanted to hear! Funny you say about the valve pockets in the 2.2 pistons, I measured my new standard 2,2 pistons last night, but only got 1cc each, 2cc total. It seems small?

Higher compression will tend to move the power up the rev band, won't it? My engine is just for the road, no track work at all.

[lamchop77]

Moodoo

It shouldn't affect it really as its only a small increase. The cam is the main influence for moving power up the rev range. More compression just gives a bigger bang per buck. My 1312 moggy A series has an MG metro 276 fast road cam (std), carb etc and runs 10.5/1 and thats fine, nice and pokey but not OTT. Remember your 2.2 will eat up the duration of cams so you can go a bit wilder with them.

FYI i've measured combustion chambers on my heads and there is about 2-3cc between the 2.2 and 2.0, the 2.0 being between 51-52cc. Don't get hung up about the small bits like that for your road motor it ain't gonna be a problem....leave the minute moddng and fretting to idiots like me!!!!!!! My 2.3 is gonna have 11.89/1 comp ratio because the design of the dome is as small as possible to aid flame travel across the top of it, i wanted 12 to 12.5 but that would have blocked the flame path which would have hurt the power so i went with the advice, but this is silly stuff for a bit of horsepower on a track motor.

Pay more attention to timing your cam properly and invest in a vernier timing gear!!! If the head has been skimmed it will retard the timing, read the Rallybob threads on it.

HTH

Chris

Edited April 16, 2013 by lamchop77

[moodoo]

OK, thanks a lot for the advice Chris.

I guess in this case maybe I need to do less research, not more!

Cheers,

Fin

[lamchop77]

No problem bud, anytime!

Chris