Yes they are all 46cc. And of course 72 NA head = 74 NA head.

This is a very good example of why it's so important to take your own measurements and do it more than once.

'cos as I stated before......the Ross pistons PDF says the '72 is 51cc.........but it also says the '74 is 46 cc

Here.
http://www.rosspistons.com/catalog.php

What does JE say?
https://www.jepistons.com/Catalogs/Spor ... /6G72.aspx 43 cc

How about wiseco?
http://www.wiseco.com/Catalogs/Automobile.aspx 48 cc

So they're all wrong.


Why are race engines so expensive?......because all the aftermarket parts are crap and to build one properly takes hours and hours and hours because everything has to be carefully measured. Go buy some pistons of XX CR........do you get what you pay for?........no of course you don't.

So to continue off at a bit of a tangent, now that it's obvious that JE, Ross and Wiseco can't agree about head CC.......look up some more specs from their catalogues.

Ross, 91.60 mm, 1.254 (31.85mm) CH, dome -2 cc, CR 9 to 1.(it says with factory gasket which is about 1.4mm or 0.055 inch)
JE, 91.5 mm, 31.5 mm CH, dome -6.9 cc, CR 9 to 1 (it says with a gasket 0.040 inch which would be a special order)
Wiseco, 91.5 mm 31.3 mm CH, dome -14cc , CR 7.8 to 1( it says with a gasket 0.050 inch, again a special order)




Aftermarket Pauter rods are
http://www.streettunedmotorsports.com/p ... t_6g72.htm
5.536 which is 140.6 mm, so using those will drop the numbers by a fraction....maybe?, only if the length is correct.

Just for my own sanity I've gone and measured a 6G72 stock conrod yet again and still get the same number.....141 mm. It's just very difficult to get an accurate measurement.

Next step is to pull the heads off my "forged" shortblock that I built a few years back but never used (only due to concerns about quality of aftermarket parts). I'll also pull the pistons and rods out of it.
The heads for measurement.
The pistons (wisecos I think) for measurement.
The rods (pauter) for measurement and replacement of the crappy pins.

Next chapter, I've pulled a 2nd gen N/A head off one engine and a TT head off another.
The N/A head was on my "forged" 4 bolt block I built years ago but never used.

The pistons have lasered into the top "6570M925" which googlind comes up as a wiseco.
Looking on the wiseco catalogue linked above it looks like the one at the bottom of the page except that one is K570M925. The 925 part means 92.50mm....or seems to.
Next step .....measure.
The bore is 92.25 mm and the cheap china head gasket on it is 94.6 to 94.7 mm dia.

Taking the rest of the specs from the wiseco catalogue, 31.75 CH, 14 cc dish, 1.27 mm headgasket, 140.9 mm rod.......should give a 7.9 CR
My calculations are 92.25 mm bore gives 508 cc swept volume with 76 mm stroke.
The 31.75 CH gives 0.75 mm out the top.
If there was a 1.27mm headgasket at 94.6 mm dia (call it 1.3 mm) there's 0.55 mm of it with air in it(the piston is in the rest of it)..........3.86 cc (call it 4)
Wiseco say the head is 48 cc
14 cc dish

Swept vol = 508
Clearance vol = 14 + 4 + 48 = 66 cc
CR = (508 + 66) / 66 = 8.69 to 1 but advertised as 7.9 to 1

Maybe I got it all wrong yet again???


edit, just gone through the calculations for the above again.
The block has been resurfaced but the amount is unknown. It's NOT 210 mm, it's a bit more so the piston protrusion numbers were wrong.....now measured and corrected, hopefully.
The pauter rod is about 0.008 inch (0.2 mm) shorter than a mitsubishi rod, measured by the difference in piston protrusion, swapping only the rod.
That gives 2 different compression ratios depending on the rod used.
I've measured the piston bowl at 14 cc
Head at 46 cc
The top of the piston sticks out at TDC, 0.05 mm with the pauter rod, 0.25 mm with the mitsubishi rod.
Assume a 92.5 mm gasket at 1.4 mm thick.
That should work out to roughly 8.3 to 1 CR or 8.5 to 1 CR.
The block height is about 210.3 to 210.4 mm


Next, CC measurements of 3T head and 3N2 head.

Maybe some of these dudes have measured the chambers, but they've gone off some of the "staged" heads that are commonly used in the States, that have combustion chamber polishing etc done. Or milled heads. Just a thought

ravensierra wrote:

Yes they are all 46cc. And of course 72 NA head = 74 NA head.

Yes, they're all 46 cc.

I've also measured some piston dishes, got more to do.
The stock TT piston has a dish 16cc.
The stock mivec piston for comparison is flat top, 4 cutouts for each of the valves along with raised lettering.it's difficult to measure but each cutout only tales a few drops or about 0.2 cc.........so the easy estimate is 1 cc.
.........................................................................................................................
(cut and paste from above)

6G75 combustion chambers........68 cc
6G75 intake ports...................117.5 cc
6G75 exhaust ports.................76 cc......these BTW are a different shape from all the others, needs different ex manifold.

3A combustion chambers..........46 cc
3A intake ports......................107.5 cc
3A exhaust ports....................84 cc

30m combustion chambers are 46 cc
30m The intake ports are 126 cc
30m The exhaust ports are 86 cc
...................................................................

today
3N chamber, 46 cc
3N intake port, 130 cc
3N ex port, 83 cc

3T chamber, 46 cc
3T intake port, 129 cc
3T ex port, 86 cc


3N head






3T head















So as a test....all the numbers are now there if you can find them, the stock TT works out as 8.03 to 1 CR, the stock 30M works out at about 10.5 to 1 just put them into the online calculator above.

Yeah I ran the numbers as well and got pretty much bang on 8:1 with that dish size. What's the factory top ring land thickness? If you take it into account, it has about a .06:1 effect on CR with a 3 thou clearance, guessing at 10mm for land thickness

Could compression ratios be worked out accurately using pressure measurements?

I'm sure there IS a formula for it but the cam timing affects the numbers, in particular the point at which the intake valve closes, the no of deg ABDC, then you have to factor in the heating effect (an extra increase in pressure) from the air being compressed.
So yes, but you need to degree the cams first.

ravensierra wrote:

Yeah I ran the numbers as well and got pretty much bang on 8:1 with that dish size. What's the factory top ring land thickness? If you take it into account, it has about a .06:1 effect on CR with a 3 thou clearance, guessing at 10mm for land thickness

There's a difference between gen 1 pistons and gen 2 pistons, the gen 1 has the top ring further down on the piston BUT any volume there is so small, it's insignificant.

When I've got a bit more time I'll go back over those numbers for the forged pistons to see what the CRs look like..........unless someone else wants a play?

magn1t wrote:

There's a difference between gen 1 pistons and gen 2 pistons, the gen 1 has the top ring further down on the piston BUT any volume there is so small, it's insignificant.

When I've got a bit more time I'll go back over those numbers for the forged pistons to see what the CRs look like..........unless someone else wants a play?

That must be how my stock pistons have survived the abuse haha. .06:1 isn't insignificant, it's worth factoring in

ravensierra wrote:

That must be how my stock pistons have survived the abuse haha. .06:1 isn't insignificant, it's worth factoring in

The second gen pistons, they normally break above the top ring. 1st gen pistons normally break between 1st ans 2nd rings so you don't know until you pull them out and look for the cracks.





Today I had a nice little prezzie turn up. 3 mm spacers.

Awesome. So you'll have to put a gasket either side of the spacer I take it?

Still coming up with a plan. I think I'll re use 2 pairs of 30M gaskets because they're a thin single shim gasket.
Today we were discussing modifying the boring bar to O ring the block. May as well O ring the spacers too...I think it's do-able.

I've got 40 thou inch which is close to 1mm on the dial gauge.
That's with the piston at TDC and the 3mm spacer, no gaskets, the piston is down 1mm from the top.

Maybe 2 gaskets 0.4 mm each....the piston dish was measured earlier, it's 8 cc
with a 46 cc combustion chamber and 84 mm stroke at 91.7 mm ish bore (the piston is 91.6 but there's 4 thou inch clearance... I think?)
That should be enough to work out the CR and maybe make adjustments either way.


edit, just done a rough calc.
The 1mm on the dial gauge, that won't be quite right because the spacers still need cleaning up a bit and aren't squashed right down. The pistons stick out of the block by 2.3mm, so 0.7 is more realistic. Add 2 gaskets at 0.4 each gives 1.5mm above the piston.
91.7 by 84 gives 554.83 cc swept........555.
46 cc in the head
8 cc in the piston
Gasket, 1.5 mm by 92 mm makes 10 cc........64 cc total.......9.6 to 1 CR
Still too high.
If I was to use one composite gasket at 1.4 mm instead of one at 0.4, that's an extra 1 mm, or about 6.6 cc (70.6 cc)
Drops to 8.8
That might work?

Good move. Copper o-rings?

There's more than one way to do everything.......we were discussing that too.
MIG wire is one option but so is getting a length of electrical cable and pulling out a strand.
I think copper would be best.

I think you need 'dead soft' copper, has a particular annealment process

I'll look into that later

Meanwhile


It's April 1st and this here seems appropriate somehow.

http://www.3si.org/forum/f1/6g74-rod-length-756826/

It's all tied up with the same thing, it affects CR.

Quite simple.....you measure in mm.
'cos it's metric, designed in mm and built in mm.
If you look through the specs, the piston pin is 22 mm...not 21.8 nor any other measurement.
Likewise the big end journal on the crank is 55 mm
The bearings stock are 3mm, well 1.5 mm all the way around so the big hole in the conrod is 58 mm
Then all you need to do is measure between the 2 closest points (113.50) and add half of 22 and half of 58.

152.50 mm....I might need that later
That's another can of worms.

But if you didn't get it straight off...it's in the service manual. A 22 mm pin has to fit into a hole that's 22 mm or bigger. It won't fit into one that's 21.9 mm. If you're measuring less than 22 mm you've fecked it all up. Likewise if the big end bearings fit into the 58 mm conrod, it's still 58 mm, not 57.xx

There's no other way to describe it apart from....if you 're measuring short .....you've fecked it up.

Now that we're measuring conrod lengths.......seems that everything out of murica is fecked up in some way or another.

Pauter conrods for the 6G72 are a bit shorter than the stock ones.
Not by much but they SHOULD be identical.
Pauter's own documentation has 2 different lengths depending on where you get the numbers from.....5.548 inch and 5.551 inch
The figure is 0.008 inch (which is the difference I measured using a dial gauge on the piston top at TDC) which converts to 0.2 mm. Not enough to affect anything other than the compression ratio and counterweight clearance which I'd like to be correct......whatever the number is. A micrometer won't work due to both ends being curved, I've used 3 different types of caliper (an electronic one, a proper vernier and a dial caliper)....electronic calipers look pretty but are not very accurate.
0.2 mm in a gasket of 92 mm makes 1.33 cc which will change the CR by a couple of points.
Looking at this
http://www.ninjaperformance.com/carrill ... -2220.html
They're probably a bit longer than stock, being 5.5551 inch.
These too, they look like cheap china rods....no mention of length.....they're probably spot on but the light weight seems like a worry......weight is strength.
http://www.ninjaperformance.com/ninja-p ... 21880.html

I've got to pull another stock block apart so I can get some better stock measurements which I'm still working on.
I've been measuring on a couple of blocks, both of which have been bored oversize , one has been resurfaced too, not by much but a stock one is better for accuracy of measurement.
Block deck height seems to be a bit higher than the usual quoted number.......as Ravensierra pointed out, it's just really hard to measure the last 0.1 or 0.2 mm in 210, I'm up to 210.35 ish mm on a resurfaced block. It's easier to measure the difference in height from piston top to deck when at TDC, that number being 0.2 mm lower with a Pauter rod fitted compared to a stock rod.

edit
I did some rough calculations based on my "old" (resurfaced) forged block , wiseco pistons and both sorts of rods.
The numbers are 8.3 for the Pauter rods, 8.5 for the stock rods. An original block at original height would have less CR, maybe 8.1 / 8.2 (Pauter rod)and 8.3 / 8.4 (stock rod)

My "old" forged block, I'll pull it apart, use the rods for the stroker, I'm not happy with the lightweight pins so a good excuse to chuck them out.

The "stroker block", after more measuring, I've fitted my "cometic" headgaskets, they're about 2 ish mm, fitted the plates, got to pull another block apart to get the 30M gaskets which will go between the plate and head.
So gasket (2 mm) plate (3 mm) gasket (0.4 mm)....work it out later. That's pushed the heads up by 4 mm over stock.
But I've test fitted the heads without the last gasket. That means I can move on to making the lower intake fit. The first step is to make the stud holes in it bigger because the heads are now wider apart. There's going to be some more CNC spacer plates made for the intake ports. Aluminium this time, or maybe plastic?. Just got to work out the angles .
Just think......if they're thick enough they could be drilled...like for jets for something?....fuel? methanol? Naaaaws? water?

Raising the heads on spacer plates, that puts the lower intake manifold out of spec and won't fit.
Not a problem......it actually opens up new possibilities.
The maths part of it is quite easy because it's a 60 deg V6.
Raising the head by 4mm (old gasket 1.4 mm, new gasket + plate = 2 mm + 3 mm + 0.4 mm)makes the gap between the heads wider by ........4 mm. Because it's 60 deg. That's 2 mm each side.
The intake ports are at an odd angle to the heads too, in fact close to 60 deg and the angle from one intake port to the opposite one is close to 120 deg.
Taking a guess at the required thickness of intake port spacer is therefore 4 mm each side. That would work with one extra gasket an a 3 mm spacer.
Just by chance I've already got some plastic spacers I got conned into buying years ago.....pretty bad quality with port alignment but they fit.
The downside is that the lower manifold needs the stud holes slotting or rather just cutting right out so the ends are open, which I've done.
Going to the next step, the lower intake is always a problem with a 6G74 block. The Pajero ones have the top holes the wrong shape for the upper manifold, a lower manifold from a SOHC is better but some of the stud holes need re drilling......both are hard to obtain.
Making a 6G72 lower intake fit a 6G74 block might be a good idea? Spares are easy to get.


I've done some more calculations for going full out on a 6G75 block and keeping the CR turbo friendly.

If it's possible to take the stroke out to 95 mm (without the rotating bits hitting other bits that might be in the way) and also boring out to 97 mm, the capacity will be 702 cc per cylinder or 4212 all up.
If we aim for a CR of 8.0 to 1 we need 78 cc clearance.
That's made up of 46 cc in the 6G72 head leaving 32 cc in the piston and gasket combined.
If the piston is a flat top then that 32 cc is all in the gasket meaning about 13 mm thick, that's if it's tapered from 97 mm down to 92 mm.

That's quite a lot.

How does everyone else do it?
They use the other heads...SOHC.
Or do they??
No, they just make it all up.

But then I found this and haven't read it all yet.

http://www.gencoupe.com/3-8-v6-discussi ... r-kit.html


Seems like this one here is the same as ours.

https://en.wikipedia.org/wiki/Hyundai_Sigma_engine


The others are different.


More pretty pictures.

Cometic gasket first, 2 mm ish, spacer, 3 mm ish, 30M gasket, 0.4 mm ish.
The extra long headbolt, that's for later for a 3.8 with a thick spacer plate because the stock bolts will be too short. I don't know what that's out of just yet, was in the "spares" box. ....Maybe an RB? Has a 12 point 17 mm head........it's threaded for about half the length so just needs cutting down a bit. Should be plenty at "pinch a part". I'm NOT buying studs.

I've partlially made a pair of 12mm plastic manifold spacers. Here I'm seeing how they're going to look on a 6G75 block with a 0.3 ish mm gasket, 3 mm spacer, mivec head and 72 TT lower intake manifold.

The one on the left, I didn't get the holes in right the first time, the one on the right, it's only paint that's in the wrong place.



They're both nice and tight on the studs and won't move around.


Cut on my sawbench I use for firewood.

Next I'll have to make some holes for the air.


The master plan here is that I'll make something that actually works,
Drop it off to OLS?
They scan it and can then copy it ............and make more from anything that can be cut with a laser.
So plastic? aloooooooominum? Steel?

I'm going to have to make several different versions.

NO I won't be matching the ports, they've got to be stepped in the right direction.......that's if you read the right books.

Here's the thick spacers on the 72 block



The old heat insulator gasket / plastic spacers on the 72 block






The "thick" plastic spacers are too thick for the 72 block but OK for a 74 / 75 block. The thinner ones will be OK for the 72.


This shows the differences between the lower manifolds.
The one on the left is from the Pajero 3.5 DOHC, the one on the right from the Diamante 30M. Notice the holes for the injectors, I think the 30M injectors are shorter than those in the N/A / TT GTO


I might even be able to space things out so I can fit a "normal" intake manifold over the 30M heads so it all sits under the lid without cutting a hole?
Maybe?

I've pulled the 72/74 all back apart again, test fitted the Pauter rods, or rather just one. Turning it over by hand, the stock rods had borderline clearance. With a Pauter rod in either end, it still turns over but there's a clunk at BDC as the counerweight hits the bottom of the piston and knocks it sideways. That's 'cos the rods are about 0.2 mm shorter.
So it's out with the crank again and back on the grinder to take 2 mm off the diameter of each counterweight.......which gives an extra 1 mm of clearance.

What we've got now is aftermarket conrods which are sub standard due to the length along with forged pistons which are substandard due to the thin light weight pins....which I've upgraded with stock pins.
It's all back together with 6 Pauter rods, 5 JE pistons and it all rotates without anything hitting anything.
I still haven't fitted rings or circlips to the pistons.

Dunno how you ever got your bits from OLS, seems nice enough but delay after delay is bothering me.
ignoring the others, ive sent 4 emails at different times asking how things were going as it had been days since id heard anything at all, didnt think it was a lengthy process after all. maybe im just being impatient?

It DID take several weeks so I wouldn't worry about it too much.
Like the cheese ad on TV.......good things take time.

Got them this morning
Pity they're the wrong bloody size haha
Gave them a call - sweet as, got the right ones under way now.
If anyone needs some 3mm thick 6G7 head spacers, gimme a yell haha

Did you ask for thicker ones?