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Opel Tinkerer and Rescuer
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Opel Tinkerer and Rescuer
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Not sure if the chamber volume is currently measured or previously known numbers from the 2.4 head. Charles?
I believe with the big valves unshrouded is 57 +/- cc in the 2.4L head and the 1.9L is a little smaller.

He does CC match them and unshroud the valves.


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This is the standard 2.4L with the big valves

The is a 1.9L Head Bob Legere did.. that was massaged probably about as big as a 2.4L in size

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The difference between mere mortals and metal sculptors like Bob.

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This is 63 cc chamber I mentioned earlier and it was on the 2.7L and was to lower the compression.

I am not sure the correct term but he cut the chamber area with a 1-2 mm pocket ?
 
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Opel Tinkerer and Rescuer
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Manta, thanks for all the great advice and running numbers. The cam recommended by Charles is the GM77 cam. I'm told it lies someplace between the OR77 and OR66 specifications. Maybe Charles can jump in here and provide the specs.
GM-77 is listed in the Cams Cams Cams thread but here it is from the sheet from Isky.

Lobe Center 109 degree

Intake:
Dur - 276
Open 29 BTDC
Close 67 ATDC
Cam Lift .310
Valve Lift .465

Exhaust:
Dur - 276
Open 67 BTDC
Close 29 ATDC
Cam Lift .310
Valve Lift .465

Overlap 58 degree

Timing checked .007 Open after lifter rise

Timing @ .050

Intake:
Dur - 238
Open 10 BTDC
Close 48 ATDC

Exhaust:
Dur - 238
Open 48 BTDC
Close 10 ATDC
So I'm still looking for combinations that can get the deck height higher as you suggest. Found some VW/Audi G60 rods that are around 135-136 mm in length. These may prove a good combination if I can find a suitable piston.
The thing you are forgetting, is piston shape, skirt shape, valve relief shape, and the interior design of the piston ( can he rework it to make it piston steered). Not to mention the internal clearance of the block.. etc. etc.. etc.. That was why my machine shop when through about 6-8 different pistons that ALL had the same "Spec", but didnt work, for the original 2.7L build. The Yamaha piston worked and the 2.3L ford turbo piston are known to work.. the 2.4L rod and the BMW are known to work. Going outside those two recipes, and your back to square one.

So unless you have a machine shop willing to do all this research and build with you. You are just guessing if these combinations works. The "Research" to make the 2.7L added a $1000 to the cost of the build and that was with a shop that does custom work. That doesn't include the cost of the pistons that were far more than I originally had budgeted for ($400 more). I effectively paid the guy that bought the motor $500 to buy it. So the 2.7L was the first and last of its design. Because the quote to do a second one.. was even more than the first one now that he knew all the work he had to do.

If it were as simple as breaking out catalogs, and going by specs in a book, everyone would do it and no one would have a problem finding a machine shop to do the work. I have gone 100+ miles from my home in search of a shop to do the work. Either I am told to go to the guy I am already using, they don't do custom work or they want at least a $3000 deposit, they truly don't want to develop anything, and if they do have to.. its $200 a hour ( on top of the $3000 ).

Just putting it out there.
 

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Opel Tinkerer and Rescuer
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Opel Rallier since 1977
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All of this discussion on the chamber size is why I asked! It goes into the figuring of the SCR/DCR. A few cc's + or - is not going to run the present set-up into a not-working situation for SCR/DCR, but you want to get it as close as you can at the planning stage...other things are bound to come up later.

Tnx for the cam spec there Charles. That 276 advertised duration indeed falls halfway between the other 2 cams, and is what I used for the DCR computation. I probably ought to dig around for the Isky spec basis.... Isky and Crane started doing lots of cams soooo long ago that they sorta 'pioneered' the cam specs used in the us but even they did not agree on what lifter lift to use to measure 'advertised duration. I've found over the year fo cams like the Isky and Crane grinds in particular, that using duration measured at .005 or .006" lifter lift give very good prediction on cranking compression and thus DCR is always close.

As far as having to go to a special shop for this, I can't agree. This is old stuff; guys have been nothcing bores and massaging piston skirts for decades. I've been engineeing up a 4" stroked 273 small block Mopar to 333, and this is all the same stuff going on there. It is all home-shoppable. In each case you have to do the research, buy the parts and see what fits, and some trial and error is part of that. I have a couple of piston bought for that project that have been fitted and rejected for various reasons. Where it gets pricey here is purchasing those GM Vortec type piston sets... they run $500 for set of 8; they might be buyable 1 at a time. (I've looked at these pistons for 1.9L stroking and boring, and if we area heading to the same type, V6Opel and I could split a set of 8.)
 

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Opeler
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Discussion Starter · #109 ·
Charles, perhaps I am missing something fundamental but how can you use a stock 2.4 rod when the journal size is 52mm? The amount of stroke increase using the 2.3 crank would only be about 1 - 1.5 mm tops given the fact the 2.3 crank rod pin is 54mm and some loss from regrinding would occur. The BMW rods utilize a 48mm journal size and therefore would certainly allow for upwards of 5.5 mm increase in stroke.
 

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Opeler
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Discussion Starter · #110 ·
"Where it gets pricey here is purchasing those GM Vortec type piston sets... they run $500 for set of 8; they might be buyable 1 at a time. (I've looked at these pistons for 1.9L stroking and boring, and if we area heading to the same type, V6Opel and I could split a set of 8.) "

Now you are talking!

So on the question of head volume, how does one go about measuring the volume accurately?
 

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Opel Rallier since 1977
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Here ya go.....
Some good thoughts about chamber size are mentioned around 3:15-3:30; this relates to the quench/squish thinking that I have been poking at you.....

Some notes:
  • The RTV or vaseline or grease use to seal the plate on the head thickness has to be sooooper thin. If you have a .005" or .006" thick seal, then you just added approximately 1 cc to your measurement.
  • I use water with a single drop of dishwashing detergent to break up the surface tension of the water. But you can use other liquids...

"Where it gets pricey here is purchasing those GM Vortec type piston sets... they run $500 for set of 8; they might be buyable 1 at a time. (I've looked at these pistons for 1.9L stroking and boring, and if we area heading to the same type, V6Opel and I could split a set of 8.) "

Now you are talking!
Indeed..... the 1.9L to 2.5L bore/stroke conversion that I have worked out on paper looks like it uses the same pistons that you are contemplating....hmmmmm.....

And just so you caught this point about eyebrows from an earlier post:

The intake/exhaust valves are all on the same side for these pistons. I.e., for the pistons oriented with the eyebrows 'up' as you look at them, the intake eyebrows are all on the left and the exhaust eyebrows are all on the right. There are no 'lefthand' and 'righthand' pistons. So I exepct the eyebrows to be recut some, which will add 1 cc or so (as a guess) to the volumes.
 

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Opeler
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Discussion Starter · #112 ·
Did some more looking and calculations and here is a suggested formula:

BMW M10 rods - 135mm, can use 48 mm rod pins/bearings, 22 mm small end and 23.88 mm width
DSS K1913-3820 pistons - 97.028 mm bore, 1.14" comp. height, 0.943" pin (that may be a big problem though), 15 cc

This would yield a 0.044 mm deck height, rod ratio of 1.534, and SCR of 9.58. Fly cut the valve reliefs as you suggest to make them symmetrical, say another 2 cc and SCR drops to 9.36.

Not sure about the pin diameter though. Would be nice to find the same pistons with a .927" pin....still looking.
 

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Opel Rallier since 1977
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That's getting things snugged up to the head!

If the BMW rods are indeed bushed, then you might get lucky with the bushing OD. If it is smaller than .943" then you could pull out the busing out, and the hone the rod end an float the pin in the rod directly. A lot of those pistons are available with a .927" pin too... .but maybe not all of them in the Summit pistons selection. Look at Mahle pistons... they have some like these. And have you been looking at the Summit Pro LS Forged pistons? One of the illlustrations for this piston is a table of all of them.

I just looked... did not see that 1.14" CH with a 15 cc dish on the DSS site. But IMHO, you'll still be fine with the 10 cc dish and the resulting SCR.

What head gasket are you thinking of?
 

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Opeler
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Discussion Starter · #114 ·
Thought I would provide an update on this project since I haven't posted much over the last year. Actually the last year was spent building the two GTs I brought to Carlisle. One being my son's blacked out red GT and the second my wife's blue roadster GT. But over the winter I did finish building the 2.6L engine and finally got it installed after getting back from Carlisle. I was able to complete the cam break-in procedure immediately upon first engine start up by running the engine for almost 30 minutes between 2000 and 3000 rpm. Kinda scary on a new engine but required to break in the cam properly. The Holley Sniper is great and it starts pretty much instantly. I only have half the exhaust done so still some work to do but it runs and drives. I've put maybe 4 hours drive time on to date and it pulls fantastic. Even at 70 mph, you can step on the gas and feel that torque pushing the car. I'm super happy so far. Here's a quick video of the engine running in my garage.

P.S. Much thanks and appreciation to Manta Rallier, RallyBob, and Charles Goin for all the advice along the way!
 
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