Don Terrill’s Speed-Talk

These are 267 castings, 1.72/1.38 valve. Anybody know the chamber CC? Chamber walls are tucked in so tight around such tiny valves it looks like it would have to be less than 58cc.

Anybody have thoughts about a 3.75" stroke 267, cut-down stock pistons to give it functional quench, 9.5:1 (or whatever it ends up at with ~.035" quench), Comp XE 206/212, Eddy 2101, Qjet? This would be a practically-zero-dollar build, all the parts I already have and have no other use for.

I only built one and it was a long time ago. Chambers are very small but I don't remember the cc. I upgraded to a 1.5 exhaust valve I don't remember why. Heads and intake got ported. Similar cam and just a rebuild. With lt1 style 1.25" valve springs it had no issue with 6500 rpm. Even with the tiny two barrel. Built it for a guy with a Monte Carlo he loved it, great mpg and fun to drive. He would stop in every year or so to thank me. It is really a poor platform for a hi output engine. It is great for a low $ run around. I would change out the intake and tiny carb before I stroked it. It is basically a square engine from the factory. Thanks, Charlie

Your plan sounds good to me as long as milling the piston top does not leave the piston deck you thin ( less then .200" with a cast piston) , nor leave the top ring to close to the piston deck so as to burn out.

I haven't mocked it up yet, but from measuring the pistons and assuming a 9.025 block I should need to cut about .095" off the tops to get to zero deck and use a typical .040" gasket. This won't cut the center dog dish surface, just the outer rim. Or to get a full cleanup cut I could use .015 shim gaskets to end up back at a total quench distance of .035-.040.

I'm a little concerned about the top ring land which would end up at about .140". Ring gaps will be opened accordingly. But if it fails have I really lost anything?

Piston deck in the middle is .350" thick, no worries there.

Don't fret even if you need to end up with a total of .045" clearance as the faster pistion speed of the added stroke will make up for it.

I would check the counterweight to skirt clearance before starting on the piston deck

turbo camino wrote: ↑Wed Oct 16, 2019 5:00 am These are 267 castings, 1.72/1.38 valve. Anybody know the chamber CC? Chamber walls are tucked in so tight around such tiny valves it looks like it would have to be less than 58cc.

They are 49 cc chambers.

Yikes! 49cc would put it at somethin like 10.8:1 and that's guessing at +5cc for piston valve notches, doubt it would need that much in reality. I'm not sure that'll work with this little camshaft...

Well go for cutting a dish into the piston tops , but that cost does start eat into the low cost of the build, but that being said don't forget that you have like a added 1.5 CCs of ring land back clearance your not considering in terms of the 2 compression rings.

I have a benchtop mill, rotary table, small lathe, etc. I can cut the tops down and probably struggle through cutting valve notches, so machining a little reverse dome wouldn't be totally impossible. It has to cost less than an oil pan gasket or tube of silicone or this whole thing is dead in the water.

Actually, since it didn't need any valve notches at all with the stock 2.7 x .125 deep full-round dish, and the piston deck is .350 thick, I could just skip the complicated notches altogether and handle it with a little inverted dome with a flat bottom instead. Right? Cam is under .450" lift and the valves are tiny...

You could also use a 400 connecting rod, unless you are really wanting to do the machine work. They should be available for $0.00 Stock Ford 4.6 Mod motors use a 3.55 dia. piston, It's possible they could be made to work If you don't mind an overbore . They should be available for $0.00 . This might be a good place to use an Edelbrock SP2P intake, I have seen them for $25. A friend had a 267 with the junk TH200 trans in a 1979 Malibu he drove to work. He put well over 300 K on it until the transmission started acting funny.

I do mind an overbore, there's only one machine shop within 90 miles in any direction and prices are through the roof. If I have to get something bored I'll drag out one of the 4" blocks and build a real 383. Actually, no, I wouldn't do that either, I'd pick up a complete drop-out 4.8/5.3 LS truck motor for about the same as what I'd spend on one trip to the machine shop.

My one and only reason for the 3.75 crank/5.7 rod is to get the pistons up high enough that they can be cut to a (near) flat top to get some actual quenchin' going on. The boost in cubic inches is almost negligible at this bore size, the added torque would be a plus, the static compression issue is looking like a negative...

When the dish gets cut in just be sure to position it such that it unshrouds the open Intake valve on the shallow side of the chamber.

I'm still a bit puzzled by this compression ratio thing. At stock 3.5 bore and 3.48 stroke, if the stock head really is 49cc, and the dog-dish pistons are +11.75cc (2.7" dia x .125" deep), deck height is .022 with a ~.020" gasket, that would put the stock CR at 9.14:1.

I thought these turds were more like 8:1? What's going on here? However it does come out to 8.18:1 if you substitute a 58cc chamber.

I have never CC'd an engine and had it come out to the advertised ratio. The late 70's 350 engines are commonly a measured 7.8:1 cr despite an advertised 8.5. If you pour the piston at tdc, you will find much more volume than the calculated dish volume. The chambers are all over the map also.