A friend of mine joined the 2 piece T crank club. One of the options we are considering is a '28 Chevrolet crank as I have one on the shelf (and the rods too!). What are the best piston choices for flathead or for overhead?
1. Egge NORS; made from old pots and pans. I just had to put in oversize pins in the Fronty.
2. Egge may make new, but doubtful. They use good materials now.
3. Ross makes anything, and you know them. Be sure they use reinforced wristpins, like modern Fords use. Clamping will distort un-reinforced pins. I have a near new set Ross +.030, with un-reinforced pins. I'm sure you saw them a few years ago.
Cranks are all same p/n, 1923-8. Rods changed about every year. All have .85 wristpin.
So at TDC where do they come to?
Do they pop up above the deck? OR?
The used Ross pistons (+.030). Are the still serviceable with new wrist pins? I wonder if model A wrist pins would work? I just used them in my Scripps boat engine and it is 3 3/4 bore
I just looked on the Egge website. I see that they go up to .125 OS (which would be .060 in a T). It looks like it has lots of "top" above the rings by the picture they show. The price at $189.27 is fair too!!
The rods are 7.42 long, so their compression height is that much shorter than a T piston. The Egges in the Fronty reach 5/16" above the deck.
My Ross pistons are NFS until I make sure I don't have a block that could use them. They have .85 pins, but un-reinforced. The original Chevy pins are reinforced .85.
Model A pins are full floating, so they are thin. They're also about .92", as are modern Ford. The T are .75 and the Chevy .85. I found a used set of '39 Buick 8 that are .875".
Ford 4.2L six like Freestar are pretty close to ideal. Their stock bore is T +.030. You have to bore the rod to take their pin. Dealer price is about same as Ross, but tbay may have them lots cheaper.
I couldn't find them on Egge site earlier this year. WHat is p/n?
E108-4 is the part number. Here is a link http://www.egge.com/site/?d=48&dt=1&SubCategoryId=2&make=CHEVROLET&rpp=10
Projecting 5/16" above the deck sounds like about perfect for CR.
What compression height do the 4.2L Ford have?
Duh, I never thought of looking at std Chevy pistons. Egge used to have a separate listing for Chevy rods in a T. I have an NOS Chev set, std, that I took the pins from for the fronty.
Those E108-4 should be near perfect if they aren't NORS. Note the fat 1/8" compression rings, which I had to buy from Egge.
Looking at my notes, modern Ford pistons just don't have enough piston above the top ring.
Thx for all the info. Much appreciated
Oops, the Chevy piston probably won't work:
T block height is 10.625
1/2 of Stroke is . 2"
Chev rod length . . . 7.44
Center of wristpin to top of ring: . . 8.625 - 7.44 = 1.185 MAX
So what is the compression distance (centre of wrist pin to top of piston) of the stock Chevy piston?
I have been thinking of another idea. If you were using a block that needed sleeving anyway AND you were going to use a OHV head AND you wanted to use a stroker crank (like a A) with A rods. Apparently there are short rods available from SCAT I think. The problem is now you end up with excessive rod angle due to the short rod/long stroke combination.
So here is my idea;
Make a plate that fits to the top of the block. The thickness of this plate would be determined based on getting the optimum amount of projection of the piston into the combustion chamber.
I would now bolt and seal this plate to the top of the block. Now I bore through the plate and rebore the existing cylinders at the same time to accept the sleeves. Install the sleeves and finish for the pistons I want to use. I am thinking maybe stock A pistons (3 7/8" bore) with a A crank (4 1/4" stroke). So now I have 200 cu in AND I still meet all the rules requiring a T block in certain events (hill climbs etc.) AND I can get a high compression ratio.
The A pistons might be too big to fit into a Rajo head and that would be where the stock Chevy pistons might be considered.
Anyway I need to do some more research.
I don't know the specs of the Chevy piston, and my NOS set is in deep storage. Egge should be able to answer.
Sounds like a good way to save a worn block. I have a '20 racing block, .125 over, drilled for oil, etc., that you could have for cheap.
Longer stroke gives more low end torque, but higher piston speed for shorter life. 4" is plenty long. High compression is the fix for power, at all rpm.
They say you can order Ross with any compression height, and ring setup.
My Frontenac R head has been shaved, and yields about 7.7:1. I could raise it more with higher popup pistones, by allowing a slot for the sparkplug.