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#90642 09/12/16 05:45 PM
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Im building a 261 cu in for my 50 chev pickup, what kind of compression ratio can I get away with and still tow my vintage trailer, It has a 5 speed with a 9" 3.5 rear end, dual carbs, headers, I occasionaly drag race it.

Last edited by Gary P Olsen; 09/12/16 05:48 PM.

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You are at that cross roads of towing vs racing and it is of course going to be a giant size compromise no matter what. Stock 261 motors were spec'd at like 7 to 7.5 for a compression ratio depending on the casting head that was used. One head had a 86.1 cc combustion chamber the other had a 95 cc combustion chamber. The 261 piston sat like .110 or better in the hole, a good bit lower than the 235. The low compression was specifically designed for big truck use, dump trucks, oil delivery trucks, at low rpm. So to get the compression up a bit, lots of people over the years used a 59-62 848 passenger car head that has a 79.1 cc combustion chamber which might get you to 8.0 with stock pistons, maybe. To get the compression higher, you need flat top pistons that are at near 0 deck height, or pistons with a big lump on the top and near 0 deck height or at lease in the hole at the same level as a 235. Ross sells these kinds of pistons, mine are from venolia but I think Ross has a better pattern. I am probably at 10:1 maybe 10.5 compression ratio and use premium gas, no pinging, but also no load other then the car itself (57 chevy). So this is a hard call but I would think that 9:1 would be safe for the dual duty you want to engage in. Just my own personal opinion and thoughts.

Last edited by mdonohue05; 09/14/16 01:46 AM.
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thanks so much for the info on the 261, I will cc the head to see what I have, I was like you thinking 9:1, I talked to Ross and they can do the pistons for $1100+ ouch, but I think I will go that route anyway, that much less for the kids to fight over :), talked to Isky and they have a mild race towing cam so will update that as well, I made the mistake of race building a 292, that was not streetable, but I love this 261 in my daily driver


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Try calling Schneider cams in San Diego. They have been in business for many years. Jerry Cantrell is the owner and has been for like thirty years maybe more. You will get to talk with him. Tell him your combo, car, weight, transmission, rear gears, and what you are trying to accomplish. He will recommend a grind for you and then grind you a cam. He did my last two cams. One cam I Am currently using in my 261, the other is in my stash of parts for another motor. The one I have in my 261 is hands down the best sounding and running cam I have used, and I have used quite a few over the years, Isky, Herbert, Howard's, one Clifford. The Schneider runs and sounds the best. You will pay a little bit more than an Isky off the shelf cam, but you get a custom ground cam that will run really well.

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Do you know what the cam specs are Mdonohue05? Just interested to see how wild or mild it is.


52 3100,235ci,Clifford In,Fenton Ex,Fitech EFI,251/254 cam,HEI,T-5,S10 rear, and much more!
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492 lift, 280 duration. Not sure of the overlap but a good bit as I specifically wanted the motor to a pretty good rumpety rump at idle, and it does. Chrome moly push rods. Street cam. It idles at 800 rpm. I have a larger Clifford, 510 lift or something, 310 duration, not street able. The second best cam I have used was from Chet Herbert. It was 280 480. It was a good runner but would not idle below 1100 rpm. I like the Schneider better.

Here is a link to a pass I made at this year's trifive nationals in Kentucky this past August. I just installed a new Clifford intake with 2 weber 38dgev carbs. Did not have time to install the electric fuel pump before the show and then paid the price for running out of time. First pass I blew the tires away and then promptly ran the carbs out of gas as I went into second gear. This pass was my second where I took it very easy coming off the line and was easy on the shifting at about 4400 (I usually shift at 5300-5500) and still ran the carbs out of gas as I got into third gear. This is with the Clifford vintage long tube headers open. As you can hear, it idles fine with a little lope to it and frankly with the compression from the pop up Pistons and the Schneider cam, I think the motor sounds pretty good.

https://youtu.be/ov5YLeDPHiU

Last edited by mdonohue05; 09/19/16 08:31 PM.

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