A late question for J. Mummert. First the power figures you obtained with the test engine are very impressive. Anyway, you stated that the 111 degree lobe seperation is intended to make the cam usuable with automatic transmissions. However, on your own site, it says it's not suitable for a Fordomatic. Can you elaborate? Thanks.


Paul

YaLinc: the Summit carb isn't based on Holleys originally. It's apparently based on the Ford/Autolite, Flattop carbs of the 1960s, that were used on Mustangs for instance. They were the carbs that Pony Carburetors in N.Y. state, considered the best overall carbs on the market. Unfortunately, it doesn't appear that Summit is making the smaller CFM version, that worked so well on smaller displacement engines. Ted has tested one or more of the original carbs some time back in a test of several carbs...

Paul

To give credit where credit is due: If you had a car with a badge, anything other than a blue oval, a 400hp Y block is ....embarrassing.

Technical discussion aside John this is a great effort. 

Grizzly (Aussie Mainline)

very nice John, good info for all. that carb looks just like the new style holley, they just changed the fuel inlets? the next time you dyno an engine could you through on a set of ram horn exhaust for comparison for the pick-up guys, thanks.

 lincoln/merc. y-blocks &mel's                                                               bucyrus, ohio.

I agree with Ted. Rod stroke ratio`s have bean "beaten" to death. My conclusion, the rod connects the piston to the crankshaft, little else.

Greg Dietrich Mt.Morris Il

Here’s my two cents worth on rod/stroke ratios.  Their significance in regards to performance or power output is generally overstated.  With that said, the smaller the rod stroke ratios, the higher the wear factor at the cylinder walls.  The scrub 400 is at the bottom of the scale for R/S and is a good example of the extra cylinder wall wear that’s comes about from using rods that are on the short side.  As far as camming characteristics are concerned, the rod stroke ratio is a very minor player compared to many of the other variables that are being dealt with in an engine.  Summarized, the frictional losses that come about from using R/S ratios that are on the low side ultimately end up being greater in many cases than the power gains seen from the increase in piston speeds.

Lorena, Texas (South of Waco)

John,

From what I've read 17deg rod angle @ 90deg ( sine of rod angle=stoke/(rod length * 2)) crank rotation are accepted safe and angles above this promote excess wear, heat (friction) and thrust on piston thrust surface.

As you know just because Government Motors does it doesn't mean it's good practice

cheers

Warren

Grizzly (Aussie Mainline)

Warren, I'm not certain what you mean by on the edge. I would like to see the R/S ratio lower than 1.69. A stock 302 Ford is 1.71 and when built to a 347 it becomes 1.588. A 350 scrub is 1.628, while a 454 is 1.533 and 400 Small block scrub left the factory at 1.48. Low rod angles make the engine more effecient at low RPM.

At high RPM a long rod angle is more desirable but that requires a lot of high RPM useage to make longevity a factor.

Unfortunately, with a 9.770" deck and rod/cam interferrence occuring around 3.55" stroke, depending on the rods used, the Y-Block is limited to tall pistons and long rod angles unless expensive rods and crankshafts are used. Even with a reworked 312 crank and reasonably priced rods it is easy to have 10K in a stroker Y-Block that will make 400hp.

The 111 lobe center of the cam reduces overlap and we had those made specifically for cars with automatic transmissions. We also have the cams in 107 lobe separation for manual transmissions. The cam in the test was installed advanced to 107 dgrees intake centerline.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

John,

Thanks this pushed me off to do some research. I knew that rod length had an effect on piston speed and dwell at the end of the stroke. A 3.61 stroke and a 6.125 gives a rod stroke ratio of 1.696 and a rod angle of 17.1391deg which is at the at the edge of a streetable engine.

A short rod favors bottom end torque and an early opening cam as the piston accelerates quickly during the first part of the stroke. Unless the breathing is aeiquate then the last part of the intake stroke can be utilized.

This new cam seems to open reasonably late.  Does this new cam take advantage of the new heads better breathing and the stroker motor's configuration with wider lobe centers and later opening so as not to over scavenge for bottom end performance?   

Thanks

Warren

Grizzly (Aussie Mainline)

Thought I would add a picture of the motor, since a picture is worth a whole bunch of words. The headers are metal sprayed with aluminum. The engine will get reproduction T-Bird valve covers before shipment. Engine color is Goldenrod Yellow to match the car, which is actually a Sunliner, not a Crown Vic as earlier stated.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico