We tried 2 carbs, a highly modified 650DP, modified to 700CFM with choke horn removed and down leg booster venturi's. Next we tried one of the new Summit "Autolite" style 600CFM vacuum secondary carbs. Power was identical. The only problem we had with the Summit carb was the fancy chrome fuel line leaked and couldn't be used. Summit supplies a 1/4" thick insulating gasket with open plenum and we used that as a spacer.

We only made 5 pulls since the engine did more than expected on the 1st pull. Timing was set at 33 degrees, no jet changes. Headers are a cobbled up set I made out of some 351 Cleveland headers, 1-5/8 to 1-3/4", runners are 34-40". Rockers are stock 1.54:1. An MSD distributor and new billet steel damper were also used on this engine.

Peak torque was 420 @ 4100, peak HP 392.7 @ 5400. Tests were stopped at 5500 rpm.

Very close indeed.

The results are outstanding and confirm what I have setting here modeling for the past 8 months.

You mention Hi rise intake out of the box, Is this what you are considering yours, or is this something new?

Summit Autolite carb? didn't know they were reproducing those, any links to pictures?

So an almost 400hp (very) streetable y block is possible. It's an interesting build as it's not that different to the mule. Of course there are considerations such as wear, exhaust (this build has headers) displacement and cam. But getting an extra 50hp difference from an already developed engine at a lower RPM with less cam duration is rare. 

I'm guessing that you may get an extra 10-15hp from an extra 15cu/i . Of course the combination of additional component but I'm guessing this is the first of the cams that have been developed for the new alloy heads? Can you tell me please what is the advertised duration of the cam? If others are going to be produced? If these cams will be available without buying a crate engine?  

Good work though.

Cheers

Warren

Don, I agree about 270-280. I'm sort of looking at building an engine in about a years time. So not looking at a purchase yet. When there is a advance in a performance part (like heads) there usually is a jump in complementary parts as the engine is developed in accordance with the change. So I'm guessing other developments and cams as well.

The high rise intake is just like the picture in our avatar, or icon. Thank you to Ted or Jim for putting a the picture on the home page!

Some improvements have been made to the heads since the first set was sent to Ted for the Mule. Also, this engine has a 3.61 stroke and 6.125 rods making the rod angle 1.69:1.

Block is "0" decked and has 1/16" rings compared to the 312's 5/64-3/32" rings.

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

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.

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

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.

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.