Author Topic: 505 inch FE solid roller, Edelbrock cross ram, Vertex magneto - 642 HP  (Read 3348 times)


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505 inch FE solid roller, Edelbrock cross ram, Vertex magneto - 642 HP
« Reply #1 on: July 23, 2016, 09:55:14 AM »
I have not done one of these write-ups in a very long time.  Just way too busy both in and out of the shop for a little while.  But the stack of completed engines that are interesting, different and worth covering is getting pretty "deep" so I figured I should at least try to cover a couple.  If you follow the Youtube videos I post for customers you will recognize that some of these have been "up" for a while.

First up is a big one both in displacement and in "cool factor".  Using an iron Sideoiler Garage block bored to 4.350, a Scat 4.25 stroke rotating assembly for 505 cubes and compression in the middle 10s for pump premium fuel.  Cam is a solid roller with 258/264 duration at .050 and .696/.696 lift.  Heads are Survival castings with the normal valve job and bowl & entry blend - not ported.

This engine is destined for a Gasser.  The cool factor comes from what's up top - a port matched Edelbrock cross ram and a pair of traditional Holley 750 double pumpers.  Ignition is a Vertex magneto - I had never run one of those on the dyno before...

The engine proved a real tuning challenge - but it eventually delivered the goods.  I ended up spending a few days sorting it out.  After intial running and checking I tried a couple short pulls and it was really coarse sounding and hard to "drive".  My O2 sensors indicated that it was extremely rich and not firing well at all.  Thinking that the problem was with the vintage ignition I swapped in a known good MSD system - and was rewarded with no real improvement.  Pointed me to the carbs...

I pulled back the jetting some and tried again - and got an improvement.  Pulled even more jet and it got better yet - to the point where it was starting to behave normally and I felt confident enough to stick the magneto back in.  The mag was within single digits of the new MSD stuff and we were finally off to the proverbial races from a tuning for power perspective.  Timing ended up in a pretty normal range 36-38 degrees total.  Tried some vintage velocity stacks and it "liked it".  Tried some open 1" spacers under the carbs and it like that a lot. 

Jetting ended up way leaner than the delivered combination - to the point where I would normally have been changing bleeds in a race carb, something much more difficult with these traditional Holleys.  Air/fuel ratios remained pretty fat below the torque peak but smoothed out and became pretty much normal once it got "on the pipe".  You can hear the change in sound as it comes around during the pulls.  I think it reacted this way because the Edelbrock cross ram does not connect the two banks - its really a pair of four cylinders that share a crankshaft and probably has some weird stuff happening in that funky plenum.  The plenum is really shallow hence the big gains from spacers.

An extra note is the valve cover breathers.  Don't do that.  Mounting them to the outside of the cover looks cool, and its the only way they fit with this intake.  But they fill up with oil and become a "P trap" (you plumbers know about that) and essentially plug up until you get enough crankcase pressure to blow them out & spray oil everywhere.  Second time I've seen that - we were ready for it this time and knew what to expect.  Make them "fake" vent elsewhere if you really need the look.

Peak power ended up at 642 horsepower at 6200 (we made some pulls to 6500).  Peak torque was 625 at 4600 RPM with 530 pounds at 3000.  We had several pulls in the 630+ horsepower range.  A really strong running package from an unusual collection of parts.  It should surprise a few folks...

Relative humidity was 29%.  Baro at 28.83, cell inlet air temperature was 83 degrees, and correction factor was 1.073 per the DTS software.

Chart data a picture and link to video below:

Link to video:
« Last Edit: July 23, 2016, 09:57:13 AM by Barry_R »