Rear Engine Modified Roadster Build

[maguromic]

Got a a few PM's on what type of head and rockers that we are running.  So here it goes. The head is a stock GMC 302 head that's been worked over and is the same as on my gas roadster. I had my mule motor on my friends Spintron machine and found some shocking things about the valve train.  Some of the gains were in valve train stability and part of the strategy was to build a girdle for the head and new rockers.

The bottom part of the valve cover acts as the girdle, where each rocker has bolts clamping down on either side for stability..  After spending some time doing FEA work on rocker designs I settled on this style of rocker.  It has no rollers or adjusters on the rocker and  is adjusted with lash caps. When I get to the shop I will takes some pictures of the actual parts and post them. Tony

 

Valve cover bottom



Valve cover top

[Col_Klink]

Nice build!  I really like the engine and those rocker arms and girdle looks very nice!  If I may ask, can you share why you designed it like that?  I am curious, as I am also planing on building a VGALT with a GMC. When I Was drag racing in the late 60's I ran into a bad vibration at about 5800 RPM.  For the rocker arms  I was thinking of modifying a roller rocker arm from another engine to work.  What RPM are you going to spin the motor?  Thank you for the information.

[maguromic]

Nice build!  I really like the engine and those rocker arms and girdle looks very nice!  If I may ask, can you share why you designed it like that?  I am curious, as I am also planing on building a VGALT with a GMC. When I Was drag racing in the late 60's I ran into a bad vibration at about 5800 RPM.  For the rocker arms  I was thinking of modifying a roller rocker arm from another engine to work.  What RPM are you going to spin the motor?  Thank you for the information.

The reason I built the rockers and the girdle was because we plan to spin it to close to 7000 and when it was on the Spinttron all the movement in the valve train meant the engine could not spin to 7000.  I tried modifying roller rockers and noticed the tip was sliding on the valve tip.  Also the end rockers on the shaft are unstable and tended to move around more than the rest.  That was the reasoning behind the girdle. However we also did allot of work on the block like aligning the all the lifter bores. The big part in this type of rocker is to get the proper angles on the tip and to find the optimal shape of the rocker and to eliminate flex.  I went through  a bunch of designs before finalizing on one.  This is one of the first ones that I did.  Its done on Unigraphics and its magnification is about 1000 to 1 or so. Since you are in the area come by the shop and I will give you the ten cent tour.  I am off to Indy today but send me a PM and we can get together next week Tony

[SPARKY]

7000  Crank Hormonics 

[Stan Back]

I like how one end moves -- and the other doesn't -- howzat work?

[Peter Jack]

Tough valve springs!!!

Pete

[theazoldcrow]

  "Puter majic!"    Crow

[maguromic]

I like how one end moves -- and the other doesn't -- howzat work?

When you do a stress analysis you have two kinds of things to apply, forces and constraints.  I put a bearing constraint on the bore; lock one end fixed and put a force on the other end.  Unless it was perfectly balanced when you put a force on both ends it would just spin.  In real life the force comes on the push rod end and the tip is constrained to the valve.

7000  shocked Crank Hormonics

It took a lot work to work through the problem.  It was almost like reinventing the wheel.  Least of it was to get the head to flow and make power at that RMP.  So far so good,  now I have to see if the great white dyno will show the same results as my budies dyno. 

Now I have to pack to go to the airport to catch the red eye to Indy. With the unification it should be a good 500! Tony 

[maguromic]

While I was at Indy over the weekend I had the chance to rummage around in a few shops at Gasoline Alley. I found the pedals off a Dallara IRL car and the rear speedway wing off a early 90's Lola Champ Car for the project. These parts will workout perfectly.  Even the cord on the wing was what we were looking for.  Tony

[Stan Back]

Sounds like a true "Garage Sale".

[maguromic]

Since I will be down in a couple of weeks to see Kent I thought I would post this. This is an old picture taken about four months ago of the nose plug before being sent down to Kent.  Can anyone (except Kent) tell what this nose is off of.  If you can, post a picture of the car its from.  Tony

[Stan Back]

Yo Mama?

[maguromic]

Actually Stan, the plug is from the car this nose is off of. I surely thought George would have guessed it.  Kent and his band of suspects will take about 4-5" off the height. Tony

[Stan Back]

I'm lost -- Joe Law?

[Stan Back]

The only nose we know is a '29 radiator shell -- and they seem to be getting smaller and slicker ala Poliform roadster bodies.