xp300

[NixVegaGT]

I was looking at this crossection again due to Kevin's thread and I was trying to figure out what was up with the exhaust pushrods:



Is that rocker sideways? What would be the benefits to doing this? Especially since the push rod has to cross the centerline of the pistons. Why not  put regular rockershafts in? Did they get in the way of the spark plug bosses? Did they build this engine?

Interesting.

[castlesid]

Nick,

I spent some time trying to understand what the drawing shows and to be frank couldn't see how it was meant to work.

The Buick engineers had obviously never seen a Bristol 2 litre IL6 which was a hemi headed engine with single cam and pushrods.

It had a very clever arrangement in the rockers in that one set of valves were operated in the conventional push rod manner and the orher set were operated by a second short push rod linked by an additional special shape bellcrank rocker.

The engine was originally a BMW 328 from 1936 which we nicked after the war and was then produced by Bristol and featured in quite a few high performance cars of the 50'- 60's and in high output road 100D2 spec  produced 128BHP.  64BHP per Litre which was not bad for the period!

And yes I'd like to know whether the XP300 actually ran.

Kevin.

[BlownMGB-V8]

That rocker is definitely sideways, and the pushrod runs between the cylinders. Only way it could work.

Jim

[Moderator]

From this source: http://www.conceptcarz.com/vehicle/z1849/Buick-XP-300-Concept.aspx

The XP-300 was the brainchild of Charles Chayne, GM's vice-president in charge of engineering. Its name is derived from the name 'experimental (XP)' and the fact that it is powered by a 300 hp supercharged V8 engine. Chayne reported that he attained a top speed of 140 miles per hour in the car.

So, apparently it ran just fine.

I haven't found any photos of its engine (installed), but the XP300 still frequently appears at car shows.

[NixVegaGT]

The Mopar Hemi works with extra long rocker arms for the outside valves, right? They did that because they wanted to use the same block as the wedge, right? I'm with you Jim, that it would only work to have the rockers sideways if the pushrod was between the cylinders.

Interesting.

[roverman]

Buick/Rover-"Semi Hemi"? I think the old Chrys. Products, ploysphere was closer to a hemi. One problem with it was int valve was at 0 deg. and exhaust at approx 15deg.  What if there was a "shallow" hemi with more like 15deg for each valve, with squish and quench? The hemi is "king" for surface to volume ratios, untill you put in a huge ,"dome" to get compression=heavy slug. I would like to build a headless, 4 cycle engine, before I run out of time. Should have the best sv. ratio for four stroke. Should be better suited for fuel like hydrogen.  I don't know ratio on Wankle,( not quite Otto cycle). Are we visualizing yet? roverman.