The stock Cadillac cylinder heads do a good job of getting the fuel air mixture into the engine and exhaust out at lower RPM's but are a little restrictive higher up the RPM range. Here is a little story about the evolution of my cylinder heads. 

First of all, a little disclaimer. I did very little of this work myself. A race engine building friend did the porting and a local automotive machine shop did the machine work and assembly. I did the research on what parts to use. 

The stock valve sizes are 1.87" intake and 1.50" exhaust and as you all know, the middle two cylinders on each bank share an exhaust port. That port is larger than the end ports. What got me started on this whole thing was I took an old head apart and slid in a couple of 1.94/1.60" Chevy valves. It looked like it would be a no brainer to install the bigger valves so off I went.

My engine builder buddy had never touched a Cadillac head before so I cut one up so we could see where the flow could be improved and where the danger areas were where you would have to be very careful removing material. Here are those discovery photos. I'll explain them in a reply.

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I've been building a mild Holden six motor (think smaller version of a blue flame six) here in Oz for a mates son. Its out of a 1960 model, so old and slow. Another good mate, gave the head a mild tickle on the bottom. We've gone with bigger valves, some flow porting in the runners and a small amount at the mouth of the port. The manifold has been ported to match and is dowel pinned to head. We whacked a bit off the face to kick the compression a tad, then topped it off with some Comp Cams 350 chevy springs and retainers. We've got twin carbs, extractors, mild cam, 40thou over pistons, alloy cam gear and stuff in the build. 

Should make the new driving experience more fun than before 


Pretty cool project. Nothing like a straight 6 for torque and smooth running. What carbs is it running? 

I had a 1985 BMW 535i (3.5 liter inline 6) for many years and put a ton of kilometers on it. I think I ended up at 385,000. Loved that car. 

Its got twin Stromberg's on it.

The poor ol early Holden 6's,known as the "grey motor", because they were grey, had one really big issue, they only have 4 main bearing in them.

Keep the revs around 5,500 to 5,800rpm,all good.

Rev 'em past 6,000, and the crankshafts tend to fall out of the block. This little thing will have 5,500 rev limiter fitted.

Nice. Should be a good little runner. Looking forward to hearing more about this project. 

Kevin, why you hijack somebody else's thread? How about creating your own instead of piggy backing? Did you eat the wax instead of putting it on the car? That would explain a lot!!!    ;-)

Oh Anders, so sorry I missed this until now...... :-) LOL

I've missed being able to tell you to go root ya boot. LOL



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