Cadillac 500 head questions

I got a 72 model, I think, 500 engine with 902 smog heads. I'm still learning about these engines but I know basic principles carry from any V8 to another. First, the 902's are 76cc I believe closed chamber. Is that head worth messing with or would a 120cc open chamber head from another year 500 make more sense for a big torque 4x4 truck motor? Second, if I use the 902 heads, I was going to install larger valves and unshroud them and do some mild porting and polishing and gasket matching. I would like to, ideally, weld or somehow block, from the exhaust port side, the heat crossover and emissions holes next to each valve guide. Can this be done, is it worthwhile, can I even weld to the heads? I don't know whether to go big open chambers and a dome piston setup for more flow or keep the small chambers and flat tops to keep CR around 9ish. What is the advice of the wise ones?

Dave get yourself over to this forum, every question you can ask about 472/500 Cadillacs will be answered http://www.cadillacpower.com/forum/viewforum.php?f=3

I'm on there as Langy, I've learn't lots :)

Here's the website for Maximum Torque Specialties if you don't get the answer you're looking for. Give them a call and they'll more than likely whip an answer on you....
http://www.500cid.com/

And here's Potter Automotive....
http://www.cadillacperformanceparts.com/

And also Cad Company....
http://www.cad500parts.com/

Here is a thread that I was involved in with a lot of good ref's and replies.One thing in summary that I think I found out about the caddy engines is in stock form the valve train/heads are fine,but if you want more the after market gets expensive.Also they are not a high rev'ing engine.

Read threw the links and I think you will see what I am talking about.

http://clubhotrod.com/forums/showthread.php?t=44826

I'm currently building a 514ci for my 26T and have had excellent advice from the Cadillac forum i posted and also have had some interesting indepth technical conversations with Marty at MTS, Marty is also on the forum under the name Nashallac.

Everyone i have spoken to have said to change out the cast pistons & conrods for forged (which i have done) then i meet up with a guy called Terry on the forum that is running a near identical setup to my engine that is running consistant 9's with his 26T except he still has the cast pistons and rods !!! the rods do have ARP bolts though.

Everyone i have spoken to has said the valvetrain needs changing to a shaft system, when you look at the stock rocker setup you will see why. The engine was never designed to see many revs but can be improved on pretty easily.
I'm not so sure about that Hotrod article as i noticed a few errors when reading, one that stuck out was that they said the stock rod length was 6.370" when its actually 6.750" makes you think twice about reading it if they get something like this wrong !!!

Quote:

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Originally Posted by 1gary

Here is a thread that I was involved in with a lot of good ref's and replies.One thing in summary that I think I found out about the caddy engines is in stock form the valve train/heads are fine,but if you want more the after market gets expensive.Also they are not a high rev'ing engine.

Read threw the links and I think you will see what I am talking about.

http://clubhotrod.com/forums/showthread.php?t=44826

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I like the 1969 - 472 Close chamber heads
those engines were 10.5 to 1 and were about 400 HP with 550 foot pounds of tourqe.

The later engines show reduced BHP figures but its because they started to measure BHP & Torque differently so the figures quoted are not as bad as they sometimes look.
The early engines 68-70 have the 10-10.5 - 1 compression although i'm not sure how well they would do on todays gas, Our gas in england is a little better than yours i believe but still not great.

Quote:

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Originally Posted by vara4

I like the 1969 - 472 Close chamber heads
those engines were 10.5 to 1 and were about 400 HP with 550 foot pounds of tourqe.

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I would still install new valves and have the heads re - worked for todays fuel because those were made for leaded fuels. I am not sure how deep you are getting in to the moter but I would if I were re - building it use the earlier 70 pistons for the 500 because they are also differant then the later 500 pistons.
Kurt

Cadillac heads don't need hardened seats as they are high nickel steel.
No need to use the earlier pistons as these days there are KB hypereutetic or Forged available.
You can't use the earlier piston with the later 120cc heads as the compression ratio would be stupid. Also the stock pistons either early or late are not recommended.

My engine will produce in the region of 600bhp @ 5500rpm built as per Docs book, my pistons are +60 thou so is 514ci the only original part is the block and crank and both of those have been heavily modified.

Quote:

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Originally Posted by vara4

I would still install new valves and have the heads re - worked for todays fuel because those were made for leaded fuels. I am not sure how deep you are getting in to the moter but I would if I were re - building it use the earlier 70 pistons for the 500 because they are also differant then the later 500 pistons.
Kurt

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Roadster I know about the high nickel in the metal the old caddy's had thats why they wore so good or lasted so long. I was just mentioning the pistons because there were several piston changes over the years. Of couse the after markets are better and you could make lots more HP. There are lots of thing you could do to a new motor like that differant cams fuel injection after market heads intakes and all. The question is how much does he want to spend $$$$.
Kurt

I've messed around with a few Caddy engines in the past and found if you want the stock intake to flow a bit better you can (see pic) re-work the center divider. With a 1"-2" spacer it will give you a noticeable increase in mid-range power. The better way is of course to purchase the Edelbrock aluminum intake but, plan on speeding $200.00 or more.

"Great" engines with excellent torque!

http://img.photobucket.com/albums/v2...gravy/0045.jpg