Another noobie... Head questions

[MY FYN 79]

I finally came across a good deal for a 500 Cadillac locally. The motor is out of a 75 or 76 rear wheel drive Cadillac.

I'm looking for info on Cadillac cylinder heads, mainly casting numbers and specs for which heads are best for a moderate buildup.

Sorry for the newb question, hopefully I can be around a little more from now on! :)

[Terrible One]

120 cc heads with stock 75 or 76 pistons will make 8.5:1, 120cc heads with KB flattops make 9.2:1, 76cc heads with stock pistons from a 75 or 76 will make 13:1, 76cc heads with KB bathtubs will make 10:1.

Then, of course there are a lot of different forged pistons and combos...

BTW your engine has 120cc heads and 8.5:1 compression as is.

[MY FYN 79]

Thanks! :)

Soo, I guess my next questions are...

Did the earlier 472s use the same heads as the 500s.. ? The guy that I'm getting the 500 from has several older 472s as well. Maybe I could talk him out of a pair of the 472 heads.

Next question,, It seems a person can work around the fact the heads have 120cc chambers as far as compression... So is the 120cc chamber head necessarily "worse" than the 76cc head as far as runner size/valve size/chamber shape etc?

[Nashalac]

This still depends on how / what your intentions are for the motor. The 76cc heads will flow better than 120 heads but a "stock" type build it is not important.

[Terrible One]

Yes, earlier 472's came with 76cc heads and 10:1 compression.

[Nashalac]

472's had 76cc heads but the compression was lowered either in 71 or 72 by changing piston design. Do not recommend putting 76cc heads on a later stock pistoned 500.

[dave_brode]

MY FYN 79,

'68-'73 472s, and 70-73 500s all have 76cc heads. The '71-'73 have lower compression, via different pistons. The '74 472 and all 74-'76 500s have 120s.

If your engine is a '74-'76 500, and suitable for re-ringing, a small block deck cut, and a small head cut can get you a 9-1 CR. Quite a nice build with the right cam profile. The earlier heads can get you more power, but not a huge amount in a moderate build.

The casting #s are on the top of the heads, under the valve cover. You can measure the stroke with a wire through the plug hole to be sure it's a 500 [a 500 will measure apx 4 & 5/16"]
Dave



"]I finally came across a good deal for a 500 Cadillac locally. The motor is out of a 75 or 76 rear wheel drive Cadillac.

I'm looking for info on Cadillac cylinder heads, mainly casting numbers and specs for which heads are best for a moderate buildup.

Sorry for the newb question, hopefully I can be around a little more from now on! :)[/quote]

[MY FYN 79]

Thanks for the tips guys!

I went and looked at the motor tonight. The guy I'm getting it from got a couple he had confused.. and I'm suspecting this is a 472.

It has a points distributor, standard BOP bellhousing pattern, still has the super long tail TH-400 bolted to it, and it has the motor mounts with the one bolt coming off the bottom of it.

He thinks its a 69ish 472.. does that sound feasible? If it is, then it should have the 76cc heads which is good... but its kind of a bummer it isnt a 500.

Thoughts?

[Nashalac]

If has a stock points dist and a FRONT sump pan it is most likely a 472. If it has a rear sump pan it COULD be a 500 if it is a 1970 or later

[tommyhawk13]

If it has both points and a long rwd transmission, then it is a pre 1974 1/2 rwd motor (unless it was a swap). That would mean it is a 472.

Does it have smog rails and a smog pump?
Double belts on the AC compressor?

Check the numbers for the year of production to find out what compression it has. The first 472's were even higher comp, 10.5:1, if memory serves me correctly.

An old 472 puts out about the same power as a later smogger 500.

[68C15]

I'm going to jump in here. does the higher (10:1 or 10.5:1) compression show bennefecial in terms of useable power? I have heard alot lately about lower (8:1 or so) being quite powerful when combined with a different cam. I know HP is a mathemetical drivitive of torque & have heard torque generaly comes from compression.
or am I just reading into this subject a little too much?

[tommyhawk13]

I'm going to jump in here. does the higher (10:1 or 10.5:1) compression show bennefecial in terms of useable power? I have heard alot lately about lower (8:1 or so) being quite powerful when combined with a different cam. I know HP is a mathemetical drivitive of torque & have heard torque generaly comes from compression.
or am I just reading into this subject a little too much?

High compression is worth about +20hp in the stock motor. When you add power with cams, headwork, etc, the benefits increase exponentially. However the cost of high compression means you'll need high octane fuel, and still a risk of detonation.

[MY FYN 79]

I'll start by saying that I purchased the MTS book on Ebay for finding out info, but until that comes I'd like to figure out what I have. :)

I got the motor and pulled it apart. Looks real good inside, very minimal ridge at the top of the cylinders. It still wears the stock bore, stroke was 4.060ish... meaning it is in fact a 472, the pistons didnt have any obvious numbers stamped in them other than an arrow and a number 7... but the thing that caught me off guard was the fact the motor is zero decked. I cant hardly see that being done from the factory, right?

Here is a list of things about the motor.. Anyone wanna see if they can pin down the year of it?

Front sump
Dual A/C belts
Points
250 heads
Crossover on the front of the cylinder heads only
Non EGR intake
Jumbo long tail TH-400
1495200 on the back of block/ E5 on the backside of the block in the bellhousing area

Once I determine exactly which block I have... I'll want to find out if the block is perfectly suitable for a 500 build. As long as it doesnt need oiling mods etc. I plan to use this block.

Thanks in advance for any thoughts! :D

[Ted in Olympia WA]

This should help.
http://www.geocities.com/MotorCity/Pit/9364/guide/Engineid.html
The 250 heads were on 68 through 73 so you have to look at the piston. If it a big soap dish than it a low compression 71-73 if it smaller than it's a 68-70. If the block number is 5200 than it a 70-73, if it 6238 it's a 68 or 69.
Dosn't really matter if you are rebuilding it anyway, you can change out the pistons for low or high compression. I guess the 5200 blocks are better for oil control.
TED

[MY FYN 79]

Thanks a bunch Ted! :D

With all that info I figured out I have a 1970 472 with 10.5 to 1. I also read that the 472 had a higher compression height than the 500, but I'm still surprised the pistons came up flush with the deck. Anyone else see that?

[Ted in Olympia WA]

They are all within .010 of the deck. Cadillac builds them right.

You got the best 472 you can get and the 2nd best cad motor in stock form. But all a them can be rebuilt to the same standards.

Terry on the other board with your engine in a G-body is running a 13.5 with high 2 gears.

Some people like the 472 better because of the shorter stroke. In the past they just did not have the pistons available for them to rebuild them to 10:1 but that is all fixed now.

What are you going to put it in, I thoght you mentioned a Camero, but may I suggest a Fox body mustang if you want to go fast.

TED

[STDog]

Thanks a bunch Ted! :D
With all that info I figured out I have a 1970 472 with 10.5 to 1. I also read that the 472 had a higher compression height than the 500, but I'm still surprised the pistons came up flush with the deck. Anyone else see that?

I'm not sure that the smog pump was put on any '70 engines. And most '70s also had the 950 heads, with out the smog rails, but some (early?) had 250 heads with the rails undrilled.

The block actuall chnged late in '69, so that all '1970 engines were made with 5200 blocks.
The 5200 block (and the 500) were designed mid year, so the othe block would have ceased production and the 5200 started well before the '70 model year to ensure enough engines. I think there was a strike in '69 too, that factored in tio the change over.

This pistons are the same for all 3 years. So if it's stock, and has a 5200 block, 10.5:1 pistons, and smog heads, it's a late year '69.

[Ted in Olympia WA]

1970 was a funny year, I have a 1970 500 with 250 heads but they are not drilled for the air pump.
Terry's engine is also a 1970 472 with the 250 heads undrilled.
TED

[STDog]

1970 was a funny year, I have a 1970 500 with 250 heads but they are not drilled for the air pump.
Terry's engine is also a 1970 472 with the 250 heads undrilled.

Right, but they never had the smog pump either.

Notice thay "MY FYN 79" said that there is a "Crossover on the front of the cylinder heads only". Un drilled 250 heads wouldn't have that, since the rails are not drilled.

I've got the GM shop manual for 1970 (since I drive '70 coupe). And there is no mention iof the smog pump (A.I.R.) in it for any vehicles. The only place I could see it would be a CA car, but wouldn't the manual mention that? Or would that be a seperate suppliment?

That's why I don't think it's a '70. The pistons say it's 68-70, and the block says it can only be 69 or 70. Only one match to all that. late '69 after the 5200 block went into production.

[Ted in Olympia WA]

Sorry I missed that smog pump thing, you are right, must be a 69, but why the 5200 block? Must be a late 69.
TED

[MY FYN 79]

Sounds like I have an interesting motor! LOL

I would also gather that the motor is a late 69 472 then, due to the block being the 5200 casting among other things.

Ted, the motor doesnt have a certain home quite yet... I just always had a thing for the big Caddy motors. Now that I have the means (and found one), I'd like to take my time and build it.

Theres a good chance that someday down the road it will end up in my 79 Monte Carlo though. The car is light and fast (see sig) with the current roller 383, but I'd like to gear it up, change the 2004-R for a TH-400 (already have) and bolt the Caddy in. :twisted:

Once again guys, I'd like to thank you for the nice replies even for a nOOb like myself... it really shows the maturity of this bunch!

P.S., expect some head work questions regarding the 250s soon! :) To big valve or not to big valve... that is the question.

[Andy V]

The high compression 472's should have the pistons at zero deck, or close to it.

What you have is a very good base for rebuild....the 5200 block has larger oil circuits (the oil pickup tube is larger for instance). The 76cc heads are the ticket depending on what you want to end up with.

What did you have in mind for the rebuild? If you want to freshen it up and not spend much money I'd just hone the cylinders to get rid of the ridge, thoroughly clean the pistons up with new rings and go. Rebuild the heads and check the crank (might need cut .010 or so)....and you're ready to go for pretty cheap.
Consider finding an HEI out of a 74 or later to replace the points distributor.
On the 250 heads, I'd plan to use 2.11/1.77 or 2.19/1.81 ish valves...have the shop give you a good bowl cut when they cut for the larger valves...you can then blend everything with a die grinder and several hours of work. Depending on the cam you may choose, get the spring seat area cut down while you're at it....allows more lift and have the dia. cut down if you might want dual springs...You may have $600 or $700 in head work but it will be worth it.

my $.02

[MY FYN 79]

Thanks for the tips Andy.

Seeing as this will most likely be a long term rebuild, I have the short block complete hiding under a bench yet. The heads are my first main focus, and they are currently by my builder waiting to be cleaned up and checked for cracks etc.

Your recommendations for the heads are actually pretty close to what I was thinking. I'm a bit of a backyard porter "Done a couple and enjoy doing it and learning", so the idea of having my builder cut a little further in sounds like a good idea. Along with that, it looked like there would be a little to gain with some bowl blending. I've never actually reshaped anything during porting, just cleaned and smoothed what was already there. Seems you could quickly do more harm than good. At least I'm a wise "backyarder" :D

As for the short block....

Seeing as how clean this motor was inside, I'm kinda stuck between a rock and a hard place. I wish the motor would have been ugly inside, then it would have been a no-brainer to get a 500 crank and build a fire breather. Like you mentioned, I bet I could get away with a hone and a freshening on this motor... But I just feel obligated that if I'm gonna take the dive and go through with this, I might as well build a 500+ motor.

If anyone else has thoughts/opinions for head work or short blocks or whatever.. feel free to toss it up here! I need to be swayed one way or the other. :)

[Andy V]

well I have done both....first I took a 68 472 and did the hone/clean/re-assy...spent less than $1800 on everything. Beat the crap out of that motor, sprayed it with a 125hp shot for about 30 drag strip passes. It was fun and had little to worry about cause my reasoning was if it blew...would give me an excuse to build a 'real' motor. Thing is it ran dang fine and I ended up pulling it just cuz I got the itch.

So now I have a 514 in the car, with forged rods, new pistons (KB's), heavily modified heads....etc. Yes it's pretty and makes more power but I spent around $3500 (makes 337hp/420lb-ft rear wheel actually).
For the money I must say beating on a basically original motor is more satisfying (just my opinion).

Personally I wouldn't worry about getting a 500 crank...if you want some more cubes go 060 over or 100 over to open that bore up some. If it's going into your Monte the big bore/shorter stroke option may actually work better (again IMO). Less low end torque that'll spin tires and more top end pull...especially if you do the heads like you're thinking with bigger valves. A cam, Edelbrock intake, and HEI will round it out nicely.

[MY FYN 79]

Some more food for thought, thanks.

I plan to focus on the heads and do a nice job on them for now. You must be correct about the zero deck also.. I snapped a picture of it today. It shows no evidence of being surfaced, so it must have been a factory thing. That was very thoughtful of Cadillac back in the day! :)

http://memimage.cardomain.net/member_images/6/web/438000-438999/438326_219_full.jpg

Also Andy, I was curious about your complete 514 combo including the car its in as well as the driveline. My Monte made 368/449 to the wheels (respectively) on a Dynojet dyno with my roller cam 383 motor. How fast is your car?

[Andy V]

info here in this post.....

http://forums.500cid.com/viewtopic.php?t=43


Car weighs around 4900lbs w/ me in it. 2.94 rear gears.
I got to the track once with the 514 in it...managed 14.25 @96.2...I think it will run a 14.0 or high 13 once I get some more tuning time.
On the bottle should run high 12's.

The old 472 motor ran 14.8's on motor at 92....on spray ran 13.8 @ 101