425 heads on a 500 and other questions

bamabob

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I have a 425 in my 52 now but have a complete 1976 500 engine in storage. The 90*water outlet on the back of the passenger side head is has rusted through and has to be replaced which means removal. While putting forth the effort of correcting this issue I might as well go big while I'm at it. Every time someone ask me what engine is in the car I almost feel like I have to apologize since it is a 425 instead of a 500. I'm thinking the 500 I have was a 65000 mile motor and was parked because of a fuel injection problem that could not be sorted out so engine should be in good shape as is.

I was thinking since I have a good bit of time and $$$ in the 425 heads I may could use them on my low compression 500 shortblock. I'm not racing and not reving high so not looking for max HP. IIRC this was frowned on because of compression being too high. Just wondering is using the 425 heads on a 500 a good option under any circumstances. I do have the ignition module that retards 10* on starting and don't mind using premium fuel. Would be open to a cam changeas well (have an old Erson RV grind now).

Any thoughts an opinions appreciated.

Bob
 

Chevlac

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The reason why Tom said "no can do" when it comes to bolting a pair of 425 Cadillac heads onto a 472 0r 500 block is because there's differences in the way coolant passages are shaped between the blocks & heads. The 1977 & later Cadillac blocks are way different (internally) than that of the 1976 & earlier ones. Some external parts are "interchangable" but the heads, pistons & ( now understood ) the 500 c.i. cranks aren't "interchangable". That's why the "425 into a454" idea won't work well. Yes in theory, it could be done, but in the "real world," it's a "no-go". Same for the heads, yes a set of 425 Caddy heads will physically bolt onto the earlier Caddy blocks but, you'll have severe overheating problems due to very restricted coolant flow between the block & heads. You'll end up blowing the gaskets or maybe even the heads or the block itself. Same thing when trying to use a 500 crank in a 425 block, too much stroke for the lighter blocks to handle. I like the 425's "as is". They may not be the super power strokers that the 472's or 500's are, but then, if one want's to use a t.h.200/4r or some other late model "overdrive" g.m. tranny behind a Caddy big block, then one doesn't have much choice but to use a 425 or,... a "dreaded, horrid 368" :yikes: Did I just say something blasphemous?
 

cadillac512

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Hold on there,fellers......it can be done and will run ok.

http://web.archive.org/web/200101211913 ... ticle4.htm

That's an archived link to Al Betker's old MTS site.He did a lot of testing on this conversion and found it is a viable setup as long as the limitations are known. As for the coolant circulation,it's similar to a 400 sbc....you just need steam holes drilled in the block decks to align with the 425 heads.
Proper modificationn sequence is:

Lay 425 gasket on 500 block
Mark steam hole locations
drill holes at slight angle

Lay 425 gasket on 500 gasket
mark steam holes
drill steam holes


Use the modified 500 gasket when installing the heads. The water passages at the upper ends will be slightly misaligned but will seal. The compression will not be as high as once thought...the 425 heads are actually 106cc vs the 500 heads at 120cc. Compression on a late 500 with 425 heads will be between 9.2 and 9.5

Terry
 

Nick Campagna

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Very nice Terry, I've been looking for the archive. FWIW, my new steel shim gaskets incorporate the needed holes for this swap.I'm in the process of cutting some heads length wise to verify the flow patterns in a visual manner.
 

JW

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Since you already have a set of 425 heads that are ready to roll

I am going to agree with TP

Use the 425 heads and mod the block as he described

JW
 

Chevlac

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Yeah, thanks Terry, I was told that the swap was a "no-go" by a few people who said that they've been working with Cadillac engines for several decades. Just goes to show that even if one has a long experience with something, doesn't mean that they know everything about it.
 

PROSTOCKTOM

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I say No Can Do, because of having to drill holes into the deck of a 472 or 500 block.

Which seems like a good way to waste a good block to me.

I'd much rather see someone rework some heads than go to all the trouble to put 425 heads on a 472/500

But everyone has their ideas of what works for them.

Tom
 

cadillac512

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Although true,the added small holes required do not compromise the integrity of the 500 block nor do they prevent you from using 500 heads in the future.The undrilled 500 gasket simply covers them up like it does many already-existing holes in the decks.

Terry
 

JW

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If he was starting from scratch on a build id say not to do it ,however since he has the heads and they are finished

Why not ?
 

cadillac512

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Doc Zinger said:
Bob do you have any pics of your '52 on the site or someplace? Looks like on hell of a rig!

Bruce,


I really like the looks of Bob's car. :thumbup:

Terry
 

bamabob

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Thanks guys for the info. Still don't know for sure what I want to do. Just considering my options. The 425 is sufficient and does have a somewhat built up 200 4r behind it that I like. The 500 would probably do it in. It all works good with the 3.42 gears. But every time I walk past that pallet with the 500 on it I get tempted.

As for the water outlet on the head, is their a work around to using the back of head outlet. Things are a little tight there and I would like to just put a freeze plug in it and reroute flow to heater (which I don't have yet)

Still trying to finish the interior and work out other details. Have put only 600 miles on it so far and it is a ball to drive. Latest overcome concern was the front end alignment. The car has a camaro subframe with narrowed control arms (all home done). None of the alignment shops in town could get it on their rack so I bought a Longacre caster camber gauge and was able to get the front end perfect in alignment. It was sort of a surprise actually how well it drives, corners, etc.

Here's a link to some additional pics I had posted a while back.

viewtopic.php?f=3&t=12891

Thanks again to all for the guidance.

Bob
 

Chevlac

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Thanks Bob, you just answered a question I posted to "Greybeard" Doc Frohmander.
That was, Can a T.H.200/4R automatic transmission "survive" behind a reletativily "stock" 425 Cadillac engine?
Well, your car has just the droivetrain combination I was concidering for "Project ImpaVille". And just like you, my "project" is taking a long time to do. You chose an early '50's style body, I chose a late '60's style Chebby. I don't know why you like the body style your working with, but I'm sure you have some "special" reason for your choice. My reason for the body style I have is because of "fond memories" of the time when I was a teenager & My Mom bought a '68 Impala 4 door H.T. that was quite the "sleeper" with a bored & stroked 327 sbc & 'Glide tranny that could ( with ease) out run even a mildly "hot rodded" 'Vette. I'm not lookin' to race on the street, just want a real nice, vintage Chebby "Sport Sedan" that will cruise the highway with ease & get decent fuel milage, but, when ever the "itch to boogy" needs a "scratchin'" well, then, if the road is clear of traffic ahead, "it's full tilt boogy time". Then slow right back down to the speed limit & just let the "unsuspecting" driver go by just thinkin' that, "that old Chevy is something I haven't seen on the road in years, sure brings back memories". I'll just glance of to my left, wave, & drive on real quiet like with just slightest of a "rumble" from the "big-0l'-Caddy" under the hood. Just letting everyone who looks at the car, think that the car is "just a 327 powered family car", no "big deal". :devil: :devil: :devil:
 

bamabob

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You'll like the 200 4r. I have the looser GN TC in mine and lock the tc in 4th only. The car pulls like a freight train and sounds like a hot rod but when it goes into 4th and locks up it quiets down and lumbers on down the highway. The first to second full throttle shift with the super servo is neck snapping. If it can break I'll probably find out soon. I didn't put the upgraded drum in mine but wish I had.
 

bamabob

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How about rerouting the coolant flow for the heater. Can I put a freeze plug in the head and pick up water elsewhere?
 

cadillac512

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bamabob said:
How about rerouting the coolant flow for the heater. Can I put a freeze plug in the head and pick up water elsewhere?


Yes. I suggest drilling the block just below the thermostat on the right hand side. Tap it to either 3/8" pipe or 1/2" pipe and install a heater hose nipple. That's where the '70 engines ran the heater supply hose and it works well. The 425 may even have a flat surface there like the later 472/500 engines do.
I just checked one of your pics and your 425 may already be drilled and plugged there....is it?
http://rides.webshots.com/photo/1490854 ... 6353EbuNAY

Terry
 

EZ

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Bamabob,
From all the studying I've done in the last couple weeks the 200-4R will hold up even behind a 500 Cadillac if it is built
properly. Of course the billet front drum and input shaft are must have items. But you should be able to upgrade yours for just a few hundred bucks.

Here's what I posted in the other thread. It's good info!! This isn't the only company building these but they stand behind the 200-4R even at 600 ft/lbs!!!! A street rod type 500 Cadillac should be just fine here.

http://www.extremeautomatics.com/home.html

Stage 2 2004R 750HP

•All Items listed Under All 2004R Plus
•Billet Forward Drum•Treated Input Shaft
•EA Billet 2nd Gear Servo
•8 Clutch Direct
•5 Clutch Forward
•Metallic Hi Energy Clutches
•Dual Feed 3rd Clutch Apply
•Hi Performance Calibrated Valve Body
•.400 Reverse Boost Valve
•1 Year Warranty
$1995 + Shipping

Q - 2004R or 700R4?

A - I have been asked this question more than any other. Straight answer some will not like. Honestly its not even a fair fight. The 2004R will handle power that far exceeds that of any 700R4 or 4L60 that can be build at any price. 2004R has a better gear ratio spread, better Overdrive ratio, will fit many more applications, Lighter, Stronger I can go on and on. The 700R4 is best left to applications where its the only option such as 4WD or All WD, tow vehicles, Lower HP applications or customers that are more concerned with budget v/s strength and reliability.
 

Chevlac

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Hey, EZ, another good "plus" for the T.H.200/4R is that those trannies don't require the need for a "computer" or e.c.m. to control the shifts. Plus, the T.H.200/4R's can & do use a "mechanical" speedo cable. I also like the fact that the T.H.200/4R's have that "wonderful" dual bolt pattern on the "bell" houseing so that there's no need for an adaptor to make them fit engines that aren't "Chevy".
Dollar for Dollar, the T.H.200/4R's are a better tranny over all. Not to say that the good ol' T.H.400's are bad, far from it. It's just that now that gasoline is at the $3.00+ per gallon rate, even for the "cheap" 87 octane stuff, the T.H.400's just aren't the "best choice" for fuel economy or low r.p.m. cruiseing.
 

bamabob

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For all these reasons I have a couple extra 200 4r's on hand. I had not seen the 600ft/lbs rating though. I was thinking once you got past 500 you were in no man's land. One of my extras is a zero mile Monster transmission that a friend gave me awhile back. Not sure which version it is but he bought it for his GN Buick when he was planning to go big but never got it in before he sold the car. Didn't have to think twice when he offered it to me.

http://racetransmissions.com/store/prod ... ts_id/208e

Oh the 200 4R is same length as TH350 and the same driveshaft fits as is. Just move the cross member back and your done.
 
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