sd4 engine

[shredeagle]

I came across a pontiac sd4 complete running engine  I was thinking of putting in my 81 sx4. im just not sure what such an animal would be worth . any input would be helpful . thanks.........

[captspillane]

The Pontiac Super Duty Iron Duke's were usually 1980 and newer, which means that they will not bolt to your Eagle transmission bellhousing. The newer ones can only use light duty "60 degree" GM transmissions. I like that our Eagles can use heavy duty cheap SBC transmissions like the 700R4. The Pontiac engines were only called "Super Duty" because of how much bigger and stiffer the crank was in comparison to a normal Iron Duke. It was an expensive upgrade at the time but I wouldn't pay much for one now because of how commonly available those super duty cranks are. Every single Mercruiser Marine Engine has the same crank. I've got 3 Mercruiser motors so far for $300 total. They're very common and very cheap once the boat rots out from around them.

I also prefer to use the Mercruiser blocks because they have a factory overbore available. The first Merc Iron Dukes were 2.5L but eventually they offered a factory 3.0L stroker version too.

The biggest problem with the Merc blocks is partially an advantage. I like the non-cross flow head. It opens up the crammed passenger side and makes the Iron Duke much easier to maintain and work on. You lose a small amount of flow advantage to the cross flow heads, but I think it is worth it to me. I'm using factory manifolds from a '77 or '78 Iron Duke and it wouldn't be hard to make your own headers if you couldn't find a set.

Alternatively you could rebuild the Eagle engine with the internals from a 2.5L Mercruiser engine to make your own Super Duty Eagle engine. The donor engine will probably cost about $100, so you'll probably have more in the rebuild kit then the Super Duty hardware itself. If you get the Pontiac Super Duty motor for less than $200 you'd probably be best to move those parts over to the Eagle block anyway, so it's about the same deal.

[shredeagle]

thanks so much for the info. I was led to believe the sd4 was a bolt in replacement. the guy wanted 3000 bucks for it. I would like to talk to you more about the mercruiser options if that's ok with you ? thanks again..........

[captspillane]

I've actually written alot of the information down in this thread, here in the same section of this forum. There is even a side by side picture of a Mercruiser crank next to the stock Eagle crank. It is visually obvious that it is stronger.

http://forums.amceaglesden.com/index.php?topic=38412.0

[carnuck]

You CAN use the 904 off the AMC 4 cyl  (909 if it's lockup) from '83 Up Eagle and '84 up Cherokee/Comanche 4 cyl or 2.8 V6 or AX-5 from the std trans ones. The flexplate/flywheel is another issue as well as exhaust, mounts, etc, but the bell pattern is 60 degree GM.

[Blip Downshift]

I know this is an old topic but the mercruiser and SD-4 are not the same.  The mercruiser is based of the old chevy 153 platform and uses a ductile iron crank, ford pistons, and a ford head.  The SD-4 is based around the pontiac iron duke (half a pontiac 302) and uses the GM corporate 60 bellhousing design so the mounting points will be different than the chevy SBC style that is found in our eagles.  With some modification, it can be made to fit but the front differential mounting may be problematic.  The SD-4 also uses a forged steel crank, SBC rods and pistons, and has a performance version of the cast iron head and two different performance variations of aluminum heads (the 431 and 801).  A mercruiser crank can be fitted into an iron duke with some extensive modifications and is much stronger than the iron duke's crank.  People have also put mercruiser engines in there eagles and spirits with some work as well.  SD-4 cranks and heads can also be fitted into iron dukes but the head bolts must be enlarged for the SD-4 head.  The iron duke has a notoriously weak bottom end which really holds the engine back.  The iron duke block in the pontiac fiero pace car with a stock iron duke block, SD-4 cranks, and SD-4 cast iron head made around 237hp.  I am not sure what else they had to do to get it up to the power and the engine probably didn't have much longevity.  The link below is from the stickman's web page which gives some good comparison info about the iron duke and SD-4:
http://thestickman.tripod.com/DUKE-HEADS
The next link is from a gentleman who goes by stroker 151, the information is top notch but the delivery is a little patronizing:
https://fiero151.wordpress.com/iron-duke-performance/strokers10s-holy-grail-of-151-performance-data-2-5l-myths-and-differences/

[Blip Downshift]

I misspoke, the mercruiser crank is made of out nodular iron.