SD4 engine information is scattered all over the place.
Maybe everyone can add what they've found in this thread.

Fiero PDF manuals.
https://fieroinfo.com/

Some discussion on the SD4 here:
https://www.fiero.nl/forum/...030531-1-023674.html

Rod Shop's G/A Fiero driven by Larry Morgan
This SD4 equipped drag car had 538hp
https://www.motortrend.com/...-1986-982-1362-36-1/




The SD4 engine was never offered in a Pontiac production vehicle.
But everything was available through GM/Pontiac Performance Parts and the engine was used in many race series.
I bought the Edelbrock 4-bbl intake manifold and Edelbrock PONTIAC valve cover through a GM dealership.

The SD4 head will bolt to the Duke block after modifications to the block have been made.
But you will still have a weaker block and internals limiting you to the Duke's 4500rpm redline.
On the other hand, the SD4 block and forged internals are good for 10,000rpm max.

The SD4 can be completely steetable, depending on how you build it as with any engine.
With solid lifters, redline is usually held at a conservative 8,000rpm.
Hydraulic lifters will limit you to about 6200rpm when you encounter valve float.

With my SD4 engine, I have a bit of a lumpy idle and gear whine but it has lots of torque and pulls strong from idle to redline.
I've taken it on city and highways drives since I've built it. On the highway I get 36 mpg (30 mpg to US gallon).

Link to my SD4 engine build in my Indy #163
https://www.fiero.nl/forum/...HTML/000077.html#p31


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My World of Wheels Winners (Click on links below)

3.4L Supercharged 87 GT and Super Duty 4 Indy #163

[This message has been edited by fierosound (edited 11-17-2023).]

Super Duty Guide download at Calgary Fieros Facebook group (need to be ON Facebook)
https://www.facebook.com/gr...ink/1821870724817695

SD4 Supplement
https://www.fiero.nl/forum/...060206-1-052708.html

Hard to find Cosworth 16-valve head kit looks like this.
https://www.fiero.nl/forum/.../HTML/075813.html#p1



Kansas Racing Products was licensed for sales/production (not sure what year).
They are now gone, but here is an archive of their website:
https://web.archive.org/web...sracingproducts.com/

Wayback Machine to the rescue again.
https://web.archive.org/web...ocks-gm-pontiac4.asp

[This message has been edited by fierosound (edited 11-17-2023).]