1984 SD4 Resurrection

[Shaun41178(2)]

Seems like a lot of work and expense to do a SD the correct way. Which is prob why there are so few of them. Def cool engines though

[FieroWanaBe1]

I think these were really only intended for sanctioned racing, which is always a lot of work and expense. And at the time all this stuff was a catalog PN, and easy to order, but racers have moved on from the tractor technology of the Duke.

[FieroWanaBe1]

I pulled the pan out off my storage shelf.
I will need to Fab up a windage screen since it never came with that component

[FieroWanaBe1]

Did some playing around.
The dry sump pans need modification, no room for a starter.

[FieroWanaBe1]

Flow of iron head with 2bbl Edelbrock intake.

[FieroWanaBe1]

I found a cheap harmonic damper on rock auto. This one is from a chevy straight six. Two v belts spaced 1/4 apart.

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[FieroWanaBe1]

Found this dry sump pan on eBay for a "Pontiac 2.5l V6" $30, has some damage.
Bought a brand new duke pan on Amazon for $70, hopefully after some careful grafting I will have a better dry sump pan.
The pump I had bought years ago was actually a power-steering pump, so I found a different one.

[FieroWanaBe1]

After reading the later version of the SD4 build book, I discovered there are 2 versions of the Fel Pro sd4 head gasket.
Pontiacs description differs from Fel Pro's and the interchange was goofy, but the aluminum head has a different fire ring arrangement to eliminate brinelling.
1015 has a steel fire ring 1015-1 has a copper fire ring.
I seen a 1015-1 on rock auto and bought it for $28. As it turns out shortly after buying the '801 head I bought this same head gasket for $65 from jegs, it just took 6 months for it to arrive.

At least I have a spare.

[FieroWanaBe1]

There is a 437 head on eBay for $1500 (I think that's a bit high)

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The chambers are interesting, they have a lot of work done to them. They must have been welded to achieve the heart shape. No other SD4 head I have seen has that much material in the chamber, they all have a sort of bathtub shape, My 801 head and iron head have almost identical chamber shapes. They also have cut channels to the pushrod holes from what I believe are oil return holes.

Compared to lilchief's 437 head chambers:

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[Shaun41178(2)]

It might be a 437 head but it's a revised casting perhaps. The coolant jackets aren't the same either in both.

Which tells me it's cast differently

[FieroWanaBe1]

It very well may be a different casting, from my understanding of the evolution of the SD4 head casting, It was:

10027776/10027775 1st Run Iron head, with Production based exhaust runner shape, and large pushrod pass through holes (must be sleeved and ported)
10031322/10031323 Redesigned Iron head with raised floor exhaust ports and reshaped intake runners that do not require sleeves to be ported.
10038433 is 1st design the aluminum head, has the same port design as the iron, with a revised cooling jacket, and guide/seat inserts.
10045437 is the 2nd design of the aluminum head, this head has raised and enlarged exhaust ports.
10049801 is the 3rd and final design of the aluminum head this head has raised and shifted intake ports, and the same large exhaust ports as the 437 head.

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According to Pontiac the aluminum head design omitted the coolant ports that go to the intake valves to better cool the exhaust vales. Both Hot Rod build guide versions I have instruct to block off those ports in the early blocks, and they where omitted in later revisions of the block.


Lil chiefs version of the 437 lacks the small cooling jacket holes inboard of the head bolt holes, my 322 head has these, as well as my 801 head. The 433 head in the 2nd edition Build guide also has these small ports.

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The 437 head feature on youtube, has the traditional chamber and the small coolant ports.

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I would think it strange, pontiac/brodix would design a special heart shaped, fast burn chamber head, then release a new head with the old less efficient chamber for their all out competition head. But stranger things have happened.

Another 10045437 Head Chamber side from ebay:

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My raw 801 chamber:


EDIT: Part numbers updated to correct casting. New ebay head added

[FieroWanaBe1]

There is a weber intake w/carbs on ebay

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List price is: $1700, more than I want to spend on carbs I wont use.
Seller says the engine was 2.7L, and made 290HP with this intake on a dyno.
I messaged to confirm it fits a 801 head, he said it was for the 801/

https://www.ebay.com/itm/115666749191?m ... media=COPY

This intake and carb setup was lightly used on am SD4 for dino and tuning and then sat in storage for the next 30 years. These are capable of making good power with the SD4. I have the dino sheet from the engine this was taken off (2.7L) and it made 290hp. If you have a built SD4 you can expect to get similar results, but of course head flow, cam, displacement and compression are going to play a big part. The intake has the fittings for dry sump oil scavenge, but can be blocked off with a threaded plug if you are using wet sump.

I still plane to use the DCOE throttle bodies, but I will fabricate a intake (still leaning towards a CF-Nylon print)
that has a upswept angle similar to how the Kinsler intake was designed, that would keep the air horns away from the trunk wall, and place them inside my big ass roof scoop.

[Shaun41178(2)]

This is why a lot of people end up turning away from sd4 builds. Parts are expensive even though there is nearly zero demand

[FieroWanaBe1]

Low supply as well demands a premium when items pop up from storages.
Being it is such a limited demand, I'm sure he may end up sitting on that a while until the perfect buyer shows up. The 801 head is much harder to find I'm seeing than a 433 or 437 head as well.

I would be more inclined to make this one work, but the straight runner design doesn't package in a Fiero with a trunk wall intact all that well.

I'm just glad I have the ability to make a similar intake myself for much lower cost. I have a spool gun for my MIG, plenty of cutting and shaping tools, and a few friends with pretty good TIG skills, as well as the software and hardware to print a test piece.

[FieroWanaBe1]

https://bringatrailer.com/listing/1985- ... -fiero-18/

caught this GT2 Fiero racer on bring a trailer.
Has a 2.7L SD4 with 801 head, converted to EFI with waste spark.
Obvious roller cam, 1.55 rockers give that away, all the roller grinds I see are for 1.55 ratio rockers.
Pretty interesting build, but left in rough condition.

The dyno sheet for the engine the weber intake on eBay was shared with me, it made 290HP, above 8000RPM.

[FieroWanaBe1]

I have Ebay alerts on for Ponstiac SD4 listings.
Someone posted several SD4 parts up yesterday.
I purchased the camshaft, looks like it fits the goals I have for power over 200, where as my current hydraulic flat tappet cam seems small for the '801 heads. (.522 lift)

It is very close to the mechanical flat regrind recommendation from another vendor, with .030 more lift.

RPM for Peak Torque = (60*(Duration/360)*(FPS of port*12)*CSA)/Cyl volume
6844 RPM = (60*244/360*260FPS*12*2.31)/ 44.25cuin
FPS = Flow CFM * 2.4 / Ave CSA
260 = 255 *2.4 / 2.35
Flow CFM = HP/(.2575*# Cylinders)
252 CFM = 260/(.2575 * 4)
AVE CSA = Port Volume/16.387 / Port Length
2.35insq = 184cc/16.387 / 4.75in

At minimum I need my heads to flow 252 CFM with a 180cc Port. The 322 head in its current state is 20CFM off the mark,

Other calculations from David Vizard recommend flow of 314CFM, the current head at .550 lift is 75 CFM off the mark.
The 437 head, from all sources i have, looks to be 300CFM capable, I can only assume with a higher port that flow is achievable, hopefully with a smaller volume to keep velocity high and rpms lower.

[FieroWanaBe1]

A video of a damaged '801 head on came up on youtube. This head has a more shrouded/quench pad chamber, similar to the 437 head I saw on ebay earlier this year.

[FieroWanaBe1]

I was curious what the oil passage to crank journal clearance would be with the IRL 1.850" rod journal:
Around .302" worst case, but should be aided by the crank pin radius.

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[FieroWanaBe1]

https://k1technologies.com/blog/what-is ... eve-length.

I have been giving this a lot of calculation and thought.
The 2.5SD block was designed and released when Pontiac Only offered a 3.25" stroke crankshaft.
It seems after the first run they switched to a "Super Duty" block with longer sleeves and that aligns with the IMSA car moving to 3.0L and 3.6" stroke.
All of the cylinder sleeves on my 2.5SD block are about 5 1/8" minimum length.

Offset Grinding to 3.48" stroke with the 6.2" rod on a IRL (1.850") journal puts the standard gauge point of a JE piston out of the bottom of the bore
by .079"

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Speedmaster offers some 6.250 2.1" Journal race Rods that should work with my Crankshaft as is:
https://www.speedmaster79.com/I-Beam-Ra ... vy-SBC-350

They happen to be on sale right now too.

Because my crankshaft and bearings show no signs of any issues, I feel confident to reinstall, check clearances, and use it as is (with new bearings).
This also means I can use a SBC/SBF piston with a few small changes, as opposed to a piston with a lot of changes.
Anywhere from a off the shelf Hyper Flat top piston can fit with some machining on the piston face, or a less custom piston could be ordered.

What is the most appealing is a standard JE piston gauge point is .086" inside to bore still.

The SD4 build manual has the piston to wall clearance measured .4" below the oil control ring, or just below it in the later manual (BRC vs JE pistons).

The 5.7" rods my engine used originally kept the pin just in the bore by a little over 1/32", which explains the severe wear on the bores.

Using the IRL spec Cup Car rods, means a very custom piston (so far about $154 per from JE so not terrible)

I am back and forth on the route to take. The difference is 7 Cubic Inches, and probably a shift in peak power and torque by 100RPM with the current cam.

But just using the SBC rod may mean I would be able to assemble the engine quicker by not sending the crank out for regrind, however it will need a rebalance regardless.

[FieroWanaBe1]

I just put my Iron SD4 head and the 2 barrel intake up on EBay.
https://www.ebay.com/itm/126067491761?m ... media=COPY

https://www.ebay.com/itm/126067465489?m ... media=COPY