Mike Simard

Stuart, there's a TSB that says test determined squirters for piston cooling weren't necesarry and elimnated as of Jan. 14 1987 engine# 81H00677 but I have engine number 81H05746 and it definately has functioning squirters.

Vilhuer

We have tried to determine engine number limit when Porsche stopped adding squirters but I think exact number is still unknown. It is known that early '87 have them. Very early '87 also have slightly different design intake. This should be almost dead giveaway that engine has squirters but it can't be kept as only indication as much later '87 had them. All '87 didn't though and thats why known engine number range is so important.

For Sc application there simply isn't perfect 928 engine. Not from factory anyway. One needs to select parts from 4 or 5 different engines to make best version possible using factory parts. Early '87 squirter block, '87-88 January S4 pistons preferably modified to have oil drain holes in skirts and lower compression tops, modified early 951 rods, '91-95 heads, GT style intake, crank scraper etc. All these parts together will result much better engine than any single stock engine can ever be.

Vilhuer

81H00677 = '87 M28/41 manual gearbox car engine
81H05746 = '87 M28/42 automatic gearbox car engine

First manual engine was 00501 and first automatic engine was 05001.
00677 = 177th manual engine
05746 = 746th automatic engine
Depending on how many automatic vs manual cars were made its possible 05746 was made before 00677.

Its impossible to know how factory stopped adding squirters. Unless some specific limit is found also for automatic engines its always possible they continued getting last squirter blocks later than manual cars.

Ispeed

Telltale signs of the early '87 engine are a cast aluminum filler neck same as '85-'86, and no cooling ribs to each side of flappy bearing on direct top of intake.

SwayBar

My car has squirters with the following:

flip rear-wing
ribs on intake manifold
plastic oil-filler neck

Engine number: 81H00572

Marine Blue

I have 0110 which has squirters, aluminum filler neck and no ribs on top just like Carl described. I have no plans to add an SC though.

The_Remora

My car is # 0224, originally automatic that was a 5-speed conversion.
So according to Vilhuer's data, all early (pre 0501) S4's that have manuals (mine, Afshin's, Holbert car, etc) were 5-speed conversions? I just took a quick look at the 928 Registry, and although it is a small sampling, the ratio of 5-speed cars to automatics from VIN # 5001 up to 0500 seems roughly consistent with later build numbers. There are 19 pre 500 build number cars and 6 of them are listed as 5-speeds (with no notes about conversions that I saw), so thats almost 1/3 of the early cars that were 5-speeds. A bit of a tangent but strange considering the data listed above. Am I missing something here?

I would love to add boost eventually but have a lot of other things to sort out before then on this car. Plus I want to do more DE days and would rather learn on a NA car.

edit: just noticed that none of the VIN's listed have four-digit VIN's that begin with '5' as automatic designation... Maybe its a ROW vs US discrepency?

BC

89 and up have larger bolt bosses and alot more material around there.

BC

I thought you said that the 89 pistons had more strength added by the pin bosses? But for that reason the crown is thinner by a mm or so? Maybe 2mm, I don't remember. Thats not a bad thing if you are not interested in changing the dish shape.

951 rods are not our only forged option. 84-85 and and IIRC, 86 and 87 928 engine have the forged rods, just like the 951. So I would say "Forged 928 rods (since its cheaper to use them instead of changing the 951 rods) with arp rod bolts"

and the heads are thicker from 89, or are you saying 91 since that is when they are port matched? Because I am sure you know that the port match started on GT heads in 89.

mark kibort

Really???

then what is my engine M28/41 81H0004 ?



MK

blown 87

81H06569, this should be a squirter block also, right.

Vilhuer

There are several different numbers in this thread. VIN has relatively little to do with what engine went into car. I believe numbers Mike gave are engine numbers, not VIN. VIN started from 0061 for '87 MY but its engine number which is key in here. Cast filler neck and early style intake are usually indication engine is early enough to have squirters but they cannot be used as definitive proof. Same thing especially with folding rear wing. It is possible Porsche started manual engine numbers from 00001 for some early S4 MY's so Marks engine can either be very early production engine or one of the prototypes. On later MY S4 engine numbers started from 00501 but '87-89 MY is little gray area. Tech spec book is notoriously unreliable on these matters. I have to admit 00001 to 00677 squirter block for manual gearbox cars would allow last automatic engine number to be way above 1500 engines made if normal 1 in 3 or 4 manual vs automatic car relationship is applied. This would mean automatic engine number 06500 or even 07000 can have squirters. Since Porsche hasn't given actual number this is just speculation and each engine needs to be checked to be sure if it has squirters or not.

Changes on S4 and GT pistons are interesting. I think there are several different piston configurations:
#1 Thick top, large compression area, weak skirt, no drain holes
#2 Thick top, large compression area, strong skirt, drain holes
#3 Thin top, large compression area, strong skirt, drain holes
#4 Thin top, small compression area, strong skirt, drain holes

Drain holes is not same thing as problematic not drilled all the way through oil ring drain hole in GTS pistons. These S4 drain holes refer to holes low down on skirts which allow excess oil to drain from plateau below wrist pin end.

I'm not absolutely sure if #2 version exists or not. GT engines definitelly should have version #4 in them but also some late S4's can have them too.

Difference between thick and thin top thickness is about 1mm. Other 1mm comes from fact that bottom of thick top is 1mm further down from imaginary top line drawn above piston on its highest point. So thin top versions have two separate disadvantages on their tops which both separately are enough to make them less suitable for SC engine. Thick top is much better for modification and it allows clearly larger compression area on top before material becomes too thin. Difference is something like 8.2-8.3:1 CR for thick and 8.7-8.8:1 for thin when same thickness of material is left to piston top.

Strong skirt is obviously better skirt. But I think low compression is much more important for SC engines and having strong skirt. No oil drain holes is not important at all as they can be added to all versions which do not have them. Squirter blocks are more trouble than good on all NA engines so its better to save those blocks to SC builds. Especially those which have thick cylinder walls.

There are at least two different forged rod types. One is weaker than another. Stronger was mainly used in early 951 engines. Weaker was used in both later 951 and some 928. Best option is probably aftermarket set made to 928 specs. They are not that expensive, are easy to find and most importantly they are new parts which are probably much stronger than any Porsche version ever available.

'91-95 heads have extra cooling passages between exhaust ports. They are slightly better than earlier long bolt heads. Port matching to larger GT intake is yet another thing which isn't directly related to short vs long head bolt change.

IcemanG17

My early 87 engine (81H 05204) in my 88 is a squirter block....the easiest way to tell is the aluminum oil filler...vs the black one on later models...... but the engine that came in my car was NOT (81J 06034) but that engine is long gone!! :>)

BC

Well, Erkka, thats great info. I may still add squirters, but, um, the rest is basically set in stone for this motor. I did get the GTS cooling mods done to the heads I think.

Well see I guess. I am hedging my bets on simple easy to do upgrades, and proper assembly and tuning. My minimum goal is 600rwhp on a stock-parts-block.

Mike Simard

While we're tossing numbers, my early 87 5 speed vin# 168 has engine # M28/41 81H00123, it also doesn't have the intake ribs and has a folding wing.

Erkka, the 81H05746 engine I mentioned earlier is from an auto car.