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Old 10-16-2015, 11:05 PM
Registered User
Join Date: Feb 2015
Location: Kansas City
Posts: 99
Turbo engine choice: M103 vs. M104

Hello gentlemen,
Over the past couple of months I have been researching both engines to decide which to pick for a turbo project. My choice is specifically between the 3.0 M103 and the 3.0-24v M104, but any general information on both generations is welcome.

Unfortunately I am still undecided, as both engines seem to have their advantages and disadvantages.
Here are what I believe to be the main ones:

-Easy to source
-Cheap to replace/rebuild
-9.2:1 compression
-No piston oil jets
-Rougher operation/more primitive (though simplicity can also be a plus)

-Looks cool (very important)
-Piston oil jets
-Smoother running/more refined
-Dual row chains
-10:1 compression
-Harder to source
-Higher costs
-Supposedly not as lively in the lower to mid RPM range

I am specifically interested in turboing an internally stock engine. I have no problem performing a rebuild, but I would prefer to shy away from custom rods, pistons, etc. The goal is an approximate 'safe and reliable' 350hp from an engine that is still simple and affordable to replace/rebuild should the worst happen.
My primary concern with the M103 is the lack of piston oil squirters, while on the M104 it is the higher compression ratio.

Which engine would you pick/recommend and why? Any input is greatly appreciated.
Thank you.
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Old 10-17-2015, 12:08 PM
Registered User
Join Date: Oct 2004
Posts: 3,225
What you describe you want sounds like a turbo'd 103. Either could meet your goals rather easy but the 103's boost friendly 9.2 is a better starting point if you're only going to 350hp. The squirters arent that big of a deal. A lot of late 103 blocks have the machine work for them, just not tapped and drilled to the main galley. You will have to strip the block to drill and tap them as well as notch the pistons to clear them. If you plan on feeding a turbo and squirters you may want to come up with more oil pump capacity too. So probably not worth it in your scenario.

The 104.980 is pretty much the same block but with the squirters installed. The 104 head flows a good deal better on the high end so suffers from a weaker low end. I own both engines. My 103 is boosted to the 300-350 range. I plan to boost the 104 to the 5-600 range.
90 300TE 4-M

Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs, 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197 intake cam w/20 advancer
4 ignition advance
PCS TCM2000 running 722.6 trans, 600W PWM fan, water injection
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff
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