Doug's LT4 swapped 86

Just CC'ing this from the LTx forum because that forum appears dead, no new posts in over 6 months. Sorry if this doesn't belong here.


Hey guys, my name is Doug. I am a long time 944 addict and currently own an 86' NA and a heavily modified 86' 951 with a big turbo, megasquirt, coilovers, ect. I just bought a 1986 944 with a 99% complete LT4 swap. This is what I know about that car so far:

The engine and ecu/electronics are from a 96 camaro, so this is an OBDII equipped 2 bolt main block. The PO said he believed the car was built with a Renegade kit. It has what appears to be an LT4 intake and possibly LT4 heads as well, 1.6 aluminum roller rockers, a pretty big sounding cam of unknown specs, and black pushrods which might not be stock. It also has LS7 lifters, an MSD ignition, BBK throttle body, and some unknown headers + full 3" exhaust. I have no idea how many miles are on it, but it sounds extremely healthy. Right now, my tach and speedo work, but the coolant temperature gauge does not. I am not sure what the best way to get it working is. The stock 944 coolant temp sensor is an M12x1.5 thread, and the LT1 sensor is 3/8" NPT. I can not find a male 3/8" NPT to female M12 adapter anywhere.

Secondly, the car keeps throwing accessory belts because the PO bent the alternator mounting bracket. Right now its setup with no AC, but does have PS. I plan to delete the PS and to get one of the brackets that mounts the alternator down low on the passenger side of the block. I will be using the wilwood manual master cylinder for braking.

Thirdly, I am interested in getting my hands on one of the firewall reinforcement brackets that wedge up against the driver side shock tower; where do I send my money?

Lastly I am interested in tuning the motor as I have lots of experience tuning 944 NA and turbo engines on stand alone ecu's and have also done Subaru and motorcycle tuning. Is it as easy as getting software and hooking my laptop up to the OBD port? I know the optispark is the weakness on the LTx motors; and I've been told I can delete it and move to an LSx type coil setup that is more reliable? Can anyone comment on that more? Looking forward to getting to know the car over the next few days. Thanks everyone!

the adapter fitting could be an issue, i havent been able to turn up anything either. it may be something you need to make, starting with a 3/8 npt plug and drilling/tapping it for m12x1.5. alternatively, you may be able to drill another port somewhere.

id recommend against the wilwood tandem master cylinder, it doesnt work. i fought manual brakes with tandem master cylinders for a year, the best i got was it would stop the car for normal driving, but start having some fun and its not very confidence inspiring. i went with a dual master cylinder and balance bar setup for my swap, but if you want your car to stop well, go hydroboost.

ive been dealing with some lt engines lately so im up on the tuning stuff a bit, you have a couple options. first off, your 96 optispark is the best they get, they are far less problem prone than the non vented 92-93 models. tuning for your obd2 lt series is limited to the Jet dynamic spectrum tuner. years ago tuner cats sold the right to their obd2 tuner software to jet, but they still support it, but its expensive stuff. the 92-95 lt1 pcm can be tuned with tuner cats obd1 tuner, its fairly cheap stuff. a friend of mine is doing a 96 lt1 in a 79 camaro, we are either going to run a 95 obd1 pcm for the cheap tuning software/cable or go gen 3 ecm (ls stuff).

now, swapping to an ls gen 3 ecm is possible, but sort of complex and expensive, but it has its upsides. i picked up a performance how to book called "how to use and upgrade to gm gen 3 ls series powertrain control system" by mike noonan. great book, covers the stuff you need to know. in this book they compare a pretty decently built 383 lt engine with a well tuned stock ecm and optispark, swap it all out for ls pcm and coils and gained 20 ft/lb torque and 10hp, along with better knock timing control, more precise fueling, better diagnostic capabilities, and getting rid of the optispark. the swap entails changing the factory crank reluctor wheel from a 4x to 24x, removing the optispark and adding a cam reluctor and cam sensor, and swapping the knock sensors. right now a side project of mine is to turn the optispark distributor into a cam sensor housing for this swap instead of having to buy the conversion kit.

eficonnection.com has the conversion kit and parts. you can also get a stand alone harness from them. its not cheap though, the conversion parts are $450, a built harness is $600 and then tuning software (hp tuners) starts at $500. add in a pcm and coils as well.

being your familiar with megasquirt there are options you can do there too. you could run a 36-1 trigger wheel and run ford edis ignition, a 60-2 and run waste spark with ls coils. add the cam sensor and you can run the megasquirt full sequential with ls coils. if your good with megasquirt the options are limitless.

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