PFF - Pennock's Fiero Forum, PDA Edition

My 1988 LFX F40 build. (Page 24/68)

RandomTask

NOV 20, 04:47 PM

OP - Many thanks for this. I actually just started the swap myself; sourced a Saab 9-3 F40 w/ jackshaft and mounts and am currently looking for a motor (technically a wrecked car so I can grab everything).

Questions:
1.) Your engine appears to be out of an impala or the sort (due to intake orientation) correct? There were no issues just flipping it? (The intake)
2.) You state you're running Cobalt half shafts; does anything need to be done to make them work? Do they go straight from the trans/jack shaft and install into the hubs?
3.) What did you do for clutch? (Are you running a Camaro clutch/FW?)
4.) Can someone clue me into why VSS is required for this engine to run? I'm having a really difficult time understanding why the engine needs and can't simply be removed from the ECU.

quote

Originally posted by msweldon:

How much clearance do you have between the valve covers and the front firewall and trunk forward wall?

After looking at your pics closely my biggest lf3 fear looks true... Not enough room to fit the stock compressor to IC pipes......plenty of room down below...just not up top........

The biggest issue I'd be worrying about on the LF3/4 is the location of the turbo's. Those motors were only ever installed in RWD applications and as such, never needed to accommodate a jack shaft. The other thing that really prevented me from going this route is price. Sourcing a used motor is still $7k+. You can find LFX's for $1250 all day long which leaves $5.5k+ to install a turbo.

Joseph Upson

NOV 20, 05:32 PM

quote

Originally posted by Will:

Are LY7 and LLT parts the same in that regard?

The LFX makes more output in stock form than the LLT, but the LLT can have headers and the LFX can't.

If by "same" you mean interchangeable yes they are as long as they're paired with the appropriate matching equipment. It seems as if GM deliberately changed crucial specs in each engine iteration to prevent mixing and matching to create a hybrid, unless you're trying to pump up the LY7. The LY7, LLT/LFX and the LF3/LF4 have different connecting rod lengths. My initial plan was to shave the heads, thin out the MLS head gasket and put the 11.5:1 compression pistons on the turbo rods for higher compression, until I discovered the turbo rods were shorter requiring custom.

In addition to that, the timing cover is pinned to the block, so if .020-.030 is shaved off the heads, the camshaft actuator interrupts will be in a new and lower position relative to the camshaft sensors in the fixed timing cover and that might be enough to cause a code to set when the cam and crank positions are compared.

The LFX has larger intake valves a little more intake camshaft duration and a power peak set 400 rpm higher than the LLT for that extra horsepower, 20 more than the LLT CTS, but only 11 more than the LLT Camaro suggesting some exhaust flow differences and possibly programming, but the major improvement would be best illustrated by comparison of area under the curve. Interestingly, GM manufactured the LLT all the way up through 2017.

Another interesting fact, the LS7 titanium connecting rods are lighter than the LF4 titanium connecting rods, although the LS7 has greater inertia loads.

[This message has been edited by Joseph Upson (edited 11-20-2019).]

Daryl M

NOV 20, 09:29 PM

quote

Originally posted by RandomTask:

OP - Many thanks for this. I actually just started the swap myself; sourced a Saab 9-3 F40 w/ jackshaft and mounts and am currently looking for a motor (technically a wrecked car so I can grab everything).

Questions:
1.) Your engine appears to be out of an impala or the sort (due to intake orientation) correct? There were no issues just flipping it? (The intake)
2.) You state you're running Cobalt half shafts; does anything need to be done to make them work? Do they go straight from the trans/jack shaft and install into the hubs?
3.) What did you do for clutch? (Are you running a Camaro clutch/FW?)
4.) Can someone clue me into why VSS is required for this engine to run? I'm having a really difficult time understanding why the engine needs and can't simply be removed from the ECU.

The biggest issue I'd be worrying about on the LF3/4 is the location of the turbo's. Those motors were only ever installed in RWD applications and as such, never needed to accommodate a jack shaft. The other thing that really prevented me from going this route is price. Sourcing a used motor is still $7k+. You can find LFX's for $1250 all day long which leaves $5.5k+ to install a turbo.

Actually,the LF3 was used in a transverse application, the Cadillac XTS-v. It did use different turbos than the longitudinal applications and made less power, but that may just be the tune to save the drivetrain.

Daryl M

NOV 20, 09:36 PM

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As for the details of my swap, this thread covers most of the gory details like axles, clutch, motor mounts and such.

Daryl M

NOV 25, 09:57 PM

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Not sure what you mean by "flipping the intake". It is installed as the factory originally installed it.

wftb

NOV 25, 11:14 PM

Hi Daryl : I was just flipping through your thread again and I noticed you have not talked about installing your drive by wire pedal assembly yet. I was on utube looking at ecotec powered sand rails and I found a guy that made a simple way to do DBW without changing the pedal assembly. He just removed the pedal from the DBW unit and mounted it near the engine and hooked his throttle cable to it with a home made bracket. I think this would save a lot of work.
https://www.youtube.com/watch?v=SHqnwrU972k

------------------
86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

Daryl M

NOV 26, 12:54 AM

quote

Originally posted by wftb:

Hi Daryl : I was just flipping through your thread again and I noticed you have not talked about installing your drive by wire pedal assembly yet. I was on utube looking at ecotec powered sand rails and I found a guy that made a simple way to do DBW without changing the pedal assembly. He just removed the pedal from the DBW unit and mounted it near the engine and hooked his throttle cable to it with a home made bracket. I think this would save a lot of work.
https://www.youtube.com/watch?v=SHqnwrU972k

I actually used the Impala accelerater DBW pedal. Real simple to bolt to the Fiero floor board.

msweldon

NOV 26, 11:50 AM

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The SAAB F40 jackshaft and mount will bolt up to the LFX perfectly and probably the LGX. Not 100% sure about the LLT or LY7. It will bolt to the LF4/LF3 but you have to shave off one of the three bolt holes from the mount as it impacts the oil return line. The LF3 intermediate shaft and mount does not line up to the saab F40.

quote

2.) You state you're running Cobalt half shafts; does anything need to be done to make them work? Do they go straight from the trans/jack shaft and install into the hubs?

The Cobalt SS supercharged axles will bolt right in from F40 to DS hub and from jackshaft to PS hub but you have to shift the engine over about two inches toward the passenger side. Ok with a V6 not so much with an LS4. These axles did have issues with breaking when pushed. The next generation Cobalt SS Turbo axles are 'seriously' more stout but use a different outer stub and hub so I had to respline them to a G6 cage/balls with Fiero outer stub.

quote

3.) What did you do for clutch? (Are you running a Camaro clutch/FW?)

As the LFX/LLT/LY7 et. al. all use the same general external block layout as the SAAB 9-3 2.8T LP9 so you can use a stock SAAB/Sachs or Sachs performance setup. Spec offers many clutch options as well as two flywheel options for the LP9. Even a 7.5" twin disk for racing only... Camaro clutch and flywheel will 'not' fit as it's made for the longitudinal 6 speed setup and too deep of a bellhousing. I worked with one of the owners of RAM clutches to see if we could adapt their Camaro LFX twin disc 9.5" clutch to the F40. The FW/PP/clutch setup was drawn up and ready for a prototype run but the F40 HTOB and input shaft doesn't have the spline depth their twin 9.5" setup.

quote

4.) Can someone clue me into why VSS is required for this engine to run? I'm having a really difficult time understanding why the engine needs and can't simply be removed from the ECU.

Well, for one the E36/E92 ECUs need the VSS for feeding speedo output, mixed with yaw sensors for traction control, steering sensitivity (VAPS), and the ATS-V 6-Speed even uses it for its No-Lift Shifting for revmatching. I have spoken to a few Miata/LFX swappers and they even have issues with engine stumbling and erratic behavior at low speed if their VSS sensor wheel doesn't have enough teeth. I think the threshhold is about 16 or 18 teeth minimum for the E36/E92 if memory serves me correctly.

quote

The LF3 did come in a transverse form in the XTS-V but the turbos are a bit on the smaller side for low end torque to lug the XTS around. The turbo's measured on my LF3 shoud fit in our engine bay but like i said, the turbo to intercooler pipes can't. The pipes perhaps could be ovalized or rerouted or a BFH against the rear firewall and the engine shifted aft but I opted to remove them and go with a custom exhaust and mount over the F40 like the LP9 SAAB layout and a more appropriate mid ranged sized turbo. Unfortunately the manifold bolt patterns are different between the LF3/LF4 and the LFX/LGX so the turbo's can't be swapped over.

The LFX's are good motors but they're built internally to be normally aspirated and will fail if pushed too far with forced induction. Do a search for GretchenGotGrowl on the Camaro forums. Granted, he eventually wrung near or at 700lb/ft out of his LFX but had to replace blocks, beef up internals, HPFP, etc.. That's where the LF3/LF4 come into play... they already have the built in fueling internals to handle forced induction included. Per Renik performance out of California their weak points, if upping the boost, are needing a bigger HPFP or larger HPFP cam on the cam, upgraded LPFP, the titanium rods on the LF4 can shatter under detonation, and the main and CR bearings are a little soft for OEM embedibility / reliability.

[This message has been edited by msweldon (edited 11-26-2019).]

Daryl M

NOV 26, 09:56 PM

quote

Originally posted by msweldon:

The LF3 did come in a transverse form in the XTS-V but the turbos are a bit on the smaller side for low end torque to lug the XTS around. The turbo's measured on my LF3 shoud fit in our engine bay but like i said, the turbo to intercooler pipes can't. The pipes perhaps could be ovalized or rerouted or a BFH against the rear firewall and the engine shifted aft but I opted to remove them and go with a custom exhaust and mount over the F40 like the LP9 SAAB layout and a more appropriate mid ranged sized turbo. Unfortunately the manifold bolt patterns are different between the LF3/LF4 and the LFX/LGX so the turbo's can't be swapped over.

The LFX's are good motors but they're built internally to be normally aspirated and will fail if pushed too far with forced induction. Do a search for GretchenGotGrowl on the Camaro forums. Granted, he eventually wrung near or at 700lb/ft out of his LFX but had to replace blocks, beef up internals, HPFP, etc.. That's where the LF3/LF4 come into play... they already have the built in fueling internals to handle forced induction included. Per Renik performance out of California their weak points, if upping the boost, are needing a bigger HPFP or larger HPFP cam on the cam, upgraded LPFP, the titanium rods on the LF4 can shatter under detonation, and the main and CR bearings are a little soft for OEM embedibility / reliability.

Great info msweldon

Daryl M

NOV 26, 10:20 PM

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Since you asked, here is a photo of the Impala accelerator pedal installed in my Fiero.