Seriously considering L31 swap into my Formula. Currently has a TPI swapped onto LO3 305. I know pretty much everything will swap over, and I've poured over this forum for answers to many questions. There are a few things, though, that I'm not clear on and would like some answers before actually ordering the engine and intake from S-D.
1. What BIN should I start with? Anyone out there have a good-running L31 TPI BIN that I could take a gander at?
2. I'm currently running an AXXB memcal through a G1; will I need to secure an L98 memcal?
3. Currently running Bosch III 19 lb injectors; will these work with some tuning, or will I have to swap out for bigger injectors?
4. Harmonic balancer: should I use the one off of my LO3 or can I just use the one that comes on the engine?
5. Will my Hooker Y-pipe work as is or will I have to alter it?
6. I'm shooting for 260 hp/375 ft/lb ballpark; will I be able to achieve this with the stock L31 cam?

You will need a Vortec intake to go with the Vortec heads.

For my daily driver, I bought a new GM L31 Vortec crate engine from Jegs about 4 years ago for $2,000. I went carb with mine. Edelbrock 600cfm and air gap intake. Heddman long tube headers with true dual exhaust, and HEI distributor. Still has the stock cam and runs much better than I thought it would.

The hp rating is with the "Truck" intake, exhaust manifolds, single exhaust, etc.

Still looking for answers to 1. and 5.

#5. I think the hooker y-pipe should be fine.

Thanks.

Guess I'll find out...

I would definetely switch out the 19 for 22 lb injectors and simply use a bin from a 350 instead of the 305. this should make it able to start and drive with less tuning

Just shooting from the hip, I'd start with a stock 350 TPI setup, and work from there. The stock Vortec cam is pretty lame, but it's debatable if it's really worth changing if the rest of the setup is going to be relatively stock TPI. That said, I'd probably want to change the cam before putting it all together.

I would like to know how this works out. Looking at the L31 and the SP350/357 for my replacement. What if any modifications that have to be done. Like EGR and if the headers work and any issues reusing the OEM TPI.

FUNIROC, both engines you listed have Vortec heads. They will require Vortec specific intake manifold.

I'll let you know. Got the LO3 out yesterday, so now it's time to "stick" the new one.

Thanks I will keep checking back on your install.

New engine is in...!

Looking sweeet. Did you do anything to that intake or do they come like that?

Only thing I've done to the intake so far is install a plug in one of the front ports (the one that's pretty much in the center front of the manifold) and installed the EGR delete.

Isn't that center port supposed to run to the top port on the water pump? To compensate for the coolant passage the Vortec heads block doesn't have? Might want to look at the Scoggin-Dickey article on the intake. Not sure it even matters, but it is a feature exclusive to the Vortec intake, Now the other extra port is for the cold start injector switch, which I'm assuming you're not using.

Edit - More info...

The Vortec heads do not have a bypass port.

Thanks, Drew, I will check it out. That center port (C) can't be used on an F-body, as the fuel lines block access to it. The port directly to the left of "C" is where I'll be running a hose to the water pump. Port to the left of that will be for CTS. Top 1/2-inch port will be for the heater bypass.

Okay folks, please correct me if I'm wrong, but it seems to me that the stock heater core diverter valve already accomplishes the same thing as running an extra hose to the water pump. When no heat is called for, the stock valve diverts coolant from the restricted nipple in the front of the intake manifold directly back into the passenger side top of the radiator. Would this not provide some coolant flow through the engine/heads until the thermostat opens? Is the problem that it would not provide enough flow?

I couldn't say either way. The issue is the later blocks/vortec heads don't have the bypass port that lines up with the TPI water pump. Depending on what theory you buy into for the bypass port in the earlier water pump/block/heads, maybe you don't need it. But that's why Scoggin Dickey added the extra port. Use your best judgement.

Just about ready to fire up. Can anybody tell me whether I should have the EST disconnected on initial start-up? I know it will need to be disconnected to set static timing, so I'm guessing yes.

Glad to see its coming along. Bet it will fire up and run just fine with just a bit of tuning. So did ya get the water pump connections worked out ok? Scoggin I would think could help with the connections.

It lives! Runs and idles great, once we got the distributor in properly; one tooth off so it was running more than a bit retarded at first. It was also running a bit lean on the stock AUJP VE tables. Bumped one point across the board to the VE before test drive and it's in the ballpark. Now more data logging and tuning. Thanks to Brian (tuned performance) for the SA tables.

Just an update: Everything is working good since I replaced the memcal that developed a bad knock circuit (thanks, Brian!). FWIW, I burned a chip with the stock AUJP SA and it seems to like it. Much snappier; took out .7 degrees at one spot where I got 1 degree of knock retard and haven't recorded a knock event since. I'm running premium "real" gas and, along with the stock L31 cam, seems to handle this SA just fine. Still fine tuning the VE but, honestly, is probably good enough for a mostly stock setup (+/-5 points on last data log). Outward appearance of the engine hasn't really changed and the hood still has the "5.0 FI" decal. I thought about updating it to the "5.7" decal, but they want $40 for two little decals, so I think I'll leave it for now.

Also wanted to express my gratitude to the many, many knowledgeable and helpful folks on this forum. No way I could have done this without the amazing resources available here.

I hope it runs as good as it looks. Great job!

BUMP! How is the project coming? OP?

Wow, that's a while ago. I must have done a couple dozen tune updates to get everything squared away. I'm sure if I had just paid Brian for the entire tune it would have gone considerable quicker, but I wanted to learn and that takes time and experimentation. I have since completed a TKX swap and, well, it is so much more fun to drive it's ridiculous. Feels like it gained 50 hp, though I know it's just the more direct connection and no torque converter sucking up the fun.

Thanks "rt66er". Who is "Brian" what does he do w/ vehicles and how would one contact him? MC

@Tuned Performance

OK, I know of TP.

@mikeceli Let me know if there’s anything I can help with.

So it's been 2 1/2 years and I'm still restoring my '89, 305, LB9 TPI/ AT, IROC Z Vert!

Still dreaming about a L31 swap. I have acquired a good set of the 350 fuel injectors and a 350 AT ECU with Memcal.

"RT66ER" How is your L31 F Body doing? Any problems? Thanks, Mike Celi

Very happy. Doing great. TKX swap really tied it all together nicely.

TKX ? Did you ever need to have a SMOG test? How much quicker does it feel, compared to the original engine? IIRC , you went through the trans, any internal mods, if you recall? Thank you, Mike Celi

TKX ? Did you ever need to have a SMOG test? I am thinking an L31, having improved heads, might run cleaner than a TPI 305 or 350. How much quicker does it feel, compared to the original engine? IIRC , you went through the trans, any internal mods, if you recall? Thank you,

The TPI LB9 305 / AT is running great, in my '89 IROC Z Vert, but I have wanted an L98 or L31, just to experience the additional torque and HP. Mike Celi

No smog tests in Oklahoma. I swapped in a higher stall converter to the auto and it was, technically, quicker, but felt slower. I was able to time a sub-six second 0-60 with the new converter. With the stock converter it was hard to get a decent launch as it would just smoke the rear tires with much throttle at all. With the manual, it feels quite a bit quicker without a torque converter sucking up HP. Lots more fun to drive, too. I've not run a timed 0-60 with the manual, but I would be surprised if it's not capable of mid-fives.

Thanks for the info. MC

1. Start with the stock bin. It'll run find. Great, even.
2. IDK what that is...but if you're already running a TPI, not sure why you'd have to swap memcal
3. I'm sure those'd work fine
4. Either will work fine. Why not use the newer one that comes on the newer engine?
5. Yes.
6. Maybe. You mentioned "Hooker Y-pipe"....but you didn't mention headers. I don't think that you'll get 260 with L31 cam (limiting), TPI (limiting) and stock f-bod manifolds (limiting). With headers, good Y and good cat back, 260 CRANK should be attainable w/the stock L31 cam.

The late, great CFI-EFI did about that in an '84 'Vette, using CFI instead of TPI, but that car already has "Headers and exhaust", compared to an F-bod.

One other thing, you CAN stack two intake gaskets and run a stock TPI lower on the Vortec heads. That aligns the ports good enough (as good as any GM intake>head port alignment ever was in that era). You also need to drill/tap the heads for the L98/traditional intake bolt pattern. Not saying you should, but you can do it, it works good, and it'll save you ~$500 for a base.


EDIT: ****. I got duped by not reading the thread start date. Actually I did read the date...just not the year. My bad.

It is an old thread, but still valuable, IMO.