Originally Posted by bluedart

So I know this is a Camaro forum, but there is lots of information that is common between Caprice's and Camaro's of similar years. And as another post stated this forum comes up regularly when searching for 350 engine swaps.

I have a 1991 Caprice Station Wagon with an original LO3 305. The car has been in the family since mile 1 (dad bought it off the lot) and I've been thinking about an engine upgrade for a long while. It has 339,300 miles on it and died on me while driving to work about 5 months ago. I went through a number of parts troubleshooting and replacing (coil, distributor, plugs, wires, hoses etc.). I was able to get it running again but can't get it timed correctly, so it runs terribly (hesitates, misfires etc.). There is a very large amount of timing line wander when using my dial back light which leads me to believe that the timing chain probably jumped a tooth (it's the original sprocket and timing chain). If I were to replace the timing chain and sprocket, it appears to be a good percentage of getting the motor out of the car and there’s no saying when the next big event would force me into an engine overhaul or replacement. This event seems to be a good “pivot point” for a new engine.

This brings me to why I’m writing this post. I've been lurking around this site and others like it for a month or so now and am starting to formulate a plan for a motor swap. The intent is to change the LO3 out for an L31-R Vortec motor. There appears to be a lot of good advice being given here especially in these threads.

• https://www.thirdgen.org/forums/tbi/...-progress.html
• https://www.thirdgen.org/forums/tbi/...-350-swap.html

My plan is to swap out the motor and, while in there, swap out a number of other components or systems for upgrades that I've been thinking about, planning and saving for for a long while. The highlights are as follows:

• L31-R Swap
• Retain TBI system but upgrade for better performance
• Refresh leaking and tired AC system (compressor makes a lot of noise)
• Rebuild the power steering gear to tighten up handling
• Upgrade to electric fan
• Upgrade to headers
• Fix a slight fuel leak that occurs when tank is really full

The vehicle has been a daily driver for years and I'd like to keep it that way. It has towed a number of things in the past, but probably will not need to in the future since I now have a truck for that. I also have a 1993 Buick Roadmaster with a 350 and although they appear to be the same vehicle from the outside, they are worlds apart when it comes to power and drive-ability. It would be very nice to get my Caprice closer to that level (or even beyond).

I am not a novice at working on cars and have a small fleet (7) that I maintain pretty well, three of which are 90’s GM TBI vehicles. However, this will be my first engine swap and I’m looking for some advice from some of the more experienced folks here.

Attached is a spreadsheet that I’ve been compiling my parts list on. It also has my calculations on injector sizing, my build plan and a list of questions that I need help with. My intent it to keep very detailed records both written and pictorially and, if desired, share them on this forum. Hopefully my experiences can help someone else.

Ok, here are my questions that I could use help with.

• Does my engine choice (L31-1) for this application (91 Caprice Wagon) make sense? Sure it does. Requires a little more work than the L30 and also costs about 300-400 more though in crate form.
• Do you see anything missing or incompatible with my part selections? Plan to replace the tank. If it is anything other than a bad sending unit O-Ring than just replace it. Tanks aren't overly expensive and why not just do the job once and get it over with.
• Do you see any steps missing from my plan?
• Are the ported TBI's from CFM-Tech worth it? No idea
• Can you pass smog without the smog pump? Depends on state. Generally speaking, you cant remove any smog equipment. Depends on shop, in any case, you will most likely blow cleaner than the LO3 even without the pump
• Can you pass smog without the EGR valve? Same as above
• If I do need an EGR alve, what part number do I use? One for an L03 or one for an L31? Use the LO3 if you are using the GMPP TBI Vortec manifold
• Can you recommend a high flow CAT with no smog pump hole? Magnaflow flows good but does have the port. Matter of fact I have mine right now. Has about 10k miles on it. Has the port capped off with a plug, but would seal better with a pinch and weld. Sell you it cheap. just pulled it off last week.
• Does the 350 C.I.D. L31-R Long Block come with an oil pump? If crate yes
• Does the 350 C.I.D. L31-R Long Block come with a correct knock sensor? No. You will need to source one from rock auto for a 1996 c1500 with that engine.
• Do the injectors spacers from CFM-Tech work/help? No idea
• Do the power plates from CFM-Tech work/help? no idea
• What makes more sense, replacing ECM with custom Harris chip only or also getting EBL Flash? Really depends on your budget. EBL will let you make the changes. A chip you obviously cant do that on your own
• Can someone share their EBL Flash controlling electric fan experience? Does it work correctly? Is the on/off temp controllable?
• Can someone recommend a good air cleaner? Need part number and/or link. Use the stock cleaner or an open element. Hold on that until you get the motor in(hood clearance)
• Given that I am replacing the accessory fan and the L31, what water pump do I need? Check my thread for the part number on the acdelco pump. You will also need to run the bypass from the pump to the manifold.
• Will my current L03/305 distributor work with this engine? Yes. Consider replacing depending on mileage.
• Will I need a new flywheel or flex plate? You SHOULD replace it. Your old is probably chewed up. Again, why not replace? You are already there. Need new bolts.
• Should I install the headers before I install the engine or after? After. Will make mating the engine easier.
• What exhaust collector should I use?

Hooker?
Any help you folks could give with guidance or answers to these questions would be awesome. Thanks!!

Originally Posted by bluedart

RS & Fast,
Thanks for the the answers! Those help a ton.

I'm actually up in the Seattle area and 2015 is my last year I'm required to pass smog. After that I'm exempt, which is why I'm leaning towards leaving as much of the emissions stuff off as possible. The last 5 years or so, they have gotten much more relaxed about things and don't do a visual inspection of the engine compartment. They simply run a sniffer in the tailpipe with a tach in the cigarette lighter and check the gas cap. I came from LA with the car about 9 years ago and it's always passed smog in both states with no problem. I'm hoping that I can leave the air pump out but plan to keep the EGR and the CAT for the time being. Might remove it later on down the road though.

Overall I would prefer to keep a small block in this car rather than make the jump to a big block. No real facts and data here, but I anticipate this being a much bigger project with even more needing replacement. Fuel economy might also be a consideration here. Again, no facts and data, just a general uncomfortableness.

RS, what would you want for your Magnaflow CAT? Also thanks for the recommendation on the tank... didn't think of that, but it makes sense especially since the price is only about $150.

Regarding a flywheel/flex plate, do I need a 168 tooth or 153 tooth wheel? Searching on Napa's website, it appears that the 5.7L engines require a 168 tooth flex plate. Would I also need a starter motor from an L31 engine? Something from a 96 C1500 5.7L perhaps?

Fast, I'm not sure what 'SFI rated' means, but do you have a recommended flex plate link or part number? Thanks for the warning about the Harris chip. I was considering picking up the custom chip kit with a high pressure pump and an 18 psi fuel pressure regulator spring. Would that be unwise? Do you recommend getting a pump and maybe a spring from elsewhere?

Fast, since it sounds like you have some experience with EBL, do I actually need a new chip or can I just use the one that came with the LO3 with the EBL and modify things? It's not totally clear that I need both the chip and the EBL or if I need a chip or the EBL.

Finally, Fast, thanks for the reminder about the distributor hole needing to be machined. I read that someplace on this forum that the B-body cars needed a bigger hole to allow the distributor to be remove with the engine in the car. I have a brand new distributor in the car right now when I thought that might be an issue regarding it dying. It was actually a bear to find the right size one since most auto parts stores don't realize there is a difference or why. My question is whether or not the height of the distributor is the same for the L31 and the B-body L03's? I can and will machine the hole if so.

Really, really appreciate both your input and help here!! Thanks again.

Originally Posted by bluedart

Thanks RS, that's a good perspective. In looking at the Summit Racing website, it looks like the prices have gotten a good deal closer between the L30 and the L31. Things might have changed a little. See below. What did you pay for your L30 and where did you get it from?

L30: http://www.summitracing.com/parts/na...0284/overview/
L31: http://www.summitracing.com/parts/na...0283/overview/

Both appear to have the same warranty.

Thanks for the info on the fly wheel and starter.

Originally Posted by Fast355

Marine 6.2 is just the HT383 smallblock based off the 350 with a cheaper price tag. I wish I had known about them back in 2006 when I put my crate L31 in the Express. I would have bought just the shortblock, bolted my heads on amd put a LT4 cam in it. 380 hp all day long with 450 ft/lbs of torque. Torque is what will move your wagon around and get you fuel economy.

Originally Posted by bluedart

Originally Posted by Schurkey

[/FONT][/LIST]Don't rebuild the PS gear. Get a rebuilt unit with a warranty from a parts store, or find a "good used" unit. Better still, get a custom-rebuilt unit from a specialty supplier with a good combination of gear ratio and torsion bar stiffness.



An electric fan is NOT an upgrade. You'd be lucky to get an electric fan system that works as well as the OEM fan and fan clutch--if the OEM parts are in good condition. You also save on the oversized alternator and wiring harness needed to run a high-CFM electric fan system.

Originally Posted by Schurkey

An electric fan is NOT an upgrade. You'd be lucky to get an electric fan system that works as well as the OEM fan and fan clutch--if the OEM parts are in good condition. You also save on the oversized alternator and wiring harness needed to run a high-CFM electric fan system.

Originally Posted by bluedart

An update... this swap is now complete!

Since this is not a ThirdGen, I posted the whole story over on the ImpalaSS forums and wanted to share in case anyone can find some value in what I learned along the way. Quite the journey to be honest.

Here's a link to the full story with pictures and videos: https://www.impalassforum.com/thread...l31-r.1319976/

Originally Posted by Fast355

Thanks for the update. Very clean swap. Had no idea those clear image tri-ys existed at the time you were planning the swap. Honestly swapping in the 383 I built for my Express van as we speak too. 11:1 6" rod 383 with aluminum heads ported by Lloyd Elliot. Because of more aggressive smog law BS here in DFW, Texas I had to go back to an intake with EGR. Its only enabled for smog testing, but I ported the heck out of the stock L31 truck manifold and picked up a 48 lb/hr high flow spider. E85 is my fuel of choice. I too now have Thorley tri-y headers and loved them on my 350. Gained alot of low-midrange torque with them. I put a larger 34x19x2-5/16" core all aluminum radiator, a new thinner parallel flow condenser to help airflow and a/c cooling and added dual 16" Flexalite Flexwave 3,000 cfm fans on a 34x19 shroud to recover the fuel economy and hp lost by the mechanical fan. Still have to clearance, clean and paint the a/c bracket and finish about 100 other things but as of yesterday afternoon the 383 is on its mounts and bolted to the 4L85e and the 2,800 stall converter in the 4L85E. I have detailed my whole Express van, swapped it out to 1-ton suspension, brakes, and running gear and added some updates like a 10.1" touch screen head unit, Rockford Fostgate 6.5" speakes with 1" tweeters in the front doors, 5x7" in the upper rear and 6x9 in the rear doors. Full exterior LED conversion as well. I too converted all the lines to AN for the transmission and powersteering and all the coolant hoses are silicone. I also had to change the compressor again (knocked the last 2 years I used the van but still blew ice cold) and flushed the a/c system. Swapping the vortec replacement Valeo compressor I put on it in 2006 (I guess for a $200 a/c kit that included the compressor, orifice tube, rear expansion valve and the accumulator I got my moneys worth) for a Sanden SD7H15 for a Vortec engine.

Originally Posted by Fast355

I am sure that hotcam in that 350 Vortec engine is fairy rowdy in that wagon. I know my 383 ended up a little different than you would expect in a luxury conversion van. Can definately tell its not the stock 350.