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09-23-2018, 12:36 PM | #1 |
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Replacing a tired 350 with a L31 Vortec 350
Just spend some time searching and really have not found what I am looking for. My goal is to install a L31 in place of my Gen1 350. Looking to get some sort of parts list together and have everything ready for the swap when the time comes.
I know I need: electric fuel pump different (melonized) for HEI dist. vortec intake manifold (not sure of the brand yet. square or spread bore ??) new flex plate (153 tooth??) rear AC bracket that mounts to the manifold Holley carb with electric choke (like the quadajet but don't want to loose choke) I want to change the timing cover out and just reuse mine off of my 350 including the harmonic balance. (going to run the original v belts and have a short water pump) Am I missing anything else? the original motor has factory AC (working) and power steering
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
09-23-2018, 09:41 PM | #2 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Which intake you get will depend on the carb you plan to use.
The new flex plate is due to the change from a 2-piece to a 1-piece rear main seal. If you want to reuse your harmonic balancer (which I don't recommend) you need to remove the reluctor behind the timing gear on the crankshaft. You might as well install a double roller timing set. The Vortec balancer is shorter to accommodate the reluctor.
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09-23-2018, 11:45 PM | #3 |
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Re: Replacing a tired 350 with a L31 Vortec 350
why do you not recommend using an earlier harmonic balancer?
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
09-23-2018, 11:57 PM | #4 |
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Re: Replacing a tired 350 with a L31 Vortec 350
You can use your quadrajet if you use an electric choke conversion.
With your electric pump you should set up a return style fuel regulator. Electric pumps don’t like to be deadheaded. |
09-24-2018, 01:01 PM | #5 |
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Re: Replacing a tired 350 with a L31 Vortec 350
That's not what I said. I said I wouldn't re-use your harmonic balancer. The rubber ring is 45+ years old. It's time for a new one. The old style is fine; that's what I have on mine.
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09-24-2018, 02:20 PM | #6 |
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Re: Replacing a tired 350 with a L31 Vortec 350
you must have missed this thread . http://67-72chevytrucks.com/vboard/s...d.php?t=763121
i have not got mine fired yet but dropped right in place and bolted up good . http://67-72chevytrucks.com/vboard/s...d.php?t=755514 even used the cam sensor block off plug in the link provided by another member . it was 20 bucks . https://www.eficonnection.com/home/p...illet-aluminum fit n finish of the edelbrock intake for square bore carbs 1450 series was o.k. for my needs going holley sniper unit . make sure to give radliy chevy a call were i got mine from . they were the best price i found for the 4 bolt main version shipped to my work . https://www.ebay.com/itm/GM-OEM-NEW-...4AAOSwysRas9qX
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77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great. |
09-30-2018, 12:11 AM | #7 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Did your gen1 350 have a 153 or 168 tooth flexplate ?
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09-30-2018, 02:09 PM | #8 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Not sure. I do remember dad having a lot of problems with the starter when new and something about Chevy replacing the flexplate. Never thought to identify what I had when I swapped a 200r4 trans for the th350
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
09-30-2018, 03:42 PM | #9 |
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Re: Replacing a tired 350 with a L31 Vortec 350
If I remember when I installed my L31 it was not so much the tooth count , its the fact of the L31 has a one piece seal and the old 350 have 2 piece seal and the bolt hole will not be correct also , you will need a flexplate for the 96-99 vortec engine,but also specify if you have a 2 bolt or 4 bolt vortec engine , I believe the 1500 series trucks had 2 bolts and the 2500 series had 4 bolts . my L31 is a 4 bolt ,So I ordered a flexplate to fit a 1998 5.7 2500 series truck , I had a TH 400 and then put in a 200 4r with no issues .
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09-30-2018, 11:17 PM | #10 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Just going off your first post on items you may need for the activity you are trying to perform, the starter maybe something to look at as well....
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10-01-2018, 03:41 PM | #11 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Ummmm yeah, the number of bolts holding the main caps to the block have absolutely nothing to do with a 1 or 2pc rear main seal, which is the only difference. Any flexplate from 1pc rear main truck would work, which is what 1986 or so?
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-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
10-01-2018, 03:48 PM | #12 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Friendly reminder. A lot of folks forget that that trans behind the "tired" engine is ALSO "tired". Then you get everything going and a few thousand miles later the trans craps behind all that new found power. I'm just saying be ready and not surprised when it happens.
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10-02-2018, 02:47 PM | #13 | |
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Re: Replacing a tired 350 with a L31 Vortec 350
Quote:
I didn't know that I would need to run a fuel return line, so that's something else I need to look into. Basically looks like my list is fuel delivery system, vortec intake manifold, probably a new carb, flexplate plugging the crank sensor hole, timing marks, and long water pump (I have a short one now, which is new) and making a rear AC bracket.
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
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10-02-2018, 05:54 PM | #14 |
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Re: Replacing a tired 350 with a L31 Vortec 350
On my 78 it had a gas tank vent line I didn't use anymore, it was like a 1/4" and with a return style regulator not regulating anything it gave me 6psi at the carb due to the return limiting flow lol. You can run the pump dead head/not return style, but it will last longer and run cooler with a return style regulator.
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-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
10-02-2018, 08:00 PM | #15 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Early Subarus with electric fuel pumps had no return pump and those pumps tended to last 100,000 miles. It might shorten the pump's life some, but you might not ever notice it.
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10-03-2018, 09:10 AM | #16 |
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Re: Replacing a tired 350 with a L31 Vortec 350
Which would be a good dependable fuel pump
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10-03-2018, 07:04 PM | #17 |
driving is in my blood
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Re: Replacing a tired 350 with a L31 Vortec 350
Every car made today uses a returnless regulator for emissions reasons. The pumps are built to handle it just like starters on vehicles with start/stop tech. Doesn't mean the old tech will hold up to that use.
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-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
10-03-2018, 09:38 PM | #18 |
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Re: Replacing a tired 350 with a L31 Vortec 350
I've had good luck with Wagner.
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10-25-2018, 01:48 PM | #19 |
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Re: Replacing a tired 350 with a L31 Vortec 350
FYI Blue Print Engines sells a Vortec 5.7 long block for $2600 that has the provision for the mechanical fuel pump. Might save you the trouble of an electric pump. I'm looking at this one to replace my Gen 1 350. You can get it through Summit and get free shipping.
https://blueprintengines.com/
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10-25-2018, 02:08 PM | #20 | |
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Re: Replacing a tired 350 with a L31 Vortec 350
Quote:
wow $2600 bucks to keep electric fuel pump . . . gm crate engine = $1800 and change shipped . not telling you what to buy just letting you know your options . do little cam swap and have about the same power level as there engine for less .
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77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great. |
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10-29-2018, 02:32 PM | #21 | |
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Re: Replacing a tired 350 with a L31 Vortec 350
Quote:
This looks like a good value to me. It's a new offering from BluePrint. You get the cam, head work, pump provision and clutch boss. Seasoned Block and heads. I think that covers the extra cost. I will see when they send the dyno sheets, then I will probably have to pay for the displacement! j
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11-14-2018, 08:19 PM | #22 | |
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Re: Replacing a tired 350 with a L31 Vortec 350
Quote:
j
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11-15-2018, 09:57 AM | #23 |
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Re: Replacing a tired 350 with a L31 Vortec 350
I recently bought a truck with a new gm crate 350. It couldn't get out of its own way so I put on new vortecs, cam and headers. Lost my a** on a POS Holley Sniper after a month so I tossed it and went back to an Edelbrock carb. She runs great, is reliable and doesn't require an engineering degree in software development. However, in hindsight, I'll never go old school again. You can get a used LS engine/trans with overdrive for slightly more money up front. It will run better, be cleaner, live longer and have OEM reliability. Buy once-cry cry once they say.
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11-15-2018, 12:56 PM | #24 | |
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Re: Replacing a tired 350 with a L31 Vortec 350
Quote:
A lot of people are going to look at this and say no 4bolt or HD heads, but its not a concern to me, neither is the seasoned block. The stock 350 currently in the truck was replaced about 100k ago. I put that engine in as a dirt cheap reman, I used to use this truck for work back in the 80s. And believe me, this engine has been both lugged and revved under load. It's been wound out rung out and beat like a rented mule. Now it's tired, but the last thing I'm worried about is its 2bolt main! So, that's always been my position on stock'ish 350s. If this engine is built and assembled properly, it will probably outlast me, or my ownership, at this point. Still weighing my options though, but I like the power for the price on this, plus it keeps my swap cheap and easy! j
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11-16-2018, 10:00 AM | #25 |
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Re: Replacing a tired 350 with a L31 Vortec 350
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