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12-18-2015, 02:59 PM | #1 |
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new L31 crate motor to replace 87 5.7 tbi
hey guys, been a loooong time since I've been on here....looks like i'm gonna be getting my 87 back from reuben when he comes back from afganistan in june, so i'm planning a few things and need some advice
I want to put a new L31 crate motor in the 87 to replace the stock 350 (just because i'm anal that way)....will it require anything different to do this? its a stock 87 5.7L tbi, will the computer recognize it? will it run ok? and can I upgrade the cam any without any problems? if so how big of a cam can I go without it having issues? rear end is a 3:42 posi with 700r4 trans, thanks alot |
12-18-2015, 05:49 PM | #2 |
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Re: new L31 crate motor to replace 87 5.7 tbi
I was looking at doing the same thing - the L31 crate is a great value (roller cam, vortec heads, 4 bolt mains block) for right around $2k. You'll need a TBI/Vortec Intake from GMPP which is pretty spendy to make it work. Also from what I read you'll need to have the ECM reprogrammed to make it work ok, I dont believe the stock ECM will be able to run it very well. I am looking at the Dynamic EFI ECM replacement for myself, but I dont have any experience tuning. Anyone else have some input on this?
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12-18-2015, 09:33 PM | #3 |
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Re: new L31 crate motor to replace 87 5.7 tbi
HT383 Truck motor...
Wide, flat torque curve that hits the 400-lb-ft mark by 2500 rpm and doesn’t dip below it through the 4000-rpm peak (435 lb-ft). It also makes 340 horsepower.
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12-18-2015, 09:42 PM | #4 |
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Re: new L31 crate motor to replace 87 5.7 tbi
There's always a way.
With what you can do with this computer, once you get a good idea of what to do, you'll love it. Not for the faint of heart, I know, and not for everyone - but, it has an amazing price point and will do practically whatever you want to do. If you plan to spend around $2k on a long block, this is a cheaper alternative to some of the stand alone options out there.
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12-18-2015, 10:23 PM | #5 |
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Re: new L31 crate motor to replace 87 5.7 tbi
Hard to beat the price on the L31 crate engine. It's perfect for trucks with tall axle ratios. I considered buying one for my 82 C10, but wanted to run a mechanical fuel pump with my carbureted setup. Ended up rebuilding a 1997 L31 block and using a RamJet 350 cam, which is still fairly mild.
If you are using stock 87 exhaust manifolds, use an exhaust gasket as a template and make sure the manifolds don't block the top 3/8" of the Vortec heads' exhaust ports. Grind away some material if they do.
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Mike 1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 23 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
12-19-2015, 01:57 PM | #6 |
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Re: new L31 crate motor to replace 87 5.7 tbi
I put an L31 in my 87 last year. Runs great. Instead of messing with the TBI I replaced it with a quadrajet.
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12-19-2015, 02:34 PM | #7 |
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Re: new L31 crate motor to replace 87 5.7 tbi
You ain't messin' around, huh? I love it!
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12-19-2015, 02:55 PM | #8 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
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12-19-2015, 09:41 PM | #9 |
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Re: new L31 crate motor to replace 87 5.7 tbi
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12-19-2015, 09:52 PM | #10 |
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Re: new L31 crate motor to replace 87 5.7 tbi
Keeping it red?
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12-20-2015, 06:56 AM | #11 |
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Re: new L31 crate motor to replace 87 5.7 tbi
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01-07-2016, 11:54 PM | #12 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
Vortec heads and that cam are also used on the HT383 crate engine, which makes monster torque. But HP is limited by the heads, especially on a 383 or larger.
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Mike 1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 23 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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01-08-2016, 01:18 AM | #13 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
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01-08-2016, 07:02 AM | #14 |
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Re: new L31 crate motor to replace 87 5.7 tbi
The L31 is great motor.In completely stock form, you can get it to run good w/o a tune, but,you will be leaving some power on the table.You will need to install an adjustable regulator on the throttlebody to be able to tweak the fuel psi.With L31 heads & better cam timing & it's roller cam, you will be adding approx 30% more airflow through the motor, so, it will need more fuel.You may also need to swap fuel pumps, or, you could run into lean conditions at WOT.
If emmisions are not a concern, you can also use a Vortec carb intake with a carb to TBI adapter. This will eliminate the EGR function tho. The ramjet cam (#14097395) is good upgrade to the stock cam, but, it will need some tuning adjustments because of it's 109 LSA.Another good upgrade is the stock Fbody LT1 cam.This can usually be swapped in without tuning issues, but, you will still be leaving power on the table.I just bought 1 last week for $35. I'm on my 2nd L31 in my 97 now.I pulled the original at 248,000 for low idle oil psi & rebuilding it.The G oodwrench crate L31 replacement has 375,000 on it now.At 248,000 miles, the original had virtually no wear.Crosshatch still visible, no ring ridge.Of course EFI & the 4 speed automatic were bid contributor to that as well. By the way, I am running the Ramjet cam in mine. Last edited by jokerz71; 01-08-2016 at 07:08 AM. |
01-08-2016, 09:06 AM | #15 |
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Re: new L31 crate motor to replace 87 5.7 tbi
There are a few things to do when swapping an L31 into a pre 96 truck.The L31 block does not have a thermostat bypass circuit.The t'stat bypass is external,so,you will need to plumb this in.There are a couple of ways to do this.
If your current waterpump has the extra port that some do,you can simply use it & run into your intake.Another method used by some,but,I'm not real fond of,is to simply drill 4 1/8" holes in the the outer thermostat it self.You won't be able to use a Vortec waterpump unless you also use the stock Vortec fan as well.The waterpump hub is threaded & the fan threads onto the pump vs using bolts.You can also use the heater hoses to plumb the t'stat bypass,but,i've not used that & not familiar with it's routing. If you opt for using a carb intake vs the GMPP vortec to tbi intake,as I said above,the EGR will be eliminated.If you don't turn the EGR function off in the tune,you could have some running issues at cruising RPM,as the computer doesn't realize that the EGR is not there & will adjust fuel as if it were. |
01-08-2016, 09:12 AM | #16 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
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01-09-2016, 11:47 PM | #17 |
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Re: new L31 crate motor to replace 87 5.7 tbi
L31 / L30 engines are very good candidates for swapping into LO5 / LO3 powered cars and trucks while keeping TBI system in place.
Easy stuff - block will bolt into existing mounts - there are no issues with tranies. Minor challenges - Vortec intake manifold bolt pattern is different from Gen1 intakes. The simplest and lowest cost approach is to get carbed intake (for example EDL 2116) with a TBI adapter plate. If you do not have to deal with emissions this is a cost effective approach. If you must have EGR functionality use GM performance intake TBI 12496821, driver side exhaust manifold and EGR tube. The L31 was rated around 245HP vs 170 for LO5. To take advantage of this engine output you'll need to increase fuel pressure from stock 13 PSI to about 18 PSI (stiffer FPR spring) and have custom EPROM burned for your ECM. Custom tune should take care of EGR delete(if needed), timing and fuel curves needed for higher output from L31. //RF
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"The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17) |
01-10-2016, 07:35 AM | #18 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
also, who does the custom tune's for our trucks nowadays? some one or someplace on the web? .....no one around me for a bazillion miles (I'm in the sticks big time) |
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01-10-2016, 10:23 AM | #19 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
Your L05 is rated @ 190 to 210 HP & pretty much quits breathing by 4500 rpm. The Vortec is rated at 255 & the heads flow 30% more air out to 5500.That HP rating is very conservative for the L31 & is net rating as installed in a factory vehicle with factory tuning.With 4 bbl carb, headers,&a decent exhaust, it will hit 300 HP easily. CFM Technologies www.cfmtech. com sells the afpr & guages along with lots of tbi upgrades. You can also find a lot of tbi info & tuning options at www.dynamicefi.com. Last edited by jokerz71; 01-10-2016 at 10:42 AM. |
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01-10-2016, 11:06 AM | #20 |
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Re: new L31 crate motor to replace 87 5.7 tbi
Also there are more economical intakes that will work great for your app than the Eddy 2116.Jeg's Champion 331 series is about half the price of the 2116 & will work great in a mild performance build.
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01-10-2016, 02:16 PM | #21 |
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Re: new L31 crate motor to replace 87 5.7 tbi
For the record, the absolutely the worst thing you can do for L31 in originally equipped LO5 is to install a carb. Leave carburetors in 20th century where they belong. Enough said.
18 PSI spring is available from a number of sources - there are couple e-bay sellers. The one I have used before http://www.tbiparts.com/. In addition I like to run adjustable FPR from Jet Performance part # 61500 to dial in FP just right. You'll have to replace in tank FP to support highr fuel pressure. For the record L30 - the 5.0L version of vortec idles just fine with a pair of 5235206 injectors (found on 350 TBI trucks and rated around 62 lb-Hr @ 13PSI) at 17.5PSI in a 89 camaro. Engine is bone stock with GM performance intake and headers and regularly beats equipped TPI cars. Finding a tuner is problem - Harris Performance is one option. The other option is DIY with EBL from Dynamic EFI. I prefer the later option since I tune my engines to suit my needs. //RF
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"The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17) |
01-10-2016, 03:46 PM | #22 |
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Re: new L31 crate motor to replace 87 5.7 tbi
I respectfully disagree, if you want to spend a bunch of time and money messing with TBI. More power to you. But after years of drive stock L05's and L31 trucks. I think my L31 with a quadrajet is better then both. L05's never felt like they had any power to me. And for years the Tbi did it's job just fine (not great just fine). But as soon as it develops it's first problem you'll spend day after day testing and replacing crappy part store sensors. One after the other, just hoping to get it just to run normal.
Stock L31 trucks felt more powerfully, But even more unnecessarily complicated. My L31 with a Quadrajet. Gets better gas mileage then it did with the L05 tbi. Has a good bit more power then it did stock and at times I'd debate more then a stock L31. Starts on the first try every time. And most importantly all I need to make adjustments is a screwdriver. But that's just my two cents.
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87 V20, Vortec 350, Sm465, Np205, Dana 44, 14bff 4.10's |
01-10-2016, 04:55 PM | #23 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
Also, I can fine tune my Holley and HEI to the nth degree while spending next to nothing.
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Mike 1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 23 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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01-10-2016, 05:24 PM | #24 | |
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Re: new L31 crate motor to replace 87 5.7 tbi
Quote:
A preL05 truck would be easier as it wouldn't be a TBI setup.Swapping the L31 into a TBI setup is an easy task. |
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01-10-2016, 05:42 PM | #25 |
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Re: new L31 crate motor to replace 87 5.7 tbi
I stand corrected. What years was the L05 engine used?
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Mike 1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 23 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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