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

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?

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.

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.

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.

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.

Re: new L31 crate motor to replace 87 5.7 tbi
 

You ain't messin' around, huh? I love it!

Re: new L31 crate motor to replace 87 5.7 tbi
 

Not to hijack but Im planning a similar build using the vortec heads and the ramjet camshaft. How do you like it? I might do a 383 to get more low end though. Depends on if I find a bare block or complete shortblock to rebuild.

Re: new L31 crate motor to replace 87 5.7 tbi
 

not at all, you know how I am LMAO:lol:

already put a deposit down and reserve my spot on a full paint job too:metal:

Re: new L31 crate motor to replace 87 5.7 tbi
 

Keeping it red?

Re: new L31 crate motor to replace 87 5.7 tbi
 

sure am, its the original paint mostly so I'm sure it deserves it.....gonna keep the chrome trim too, it'll look mostly stock all but the rad support and the stance:smoke:

Re: new L31 crate motor to replace 87 5.7 tbi
 

My combo works fine and makes good torque for use with the truck's 2.73 (eek!) axle. I don't have a tach, but it eventually revs up pretty well, although I've probably never revved it past 4500 RPM. Most of the time I'd guess it runs in the 1500 to 2500 RPM range. I'm thinking some headers may be in the the truck's future to replace the 1996-2000 manifolds.

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.

Re: new L31 crate motor to replace 87 5.7 tbi
 

Yeah been thinking of copying the HT383 build for my truck. Dont want anything crazy but want plenty of low end.

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.

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.

Re: new L31 crate motor to replace 87 5.7 tbi
 

The heads are not the bottleneck to making power on that engine.Those heads,while small ports for a 383,can still support 400 to 450 HP easily with a correct spec'd cam & a little more compression than the HT383's 9:1.That cam is designed for lowend torque & in a 383 is pretty much done by 4600 rpm.

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

Re: new L31 crate motor to replace 87 5.7 tbi
 

where would I find a stiffer fpr spring to get the 18 psi?

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):waah:

Re: new L31 crate motor to replace 87 5.7 tbi
 

Harris Performance does chips & sells the springs, however, for your application 18 psi is gonna be too much & will likely cause you problems at idle & lower rpm operation.For a stock Vortec long block, you won't likely need more than 14 to 15 psi.The best route to go is to install a higher psi pump (I use the stock vortec pump)& then install an adjustable fuel psi regulator.This way you fine tune the psi to your exact needs.You can usually get the Vortec to run fine with this setup without farther tuning, but, a custom tune would really optimize performance. If you do delete EGR, you could have some issues at cruise rpm.This may, or, may not require a tune.
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.

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.

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

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.

Re: new L31 crate motor to replace 87 5.7 tbi
 

That's well and good if you have the complete intake system, fuel tank with integral pump, computer, wiring harness, head pipes with dual cats, and electronically controlled trans. Unfortunately most guys with 73-87 trucks do not have those 96-up parts.

Also, I can fine tune my Holley and HEI to the nth degree while spending next to nothing.

Re: new L31 crate motor to replace 87 5.7 tbi
 

An L05 equipped truck will already have everything needed to swap the L31 in & retain tbi.You don't have to use the 96 up equipment. If your looking for high HP(over 320HP), then a carb setup is easier to deal with, not cheaper, as an L05 equipped truck will need to be converted back to a carb setup.New distributor, fuel psi regulator & return line, along with other various nit picky things.
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.

Re: new L31 crate motor to replace 87 5.7 tbi
 

I stand corrected. What years was the L05 engine used?