Researched this for awhile and decided to replace the 305 lg4 in my 86 iroc with the( l31 think it is)350 from gm.Plan was to use everything from the old engine on the new except fuel pump but now I see I will need a vortec intake and Im wondering if I will be able to retain my c/c carb and dist.Will my c/c carb bolt up to any vortec intake or is this going to be another issue?or should I go the low compression 260-290 hp in a earlier 350 knowing all my old stuff will work including stock fuel pump?Speed and power are less important then price at this point just need to get this done.Those $1500 260-290 hp 350's should be good for around 200hp right?which is better then my stock 305.
looks like the vortec intake will work for around 200.00 so guessing I would need electric fuel pump and intake with the L31. will the intake have all the plumbing holes,etc I will need?Just dont wanna get this thing in the shop and get 5 calls a day that this and that wont fit.So looks like the older lug 350's will be a simple take off old 305 accessories etc. and bolt on new one and changing to the vortec 255hp 350 will take some more parts and time,correct?thanks

 

Edelbrock makes a Vortec Spreadbore Performer intake. It'll work fine with the factory carb and distributor.

The primary issue will be the EGR. Your valve will mount to the Vortec intake, but the L31 heads don't have the exhaust cross-over passages that the EGR uses for the exhaust gas source. Most likely this won't be an issue - just mount the valve and let it do nothing. But, if you live in an emissions area that verifies the function of the EGR valve by test, you'll have to plumb exhaust up to the intake manifold (using the hot air choke boss on the intake).

The 260 & 290 HP crate engines are pretty lame. If a shop balks at doing the L31 swap, then get the L31 shortblock and put your 305 heads on it.

 

thanks five7.thats part of my problem,the car is registered as a classic now and doesnt get inspected but that could change and at some point if it needs to pass under hood visual then I want it to pass.I've got about a month to get stuff together so I will look further into the L31.Is there anything else you can think of coming up during this swap other then mentioned above,like plumbing, accessories?

 

The vortec Performer won't have a boss for the EGR valve. The vortec heads will be less prone to pre-ignition though, and the motor should run fine without EGR.

Whatever you decide, I'd highly recommend going with a roller cam and one piece rear seal motor. The L31 fits the bill but those generic goodwrench motors won't.

 

The computer-controlled system itself has no way to know whether the EGR is there or not, or working or not; and so, won't care.

Depending on where you live, its absence could be an issue though. Where is that? Do they do complete underhood "visual" inspections there like they do in CA? If so, you're kinda hosed with anything that has Vortec heads, as those don't have the passage to feed gas to the EGR and therefore there is no provision for the valve on any of the intakes. If not, it's not likely to cause any problems.

 

The GM version does: http://www.summitracing.com/parts/na...make/chevrolet

(Supposedly it's made by Edelbrock, a Performer with GM markings.)

 

Never noticed that, but, OOF, $320?

Wonder why, or how it's plumbed.

Still would be missing the fitting for the EVAP's TVS, at least not in the stock location. Did 86 use the TVS or was it computer controlled like the 87 LG4? 86 was kinda a bastard year for a lot of stuff.

 

'86 used the TVS for purge and EFE. One in the manifold, the other on the thermostat housing.

Looks from the pic the port is there:



Pace seems to have the parts for EGR:
http://paceperformance.com/i-6255260...-with-egr.html

 

but the stock location for the purge TVS should be front, right of the water neck.

I also dimly now recall considering retaining EGR function when I did the swap oh so long ago. Went with the standard Performer. Super happy. The only serviceability issue I've had is a little light bucking on down hill coast/decel when the converter is locked. Otherwise good performance vs. mileage.

 

yea no egr or provision for it will be a issue.If I am going to go that route then I might as well do away with all emissions and computer.Yes in Va a under hood visual is done but kinda up to mechanic on how deep they go.Over 300.00 for a new intake is an issue to.Really wanted the L31 to work but for what I need and budget it may not.How about going the 260-290 route then getting some better heads and a cam once the warranty is up?Right now I need the car reliable more then anything and I have driven it for 20 years with a 150hp lg4.If I can upgrade the motor over the years to make 200-250 hp then I'd be happy.Or is this a dont do it If I cannot afford the roller/vortec motor.gonna look at the intakes,routing,plumbing again and try to come up with actaul cost over the cheaper motor and install.thanks

 

L31 shortblock is an excellent deal. Combine them with a quality set of 64ish cc iron heads and you could get a good combination that provides decent power, economy and 87/89 octane.

Your existing 416 heads on the LG4 are a fair casting but on top of the L31 shortblock the compression would be a little iffy, unless you want to always use the expensive gas.

Going with a dished piston now so you could use your 416s may leave you with little upgrade options in the future.

I would NOT consider anything except a roller cam today when replacing the shortblock. Better, more efficient valve train, no risk, get to run synthetic without addititives. No downside.

For some pricing comparison on rebuilds, check out carolina machine engines. I've dealt with them in the past, although face to face.

 

If he goes ahead with his L31 swap won't be have to change his distributor gear also to run the roller cam? I believe I have read on here to change to a melonized gear to go from flat tappet to roller, correct?

 

yes chad that to.So in the end looks like I have to spend about $700.00 more for the roller.New fuel pump system,manifold,dist or gear and this thing with a rigged egr just sounds well rigged.Not sure if anyone listened but my state does require underhood visual and all smog to be on car which I just know is going to be more of an issue then gone over here.This is a tuff one,I know the roller is better but for around 1000 more money and being called out if inspected ,got some more thinking to do.Thanks for all the input guys.oh and the computer on the lg4 will throw egr code if missing,I know ive seen this code before,correct?

 

You can get a roller cam motor that is not the L31. The 87 LG4, in fact, had a roller cam.

 

yes I looked at those also.The L31 will not use my exhaust manifolds either?Planned to do headers but figure If I drop them from budget for awhile it would pay for intake and some other stuff I'm gonna need for swap.So far I will need electric fuel pump,intake,maybe manifolds or headers,dist. gear and then still not sure by reading above if egr or no egr will cause issues.Not too bad and think i can swing that on budget unless someone else wants to add to the list of needs?thanks

 

Passing visual with the Vortec heads may be difficult. The manifold difference alone is going to be a flag. The heads will also have centerbolt valve covers, which I 'think' only appeared in '87?

 

youre right. Add most accessory brackets not fitting from 305 to newer 350 as seen in another thread.Plus headers would stick out so I would have to run my 305 manifolds,I assume choking the vortec anyway.Sounds like a big pain once I look at the whole picture.Looking at the smog older 260hp 350,maybe add a cam and headers and drive the thing for 20 more years with around 200hp.If at some point I want I can change the heads.If anyone who's done this exact swap with all emissions intact can chime in it would be great.thanks again

 

I believe I'd put the 305 heads and everything else off the 305 on the vortec block before I'd put that other POS in there. You might have to run premium gas, but that really wouldn't bother me. I wouldn't even consider putting anything w a flat tappet cam in anymore and that "260 HP" crate engine has a flat tappet cam. I know a guy that has one of those POS crate engines in a chevy truck and I'm pretty sure a 305 in the same truck wouldn't run any worse.

 

running premium gas will bother me.Gonna look at some other options with a local shop and go from there.Not going with the vortec heads for the reasons above.There is no way to pass inspection if needed with that egr set-up plus with a budget of around 2500 there's no way.The intake is 330 alone

 

just read in another forum that all brackets will work.Anyone know if the vortec heads/block have all the accessory/sensor bolt holes?A/C can be dropped but didnt 86 have some weird bracket set up?doing away with the egr would lower the intake price and I can paint it black so it doesnt stand out.I run a dual snorkel air cleaner so that hides most of intake egr anyway.Inspectors have never removed this.Does the edelbrock vortec without egr intake have all the holes for sensors I need?

 

The heads definitely have all the holes you need. 86 has the same weird A/C bracket my 85 does and you can put it back on also. The intake has the same holes yours does, main difference is the vortec bolt pattern.

 

It may not have the boss for the purge valve TVS. I'll check my Performer tonight. Everything else will bolt up with some finagling. The throttle bracket, for example, has to be bent a little to fit the different location of the manifold to head bolt in the rear, but nothing serious.

 

thanks for the info.If it has the holes i need for the sensor I dont care where its located.Good to know about the brackets and if I need more brackets those can be had from junk yard.I have a hypercrap chip in this thing now,will that run the 350 or should I get a 350 chip,and will I need 350 knock sensor?heard some say the 305 puter runs the 350 fine,some say better tuned with 350 computer.

 

305 computer is fine though you can use the chip. The only 350 computer available is supposedly the old GM ZZ conversion kit.

You'll need the 350 KS and the module.

 

Early 80's B-bodies (until TBI came out in '88, I believe) used 350s with computer q-jets.

 

Seen the ccc-qjet systems on them, but assumed they were all 305s. I'll pay more attention in the future.

 

guess the worst that can happen is I get it in and cannot tune good with c/c set up I would have to ditch computer and install carb and diz.If this happens my only issue would then be trans,right?Didnt see the answer for the exhaust manifolds I am doing away with egr anyway cant I just go with headers and whats the best budget option for them?The egr version of the intake has the holes for sensors Im gonna assume the non-egr version does but will check it out.naf did you ever check for the purge valve?thanks

 

'86 LG4 carb & ECM, 350 with World 305 heads, ZZ4 cam, Hooker 2055 headers, 3" catback. Used 350 knock sensor and module. The computer ran it fine. Changed the secondary rods & hangers to DR/G. With 2500 stall and 3.23 gears, 3450 lbs going down the track, ran 13.4's.

There really isn't that much to tune. Secondary rods/hangers, adjusted everything to factory specs (IAB, TPS, etc.). Advanced timing a couple of degrees at a time until it was happiest (ended up with 8 degrees base timing).

 

good to know.Have plenty of rods hangers,fact think im already running that combo but have to check.I am going to have tranny rebuilt during this process,can I retain the stock stall and my rear is 3.42.thanks

 

Looks like the vortec performer has a fitting for the purge TVS, left of the water neck.

If you're rebuilding the trans you need a new converter anyway. You'll want a tad more stall. I went with a corvette converter on my 87 (same model year) and it's a tad looser. I installed an 85 VIN "G" converter in the trans I've installed in my 84 Berli, but have yet to drive it (other than to back it in and out of the driveway so far).