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Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
nothing as of yet . I plan on putting a few more miles before I decide if I need to . I do want to eliminate VATS & EGR on the computer . good luck ...
I used my stock starter from the old 305 . I also used the same flywheel . I have a T-5 manual transmission (much more fun than an auto.) . for an auto. I'm afraid I cant help you . I'm sure some others on this forum could help you . good luck .
Uncle Tom I have my car running with the l31 but doesn't seem to be running right. It dies around 2500 rpms. Do you have 350 injectors in yours? I have a bored throttle body and 350 injectors. I did buy a custom chip. Are you also using the stock 305 chip? And what did you set your timing at?
everything is stock from the 305 . timing is about 8-9 degrees , I worked up from 6 degrees . I suspect your timing is off & other ignition/fuel problems . my engine was a NEW G.M. crate engine . all engine sensors/switches I used were NEW . the distributor & wires were almost new , I also used NEW sparkplugs for a 2001 truck engine . the plugs are different . my fuel pump & filter were pretty new . good luck ...
Uncle Tom if your car continues to run so good you make it a hard decision for me not to buy and just drop the stock L31 in mine for the simplicity of it. Id love to see dyno results or 1/4 times on that car just as an idea of the power its making on the 305 tune.
Mine is a brand new crate motor, all new items as well. Nothing is reused from the 305 on the motor. Yep I have new plugs for a 2001 truck.
Originally Posted by UNCLE TOM
everything is stock from the 305 . timing is about 8-9 degrees , I worked up from 6 degrees . I suspect your timing is off & other ignition/fuel problems . my engine was a NEW G.M. crate engine . all engine sensors/switches I used were NEW . the distributor & wires were almost new , I also used NEW sparkplugs for a 2001 truck engine . the plugs are different . my fuel pump & filter were pretty new . good luck ...
Uncle Tom if your car continues to run so good you make it a hard decision for me not to buy and just drop the stock L31 in mine for the simplicity of it. Id love to see dyno results or 1/4 times on that car just as an idea of the power its making on the 305 tune.
I did re-cam the engine , I took my time on everything . I was overly **** on ALL details . dyno results , 1/4 mile times ??? yes I suppose it would be interesting to know . will I find out ? most likely not , I really don't care . I'm 76 years old , all I wanted was a few more pony's under the pedal . (never expected this much response on my engine swap) I'm very happy with my swap . good luck if you do the same ...
Thanks Unc, id love to run into you in Oct at cruising the coast and check out your car. I may go the same route as you did.
if I'm still kicking I will be there . I'm pretty close , I live in wade so it's not much of a drive . I always enjoy but never get to see everything . always much to see & do . good luck ...
Uncle tom I completed my swap and yes this engine does pull like a bat out of hell. My issue was the iat sensor wire was bad and causing all kind of issues. Fixed that and now it drives excellent.
Your post was my inspiration to do the same swap.
I do have slight differences. I kept the stock cam in it. I ordered the motor from summit. I did add a bored out tbi unit, hooker headers, delete cat, hooker catback, 350 injectors, 350 module and custom tune, 3.73 gears and posi unit. Ill take some pictures when the weather clears in my area. I don't want to pull it out of the garage in the rain.
Hope you don't mind if I chime in. I'm also doing a L31 swap and have heard some good and bad about the vortec plastic timing cover. Notorious for leaks where it meets the block. The instructions say to apply a bead of RTV on part of the bottom of the timing cover onto the part of the block. And I'm assuming the pan gasket goes over this. Can anyone say exactly where the RTV needs to go? It's on the stand now and I'd hate to have to come back to this. Timing cover is brand new. I went with a 93 LT1 cam, didn't need special springs so I was told cause the lift was supported by the 906 heads in stock form.
WOW I created a monster when I started this thread . (damn I love it) I also wondered about the plastic cover . on the RTV , with the pan off a dab of RTV on each corner where the pan gasket forms around timing cover and rear main . in the groove on bottom of cover & rear main just a light coating of RTV . I must admit I messed up (my fault) the crank seal and had a bad leak . the plastic cover does not like crank seal only to be replaced . after 2 try's I replaced the entire cover . (GM recommends this for crank seal leak) as do I now . anyway all is fine now . HINT , when using RTV on anything just tighten down finger tight at first . take a break , have a beer , coffee , or what ever . let the RTV cure a bit before final torque . once again I am very happy with my choice of a new GM crate engine . I got mine from JEGS , 2K delivered to my door . would have cost much more had I sourced & rebuilt a JY engine . good luck with your project ...
L31 block, 906 Vortec heads, 395 Ramjet cam, (thanks gary1, and Uncle Tom) SD intake manifold, Hooker 2460 shorty's, custom 3" Y pipe and exhaust, few bolt-on's, l98 pulley's, plenum, wire harness, map/speed density, etc.
I ditched that plastic cover right off the rip.. granted I had the one off my l98 layin' around. Why take a chance if you're uncertain, or have heard bad things.. that's the way I look at it anyways. This has been such a helpful thread! Thanks all!!
Last edited by Nathaniel92; 08-21-2015 at 10:23 AM.
L31 block, 906 Vortec heads, 395 Ramjet cam, (thanks gary1, and Uncle Tom) SD intake manifold, Hooker 2460 shorty's, custom 3" Y pipe and exhaust, few bolt-on's, l98 pulley's, plenum, wire harness, map/speed density, etc.
I ditched that plastic cover right off the rip.. granted I had the one off my l98 layin' around. Why take a chance if you're uncertain, or have heard bad things.. that's the way I look at it anyways. This has been such a helpful thread! Thanks all!!
Looks great! I agree with you but everyone has opinions. Some say there isn't a problem and others say forget about it. What year is your block? I have a 97 block which doesn't have the hole under the water pump to allow constant coolant flow which in turn the same block is missing 2 bolt holes for the older sbc timing cover. Did you remove the reluctor ring and use your L98 harmonic balancer or did you use the vortec balancer?
Thank you. Talk about looking great... you got a beast there man!!! I'm really wishing here recently I went with a Ram. O-well, maybe next year, lol. Yeah, mines also a 97 Tahoe block/heads. But that's all I used. The rest of the 90k mile "running truck" parts are in my garage, lol. I used everything off my l98. Water pump with hole, (so I could run the coolant bypass) l98 harmonic balancer, all pulleys, OIL PAN (didn't wanna chance dipstick accuracy, etc.)
It'll definitely be in by then but sounds good to me! I hope I'll be okay with using some of the vortec parts. I'll be using the vortec balancer, oil pan with dipstick. Pretty sure pan will be fince especially as all the auto part stores lists the same one for a 87 T/A 350 and a 97 Tahoe 350. Everything else I will use from the L98. I started it up on the stand today, here's a video.
Awesome man!!! You should be fine.. I just made it easy on myself putting everything back on that came off (dummy proof) lol. I did use a power master high torque mini starter, and the 168 tooth flexplate off the l31. I always forget to mention that. Had to use the mini starter cause of the headers. Had to fab my own dust shield too.
Right on. My GTA is my daily so don't have any l98 stuff laying around yet. This is going in because I have low compression on one cylinder, but still runs great. I noticed the staggered starter and large flexplate. I'll be using a LT1 starter and flywheel as a T5 will be going behind it.
I can't find anything but did anybody have to switch to a longer serpentine belt when they did the swap? My l98 belt was insanely short and I used all pulleys and brackets from my l98. I bought a longer belt but what gives?
NORMAL , with the elimination of air pump . I know sounds weird but routing of belt is different and does require a longer belt . good luck ...
OR I've in the past dumbed out on which way it went... It's one of those last exciting steps, the belt then the radiator/fans then DRIVE! Easy for me to get overly excited and start dumbing stuff up, lol. Me anyways.
OR I've in the past dumbed out on which way it went... It's one of those last exciting steps, the belt then the radiator/fans then DRIVE! Easy for me to get overly excited and start dumbing stuff up, lol. Me anyways.
Lol this is exactly what happened. Went to put the stock belt on and absolutely would not fit. Spent an hour on trying to figure it out and ultimately went to the part store and got a longer belt. Finally realized I was routing it completely wrong lol. But here it is!!
LMFAO!!! Kick *** man!! Looks fantastic!! It's good to know I'm not the only one that did that also.. I took a trip to the parts store and wasted money too. And the screwed up part is that I was trying to find a routing pic on my phone (there's not one in Chilton's) and couldn't find one ANYWHERE online, not even on this site. After I figured it out I was sliding the fans in and realized there's a damn diagram right there on the fan shroud, lolol.. hints the reason I posted that pic for ya..
There's two ways to route the belt... short vs long. Belt lengths from AdvanceAutoParts
98.03" = Air - crank - water pump - power steering (88), or...
94.50" = Air - water pump - crank - power steering (89-92) as see in the previous pictures.
Thank to SEThirdGen for the diagrams (88 vs 89-92):
LMFAO!!! Kick *** man!! Looks fantastic!! It's good to know I'm not the only one that did that also.. I took a trip to the parts store and wasted money too. And the screwed up part is that I was trying to find a routing pic on my phone (there's not one in Chilton's) and couldn't find one ANYWHERE online, not even on this site. After I figured it out I was sliding the fans in and realized there's a damn diagram right there on the fan shroud, lolol.. hints the reason I posted that pic for ya..
It was definitely a wow moment. Do a engine swap and get something as simple as the belt routing wrong. If you look at my upper radiator cover you'll see the same diagram lol. I'm trying to get my timing situated. Since using the l31 timing cover I have no timing marks except for one notch that protrudes out of the cover.
If you have the routing in the 2nd diagram and take off the smog pump, if you use the routing in the first 1st diagram, minus the smog pump, you can use the original belt.
I'm not sure , but I don't see why not . remember the timing mark will be at 2 o'clock now . if it (the metal cover) does not have it in that location you will have to add one . good luck . cheers ...........
Just thought I'd drop a word on the vortec coolant bypass - if any of you guys are not running coolant constantly through your heater core, then the intake manifold needs a coolant route plumbed into the water pump intake. This is because the vortec heads and block do not have internal coolant bypass like the old heads have. This prevents hot spots from forming in your coolant passages when the engine is warming up.
Awesome builds, guys! I'm working on mine too, and hope to have pictures to show soon enough.
Just thought I'd drop a word on the vortec coolant bypass - if any of you guys are not running coolant constantly through your heater core, then the intake manifold needs a coolant route plumbed into the water pump intake. This is because the vortec heads and block do not have internal coolant bypass like the old heads have. This prevents hot spots from forming in your coolant passages when the engine is warming up.
Awesome builds, guys! I'm working on mine too, and hope to have pictures to show soon enough.
Not exactly correct on the bypass. I have rebuilt a 1996 L30 305 and a 1997 L31 as well as have a crate L31 in my 1997 Express and ALL have coolant bypass ports in the block. Bypass has nothing to do with the heads for what its worth either. That being said the easiest way to bypass water and not have it affect the coolant temps of the engine once it is warmed up is to drill the thermostat itself. Its actually the method I prefer.
What plugs and plug gaps are you guys running with your efi vortec setups?
I am running AC plugs for a 97 V8 3/4 ton p/u truck . the reach/length is a little longer than older engines . I don't recall the plug gap , think I used same as the old 305 . good luck ...
HI uncle tom whot did you do with the chip ? many say cant run stock others disagree gathering parts to do same as you but mine is a 700r4 glad u ok thanks steve
What Horsepower are you getting with that setup? Lately I've been leaning towards swaping out my l98 to go to a L31 with the tuned port setup to keep it looking stock.
L31 block, 906 Vortec heads, 395 Ramjet cam, (thanks gary1, and Uncle Tom) SD intake manifold, Hooker 2460 shorty's, custom 3" Y pipe and exhaust, few bolt-on's, l98 pulley's, plenum, wire harness, map/speed density, etc.
I ditched that plastic cover right off the rip.. granted I had the one off my l98 layin' around. Why take a chance if you're uncertain, or have heard bad things.. that's the way I look at it anyways. This has been such a helpful thread! Thanks all!!
What kinda horsepower are you making with that setup, Ive been leaning towards swapping out my L98 for a L31 and keeping the Tuned port setup to keep it looking stockish.
05-19-2015, 07:16 AM
OR I've in the past dumbed out on which way it went... It's one of those last exciting steps, the belt then the radiator/fans then DRIVE! Easy for me to get overly excited and start dumbing stuff up, lol. Me anyways. 
Kick *** man!! Looks fantastic!! It's good to know I'm not the only one that did that also.. I took a trip to the parts store and wasted money too. And the screwed up part is that I was trying to find a routing pic on my phone (there's not one in Chilton's) and couldn't find one ANYWHERE online, not even on this site. After I figured it out I was sliding the fans in and realized there's a damn diagram right there on the fan shroud, lolol.. hints the reason I posted that pic for ya..
