My L98 is somewhat tired and money is a factor. Would the L31 Vortec 350 from 96-99 Trucks be a good swap candidate?

I know I would need the Vortec TPI base from SDPC.

Any other concerns?

They are getting cheaper, and my wives Tahoe had TONS of Torque and great mid range power too.

Thanks,
Ernie

 

There seems to be two camps on this one. Myself, I'm in the "why bother" camp for the heads, although the shortblock is fine. Others think the Vortec heads are the best thing since sliced bread.

To me, it makes more sense to spend your money on real performance heads and use your factory base (ported while things are apart), rather than on a unique and pricey base. The one writeup I have seen on the base, they had interference problems with aftermarket runners. An upgrade cam would also be a good idea, and if you do that, the Vortec springs are going to become the weak link in the chain.

I suppose it really depends upon what all you intend to do eventually. The Vortec engine & base would run fine, but upgrades would be easier with aftermarket heads (even worked over L98 heads).

 

I agree, there are 2 sides to these heads. I stand on the take them side, only if you don't need to upgrade the springs. After that, they start getting expensive. I did a lot of work to mine, but I found good prices on valves, springs, and did the port work myself. All in all, I spent $250 for Elgin valves, Crane H-11 springs, 2 porting kits, ARP studs, and cutting for studs. I got the heads with an engine I bought for $500, so I saved money there. My point is, if you can get the heads cheap, go fo it. If you are having to spend the going price of $500 for the stock set, and plan on doing anything at all to them, I would go with some aftermarket ones. Even if you have to wait a few months for the money, it will be worth it.

 

I'm in the Vortec camp because the efficiency characteristics of the Vortec heads are of the latest technology and even the aftermarket heads haven't picked up the technology (except Edelbrock who realized that it was excellent technology and they could cash in by copying GM). The L98 heads have the old intake style, old combustion chamber and old exhaust runners which is where it loses power on the dyno to the Vortecs. The Vortecs will also outflow the L98's unported and ported. Ever notice the pushrod clearances in the L98 heads? well the Vortec intake runner design eliminates that problem and you can port more of the initial runner that way too.

 

I'm interested in this primarily because they are available and they are getting cheap and they have:

4 bolt mains (some if not all)

One piece rear main seal

Low miles (some)

Vortec heads

Would the accessories and all of the other stuff from my car bolt up?

Even if I don't end up running the Vortec heads forever they will be a good start.

Thanks for the replies.
Ernie

 

what about the HT383 crate engine? Truck block, vortec heads and stroked.

wes

 

That is not cheap. If I had that much money I would build my L98 into a 383 and put AFR190's on it.

I'm reallllllly on a tight budget and I think this motor might be a player.

Any thoughts as to fit / hookup anyone?

Thanks!
Ernie

 

Fit-up doesn't seem to be a problem. CHP mag had an article on the TPI base a few months ago, and the only problem they had was with aftermarket runners needing some grinding to obtain clearance to the Vortec pattern bolts.

Think about this, though: For $400, you could get your L98 heads reworked (and probably pocket ported), put them on the L31 shortblock, and everything would bolt up the way it was originally intended. Either way you go, you should port the plenum, get an adjustable fuel pressure regulator, and if you go the L98 head route, port the base while you're at it.

Again, either route is viable. Needing unique parts bothers me, but if you're comfortable with that factor, go for the truck engine.

One other thing to consider: CHP did the base on a 330HP crate engine. They had to go with aftermarket runners and Hot Cam to get the 330 equines that a 650 CFM carb produces with the crate cam. Translation: Just going Vortec may not be a guarenteed HP increase over the L98. If budget is tight, you may actually lose power just sticking with the truck cam, or even with the L98 cam in it, and stock runners.

 

five7kid - Great feedback! Man I'm really thinking now.

I really like the idea of not needing a special intake so I'm kinda with you on your line of thinking.

If I weren't so stuck on keeping the TPI iwould just do a performer air gap and run it with a carb.

I guess from the block side everything would be a DIRECT bolt in?

Thanks,
Ernie

 

Blocks are the same. I've considered a new L31 shortblock for my Camaro, in fact.

I did mis-speak on one point. The actually testing was done by Scoogin-Dickey themselves, the mag just quoted them. So, reading between those lines: the TPI base, by their own admission, is a power-robber compared to carb on a 350 HO crate engine.

I don't fault you for wanting to stay TPI, by the way. If I had it, I'd keep it, too (in fact, I have a nearly complete setup in the garage attic, just haven't gotten the motivation to complete it and turn it into the high RPM system it would have to be on this engine - can you say, "Cha-ching"?).

 

Camaro Performers actually dyno'd a direct comparison in Summer 2001 issue. The GM dual plane intake was swapped for Edelbrock Victor and obviously the heads were swapped. Both untouched, the Vortecs made 35 more hp than the L98 Aluminum heads and the torque remained the same.

 

If you go with a truck engine and intend to run it without a rebuild, budget some cash for a new cam and timing gears. Not sure what the specs on a Tahoe cam would be, but generally truck cams tend to be very conservative on lift and duration to build low-end torque.

I'd either ditch the stock heads or buy the truck engine as a shortblock from the junkyard. The stock Vortec heads have pressed-in studs which suck. Add a big cam, you need stiffer springs. Add stiffer springs, you'll pull one or more of the pressed-in studs right outta the head casting at an inconvenient time.

You can get reworked Vortec heads with better springs and screw-in studs from Wheeler Motorsports for ~$300ea.

 

The point is he's staying TPI, and talking about putting a complete Vortec engine in as-is. Have you seen a comparison with those parameters?

Neither have I.

But, based on the available information, I wouldn't be surprised that an L98 would have more power than a directly-swapped-in L31 w/TPI.

 

Why? They're the same setup except for the heads. The L31's make 270hp with a SFI setup though. The cam in the L31 has a little less duration however, which in turn with the TPI would probably build more torque making it more of a towing motor than all out race motor.

The point with the magazine test was to show that there was a 35hp difference between the two heads. Regardless of the induction/injection system.

 

im probably gonna get a vortec. I dont plan to do any mods or anything. 250 hp is more than enough for a daily driver and i can get one cheap (<$1100 for one with 40k at the local yard). Oh and i have to have the car running asap which really effects my descisions.

 

I think $ 1100 is a little high for a motor with 40,000 miles on it. I bought a '96 vortec complete long block with 20,000 miles on it 4 years ago for $1200. I bought this engine from a wrecking yard that first had to find one then had it shipped in from out of state. I would shop arround to find a better price.

 

how much was shipping? ive found low milage motors for around that price but shipping costs make the deal not so sweet anymore.

 

For the $1200 I payed, they included shipping. I just had to pay sales tax which was $85. These engines have alot of potenial. I would say a cam change with new valve springs, headers, and a good ingition system these engines will make between 350 and 380 hp. Remeber these engines are very simular to the 330 hp GMPP crate motor. Those crate engines have only a mild cam. The GMPP LT4 hot cam is a great cam for this engine. I have a compcams x-trem energy roller in mine that is very simular to the hot cam in spec's. With the changes I made to my engine I would estimate my hp at round 380 hp. This number is based on a number of other engine combinations that are simular to mine that have been dyno tested.

 

Todd:

Are you running a carb on that vortec motor?

What Comp cam did you get?

Is the motor stock otherwise? Sounds real sweet.

Thanks,
Ernie

 

the l31 in the 96-99 trucks is rated at 255 hp and 330 ft lbs of torque. that's more than any L98 was rated at, although just barely. i think it would be a fine swap for a clean and reliable daily driver that runs as fast or faster than an L98. L31s rev higher than L98s in factory form also.

 

well... im most likely gonna go with this engine. Im not gonna mod it because im sticking with the stock tbi setup so even with mods i wouldnt see that great of a return. Anyone recomend a good intake to use with this engine? I need a new one anyway so i might as well get a decent one while im at it.

ps: will the flexplate on my 88 305 work with this?

 

Yeah it should, it's still the one piece rear seal.

 

I don't undrtstand what the big deal is on this manifold, it costs a little more than the Edelcrock 3860 and a lot less than Accel or TPIS and the benefits speak for themselves.

That is why I chose to use it. It sure beats a stock one ported.
(and it does come already ported)

Don>>>my.02

 

I am run a 750 edlebrock carb w/ GMPP non-EGR Vortec intake. (This is the same as Edlebrock's RPM)

The cam I have is Compcams # XR270HR

Intake / Exhaust

270 / 276 @ lash
218 / 224 @ .050"
.495 / .502 w/ 1.5 rockers (.528 / .534 w/ 1.6 rockers)
110 deg lob sep.
$240.00

GM LT4 hot cam

218 / 228 @ .050"
.492 / .492 w/ 1.5 rockers (.525 / .525 w/ 1.6 rockers)
112 deg lob sep.
$180.00

As you can see they are simular.

I have headers w/ Flowmaster American Thunder II exhaust, Mallory distributor, and a MSD 6AL box. Right now I am running compcams magnum roller tip rocker (1.52 ratio).

 

you def. should get a cam either way.....try the lt4 hot cam, great power at a good price....

 

I know that this post is about 9 years old....but I was using the search function!!!

I was thinking of getting a L31 short block and heads to do a swap in my 90 Iroc and was wanting to know will the stock intake TPI setup bolt up to the heads? I wanted to keep my TPI only cause I spent the cash (600.00) to have one of the thirdgen members do all of the porting work on it. I wanted to keep everything looking like a stock setup, but wanted to swap the engine for something similair to the stock HP/Tq numbers or a little more, but didnt want to mess with dealing with re-tuning the ECM if I can help that.

I dont have any ECM equipment to do any re-tuning.

I also have hooker headers without AIR and the magnaflow dual cats and catback system.

Thanks for any info and advice!!!

 

then you must not have read much when you did use the search function.

No. Your stock TPI base will not bolt to any motor with vortec heads. You have to use another base.

 

Hey 3rdGenMaro....

Thanks for the answer...and if I didnt use the search function...how did I find a post that was 9 years old??!!!

Anyways...just looking for possible other ways to make my stock intake work. Guess I wont be using the vortec heads then.

Someone was saying something about having the vortec heads drilled out at the machine shop...

Thanks for any other information from anyone else....

 

anybody that tells you to just drill the intake to fit the vortec heads is an idiot.

Will it work? yes. Is it right? NO!!!!

The ports dont line up. Vortecs have a raised runner design. So why would anyone ever recommend doing this? Ignorance.



If you already have the intake ported the way you want it and you want to keep the TPI, just put your money into a set of Dart, Brodix, TFS, etc aftermarket heads.

 

Problem solved

Vortec TPI base
https://www.thirdgen.org/forums/engi...pi-intake.html
($450 new )

Sell what you don't need to someone else

 

not all, My L31 shortblock came out of a 96 tahoe and is a 2 bolt main

 

Not to pounce on you, DJK90IrocZ, but in the very first post the OP said, "I know I would need the Vortec TPI base from SDPC."

The only thing that has changed over the years is you can get the base from other sources now, such as Summit.

 

I'm doing the vortec engine swap and I'm using the edelbrock tpi base. Got the engine cheap and had it rebuilt. I almost have everything to start the swap, has anyone run into problems using the edelbrock base? Will it work with SLP runners?

 

I'm planning on the same swap. But I am going with the Stealth Ram.

 

I am currently doing a 350 vortec swap. I have two question 1: the external coil like to know any Ideas on how to mount on the new intake base. 2: the distributer on my 88 will i have to change the gears to a melonized ones, I heard that the distributer gears are different.

 

My mad distributor had the black gears and was a bitc* to put in and line up. So yes use the bronze looking one

 

Factory roller cam engines have the melonized gear ; your '88 dist should be correct for any roller cam

SBC Dist gears are identical dimensions on the outside so gear type should have no effect on fitment in engine

 

So although I did just trade my 3rd gen F (92 rs) for a rwd G body (88 Monte SS), the project remains the same...I have an L31 062 head 350 vortec that btw uses the same block as the ZZs. I just discovered the ramjet setup (7425) that uses the L98 throttlebody (or other gens w/ an adapter) etc w/ the vortec port pattern..so woohoo for full injection. I plan on throwing in an LT4 hot cam, keith black flats to bring it to 10:1, swapping out the springs (instead of having the seat work done), having the push rod holes stretched to accomodate 1.6 rollers. From all the virtuals I ran w/ just a 350 cfm tbi it was at LEAST 390/415-not even stroked, ported etc. Haven't gotten all the new intakes flow numbers but I'm guessing it will make way more power. Now with that said WTF am I to do about a trans? lol I loved my early 4L60E that I had built in my 4th before it got smashed but Idk what will bolt up to this thing or what controller I should use, not to mention lengths for the crossmember bolt up. I don't do stick -which is actually how I wound up w/ this car bec the guy wanted something easier to swap in a t56. was thinking the easiest route would be just get an LS harness/pcm as standalones seem to be more expensive than a quick tune on stock. What does everyone think? Thanks in advance, David