How well would a stock Vortec 350 with an L98 cam run on a stock 350 TBI tune running 68lb injectors? Ive thought on this build and it should make 250 fwhp and be easy on gas and a simple build without getting into a lot of tuning I suppose? The L98 cam has a lil more duration than the L31 cam and less lift so I know its good for stock vortec heads and maybe mild enough not to throw the stock tune out of wack. Im at the point of weighing out whether I want to stay TBI or go carb on my next build.

 

I dont know about the stock TBI tune with 68lb injectors, what fuel pump are you using?

 

Well im sure if I do the swap I will use the Walbro pump I hear good things about. Im sure my stock TBI pump probably wouldn't be enough. I would plan to install a regulator probably having to get the pressure bumped up some

 

A TPI fuel pump will also work well.

I think I would go with an LT1 cam as opposed to the L98 cam. The Vortec 350 flows well and the larger cam will wake it up. It is still small enough to work with the Vortec lift limits and will not need additional machining of your valve guides. I swapped from a 305 TBI to the Vortec 350 with TBI and would suggest getting EBL Flash. It's not cheap, but is worth every penny. Wasted money on mail order tunes but results were not even close to being able to tune it myself on the fly. Also, your stock TBI unit most likely will not flow enough CFM for the Vortec 350 with either cam. You will most likely need a 48 MM or 50 MM bored out one. I think your stock tune will be off both in fuel curve and timing table. It may run, but will leave a lot on the table.

 

would also recommend using a LT1 cam

 

Those injectors will keep the tune tricky I would go down to stock to minimize fueling tunes from injectors and just work on cam tune. I wouldn't think it would be much tuning for an lt1 cam but prom board should be able to chip in

 

68# is not enough injector, it needs the 80# 454s.

 

^^^sorry I misspoke but after searching it seems 68# maybe ok not sure higher but I'd probably chime in prom board.

 

68s will not be enough fuel for even a stock cammed L31. With the tiny 395' marine cam my L31 with the stock truck intake, tri-y headers into stock cats and exhaust put down 230 rwhp and 303 rwtq through a 4L80E and GM 9.5 14-bolt. The stock truck MFI setup is 23.1 lb/hr each at 62 psi and I am running 70 psi for about 24 lb/hr. Running at 86% injector duty cycle to hold 12.6:1 at 5,200 rpm.

 

I imagine if I do build another engine then I will NOT be keeping my TBI. It just limits power so much its so much easier to go with a carb.

 

Doesn't limit it much at all if you have the EBL or newer P4 PCM and a 454 TBI on a carb intake.

 

Honestly I wouldn't go anywhere near an LT1 cam with Vortec heads. The smallest cam I would run would be a ZZ4 cam with 1.6 rockers on the intake and 1.5 on the exhaust using Blue LS7 springs to accommodate the lift. With a 454 throttle body I could damn near guarantee 300+ hp.

 

Looking at a Herbert Roller cam. 215-225 440 465 lift. 2000-5700 RPM range. Upgraded Vortecs with Beehive Spring set. And instead of keeping the TBI and the hassle of tuning just going with a good Holley 650. But im still in planning stage at this point. First im getting paint between now and Octobers Cruisin the Coast.

 

Might check out the lt4 hot cam they do pretty good with the l31 vortec. Use the right springs and retainers without machine work on the heads.