Hey I first want to say I've been looking all over the internet about TBI 350s and whenever I searched with a question on Google, it took me straight to your forums here at Thirdgen.org, and there is great help from these forums, Thanks! Anyways, I'm rebuilding a TBI 350 for my K1500, the engine is from an 87 truck..will an LT1 rotating assemblyfrom a 97 Camaro work in the block? I'm trying for better highway speeds...my truck will downshift at 60 or so and nothing really happens except wasting more fuel.... Thanks!

 

Changing the rotating assembly isn't going to give you any increase in mileage. Also the LT1 assembly will not work in the Gen1 block. Check eBay for a scat rotating assembly for the 1pc RMS style block. You can find them for around 600 bones or so. If the engine is still running you should just do a tune-up using Genuine AC-Delco or Delphi(when AC-Delco isn't available) parts. Also check your base timing to see if it's at 0* with the EST disconnected. If it jumps around alot you may have a worn out timing chain and/or distributor. If your truck is lifted with oversized tires and you haven't regeared yet you could step up to lower gears (higher numerically) to put the engine back in it's original powerband and reduce the load that your engine has to turn, or you could put stock sized tires on it and restore the ride height to stock. Either will accomplish the same thing. Hope this helps.
Chris

 

The engine is a second TBI 350 I bought from a friend so i can still use my pickup as a daily driver. It needs a new rotating assembly because it threw a rod from poor maintenance. My truck did have 35" tires on it but I've removed them and added newer chevy rims with stock size tires on it for like you said better mpg and highways speeds. I've found this kit from jegs and is looking like its the best deal for the money other than finding a nice used set.

http://www.jegs.com/i/Eagle/356/B134...oductId=763943

I'm using the stock 193 swirl port heads, trying to find a 454tbi for the intake and not sure what the best cam to use would be, any suggestions?

 

You probably aren't going to need a 454 TBI unit. I would just do the UltimateTBI mods and go with a stock cam unless you are willing to invest time and money into learning how to tune your vehicle. I have a LT4 hot cam in my 383 and used an EBLflash to help speed along the tuning since I don't have an electronic transmission. Even with the EBL it wasn't like the tuning was "are you smarter than a 5th grader" easy.

 

Wait wait wait....I just opened the hood of my truck and looked under the valve covers at my head and it says the cast number is 1402191 or something like that? 191 heads?? what are those?

 

1.94"/1.50" valves 76cc chambers swirl port heads the 193's have same size valves except smaller chamber (65cc I believe)

 

What do you think would be the best compression ratio for the tbi 350? I'm looking at using the -10cc flat top pistons with the 193 heads with 65cc for about 9.3 ratio? or use the -5cc flat top pistons with the 191 heads with 76cc and get about 8.7 ratio? the ratios were figured from the Jegs website under the parts kit at the link.

All while using 87 octane fuel.

 

LT1 rotating assembly WILL WORK IN A 1-piece rear seal block. EVERYTHING will transfer over on the rotating assembly and it is actually a stronger setup than the stock TBI or scat crap. A well machined LT1 crank is equivalent to the ZZ4 crank along with the rods and pistons.

As for power its heads/cams/intake/exhaust/tuning that makes the difference.


ALL the TBI 350 heads are 65cc chambers, 191/193/810 castings are all 65cc. The compression ratio differences are the pistons. The light duty truck engines had 12cc dished pistons with 4 valve reliefs. The heavier duty truck engines had 18cc dished pistons with two longer piston reliefs. The B/D car engines had flat-top pistons with 4 valve reliefs for around 6cc dish.

If you have a roller cam block the LT1 F/Y car cam runs very well on an otherwise stock TBI setup.

 

ALL TBI 350 heads have 65cc chambers, 191/193/810 castings all share the same chamber.

 

True I got mixed up with the 70's 991 truck heads with large chambers my bad..

 

So what would be the difference between my two sets of heads? the 193s and 191s? I just want to know which will have more power or at least better economy, really. I'm going for longevity, economy, and more power!

 

The swirl-port heads are the crappiest performing heads you can get.

It may be that they will idle nice; and be efficient at low RPM and part-throttle. Other than that, they're junk.

'96-up Vortec heads, or aftermarket equivalent would be the way to go. Enginequest sells a "Vortec replacement" head that has the exhaust crossover and the older-style intake bolt pattern.

 

To the original question.... the LT1 rotating assembly will physically bolt into an earlier TBI engine. However, there is one main difference.... no keyways machined in the crank snout. You would have to have the keyways machined into it by a shop that has the right equipment and knows how to index them properly to the crank so that when you put on your earlier style balancer (which has a matching keyway machined into it) the TDC mark actually lines up with TDC on the timing tab.

Other than that, they are compatible.

 

I learn something new every day.

How is the torsional damper aligned on the LT1 crank if there's no key?

 

I am waiting on the answer here too, as all the LT1s I have seen have a crank keyway for both the timing chain sproket and the hub the dampner/pulley assembly bolts onto.

 

My bad, guys. I just stuck my nose under the hood of my neighbor's 97.... it's got a keyway. Don't know why I've been carrying that bad info around in my head for so long but it was definitely wrong. Apologies.

The balancer on an LT1 has no timing marks and is neutral balanced so it doesn't really matter how it's indexed. I guess GM retained the keyway just to prevent any chance of it from slipping on the crank snout.

Which means.... it's a total bolt-in on a TBI block.

 

Awesome! I have all the parts for the rebuild with the LT1 rotating assembly, performance cam that should be friendly with the computer, and did some *minor* porting and polishing of the 193 swirly heads! The swirlies gotta go back on there for now until next summer..going back to college. But I'm happy with the camaro bottom end and nice cam in it for now, the engine should be better than the one in my truck now, for sure! maybe by next summer I can find a cheap vortec from someones rig and use the heads off that and get the edelbrock tbi to vortec intake manifold.
The rebuild is slow going right now, but it should be done within a week's time..still preppin some of the parts for paint, cleanin up the valves and their seats. The engine took A LOT OF CLEANING and the heads had a few imperfections from the casting in the intake ports i ground smooth.

Here's hoping it runs when its all said and done Lol

P.S. So the keyway is good to go, no indexing necessary? Can I use the 87 flywheel and balancer with the LT1 assembly?

 

I'm told to avoid the Eagle if they are not Forged; Many "sellers" on auction sites have dumped their inventory for good deals to replace with Scat.