I've got a '94 z71 with a TBI 350, and I am planning on changing the valve stem seals here soon. while I am at it I plan on tossing the stock valve springs, seeing as they have about the same pressure as a 5hp briggs&stratton.

is there any problem with running a stock LT1 camshaft (203/207, .459"/.468") and springs, or some aftermarket springs on this motor?
I've heard many times that TBI heads are like vortec's, and have a max lift of .475" without cutting down the guides.
the only reason I would use the lt1 cam is 1. I already have one, and 2. it's bound to be better than the cam in the truck (169/179, .382"/.402"). I know the heads and intake are a huge restriction, and the power potention of the cam will be cut short because of the heads/intake.

 

Your 350 TBI K engine is a flat tappet engine. You would need to get hyd roller lifters, spider plate and link bars out of a hyd roller engine and drill & tap the bosses in the block for the spider plate. You would also have to get a different timing chain due to the bolt pattern being different to make room for the step on the snout for the retaining plate. you would also have to drill and tap the front of the block for the retaining plate as well. You could get an aftermarket set of hyd lifters with link bars and bypass some of the steps. It isn't a direct swap but I have done it. You would be best off getting a $59 flat tappet cam from summit. You can reuse your lifters since the late models lifters have hardened surfaces against the cam. They don't develop wear patterns like std lifters. I'd recommend putting a set of old style z28 springs in it at least since you will have them off already.

 

I already have the roller hardware from a previous motor. a friend of mine has a TBI 350 vin code K block from a truck that HAD a flat tappet cam in it, but the studs/pedestals for the "spider" were already drilled and tapped, as well as the cam retainer plate holes.

but, I had a '92 motor that was a flat tappet motor, had the retainer plate holes drilled and tapped, but the "spider" studs were not. WTF?


basically what I am looking at, is there enough retainer-to-guide clearance on the head?

all of the parts: lifters, guides, spider, retainer plate, timing set... the whole nine, is already in the garage, just worried about the retainers hitting the guides.

 

Yeah, I have seen some blocks that are already drilled.

I would think you would be fine with retainer to guide clearance up to .480 lift easily but I can't be for sure since i've never put a larger than stock cam on the TBI heads. The heads are really not much different that earlier 76cc chambered heads and they will clear .500+ lift with no mods. If you are worried about it then check it when you put the cam in. You may have rocker arm slot issues. If so, you can get long slot rockers for pretty cheap or grind your out a little.

 

not so fast... even with the spider plate, roller lifters/etc, there's one thing that's different about your flat tappet block... the roller lifters are a different size! The lifter bores are smaller on a non roller engine, which is why aftermarket companies make retro-fit roller lifters. KACHING $$$

Your only option would be to use the smaller bore 2.2 four banger, or 60 degree V6 roller lifters. They will fit the spider trays/etc, and fit your earlier SBC lifter bores, but they will require longer push rods since the lifters are shorter than their V8 cousins.

Either way, it's probably better and cheaper for you to purchase a cam made for your block instead of buying all of the parts needed to run your cheap cam. It doesn't make money sense.

 

???? are we talking about the same small block chevy here?

in all the years I've messed with these I've never heard such a tale. I mean, I don't know where to begin... aftermarket companies make retro fit roller lifters to put roller cams in a pre-87 block, which, yes were all flat tappet, not a 1pc block with a flat tappet.
maybe I should re-itterate my post:

I already own the required parts to do this cam swap. been down this road before, only with vortec heads, and a larger cam (guides already milled). I am not questioning the compatibility of the flat tappet and the roller valvetrain parts, I know they work together, always have, '87-up. what I was merely looking for was the specs in the retainer to guide clearance. if it were in my favor, this would dictate whether I tore down the motor for a cam, or just put valve springs in and left it alone for a later day.

 

Not sure i've ever heard of any of this either. I have a 1995 block "K" engine that was flat tappet, I put the roller lifters and associated hardware in it from a 96+ 305 Vortec engine and it has 20k+ miles on it.


Mighty Whitey- I wouldn't hessitate to do the cam swap if it was my engine. I'm fairly confident you won't have any retainer to guide clearance issues with that .468 lift. From my knowledge the TBI heads are very little changed from earlier heads and I have run as much as .600" lift on older heads with no clearance issues.

 

Sorry about that. Perhaps the flat tappet engines post '87 came with the taller lifter bores??? All pre'87 flat tappet engines have shorter lifter bores that the V8 rollers will not work with. I had to use the shorter 2.4L/3.1/3.4 roller lifters from the I4/V6 (pictured left compared to the taller V8 roller lifter) for my '86 because the oil holes/groves will not line up with the earlier block's shorter lifter bores/oil gallies.



With the taller V8 roller lifter, the top part of the lifter stuck out of the bore and would have been a huge oil pressure leak (let alone wouldn't have cleared the spider tray).