therealmark

Stock '89 350 truck TBI Swirl port heads. First off, I KNOW they suck so please don't waste paragraphs trying to convince me you're right. I've been searching trying to figure out what the maximum lift I can get out of them without machining anything, but I haven't really come up with any solid answers. I believe fast355 had a post that mentioned he was over .500 on exhaust but beyond that all I can find is a buncha heated opinions. I intend to change the springs anyways and I'll even buck up for retainers but I want to accomplish this without removing heads from the block so machining is out. The cam I'm intending has .465 lift, so corrected the 1.6 is .496, at least according this calculator I found online- http://www.wallaceracing.com/rockercalc.php I'd imagine I'm at about the edge of what I can get away with there. Anyone have a solid answer? Thanks! M.

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kdrolt

I don't think the 1.6s will work. IIRC the valve seal boss (around the valve stem) on the L31/LT1(iron)/L05/L03 is the same in terms of dimensions, and going above, or near, 0.480 valve lift on the LT1 (iron) is risky due to the mech interference. So I think the same "rule" applies for the L05.

Searching for Fast355's posts is a good idea. HTH.

ShiftyCapone

.480" is about as far as you can go. There are slight dimensional differences from head to head but the norm is around that number. My 187 heads (305 TBI heads) had that limit exactly (baseline before I cut the guides). Even if you could hit your goal on stock heads you would risk pulling out the pressed in studs. To run that lift you will at a minimun have the pressed in studs removed for screw in units. Having a shop cut the guides at that point is another $20 or so. Fast has run some high lift cams on stock pressed in studs but I don't think he made it very far without them working loose.