gex598

I just finished installing a set of ISKY guide plates on a LT1 motor with Dart heads. Things lined up much better then the guideplates that were on there. Now my question, I tried to put the guideplates on with out opening up the slot for the pushrods but they were bottoming out on the guideplate. I started it and adjusted the valves and it sounded horrible. Took them back off and ground down the guideplate some to clear the pushrods. Put them back on perfect! Are the Isky guideplates hardned thruout or just the black coating? After grinding them I removed most of the black coating clearancing for the pushrods.

Steve in Seattle

I had the same issue on my build. LT1 heads, block machined to 9.000", 1.6 ProMags, and shorter valves... it all added up to 7.000" pushrods. Going with 3/8" pushrods probably didn't help much, but I was getting rod-to-plate groove touching around 0.550" lift... once I clearanced it went to full lift. I don't remember needing to clearance every slot, only the exhaust ones in my case... but I wasn't about to take a chance on redoing it all over again so I'm pretty sure I notched all of them down ~1/8".

Couldn't tell you about the hardening, but I would IMAGINE (wild guess) that they use Induction Hardening... which most likely goes through and through considering the thickness of the plates.

From their catalog:
Note: "Grind centers for a closer setting". They're designed to be bottom-ground to keep a close fit... don't sweat it. Just make sure you have more than 0.010" clearance (though a bit more wouldn't be tragic, less could be an issue). Remember that the push-rod may flex a bit, so I'd be careful about insisting on a super-tight fit... 1/32" (0.032") is what I checked for on my build... YBMV (Your Builder May Vary ).

A good overview/reading related to guide-plate use/modification:
The Step-By-Step Guide to Engine Blueprinting: Practical Methods for Racing and Rebuilding
By Rick Voegelin

SS MPSTR

no issue at all with grinding the centers - most instances require some modification in the quest for perfect alignment.

mzgp5x

I installed Comp ProMag 1.5:1 rockers with trick-flow 5/16" 7.3" Lg pushrods and AFR 190 LT1 heads - CamMotion blower cam. The rocker/roller valve tappet did not center with gm guide plates ( purchased from Summit). The guide plate slot clearance was good for the PR. So, I cut them in half. reinstalled and aligned the RR's over the valves. Took them out and re-welded them, and, ground the weld flat. Worked great. Everything in alignment. I did take some time. I appears that the AFR heads have a different valve center distance relative to the stock heads due to the larger 2.02/ 1.60 valves. B.

Steve in Seattle

Sounds like the same process I used with my ISky's... though I obviously didn't have to cut them in half, and the slider middle-section probably made aligning them a tad easier (no rotational issues... just horizontal adjustment).

Some don't weld the Isky GPs, but I was more comfortable with a tack weld on the engine, then removing the plates for a full MIG line just to be sure.

Of course after you tack and weld, you have to reinstall and make sure everything is aligned again... the grind-the-center issue didn't pop up until I did the second alignment and turned over the engine a few times... then it was pretty obvious. Glad we caught that before putting the engine under its own power!

3 times the charm for my engine, but you could easily do the slot grinding when taking them off for the full-weld.

mzgp5x

Sorry I did not add this... After I cut the GP's in half, and, aligned them with the rockers on the valves, the studs were torqued so they could not move. Rocker arms were removed @ this point. PR guide surface was preped with brake cleaner, and, I used duct tape to hold their rotational geometry. They were moved to a vise, clamped flat, then MIG tacked @ ends and full welded along the cut line. The weld was ground flat. The result was a flat PR guide with no heat affecting microstructure @ the rod guide slot. B.

Steve in Seattle

Wow... glad I picked up the Isky plates... was a bit easier than that.

I didn't grind the weld seams flat... I figured I was pushing my luck by pumping even more heat in to a heat-treated plate. Not a problem when MIG'ing in a vice, but grinding the seam was just beyond my patience and paranoia

mzgp5x

I noticed the Isky plates are sloted @ the stud. Can the PR plates shift Rt - Left on the studs after they have been welded??? Of course, this would only happen if both studs were to come loose with minimum clamp load (a remote chance). I red-loc_tite all my studs.

Steve in Seattle

Stud slots? yep. That would be part of the whole "adjustable" part.

Still, it's a decent idea to MIG the two halves together... but if you think the slots will allow the plates to shift if they get loose? I'd say you have serious problems beyond a wiggling plate once the stud gets loose (like a sheered stud, stripped threads, or worse...)