Rebuilding my '65 Riv 401 with 120k on original, untouched block. My machinist called to let me know that he got the thing squared up by taking .007" off and the new deck height is 9.978". He uses the equipment that follows the crank axis(?) to measure & machine. Some simple math would indicate that he started with a virgin 9.985". With what I've read on here I would've thought that over 10" is what is normally found. Should I be concerned? While disassembling I found the original pistons to average .040" in the hole with one at .050 and one in the high .030's so I thought the deck would've been a bit taller. Steve
Is there any plan to have your pistons end up at a specific height? How does everything you have measure up so far? I'm confused as to whether this project will end up where you put it intentionally or if it's going to end up wherever with a bunch of questions and concerns after the work is done and the budget is spent.
for the piston to be in the hole in the high .030's the block would have to be 10.005 to start with. i do not think the block was 9.985 to start with. the machinist might have miss measured, hard to measure the height of a block.
I wouldn't worry about what happened between back then and now, he gave you a new deck height. I suppose it can happen, but the graduations on the gauging make it kind of tough to make a mistake that big. Maybe a calculator mistake from the main bore? Never hurts to double check. Rather than question the measurement or tell them your buddies on the internet think he F'd up maybe say that you are considering a custom piston and just wanted to double-check the dimension.
The PLAN is to get all of the necessary measurements to order pistons. The only thing he's been able to get done so far is what I described. The rods need to be checked & re-sized, crank polished, bearings, etc.,. He just wanted to let me know that he'd done something. Steve
Eh...no worry. Maybe yours overheated along the way and got fixed? I wouldn't be concerned if the decks were a bit lower from the factory, it's precisely THE reason they make things a bit tall in the first place. I have visited HUGE warehouses full of GM castings waiting their turn for corrective machining (peanuts compared to how many they made each year) I have also seen plenty of factory castings with welding, OS cylinders and a matching piston stamped, etc. I have a supposed unmolested nailhead block that calipers at 10.000 and has the timing area/oil pan rail welded. o No: Who knows where or when this stuff happened. The deck looks broached though. I've read here that it's uncommon or unlikely though.
On ALL the "Nails" that I've done Steve the decks have ALWAYS been between 10.009"-10.021" on 401's. Only ONE engine had the pistons in the hole at approx. .040" but had a deck at 10.008" One virgin engine I did the block measured 10.0135" in the front & 10.0085 in the rear. Was the SAME on the other side but reversed. 10.0085" front & 10.0135" rear. Figured cut .006" off the deck to square it up. That didn't clean up the very outside edges. Figured must have done something wrong & re-did the mounting & measuring just to be sure. ALL was OK. Ended up removing another .003"for a total of .009" & still had a witness line on a couple spots on the outside edges. 1st. one I've EVER come across like this. Normally "Nail" blocks are pretty square from the factory with about .001" side-side. DON'T let them talk you into align honing. If nec. align bore ONLY. This way they can take MORE material off the caps than the block or else you end up with a FOREVER LOOSE timing chain. We with "Nails" don't have options like timing gears or chains for a loose fit. Usually the main bores are pretty straight. I've NEVER had to align bore ANY blocks I've done. I'm sure you've read the problems Deadsled59 (WILL) has run into. Tom T.
That's the source of my concern. The machinist and I have had that conversation. Yes, I've read that entire thread. Will keep you all posted as to what transpires here. Thanks for everyone's input. Steve
Im glad to see that my Machine Shop woes posted here are potentially helping someone reach their desired outcome without the setbacks I've had! Seems like you're attentive enough to be catching things as you progress. Persevere, and you'll succeed. Keep us posted!
As a guess maybe the main saddle diameter was miscalculated or improper specs. supplied/read/???. Without the bearing the diameter is 2.687" which you divide in half which = 1.3435". Then you add this to the deck height actually measured. Just a thought. Tom T.
