STOP BITCHING ABOUT YOUR BILL!
nice little tutorial:
thats a good write up. T-up to old guys who know what theyre doing
sexy…i’ll get one.
pricing is very good on these motors also. mmmm 408…
Very cool. They’re going into a lot details which I didn’t mention in the post I just made about our engines. When I said “clearance rods” that may have sounded like a quick step to some, but once the Weber guys get to that part of the writeup the time involved will probably start to become clear.
I only skimmed it very briefly, but I do take issue with boring and honing before they have the pistons. That’s something we definitely don’t do. Each cylinder is matched to each piston.
The difference in the time and quality of equipment involved in building an engine the right way vs. the way a lot of places slap them together is enormous.
Yeah please explain “clearance rods”?
Nothing wrong with boring and honing before pistons arrive. Most piston manufactures like Diamond and Wiseco tolerances are very strict from the factory
Clearancing rods is typically done to the Block to account for longer stroke cranks. There are areas where the block needs to be ground out (typically with a die-grinder) to allow for proper clearance for the rod to pass by the block when the engine is rotating.
Both ends of the rod, the journals, the wrist pins, and all bearings are measured and clearances are adjusted as necessary. On the 6 Pauter rods for the Supra 4 of the big ends were one size and the other two were unique so there were three different sizes all from one set of rods. Even the best have problems. Some places assume everything is made right and slap it together. Often they get away with it. We don’t try to. Another set of rods was sourced and that set can be machined by Pauter to even all 6 up. I’m not saying we machine out every rod, but those clearances are checked before the engine goes together.
The same goes for pistons. Sure they’re supposed to be the “same”, but there are tolerances on any part. We build to tolerances tight enough using machines that can hit those tight tolerances so it’s essential to hone each cylinder to match the piston it’s being fit with so the piston to wall clearances are to the same spec.
Again, different setups require different tolerances. You can get away with much larger tolerances in many cases, but we don’t try to. Obviously factory engines don’t just fall apart and we’re going way beyond those tolerances in most cases. Heck look at what VW gets away with for factory tolerances. When you see an acceptable compression differential across the pistons of 5 bar on a compression test you have to laugh. LOL
I’m curious how much tolerance you can see in pistons??? ±.0001? ±.00001??? roughly??
The instrument used can read ±.0001
Variation on one recent set was ±.0002. Again, definitely not the end of the world, but variation is always there. I’m not trying to scare anyone into thinking their stock engine is going to fall apart because of a .0001 difference in piston to wall clearance. The .0002 variation was acceptable.
On the other hand, some manufacturers i.e. Subaru have A, B, and C pistons for one model block casting so they can match a piston to each bore from the factory. We certainly don’t want to take less care than the factory does since we’re building engines that will be subjected to higher RPMs, greater cylinder pressure and heat, etc. than a stock car was meant to see.
On some V8 setups a performance build still may have looser tolerances than some factory 4 cylinder tolerances and I’m guessing that’s why Jesse was surprised.
Curiousity question, why do they chamfer?
the cylinders? so there is no rough edge. and when you install the pistons it helps compress/slide in the rings. also don’t want bits of casting blowing off during combustion
I thought that was the whole point of the sleeves. just seems like a lot of chamferring. that does make sense during combustion though. Thanks 
sleeves are more for strength, bore and stroke, cooling, and block clearancing (in more aspect than 1) purposes. chamfering in this case is for the reasons mentioned. in other cases it does things like reduce restrictions, increase oil (or any) flow, make things more rigid, etc
lol sorry i meant this sleeve
albeit a very tiny one lol. I had the words all goofed lol
oh lol.
ya its still a PITA.
there are much better “sleeves” available. the summit ones that work as a solid cone work well
Think you have a few too many zeros there.
.0001 = 1 ten-thousandths of an inch
.00001 = 1 hundred-thousandths of an inch
You are correct. I had one extra zero on the instrument, but the piston spec was correct.
The measuring instrument does ±.0001" and the hone is accurate to ±.0002" (2 ten thousandths of an inch).
I forgot to mention…there may not be a significant difference in diameter on Wisecos, but they actually measure very different from one to the next in terms of weight AS COMPARED to CP, for instance, so I’m not a big fan. Again, it’s a matter of the tolerances you’re shooting for. Wisecos work fine for plenty of people and if someone was using them we’d have them machined so they match up better before installing them. It’s just an extra step the customer would be paying for vs. buying pistons that come matched better right out of the box. CPs have never needed machining to match them up, but they all get individually weighed to a quarter of a gram just in case.
1/4 gram? wow!