"Auto Tec will tell you you will have to go through myself to get these pistons that we spent over 1 1/2 yrs. working on." That's only fair. Have you made any 322 pistons?
Actually, that compounds the problem. Power adders increase the temperature (even with inter-cooling) of a larger more volatile charge subject to greater cylinder pressure. You want a good quench in that situation along with anything else that will cool the charge (porting or increased intake dwell time). We have learned a few things with our supercharged Cobra over the last 13 years. Cheryl
ok tom im getting to that point so basically putting p600b if I win the bid or another centri supercharger on the car. My engine is a stock 62 401. what exactly do I need? im going to have machine work done so 30 over isn't out of the question at all. it will be intercooled and tbi fed. im looking for that 500 hp number.
You could use a std 454 BBC forged piston and 6.535" rod with .062" over bore and grinding .050" from the crank. It would be much stronger and a lot less expensive for your boosted application. There are other combos that work, and obviously the machine shop would be doing valve notches and other minor mods if need be. If you were starting with a heavily ground crank or already bored block, you would be close to this anyways. If you weren't in a super rush, those pistons seem to pop up often here and there. I don't think many 454's get built with forged pistons at a std size these days, many were made and are out there.
I've bought the last 8 or 9 sets for $125-225. New rods are in the $125-175 range. I've used +.100" hypereutectic for the 425 bore. 455 rods will work if piston guided, bushed, and some piston top trimming. I'll admit to being spoiled because I have the machines to do this though. Already stated, many of them were made and sitting on shelves, not likely to be used as a std bore build. Gotta do some snooping to find them I guess.
yeah I don't have those tools so a toms would be more ideal for me. plus some of this is greek to me.
The shop you use would do the exact same things to yours as a simple rebuild, with the addition to possibly cutting some more to the valve reliefs and very slight milling of the piston dome. They are off the shelf parts that are extremely close to fitting, requiring simply choosing a slightly different dimension to finish to...all done for less than the cost of the custom piston. The very slight dome you would use on a 454 piston for your low compression nailhead only needs slight massaging to clear the nailhead chamber. I do respect the convenience of a drop in part for the garage builder though.
I don't know this for a fact, but I don't believe the BBC piston your talking about has enough of a dome. Don't forget the "Nail" has a fairly large combustion chamber in the head. Approx. 120 (minimum) +CC's. I WOULDN'T bore a 401 .062" over WITHOUT sonic testing. Even IF it does measure OK (approx. .150") the rebuild won't last as long as it should because of the flexing at the bottom of the block. Here's where the Epxoy I add on EVERY rebuild comes into play. Don't forget the cast pistons you get will be .050"-.065" in the hole. Now you need to deck the block to gain back some compression & correct the Quench area. Then, if you use the composite head gaskets you will lose approx. .77-1 on compression. Now you need to cut the heads, but this will do NOTHING to improve the quench area. Now you run into the VERY real possibility the corners of the pistons will hit the heads. ALSO, most times the valve notches will have to be deepened making the piston WEAKER in this area. OR, spend the EXTRA $$$ for a set of OEM steel gaskets. None of this will make up for the shortcomings + you've added MUCH MORE to the machining costs. Now the CUSTOM designed pistons I sell will be close to what the EXTRA $$$$ it would cost for the EXTRA machining nec. to correct all these shortcomings. Price it out some of you machinists out there. AND, no discounts for your buddy's. Real world costs & $$$$. .040"-.065" removed from the deck. You CAN'T make this in one cut, it has to be multiple times!!! ALSO, your weakening the deck. Cutting the heads .020" .030", .040". AGAIN, you CAN'T make this in one cut. Now your weakening the head surface. Cutting the valve reliefs. Cutting the corners of the pistons so they DON'T make contact with the heads. The additional cost for OEM steel gaskets. How MANY times are you going to take it apart, measure, make changes, etc. & put it back together???? It ends up being VERY frustrating & time consuming. A machinists time & paying attention to details at his hourly rate will quickly add up, unless of course you can & have the ability to do it yourself which MANY don't have the luxury of doing. Just my thoughts on the subject. Tom T.
that was my thoughts tom. So basically I want low comp forged piston for this engine tom. what exactly am I looking for I know you sell these. I'm not a engine guru so some of the numbers are greek to me. my engine is pretty low mile so the rods and crank shouldn't need much more than a clean up. also its a stock cam engine should I switch to a more of a boost cam. do I need a full roller or will flat tappet work?
Add up 1.645" and 6.535" and see how close to zero deck you get. No more surfacing needed than any other rebuild. A 16cc dome is a smidge over 8:1, perfect for supercharging. The sides of the dome need minor milling to clear, as stated. (If mocking up an engine to solve that simple problem is too worrisome, then my suggestion is for a different level of engine assembler) Minor valve notches in a piston top that are quite thick already... easy. No different than when you used to buy semi-finished dome pistons. Roughly $100-120. Maybe costs are different in your area. The rod/piston combo is slightly lighter, requiring a bit of drilling on the crank, but then you might be balancing it anyways. (25 grams difference in bobweight is about 1%, so use your judgement) Definitely agree on the need to verify the bores' thickness and filling. I've done them using the 455 rod (with a bushing), saving some $$. I believe that any home builder skilled enough to use the head as the jig to cut valve notches or carefully set up a router jig to trim the domes could easily skip the machine shop for that. The post was asking about piston options and I do not know everyone's experience level, just offering what's been done before. Other than that, Tom's pistons are by far the best option for plug-and-play.
well Id rather have a plug in play option. so maybe tom you could pm me some what I need and pricing.
My advice..... Make sure you specify of the machine shop to use the wrist pin clips!!! 5 minutes after starting my new engine with the new Telesco pistons it developed a knock. When I tore it back down it was found that a wrist pin worked it's way out. Now it's back at the machine shop getting reworked with a sleeve!!!! The wrist pins supplied "might" be a smidgen smaller than stock. BTW, I had the machine shop assemble the short block along with boring to .060, epoxy in the water jacket, balancing the assembly, degreeing the cam, polishing the crank, cam bearings etc. soooo....... all warranty but lot's of frustration. I can tell you that right now they are not happy with the pistons I supplied. My response to them was "why didn't you use the clips that were supplied with the pistons????
I respect your frustrations but that post begs clarification on what really happened. If they truly are blaming the pin size after not measuring things (rods too) AND forgetting the clips if not press fit (which you can feel during the heat fit process) then they probably shouldn't be doing this stuff as professionals. If a novice enthusiast/customer has to 'remind' them to use clips, you've chosen the wrong shop.
Cobravii, that just plain suck whatever happened. I am however happy to say that my Telasco pistons have survived at least one heat cycle! In all seriousness, they are manufactured by probably one of the better piston companies out there and only spec'd by Tom for our application.It's the first time I have heard of a manufacturing tolerance issue from them, pin clips aside.....
There's something else going on here Larry that your NOT being told. I'm NOT just saying this. I HAVE HAD NO PROBLEMS SUCH AS YOU SPEAK OF. ALL HAVE BEEN SATISFIED WITH THE FIT & PERFORMANCE. THIS IS VERY UPSETTING TO MYSELF PERSONALLY. I will do whatever is nec. on my end to make a satisfied customer. Tom T,
if you are using the stock rods press fit you can not use the clips. the clips are for floating wrist pins only. really you should not heat fit the pins. to guess what happen the one rod it self was not right. if the pins were wrong size all the pins would fall out not just that one. what ever was wrong, the machine shop should have check the clearance specs for rod and wrist pin. you really need to get to the bottom of the problem, there is an answer there.
