Moose2

Need some help finding pistons for my 66 Starfire 425 (375hp). It was just bored 0.040 over and the only pistons I could find weren't good quality and I've got a wrist pin issue. the big names in pistons (?) don't have anything. Where does a guy look for 425 pistons????

dancutlass

Hey, take a look at Kanter.com, I think they do have pistons for the 425...

MDchanic

Egge machine company in California should have something for it, but probably not racing-type parts.

Call 'em up and ask - they've got more in their shop than they have in their catalogue.

- Eric

Oldsmaniac

Before the block was bored pistons should have been in hand and for this also so the cyls could be finish honed for proper clearances. .030 is usually the first overbore size and pistons would be more readily available. Try vendors that were given. You may end up going to an .060 overbore for pistons or need to have custom pistons made...

Moose2

Thanks guys. I contacted Kanter and asked if they had .040 over, and I'll contact Egge too. FYI Oldsmaniac, I did have the pistons in hand and they were brand new; and I'm aware that .030 over is the usual overbore. Didn't have as much choice as I would have liked......... hate to go .060 over before I find out for sure if I'm out of options. Lemme know if there are any other suggestions.

Oldsmaniac

[QUOTE=Moose2;468736]Thanks guys. FYI Oldsmaniac, I did have the pistons in hand and they were brand new; and I'm aware that .030 over is the usual overbore. Didn't have as much choice as I would have liked......... hate to go .060 over before I find out for sure if I'm out of options.

Ok, seems some info has been left out... you had .040 pistons? What happened to them....or you had .030 pistons in hand? More info please.

Moose2

The engine needed a total rebuild, and had to be bored 40 over. I bought brand new 40 over pistons and the machine shop did the overbore. I rebuilt the engine and primed the oil system through the distributor shaft hole as usual. Put about 75 miles on it and it started knocking on the driver's bank. Didn't sound like valve train clatter but I took off the valve cover on that bank and inspected the mickey mouse rocker arm assemblies that 425s have. No problem noted, and I'm tearing it down to look at the rotating assembly, but the knock seems high enough in the engine that I suspect I have a brand new piston with some sort of defect in the wrist pin/wrist pin fitment. Not sure yet, but the pistons were essentially the only ones I could find, and if I do need to replace them, I don't want to get stuck with the same supplier I used the first time. Don't want to name names, but I'd be happier if I could source pistons from a brand name I've seen. The ones I bought were off-brand and the boxes did not state the manufacturer. I'd guess they were made in Taiwan...... so anyway if I do need pistons I'm trying to figure out who's got 'em for a 425........ Long answer, but hey, you asked (grin).

Run to Rund

Any cast piston is iffy. Contact CP etc. and pay the tariff for good stuff. Unless the shop has a rigid hone, you may need to sonic check for wall thickness and go to .060" over. Those rockers may look iffy but they hold up well, even with fairly high spring pressures and high lift. Be careful the rocker bolts are clean, oiled and carefully torqued to 25 ft lb. If one valve is partly open, tighten that one first in steps, keeping up with the tightening on the other one so the bridge doesn't get cocked.

Moose2

Thanks Rund. You need to know it was never about the money. When I bought the first set of 40 over pistons, I was convinced I was buying the only ones on the market; I could not find 40 over pistons for a 425 from a different source at any price. I would have been willing to pay good money for good stuff all the way; couldn't find anything; that is exactly why I'm asking for help this time around, and BTW, unless CP is not showing all their options on the websites that sell their products; they do not have anything for an Olds 425. Olds 455 yes, Olds 425 no. I may have to step up and pay premium for custom made pistons...... but if that's the case I only want to do it after I've burned through all my other options. Make sense, or am I still crazy (like my wife keeps insisting)??

Moose2

I appreciate your feedback on tightening the rocker arm assemblies also. I used new ARP bolts and cleaned them anyway prior to installing. I rotated the assembly and only tightened the rockers that I could rotate both pushrods and didn't see much lifter barrel showing above the edge of the lifter holes....... Am I OK in assuming I would not have tightening bias doing it that way or did I overlook something?????

Oldsmaniac

I would say dont assume a piston or pin problem untill you are sure. It is likely a rod bearing is going south. It is hard to pinpoint an internal noise in an engine... we would like to know what you find.

Moose2

Yup I agree Oldsmaniac, and I wouldn't order pistons until I've done the teardown and inspected everything. It could well be something like a rod bearing although the assembly rotated very smoothly (by hand) and like I said we primed the oil galleries and we also lightly lubed the rod bearings when we installed. Used new ARP big-end bolts and tightened to spec in a two-step process. But you're right; I shouldn't jump to conclusions without the tear-down. I just wanted to get my ducks in a row on pistons in case it shakes out that way. BTW Kanter does have them available in .040 over, and I've emailed them to ask who the manufacturer is. I'll keep you guys posted on all this as I do the tear-down. Should be easy, I just assembled the darned thing a month ago!!

Moose2

The engine is at Old School Horespower. They're good friends of mine. Got the pan off and took off the rod caps. Rod bearings look good and the rotating assembly doesn't seem flawed when we turn it by hand. I'm not sure if a wrist pin problem would show up when we turn it slowly. Still hunting and have more to tear down..... I'll keep you guys in the loop and your thoughts would be most appreciated. I'm in over my head on this kind of troubleshooting.

Oldsmaniac

Hopefully your guys at Old School can find the problem. At this point all that can be done is inspection upon disassembly.

Moose2

I agree. I was curious about one thing when we took off the pan. There are notches for oil spray holes in one side of the big end of the rods and I thought maybe I got stupid and put one piston in backwards and the spray hole was pointed the wrong way and wasn't throwing oil where it would lube correctly, but I put 'em all in correctly. Thought that might have been an easy fix, but it wasn't the problem. So more teardown is the plan......

Oldsmaniac

Check your flexplate/flywheel good. A crack there can sound like the engine is coming apart....

Moose2

Good point!!!!!

Delmont 88 PA

If the engine were still running you could "kill" the cylinder (interrupt the spark plug from firing) and if it is a rod bearing, piston slapping or wrist pin the noise will change noticeably. This will at least target the cylinder(s).

In the days of points and condensers you could pull individual plug wires with plastic or well-insulated pliers to accomplish this. With HEI I had heard that this could cause the cylinder to arc to the module and cause damage. When I did this many years ago we had an oscilloscope that allowed you to "kill" individual cylinders.

Some of the guys on the site who are more current may be able to comment on whether pulling a plug wire on a running HEI engine will really cause damage.