Does anyone know of a source for the correct pop up style pistons for a std bore 327? My dad ordered a set of Sealed power pistons though summit racing at the end of Feb of this year and was told they would ship in a month. Sumit keeps on contacting him if he still wants them. and they have no answer when they will ship?
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Re: L79 std bore piston source
Keith what did he order? Maybe napa online has a listing? Of the many napa stores around the country, one may have a set sitting around.
If you get me the SP# I can look it up on my Napa-Prolink account which tells me where ANY would be in the US.
Rich -
Re: L79 std bore piston source
Richard here is the part number SLP-L2166AF. Now the summit web site says ship date of Oct of this year. When he ordered them back in Feb it said a month lead time.Comment
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Re: L79 std bore piston source
As you may be aware, Carl Icahn took Federal Mogul private a few years ago, cut costs like low volume product lines including vintage Chevrolet engine parts, and then sold it off... I recall to Tennaco. So don't hold your breathe on those OE equivalent forged pistons.
I don't recommend the OE design 327 forged pistons for road engines. They are heavy, expensive, and the oil return "slot" behind the oil ring is a weak point that can cause the skirt to break away. The 350 forged SHP pistons have a series of holes in lieu of the slot and are much stronger in this area.
My recommendation is Keith Black hypereutectic pistons. The KB 157 has a 0.5 cc net dome, which with a low to medium thickness head gasket will yield a CR in the low tens depending on deck height, which will be okay with modern E10 premium.
As far as the camshaft is concerned I recommend using the L-46/82 cam in place of the L-79 cam. It has better lobe dynamics. The two degrees more .050" lifter rise duration is insignificant, and the LSA is the same 114 degrees. The primary difference is the IPOML, which is retarded four degrees to 114 deg. ATDC relative to the L-79 cam's 110 deg. ATDC IPOML. For this reason it should be installed with an adjustable timing chain sets that allows it to be installed four degrees advanced to bring the IPOML back to 110 deg. ATDC for the shorter stroke 327.
Auto parts chains like NAPA sell an OE replacement truck roller chain (made by Cloyes) that offers this adjustment feature. A few years ago it cost about 25 bucks for the set, but you have to adjust that for Bidenflation.
Both OE equivalent cams can be ground by Elgin or Howard's cams. Don't use their recommended valve springs. The OE valve springs when set up for .090-.100" coil bind clearance allow at least 6500 revs before lifter pump up. Unfortunately the Sealed Power VS-677 springs, equivalent to the OE 3911068 appear to be MIA. They're about 80-84 pounds on the seat and a rate of 267 lb/in for about 200 pounds open with a 0.3" lobe. Find something close to these specs.
I recommend you read my "Special 300 HP Technical Support" paper that you will find in the "restoration documents" thread at the end of the sticky section. You might also find the compression ratio paper useful. Bothe apply to any precision rebuild. In fact, the only major difference between the Special 300 HP configuration and any SHP/FI small block is the camshaft. Head massaging is optional (It's MANDATORY with the McCaw Special camshaft), but it will provide 10-12 percent more top end power and useable revs to the lifter pump up speed of at least 6500.
DukeComment
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Re: L79 std bore piston source
Keith, Duke has given you a very sage recommendation.
Of the small blocks I've rebuilt, I went with his and others recommendations to use the hyperuetectic pistons.
My Napa Prolink has 0 of the SEP-L2166AP in stock anywhere in the US. I call my store and no availability confirmed.
Screenshot_20240524_154950_Chrome.jpg
With that, here is the KB157-STD, in stock at Summit....
uem-kb157-020_xl.jpg
Rich
P.s. on my dUmbphone so there may be some spulling and gremmer issue.Comment
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Re: L79 std bore piston source
Just a reminder. KB pistons have a high mounted top ring and REQUIRE higher than normally required top ring gap - like what you find in the service manuals for OE type pistons because they run hotter due to their higher placement, so they expand more. The instructions are clearly on the United Machining Web site and likely the packaging.
If the minimum recommended top ring gap is not obtained, the ring ends can butt, which will break the piston. A lot of so-called "engine builders" won't use them, but the problem with ring butting and piston breakage is because the moron who assembled the engine did NOT FOLLOW THE KB INSTRUCTIONS ON TOP RING GAP.
They may require "file to fit" rings. I'm not sure but any "engine builder" worth a damn should know.
Another issue may be the fact that they are supplied with pin retainers. They are for those who elect to use "floating pins" in the rods, something I only recommend for engines that are destined to be disassembled frequently for inspection, like racing engines. For a road engine that is intended to last for years and many tens of thousands of miles use press fit rods.
If you use pressed pins simply discard the retainers. If you use the retainers with pressed pins you will shortly be disassembling the engine for another rebuild.
The price is also a lot more reasonable.
DukeComment
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Re: L79 std bore piston source
Duke------
I recommend the use of the KB hypereutectic pistons, too. They are excellent for street driven cars. I believe GM would have used them for SHP engines of the day but they had not been invented yet. Forged pistons require greater bore clearance and, thus, more "piston slap" and shorter life can be expected. Forged pistons are best relegated to all out racing applications.In Appreciation of John HinckleyComment
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Re: L79 std bore piston source
thanks to all. all this info has been passed on to the machine shop who we be doing the work and making a short block. hopefully this will work outComment
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Re: L79 std bore piston source
I'll also add that the KB piston clearance requirement is about one to one-and-a half thou, which is slightly more that the OE cast piston clearance of about one thou max. Of course don't believe me. Look at the united machining web site and read the instructions.
Here's a story about the OE forged 327 SHP pistons with the oil return "slots".
There are two alloys that are used for forged pistons. I won't state the numbers because I might get them confused, but the one recommended for real racing engines should be fit with about six thou cold clearance, but the one used for production car forged pistons, like the 327 SHP/FI pistons, should be fit with about half that cold clearance.
One of my roommates in my last couple of years at Udub also had a '63 340 HP SWC he bought used, and the engine was weak, so he decided to rebuild it with the help of our buddy who was working on the '67 L-88 he bought from Alan Green Chevrolet to turn into the "ultimate Corvette drag car". I don't know if it was our L-88 buddy or someone else, but they ended up fitting OE replacement pistons to six thou clearance.
Even when warm you could hear the pistons slapping back and forth and within a couple of thousand miles a skirt broke away.
Always follow the manufacturer's instructions unless you have a lead pipe cinch reason why you should deviate.
DukeComment
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