1967 427 L71 Piston Source
I am looking for a source of forged aluminum pistons for my engine rebuild. I want to maintain the 11.0:1 compression ratio. Napa Speed-Pro do not carry a replacement. Thanks for any help.
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In Appreciation of John Hinckley -
Re: 1967 427 L71 Piston Source
Federal Mogul and Dana Corp. have traditionally sold OE replacement parts under various traditional "brands". The F-M number of the 427 SHP OE replacement forged piston is L2268, also available in 30 and 60 thou oversize, however, recently there have been increasing reports that many OE replacement parts are getting hard to find and may be discontinued. Given the low margins and multiple bankruptcies of the major parts supplies over the last two or three years, they have to cut costs and discontinuing low volume parts is one way to do so.
napaonline.com is a good way to search for OE replacement parts. In input your vehicle data the insert part names to get F-M OE replacement part numbers.
As with other GM engines the actual CR of most OE engines is less than advertised by up to half a point. I know it can be a real PiA to buy "race gas" or avgas in cans and have to blend it in with pump premium or use it staight. In the long run it's much better to keep the CR at a level that modern pump premium with satisfy without detonation. That would be a maximum of 10.25:1 for your engine. The slight loss of output from the slightly lower than OE CR can be more than made up with other operations like head massaging.
I co-wrote an article on compression ratio management. It was published in the Corvette Restorer about ten years ago and I believe it's on this Web site, and it's also on the Corvette Forum in a thread started by SWCDuke... easy search.
DukeComment
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Re: 1967 427 L71 Piston Source
from Post #3: I co-wrote an article on compression ratio management. It was published in the Corvette Restorer about ten years ago and I believe it's on this Web site, and it's also on the Corvette Forum in a thread started by SWCDuke... easy search. Duke
Here's a link that I think includes the article you refer to Duke - plus two additional ones you had attached...
thx,
MarkComment
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Re: 1967 427 L71 Piston Source
Summit has the Speed Pro L2268 in 0.030 over available.
They also list the 0.060 over but with a longer lead time.
Comment
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Re: 1967 427 L71 Piston Source
Summit has the Speed Pro L2268 in 0.030 over available.
They also list the 0.060 over but with a longer lead time.
https://www.summitracing.com/parts/s...make/chevrolet
Richard------
Yes, I was aware of the L2268NF. However, I'm not sure if these actually are the same as the 1967 L-71 pistons. However, they are likely as close as anyone is going to get.In Appreciation of John HinckleyComment
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Re: 1967 427 L71 Piston Source
Thanks for all the information. Going to napaonline.com gave me "no results found for Speed Pro L2268". The Summit Speed Pro L2268 gives no information on compression ratio or dome height but it does give a way to calculate the compression ratio. For my application I will be using 1967 closed chamber aluminum heads. While stock cast iron heads have a 2.19 intake valve and a 1.72 exhaust valve, the stock aluminum heads have a 2.19 intake valve and a 1.84 exhaust valve size. I will also use the recommended Fel-Pro # 1027 head gaskets for aluminum heads which have a compressed gasket thickness of .039 inches. The summit web site does give a compression calculator. I will use a 4.251 bore diameter, a 3.76 stroke, a cylinder head volume of 108cc ?, effective dome volume of ?, a deck clearance of .020 from the Summit information, a compressed head gasket thickness of .039, and the number of cylinders of 8. Can anyone confirm the cylinder head volume and determine the effective dome volume of the stock L71 pistons so I can calculate the compression ratio? Thanks again.Comment
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Re: 1967 427 L71 Piston Source
Joe , After Duke mentioned the piston number I started doing some searching and found them there at Summit. Good point about if there is similarity with the original GM part. Maybe from the original print?
Was this piston available from the GM parts system?
Gary, The LF2268NF is not available in standard bore size according to the Q&A in the link I referenced.
The spec section shows dome height of 0.300" and dome volume of -36.30 cc.
Rich
ps Duke's document in the link that Mark referenced is excellent reading.
edit.... Here's a copy paste of the spec page....
Brand:Speed Pro
Manufacturer's Part Number:L-2268NF 30
Part Type:Pistons
Product Line:Speed-Pro Forged PistonsSpeed-Pro forged pistons are made from extruded VMS-75 aluminum alloy that's forged under 3,000 tons of pressure to "near-net" shape. After that, they're machined to their final configuration. These pistons offer excellent strength and durability—and are capable of taking the punishment that's dished out on the street and in competition. They're available for a wide variety of applications, including OE replacements and all-out racing engines.Last edited by Richard M.; August 2, 2020, 06:13 PM.Comment
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Re: 1967 427 L71 Piston Source
Gary- The Speed Pro L2268NF is the successor to the TRW L2268F. I think Speed Pro bought the TRW piston and cam business. The TRW piston is identical to the original equipment pistons for the 67 L-71 and L-89 with a dome height of 0.300 inches and a dome volume of 36.34 cc. The OE pistons were made by TRW and even have the TRW script on the inside. The Speed Pro may also still have the TRW script inside since they are probably forged with the same TRW tooling. According to Richard, they are no longer made in standard bore. I may have a standard bore set of TRW L2268F. Let me know if that is what you need and I will look for them tomorrow.
Have you been able to find any 1.84" exhaust valves. I need some and have not been able to find a source.Comment
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Re: 1967 427 L71 Piston Source
Pat, Manley lists the 1.88 exhaust valve in their catalog http://www.manleyperformance.com/dl/cat/catalog.pdf Summit list them in their catalog https://www.summitracing.com/parts/man-10727-8Dick WhittingtonComment
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Re: 1967 427 L71 Piston Source
Patrick------
The standard stem size GM 1.84" exhaust valve was discontinued without supersession in October, 1987. The oversize valve stem versions were discontinued in 1976-77. I do not know of any aftermarket replacements. Since the original PRODUCTION use was so limited (less than 2,226 total Chevrolet vehicles ever made using these heads), it's not too likely that the aftermarket is going to "step up to the plate". Still, there could be one specialty manufacturer that might still offer them.In Appreciation of John HinckleyComment
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Re: 1967 427 L71 Piston Source
Did that on my open chamber L/88Dick WhittingtonComment
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