Author Topic: L-2291F Clearance?  (Read 6048 times)

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66FAIRLANE

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L-2291F Clearance?
« on: September 15, 2019, 05:43:22 PM »
I am going again with my +.040 L-2291F's & a different block. Attached is the sheet I got with them 20 plus years ago. My machine shop was extremely surprised at the small clearance. I did measure everything up when I first built this but no way can remember what my original machine shop did.

Is this clearance, .002, correct?


falcongeorge

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Re: L-2291F Clearance?
« Reply #1 on: September 15, 2019, 05:58:35 PM »
Sounds about right. TRW/Sealed Power forgings don't need as much skirt clearance as aftermarket forgings. You may want to go a LITTLE looser (like .0005-.0007 more) depending on application and how the engine is going to be used, but .002 is about right if its a motor that is seeing predominately mild street use. These pistons were originally intended as an upgrade for stock rebuilds, but they are very durable, and have a nice skirt design that is easy on the cylinder walls. The thick rings are a little dated, but I like 'em, still use them a LOT. Much prefer them to hypers.

67428GT500

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Re: L-2291F Clearance?
« Reply #2 on: September 15, 2019, 11:51:50 PM »
The 70 TRW forged 428 pistons I had in the other block called for .007-.009. That is WAY too tight for TRW pistons. The new JE forged pistons have a minimum of .004 with modern material.

falcongeorge

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Re: L-2291F Clearance?
« Reply #3 on: September 16, 2019, 09:59:20 AM »

wayne

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Re: L-2291F Clearance?
« Reply #4 on: September 16, 2019, 12:00:10 PM »
Yes that is tight for trw pistons unless they have changed.007-.009 sounds right. A guy i used to work with ran a boss 302 bored it .010 and ran std pistons he turned it 8000+.It broke the stock forged pistons after he made the bore larger it never broke a any more.

C6AE

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Re: L-2291F Clearance?
« Reply #5 on: September 16, 2019, 12:14:25 PM »
Maybe put one in a 250° oven and measure it?

frnkeore

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Re: L-2291F Clearance?
« Reply #6 on: September 16, 2019, 12:18:05 PM »
Back in the late '60's, I had 3, 271 HP, 289's (all 5 bolts). I only tore one of them down, but all 8 forged (TRW I believe) pistons had cracks in the oil return slots. I did flog it a lot, in those days. I've never bought any kind of pistons, that used slots, after that. Overall the slots create a very weak area in the piston. That said if, if these L-2291F, are sloted.

If they are sloted and your going to run them, I would install them at .002 and no more than .003. I think any additional clearance will cause them to crack early.

Frank

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falcongeorge

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Re: L-2291F Clearance?
« Reply #7 on: September 16, 2019, 12:49:33 PM »
Back in the late '60's, I had 3, 271 HP, 289's (all 5 bolts). I only tore one of them down, but all 8 forged (TRW I believe) pistons had cracks in the oil return slots. I did flog it a lot, in those days. I've never bought any kind of pistons, that used slots, after that. Overall the slots create a very weak area in the piston. That said if, if these L-2291F, are sloted.

If they are sloted and your going to run them, I would install them at .002 and no more than .003. I think any additional clearance will cause them to crack early.

Frank
L2291's are a replacement piston with the slotted skirt.

Falcon67

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Re: L-2291F Clearance?
« Reply #8 on: September 16, 2019, 04:50:58 PM »
Don't know specifically about those, but the old TRW forged I put in the 302 (4.030) were set at .0035 and the shop said "make damn sure it's warmed up before you hit it."  That was in 1996, and it's still running fine.
« Last Edit: September 17, 2019, 09:02:04 AM by Falcon67 »

falcongeorge

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Re: L-2291F Clearance?
« Reply #9 on: September 16, 2019, 06:21:37 PM »
Crap, how do I get myself into these situations, why cant I learn to just KEEP MY BIG MOUTH SHUT!  ::) ;D
OK, this is basically all in reference to the "old days" when all these pistons were made domestically, but under the old system, there were basically two different species of TRW/Sealed Power/Speed Pro forged pistons, there is the "stock replacement line" pretty much direct copies of OEM pistons and were boxed as TRW or Sealed Power, these generally had a slotted oil ring land, were the same weight as the oem piston, oem pin offset,  and were designed to replace an OEM piston. They were listed in the old TRW and Sealed Power catalogs by OEM application, you would look up the year and engine in the TRW/Sealed Power catalog, and they would list all the parts they made for that application across the page, lifters, bearings, pistons, rings, ect. They were available for pretty much any domestic engine, and honestly, if you used them properly, they were a pretty damned good piston for the price. I'd way rather have them than a goddam hyper, that collapses the ring lands at the first hint of detonation, and fails catastrophically when it fails. I still use them a LOT, and often pick them up good used or NOS for around $100-$150 a set for chevies and small block fords, a little more for FE or BB Mopar. When I first started building motors, if you went to a cruise night or a bracket night or street race, that was what would be in about 98% of the motors there.
 There were also the so-called TRW "racing pistons, which were also sold under the old "Speed-Pro" label, and also Manley and Duffys sold pistons based on the same basic forging, but with slightly different machining. In the case of TRW, these were actually listed in a separate "racing pistons" catalog. These pistons were machined for 1/16 rings instead of 5/64, had drilled oil ring lands rather than slotted, centered pins, most numbers also had floating rather than pressed pins and the majority of applications were domed. A lot of these part #'s could even be ordered without ring grooves and an unfinished dome, so hard-core racers could finish them the way they wanted. These pistons were also designed to run at typical "race piston" clearances. Some of them could even be ordered with grooves pre-cut for head-land or dykes rings, and they didn't weigh the same as OEM pistons, so required balancing. They are a COMPLETELY different deal than the OEM replacement pistons, I know, because I made my living selling all this shit in the late seventies/early eighties. These pistons were also only available for a fairly limited range of engines, compression ratios and pin heights, especially if you raced anything other than a chevy. These ran about $100 more than the OEM replacement line, but to give an example, in the early eighties there were only two FE pistons in this line, a std bore 12/1 428 piston, and a +030 12/1 428 piston.  Any other FE? Forget about it, it was get something from the "OEM" line, or Venolia/Arias.
At that time, you didn't have the myriad of different aftermarket piston manufacturers like you do now, and the price leap between a OEM replacement TRW/Sealed Power piston and a true race piston, like a Venolia or Arias was profound, we are talking the difference (in Canada, were I am) between $200-$250, and $700-$800. there were no mid-priced race piston makers like RaceTec, SRP or Ross, there were the OEM replacement pistons, there was the limited range of TRW/Manley/Speed-Pro "race" pistons, mostly for chevies, and there was the custom race piston, like Arias, Venolia or BRC. So most of us learned how to use the OEM replacement pistons in the vast majority of engines we built, and make them work. And we sure as hell didn't do it by doing things like running them at 4 times the recommended wall clearance. ::) But hell, its not my motor, I don't have any skin in the game, so....
« Last Edit: September 16, 2019, 06:31:46 PM by falcongeorge »

66FAIRLANE

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Re: L-2291F Clearance?
« Reply #10 on: September 16, 2019, 10:01:34 PM »
Thanks falcongeorge for all of your input. There would have had to be some pretty compelling arguments (known typo etc.) for me to go against the sheet that came with the pistons. But my machine shop guy said he had been bit before by people coming in and demanding tight clearances on forged pistons only to be blamed when they locked up. He was still surprised after I produced the sheet but will go with .002. I really do appreciate the input & knowledge on this forum.

My427stang

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Re: L-2291F Clearance?
« Reply #11 on: September 17, 2019, 05:49:55 AM »
I think you are on the right track

- Instructions came in the box
- Modern L2291s are run tight like that
- 20 years ago wasn't the 60s, is was 1999-2000, so these pistons aren't that old
- You are choosing the high side of the given spec

All sounds good

If your machinist is really concerned, I can't imagine .0025 -  .003 would rattle cold, a .030 over 390 likely flexes more than that anyway
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Falcon67

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Re: L-2291F Clearance?
« Reply #12 on: September 17, 2019, 09:07:11 AM »
Per Falcongeorge - "L" in the catalog meant Forged Racing piston as I recall.  I sold a bunch of those too.  I have a set of 8 new L2249NF-30 popups for a 289/302 build.  ( and maybe someday I'll use them - he said since buying them in 1980). I still have a nice 1979 TRW Engine Parts catalog, I'll get some particulars on that L number tonight when I get time. 

falcongeorge

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Re: L-2291F Clearance?
« Reply #13 on: September 17, 2019, 09:33:04 AM »
Per Falcongeorge - "L" in the catalog meant Forged Racing piston as I recall.  I sold a bunch of those too.  I have a set of 8 new L2249NF-30 popups for a 289/302 build.  ( and maybe someday I'll use them - he said since buying them in 1980). I still have a nice 1979 TRW Engine Parts catalog, I'll get some particulars on that L number tonight when I get time.
I have TRW, Sealed Power and Speed-Pro catalogs from the late seventies too, theres a lot of very useful information in the TRW catalog especially.

falcongeorge

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Re: L-2291F Clearance?
« Reply #14 on: September 17, 2019, 09:49:45 AM »
Per Falcongeorge - "L" in the catalog meant Forged Racing piston as I recall.  I sold a bunch of those too.  I have a set of 8 new L2249NF-30 popups for a 289/302 build.  ( and maybe someday I'll use them - he said since buying them in 1980). I still have a nice 1979 TRW Engine Parts catalog, I'll get some particulars on that L number tonight when I get time.
some of the cast pistons in my catalog have the L prefix. The most consistant thing I have found is the cast pistons had a C as the first letter of the suffix after the number. The old TRW part numbering system is a little odd, and can be difficult to de-code. For instance, a Ford 400 piston, L2414F is forged, L2414CF is cast. Occasionally, you will also run across a number with an AF suffix, this is mostly on pistons dating back to the late fifties/early sixties, I'm not sure if those were forged or cast, maybe I can read the catalog and figure it out. For example, the piston listed for '61-'65 390s is L2143AF. Of course these haven't been made for decades, so theres probably not much point in calling your local NAPA and giving them that number. I was thinking last night about scanning a couple of pages of FE pistons and posting them, kinda help make this the "definitive FE TRW piston post".

gt350hr

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Re: L-2291F Clearance?
« Reply #15 on: September 17, 2019, 12:40:08 PM »
   TRW/Speed Pro pistons  "were" forged from an alloy called MS75. That is a high silicon ( up to 12%) alloy so it is typically a low expansion material. To confuse things even more they did use 2618 (low silicon) alloy in some applications and "tin plated" them for scuff resistance. They obviously ran at greater clearance. Clark - Wellever the actual company that made the pistons , had a limited amount of "cam turn" profiles and a common way to make the piston live was to add clearance. While they were "the industry standard" and most of us used them , they are way outdated compared to modern computer controlled , complex skirt shapes. The "contract was not renewed with C-W and they disappeared for some time. Now back in production , Speed Pro has tried India and Mexico for manufacturing bases. The alloy has changed and the surface texture has also changed possibly due to a material spec change. Pricing has also shot upwards making other aftermarket pistons more attractive.
« Last Edit: September 18, 2019, 10:19:28 AM by gt350hr »

wayne

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Re: L-2291F Clearance?
« Reply #16 on: September 17, 2019, 02:12:02 PM »
Google forged piston clearance for some good reading

gt350hr

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Re: L-2291F Clearance?
« Reply #17 on: September 17, 2019, 02:23:35 PM »
   Be careful on generalizing about piston to wall clearance. It "can be " very manufacturer specific besides alloy changes and where the piston is measured .

frnkeore

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Re: L-2291F Clearance?
« Reply #18 on: September 17, 2019, 03:24:19 PM »
I have the 1978 TRW Engine Parts catalog, I got it new and it's one of my favorite books. To bad TRW are not still around.

Here is all the info I could find on the meanings of the part numbering system they use. The A suffix isn't directly addressed but, I think I found the meaning of it, seen in the one picture but, not in the general description areas. Do later versions add the A in the general info area?

Frank


 
Frank

falcongeorge

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Re: L-2291F Clearance?
« Reply #19 on: September 17, 2019, 05:23:31 PM »
   Be careful on generalizing about piston to wall clearance. It "can be " very manufacturer specific besides alloy changes and where the piston is measured .
Damn straight. And VERY material specific. And there are a TON of different ways to make an aluminum alloy, and a TON of different material characteristics based on those differences. gt350hr, IIRC, you work for, or used to work for Racetec, correct? For anyone getting hard engine building advice from google searches alone, well, you would want to proceed with considerable caution...  :o  ;)
« Last Edit: September 17, 2019, 05:36:59 PM by falcongeorge »

falcongeorge

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Re: L-2291F Clearance?
« Reply #20 on: September 17, 2019, 06:12:51 PM »
   TRW/Speed Pro pistons  "were" forged from an alloy called MS75. That is a high silicon ( up to 12%) slloy so it is typically a low expansion material. To confuse things even more they did use 2618 (low silicon) alloy in some applications and "tin plated" them for scuff resistance. They obviously ran at greater clearance. Clark - Welliver the actual company that made the pistons , had a limited amount of "cam turn" profiles and a common way to make the piston live was to add clearance. While they were "the industry standard" and most of us used them , they are way outdated compared to modern computer controlled , complex skirt shapes. The "contract was not renewed with C-W and they disappeared for some time. Now back in production , Speed Pro has tried India and Mexico for manufacturing bases. The alloy has changed and the surface texture has also changed possibly due to a material spec change. Pricing has also shot upwards making other aftermarket pistons more attractive.
There were a LOT of problems when they transferred production to India, especially with pin bores being out of square. Although I recently talked to some engine machinists that have told me those issues have been fixed, I wouldn't bother buying the current ones, especially when you can find lots of NOS or lightly used ones that were made before the transfer to India for $100-$250 like I mentioned. If you are going to go out and buy new "TRW" or Speed Pro forged pistons, the price is close enough that you may as well just buy Racetecs.
FWIW, I think modern skinny rings with a napier cut second and the lower oil ring tension that the napier second permits is probably worth a solid 20hp on a 500hp motor, but I don't see that many guys really taking advantage of that on street motors. They will buy modern pistons, but put very little thought into the ring package, and that's where the power can be found. For sure, if you are going to step up to a modern piston design, there is considerable power on the table in the ring package, if you are going to really pursue that.
There are also the Total Seal spacers designed for use in Stock elim motors, so you can conceivably pursue a state of the art ring package with older 5/64 ring groove pistons, but the cost of the ring spacers is such that you just as well pony up for a Ross or RaceTec forging at that point.
« Last Edit: September 17, 2019, 06:21:56 PM by falcongeorge »

gt350hr

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Re: L-2291F Clearance?
« Reply #21 on: September 18, 2019, 10:28:50 AM »
    Yes I do work for Racetec but am looking forward to retirement soon as in "the next few months". Before here it was a 14 year stint at JE. That's where I got "inside information" like the stuff about C-W as they were searching for someone to buy their operation.
   Randy

427mach1

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Re: L-2291F Clearance?
« Reply #22 on: September 18, 2019, 11:09:57 AM »
I still have a nice 1979 TRW Engine Parts catalog, I'll get some particulars on that L number tonight when I get time.
I was thinking last night about scanning a couple of pages of FE pistons and posting them, kinda help make this the "definitive FE TRW piston post".

Would one of you please post or send me the page showing the L2298 pistons (427 bore, 428 crank)?  I believe it should indicate which heads the pistons will work with.  I had to modify mine to get them to work with CJ heads....
« Last Edit: September 18, 2019, 11:11:50 AM by 427mach1 »

falcongeorge

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Re: L-2291F Clearance?
« Reply #23 on: September 18, 2019, 11:17:18 AM »
I still have a nice 1979 TRW Engine Parts catalog, I'll get some particulars on that L number tonight when I get time.
I was thinking last night about scanning a couple of pages of FE pistons and posting them, kinda help make this the "definitive FE TRW piston post".

Would one of you please post or send me the page showing the L2298 pistons (427 bore, 428 crank)?  I believe it should indicate which heads the pistons will work with.  I had to modify mine to get them to work with CJ heads....

That piston would be in the "Racing Pistons" catalog, not the Main catalog, I'll dig around and see if I can find that catalog.

thatdarncat

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Re: L-2291F Clearance?
« Reply #24 on: September 18, 2019, 12:55:41 PM »
I still have a nice 1979 TRW Engine Parts catalog, I'll get some particulars on that L number tonight when I get time.
I was thinking last night about scanning a couple of pages of FE pistons and posting them, kinda help make this the "definitive FE TRW piston post".

Would one of you please post or send me the page showing the L2298 pistons (427 bore, 428 crank)?  I believe it should indicate which heads the pistons will work with.  I had to modify mine to get them to work with CJ heads....

Yes, the edge of the 428 CJ head combustion chamber will possibly interfere with those 427 pistons. I used 428 CJ heads on one of my 427’s with the L2299 pistons and modified the CJ chamber to make it work. The recommended heads were the 427 MR/HR/TP. Here’s the info from the TRW catalog.

« Last Edit: September 18, 2019, 01:13:45 PM by thatdarncat »
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falcongeorge

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Re: L-2291F Clearance?
« Reply #25 on: September 18, 2019, 01:00:54 PM »
Wow, that was fast^^ :)

TomP

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Re: L-2291F Clearance?
« Reply #26 on: September 18, 2019, 01:54:22 PM »
I have L2298F-30 in my engine. Bought them in 1980. I first ran Cobra Jet heads so the domes were milled off to clear the chambers. Now with the High Riser heads the compression is lower than ideal but it'll run on 94 octane pump gas.

Oh , and 010" clearance too, mostly because of a couple rehonings.

falcongeorge

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Re: L-2291F Clearance?
« Reply #27 on: September 18, 2019, 02:08:47 PM »
I have L2298F-30 in my engine. Bought them in 1980. I first ran Cobra Jet heads so the domes were milled off to clear the chambers. Now with the High Riser heads the compression is lower than ideal but it'll run on 94 octane pump gas.

Oh , and 010" clearance too, mostly because of a couple rehonings.
Those pistons are from the race pistons line, different alloy and drilled oil ring lands, so they are supposed to be out around .007-.008, so .010 isn't that bad.
FWIW, that fake 270hp 283 you saw hanging on the engine stand at my place has +060 L2148F/2149F TRW 270hp/fuelie replacements in it, which are from the OEM replacement line. The block is a '57 283 (no side mounts, one year only, rare as hell) and it was already .060 when I got it. The bores were round and straight, so I CAREFULLY ball honed it, but I am still at around .006-.007 on several holes, that's a LOT looser than I would like with those pistons, they should be around .002/.0025. Hopefully I wont hear the piston slap over the .028 valve lash ;D. But with '57 283 blocks being as hard to find as they are, the only other option would be to go out to 1/8 and build a 301, I'd rather not do that, so I will just have to cross my fingers. 283's are REALLY forgiving, and the bottom ends are like anvils, so its probably ok, but its far from ideal, and I do worry about it a little.
« Last Edit: September 18, 2019, 02:11:39 PM by falcongeorge »

427mach1

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Re: L-2291F Clearance?
« Reply #28 on: September 18, 2019, 02:50:27 PM »

Yes, the edge of the 428 CJ head combustion chamber will possibly interfere with those 427 pistons. I used 428 CJ heads on one of my 427’s with the L2299 pistons and modified the CJ chamber to make it work. The recommended heads were the 427 MR/HR/TP. Here’s the info from the TRW catalog.


Thanks, that is exactly what I was looking for.  I had the domes milled down and modified the chambers on my CJ heads, ended up with a little over 12:1.  I knew they recommended certain heads but couldn't recall if MR were included.  I'm thinking about a pair of Edelbrock heads CNC'd by Craft Performance.  Edelbrock advertises a MR chamber so they should work...

Pentroof

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Re: L-2291F Clearance?
« Reply #29 on: September 19, 2019, 09:34:38 PM »
I went through this with these pistons on my last 390 truck build. I couldn’t believe it, but it’s true. Minimum clearance for those pistons is 0.0015”, according to the card that came in the box with my pistons.
Not all forgings grow a lot. Those pistons have a ton of Silicon that contributes to the low thermal expansion. Your choice of 0.002” is right on the money.

I posted my findings here
http://fepower.net/simplemachinesforum/index.php?topic=6818.msg74661#msg74661
Jim