new engine parts help

[Mark #44888]

Next month, I'm pulling my L46 out of my '70 and want to rebuilt it to as close to stock as possible. (108k miles and smoking!) I figure it will probably need boring and maybe a crankshaft bearing grind at the machine shop, but other than that, I want it put back together with stock specifications.

Where can I find the camshaft specs for an L46?

More importantly, can you recommend a source for OEM or OEM style engine parts?

I'm going to need pistons, bearings, cam, timing chain, oil pump, gaskets, oil pump, etc...

Thanks - Mark

[Mark Milner]

Re: new engine parts help

Don't assume you need to have the crankshaft turned. I have run stock small blocks to 200,000 miles without ever opening the bottom end. Have them check the crank first and turn only if needed.

Several books have the specs. Also, you can do a search on Yahoo.

http://forums.corvetteforum.com/showthread.php?t=804206

http://forums.corvetteforum.com/showthread.php?t=656387

http://www.geocities.com/MotorCity/Downs/3000/cmspec.html

Chevy tended to include the long ramps in the duration specs originally, making their cams seem like they had huge amounts of duration. However, when measured in the real world, typically at .008 lift and .050 lift, these duration figures become much shorter.

Intake: 195 Duration @ .050" , Lift .390"
Exhaust: 202 Duration @ .050" , Lift .410"
Lobe Seperation 112

Personally, unless you are judging, I would run the L82 cam or another cam that had roughly 260 degrees duration and around .460 lift. I think you will like how it drives much better.

[Duke W.]

Re: new engine parts help

Those are base cam specs.

Duke

[Duke W.]

Re: new engine parts help

Your crankshaft has the Tufftride surface hardening, and you DO NOT want to grind it unless ABSOLUTELY necessary. Tuffriding improves durability.

The crank and rods should be Magnaflux inspected, and they will probably pass. Resizing rods is common, but not necessary in most cases. If the bearings and crank journals are in good shape and the big end is not out-of-round, resizing in not necessary.

The crankshaft should be checked for straightness and journals checked for proper diameter. The only other task would be to polish the journals.

The cam has 224 degs. duration at .050" lifter rise and the points of max. lift at 114/114. You could also install the LT-1 mechanical lifter cam, which offers broader torque bandwidth and extended rev range.

All OE cams are available from Federal Mogul, and you can buy all your other parts from quality suppliers like F-M, including the forged pistons.

If you want more top end power, pocket port the heads and have a multiangle valve job done, have the valve guides rebuilt using a quality procedure. You also want to pay close attention to compression ratio, which starts with measuring piston crown-deck height clearance at teardown. Then use a CR calculator to determine the required head gasket thickness to achieve no more than 10.5:1.

This has all been discussed in detail. Suggest you buy some books and search the archives. I expect you have a lot to learn if you are to avoid mistakes.
You need to determine exactly what operations are required and find a machine shop that will do it YOUR way, or you might end up with a decked block, turned crank, knurled valve guides, and an aftermarket cam that's not as good as the OE cam.

Duke

[Mark #44888]

Re: new engine parts help

Mark - I have the L46 350 hp engine. With 11:1 compression, that should be enough for me. I really want to keep this original, so I don't think the L48 links you mention are for me. I do want to get it judged, but that is years away.

- also Mark

[Mark #44888]

Re: new engine parts help

Duke - thanks for the advice. I intend to write out exactly what I want the machine shop to do and hand them a copy. Less is better, so I won't know until it is torn down and looked at.

I do plan on hitting the books, as it's been 23 years since I've rebuilt a motor.

The cam specs you posted, are they for the L46 350hp ? If so, that's what I want to go with. I want it to be just how it left the factory back in '70. No mods, and I'm running the original distributor (though it needs to be inspected by a pro).

The L46 was 11:1 compression ratio. Do you know what octane they used back then? I know it was leaded, and the owner's manual says to use "premium". Wonder if 93 is enough or will need to add a booster?

I will search the archives and start "cramming" for next month.

Thanks again - Mark

[Verle R.]

Re: new engine parts help

Mark,

Be sure to give the machine shop written instruction for what you want done.
Include specific instruction that they do NOT deck the block. Also tell them, with emphasis, to NOT deck the block.

Depending on your perception on how they respond, include a threat to sue them if they deck the block as that will cause considerable damage to the value of the block and your car.

Verle

[Duke W.]

Re: new engine parts help

Yes, the basic specs I listed was for the L-46 cam, which was also used on the later L-82.

Actual CRs are typically less than specified by about half a point because decks were typically machined ten to fifteen thou higher than the nominal 9.025" and measuring deck clearance along with knowing the specified piston compression height allows to to determine how high your decks are and what the actual CR is.

The engine should operate detonation free on today's 93 PON fuel if CR is limited to about 10.5, which should not be a problem went you know all the critical dimensions and select a head gasket thickness to not exceed 10.5.

If the engine operates okay on 93 now, you measure the actual CR at teardown, and then do not exceed this value on buildup, it should be okay.

[Mark Milner]

So shoot Me, I misread L46 as L48

The same advise applies, get a book, look it up!


If not, do a search on Yahoo and Google.

http://www.geocities.com/MotorCity/Downs/3000/cmspec.html

69-77 350 hyd p/n 3896962 c/n 3896964
69-70 350hp, 73-81 L82
open close dur lift open closed dur lift overlap
52 114 346 .450" 98 62 340 .460" 114
@.008" 31 73 284 .450" 77 21 278 .460"
@.050" per Chevy 222 222





Or simply ask your cam supplier for an L46 or L82 cam. If you look at most cam supplier books, they will give specs and equate the Chevy name to their cam of nearly the same specs.

[Mark #44888]

Re: So shoot Me, I misread L46 as L48

Thanks for the specs Mark. And I will be burning the midnight oil with the books

[Joe L.]

Re: new engine parts help

Mark-----

So, you want it to be as "original as possible"? OK, here's what to use

pistons---no longer available from GM. Federal-Mogul/TRW has more-or-less equivalents, though. L2304F in your required oversize is as close as you are going to get to original. I don't recommend these, but if you want original, this is as close as you are going to get (other than a custom-made piston at high cost);

piston rings----GM #88894219 (standard) or GM #14089026 (+0.030). These are the only sizes available from GM. By the way, these are sold only on a "per cylinder" basis; NOT an engine set. The 88894219 GM lists for $53.88 EACH and the GM #14089026 GM lists for $43.79 EACH. These are PRODUCTION type rings, though, as close as you'll get to the originals and also GM parts.

Cam bearings-----GM #GM #12453170 (No. 1), GM #12453171 (No. 2,5), GM #12453172 (No. 3, 4). Once again, GM sells these only EACH, not as a set. The GM #12453170 GM lists for $43.02 EACH, the GM #12453171 GM lists for 42.28 EACH; the GM #12453172 GM lists for $42.28 EACH. So, does that mean $212.14 for a set of cam bearings? Yup, that's what it means. Sounds high? Well, you want as close to original as possible, don't you?

Main bearings-----GM #10120990 (no. 1-4 standard) and GM #10120993 (no. 5 standard). GM #12329428 (no. 1-4 0.010 U.S.) and GM #12329793 (no. 5 0.010 U.S.). The GM 10120990 GM lists for $20.31 EACH, the GM #10120993 GM lists for $41.56 EACH, the GM #12329428 GM lists for $32.51 EACH and the GM #12329793 GM lists for $40.24 EACH. 5, total, are required, of course

Rod bearings-----GM #GM #12523924 (standard), GM #12523926 (0.010 U.S.). Once again, these are sold by GM only on a "per each" basis. GM #12523924 GM lists for $29.18 EACH; GM #12523926 GM lists for $26.24 EACH. 8, total, are required, of course;

Cam sprocket----original was nylon tooth aluminum. No longer available from GM. It is available through Cloyes and Federal-Mogul, though. I DEFINITELY don't recommend this sprocket, but if original is what you seek.....

Crank sprocket----GM #10128346. $39.07, GM list;

Timing chain----GM #14087014; $56.13, GM list;

Oil pump-----GM #12555284; $122.37, GM list;

Camshaft----GM #3896962; $182.68, GM list

Lifters-----GM #5232720; $17.76 EACH, GM list;

head gaskets----shim steel type. No longer available from GM, but available from Victor-Reinz, Fel-Pro, etc. I DEFINITELY don't recommend these gaskets, but if originality is what you seek......

intake gaskets-----GM are no longer configured like original. Use Paragon reproduction

[Mike McKown]

Re: new engine parts help

This totals $14-1500 for parts from GM alone off the top of my head. That's not counting the cost of the pistons. If they're forged that's another $350-400. $6-700 for machine work. Better be one sweet running engine for that kind of money.

[Joe L.]

Re: new engine parts help

Mike------

Yes, keeping things as "original as possible" can get QUITE expensive. If one were to go to the FURTHEST LENGTH towards that goal and seek out all NOS parts of the ORIGINAL PART NUMBERS, it would get a LOT more expensive. I've noted lately folks paying HUGE amounts for original, internal engine parts on eBay.

Some of these parts are INFERIOR to internal engine parts available today in the aftermarket or from GM under replacement part numbers. Absolutely NONE are any better than internal engine parts available today in the aftermarket or from GM. Originality is fine. However, would I pay huge premiums to obtain original internal engine parts that are inferior or no better than those available today just so I could say that I have original internal parts in my engine? Plain and simple----not on your life! While I MIGHT buy such parts for REFERENCE purposes, you'd NEVER, EVER catch me using them in an engine that I intended to run. Absolutely. Positively. Period.

[Duke W.]

Re: new engine parts help

I recommend buying all internal engine replacement parts from Federal Mogul or other Tier 1 OEM suppliers.

Few if any of the parts you buy from GM are actually made by GM. They're all made by F-M, Dana, Delphi and other Tier 1 suppliers, and many are now made in Mexico or oversees, but that does not mean they are inferior quality.

Duke

[Joe L.]

Re: new engine parts help

Duke-----

Yup. Some folks might think that aftermarket parts are not "original enough" for the restoration of a classic Corvette engine. However, as you say, many of the internal engine parts were always manufactured by outside-GM manufacturers.

There is one legitimate caveat, though: just because a part is made and sold by one of the major suppliers does not mean that it's the same as the OEM piece. Engine parts can be made DIFFERENTLY by the same manufacturer for the OEM and aftermarket parts channels. The secret is being able to tell when the parts are the same as OEM and when they are not. Most of the major OEM manufacturers have seperate divisions that manufacture and market OEM and aftermarket parts. Sometimes, the parts are made in the same plants, sometimes they are not. When they are made in the same plant, they may be made differently.

In today's autoparts marketplace, VERY often the GM internal engine parts, particularly for older applications, are the same as aftermarket. OEM-type parts are just not being made for these applications anymore since there is only a SERVICE requirement and no PRODUCTION requirement. So, assuming that GM continues to SERVICE a particular part, it's very likely to be just an aftermarket item in a GM or Delco box.

It is possible to acquire NOS GM parts of the original part number; I have many. However, for the most part, many of these will not be as durable as today's aftermarket parts. Once again, one has to know when they are and when they are not.

Let's take cam and rod bearings, for instance: GM used to make their own bearings. These were the GM-Moraine line of engine bearings. In my opinion, these are the best bearings that GM ever used or sold. My "ZL-1" contains them, even though they have not been manufactured in a long while. For most Chevrolet V-8 applications, these bearings were "AP" type bearings-----meaning that they were premium aluminum over steel shell. I consider these to be the absolute best bearings for a STREET application.

GM PRODUCTION and SERVICE bearings are now mostly supplied by Federal-Mogul. The ones used and sold by GM are mostly "AP"-type, as always. However, if you buy a Federal-Mogul bearing in the aftermarket, you generally won't get an "AP" type bearing---you'll get a tri-metal type bearing. You can get a premium aluminum Federal-Mogul bearing, but you'll probably have to special-order it and pay a lot more than for the standard tri-metal type. However, I do think that the Federal Mogul premium aluminum bearings are virtually as good as the old GM-Moraine.