engine rebuild

[Carl R.]

I am in the process of rebuilding the engine in my "62". It's the 340 HP model. I would like to try and stay with the original style of parts in the engine as best as it can get with todays replacement items that are out there today. Does any of the engine parts makers like TRW still make domed pistons for this engine, an the other items like steel head gaskets, rings, etc. I have read in the past on this forum that the rods in this engine were prone to failure, so I would like to replace them while I am doing this overhaul, so who has a good replacement rod for this engine that I can use. One more thing, does any one out there still do re builds on the 8 inch front balancer. Thanks for any help that can be given to help steer me in the right direction on this rebuild.

[Joe L.]

Re: engine rebuild

I am in the process of rebuilding the engine in my "62". It's the 340 HP model. I would like to try and stay with the original style of parts in the engine as best as it can get with todays replacement items that are out there today. Does any of the engine parts makers like TRW still make domed pistons for this engine, an the other items like steel head gaskets, rings, etc. I have read in the past on this forum that the rods in this engine were prone to failure, so I would like to replace them while I am doing this overhaul, so who has a good replacement rod for this engine that I can use. One more thing, does any one out there still do re builds on the 8 inch front balancer. Thanks for any help that can be given to help steer me in the right direction on this rebuild.

Carl------


Most engine parts (pistons, rings, etc.) for your application are manufactured by the Sealed Power/SpeedPro Divisions of Driv Automotive. This includes domed, forged pistons, as original. Steel head gaskets are manufactured by Fel Pro Division of Driv or Mahle. Any of these parts can be obtained from Summit Racing or, even, your local full service auto parts store. Rock Auto is another source for many.

The best factory connecting rods for your application were the 1965+ GM #3864881. You may be able to find these NOS or reconditioned on eBay. Otherwise, Eagle manufactures good aftermarket rods.

Your balancer can be rebuilt by one of a few companies in Oregon. Search the archives for contact info.

[Carl R.]

Re: engine rebuild

Thanks Joe for this information, this will give me good places to start making some phone calls.

[Duke W.]

Re: engine rebuild

A set of Eagle SIR5700 rods was $250 a few years ago and are stronger/more durable than even NEW second design 327 rods.

I also recommend installing the LT-1 cam in lieu of the Duntov. Both Howard's cams and Elgin can grind OE cams. Keith Black KB 157 pistons should get you to about the 10.5 CR range assuming you have 93 PON fuel. Reduce 0.1 for every lower octane number, e.g. 10.3 for 91 PON

Head massaging is optional that will give you close to 300 SAE corrected RWHP with usable revs to about 7200.

Toughest part might be finding 3911068/Sealed Power VS 677 second design valve springs.

Go to the restoration documents in the sticky section under engine rebuild headings and download the "Special 300 HP Technical Support" paper. The only significant difference between the "Special 300 HP" and "327 LT-1" configurations is the camshaft

All the system engineering and testing of the '327 LT-1" is on the Web. It is probably here on the TDB, but is likely easier to find on the Corvette Forum. Search for threads started by users Dave McDufford, and ghostrider20, 2006 time frame.

Duke

[Patrick B.]

Re: engine rebuild

Duke is right about the lack of availability of VS677 valve springs. I found a very near equivalent made by Elgin. They list the same specs as GM, but they are a little stiffer. I believe the wire diameter of the GM springs was 0.170 while the Elgin spring wire diameter was 0.175. It made an easily measurable difference on a spring tester. Spring rate is proportional to the wire diameter to 4th power.

[Carl R.]

Re: engine rebuild

Thanks for the information Duke and Patrick. Duke - I have read and printed out your article on the " Special 300 HP ", lots of good information there. I contacted Elgin about the LT-1 cam and they told me they had a kit with that cam - kit #E-904-P. They said to use Z-28 valve springs #RV-943X. Now I don't know if these are there springs or GM, the man that I talked to Scott Stier didn't say and I forgot to ask. I asked about buying the kit right then but he said that they don't sell to private persons, it has to be a shop. So when I take the engine to the machine shop I will make sure the shop can get this kit for me. I will also be checking out the other people that you and Joe have listed about pistons and rods. Thanks for all the help.

[Duke W.]

Re: engine rebuild

The so-called Z-28 springs were designed by GM for the first design Trans-Am racing cam. The part number ends with 140, and I recall these these springs part number ends in 142.

THESE SPRINGS WERE NEVER USED ON ANY PRODUCTION ENGINES. The 302 DZ and 350 LT-1 engines used the exact same second design springs as did your grandmas '67 283 2-bbl. Powerglide, GM and Sealed Power part numbers in my previous post.

Tests prove that with proper spring height setup these springs will rev to 7200 with OE mechanical lifter cams and 6500+ with hydraulic cams, but you need massaged OE heads or better flowing than OE aftermarket heads to make usable power to these rev levels.

I don't know why these aftermarket cam grinders "recommend" stiffer than OE springs. It's just plain STUPID, and a good way to end up with wiped out lobes and lifters.

If you can't find a reasonable facsimile of these second design SB springs, reuse the existing springs, that I assume are original. Just test them that they meet spec within reason. SB valve springs are very reliable with virtually infinite fatigue life, and failures are rare.

These springs were used on millions of SBs from 1967 to at least 1979 and it's amazing that no reasonable facsimiles appear to exist, but maybe it's just a matter of more searching by those in need.

Duke

[Joe L.]

Re: engine rebuild

The so-called Z-28 springs were designed by GM for the first design Trans-Am racing cam. The part number ends with 140, and I recall these these springs part number ends in 142.

THESE SPRINGS WERE NEVER USED ON ANY PRODUCTION ENGINES. The 302 DZ and 350 LT-1 engines used the exact same second design springs as did your grandmas '67 283 2-bbl. Powerglide, GM and Sealed Power part numbers in my previous post.


Tests prove that with proper spring height setup these springs will rev to 7200 with OE mechanical lifter cams and 6500+ with hydraulic cams, but you need massaged OE heads or better flowing than OE aftermarket heads to make usable power to these rev levels.

I don't know why these aftermarket cam grinders "recommend" stiffer than OE springs. It's just plain STUPID, and a good way to end up with wiped out lobes and lifters.

If you can't find a reasonable facsimile of these second design SB springs, reuse the existing springs, that I assume are original. Just test them that they meet spec within reason. SB valve springs are very reliable with virtually infinite fatigue life, and failures are rare.

These springs were used on millions of SBs from 1967 to at least 1979 and it's amazing that no reasonable facsimiles appear to exist, but maybe it's just a matter of more searching by those in need.

Duke

Duke------


Yes, the so-called "Z-28" cam was GM #3927140. It was released in very late 1967 and discontinued without supercession in September, 1995. As you mention, this cam was NEVER installed in any PRODUCTION Z-28 or any Corvette. It is not suitable, at all, for normal street use. The associated valve springs were GM #3927142. They're discontinued, too, and not suitable for street use.

The 1967+ PRODUCTION small block valve spring, GM #3911068, is still available from GM. They're a bit expensive at about 14 bucks each, GM list, but if I were building a small block I'd pay that if I had to to get them.

The 1955-66 small block springs, GM #3735381, are also still available from GM. They're much more expensive at about 24 bucks each, GM list. But, if one wants authentic 1955-66 valve springs, one can still get them from GM 68 years after they were first used! Of course, the 3911068 could also be used in replacement.

GM has another valve spring now available which has specs virtually identical to the 3911068. It's GM #94666580. It GM lists for a bit less than the 3911068.

In addition, although I have somewhat conflicting information on this, it appears to me that the Sealed Power VS-677 is actually still available. It's a lot less expensive than any of the above but, if it were me, I'd go with the GM springs.

One last point: as I've said many times before, I'd never use a flat tappet cam, hydraulic or mechanical, in today's world. Never, ever. Hydraulic roller is the only way to go.

[Duke W.]

Re: engine rebuild

I recall not too many years ago that you could buy a 16-piece set of the VS-677 springs for about 20 bucks at NAPA!

Duke

[Patrick B.]

Re: engine rebuild

Carl-- You can buy Elgin cams directly from Competition Products (800-233-0199). I don't know why the kit would come with the trans-am racing springs. As Joe and Duke have said-- Do Not Use Them. The Elgin springs I was referring to are RV-880X. The stock Chevy springs have only 80 lb of seat force with the valve closed. The trans-am springs are 120 lb or more so they greatly increase the risk of ruining the cam unnecessarily. The spec for the RV-880X springs is the same as for GM stock springs open and closed, but I measured the seat pressure to be slightly more than the GM springs at about 90 lb, because of the small difference in wire diameter. Still, I think these are as close to GM stock springs as are now available. Buy the E-904 LT-1 cam separate from Competition Products and get the RV-880X springs. The springs are available on Ebay for about $60 a set if Competition Products does not list them.

[Carl R.]

Re: engine rebuild

Hi every one , I took the engine block to the machine shop to get it cleaned out and ready for the rebuild process. I see that I have a lot of new information to sort through, this is really good stuff. I went on the sealed power web site after coming back from the machine shop, there web still showed the VS 677 springs not in stock. I also looked at the Keith Black pistons and they look just like the ones that came out of the engine so I will be getting a set of them. I also looked at the Elgin rods and will be getting a set of them also. I will be taking the heads to a head shop in the next few days and I will make sure they check out the springs before I look about getting any new ones like you guys have suggested. This engine is original, so with some luck they might still be in good shape. If not I will still have these part numbers that you guys have given me to fall back on. Thanks for the phone number Patrick, I will be calling them tomorrow to see what they have. Thanks for all this information, this will keep me busy for a few days now and Mr. Visa is going to love me this month. Thanks again every one.

[John F.]

Re: engine rebuild

Let us know how everything works out once running.

[Duke W.]

Re: engine rebuild

Hi every one , I took the engine block to the machine shop to get it cleaned out and ready for the rebuild process.

I assume you disassembled the engine yourself. Did you measure the deck clearance of all 8 cylinders before you disassembled the short block, so you can get going on compression ratio management?

Duke

[Carl R.]

Re: engine rebuild

Duke- I did the disassemble my self and inspected all the parts as I took them off the engine to look for any noticeable wear. I did not do any measuring for the deck clearance. I am thinking that the best I can hope for will be around 10.5 and hope that this gas we have now won't cause any problems. With the information I received last night on the valve springs, I went to my friendly chevy dealer and had them look up the springs that Joe had listed. Like he said the springs are still available and at the price he quoted. GM really likes those 3735381's, they must be made of gold. I have been able to look up most all the stuff that I have been talking about, I have not ordered any thing as of this time, but at least I have a much clearer picture in my head on which direction I need to go with this project.

[Joe R.]

Re: engine rebuild

A set of Eagle SIR5700 rods was $250 a few years ago and are stronger/more durable than even NEW second design 327 rods.

I also recommend installing the LT-1 cam in lieu of the Duntov. Both Howard's cams and Elgin can grind OE cams. Keith Black KB 157 pistons should get you to about the 10.5 CR range assuming you have 93 PON fuel. Reduce 0.1 for every lower octane number, e.g. 10.3 for 91 PON

Head massaging is optional that will give you close to 300 SAE corrected RWHP with usable revs to about 7200.

Toughest part might be finding 3911068/Sealed Power VS 677 second design valve springs.

Go to the restoration documents in the sticky section under engine rebuild headings and download the "Special 300 HP Technical Support" paper. The only significant difference between the "Special 300 HP" and "327 LT-1" configurations is the camshaft

All the system engineering and testing of the '327 LT-1" is on the Web. It is probably here on the TDB, but is likely easier to find on the Corvette Forum. Search for threads started by users Dave McDufford, and ghostrider20, 2006 time frame.

Duke

I agree with Duke that the Eagle SIR5700 rod ($290 for a set for the press-fit version at Summit) is a very good budget performance rod that is much stronger than the stock rods from the 1960s. Another excellent budget performance rod that I like a little better is the Scat Pro-Stock rod for about $330 per set.

You mention looking for steel head gaskets, but I think that might be risky. Both the original GM steel gasket and the newer MLS gaskets seal best with freshly-machined surfaces on the heads and cylinder block decks. If you are trying to preserve your stamp pad and not deck the 60 year old block surfaces, I think it may be better to use a rebuilder gasket such as the Fel Pro Perma-Torque Blue gasket.