62 340 rebuild thoughts and advice. PICS!

[Bill O.]

I recently pulled the original engine on my 62 because of some running problems and just decided to rebuild so I know exactly what i have. I found it had been bored .030 over with flat top pistons and a solid cam, but not sure what. The balancer is not original as it is not finned and the oil pan is a replacement although it is a 5 quart (6 quart system) and is baffled and has a trap door. I also found that the decks still have the factory broach marks and included a picture with my stamp pad although it didn't come out very good.

I have been reading up on the archives of this board and my plans for the motor are to replace the pistons with stock at whatever bore we end up with. Replace the stock rods with either the Eagle's or Crower's, pocket port the bowls and port match the intake and exhaust. I am going to run the LT-1 cam as it seems through reading here it will perform better than the 097, especially with 93 octane, with less chance of detonation. I will shoot for a compression ratio of 10-10.5 to one which should be easy with an undecked block. No hardened valve seats, no decking or align boring unless we find something really out of wack. I assume the LT-1 cam will run fine with my stock "397" intake and 3269S AFB.

Thank you Duke Williams and many others for the excellent info found in searching this site, awesome stuff!

I would love to hear anyone's thoughts on anything I may have missed. Thanks in advance. Off to the machine shop tomorrow. Here are a couple of pics.

[Tim S.]

Re: 62 340 rebuild thoughts and advice. PICS!

I have installed the LT-1 cam in both my 65 L76 and my 63 L84 and cannot say enough about it. Me personally, think you are on the right track. I'd think about a real mild port job to wake up the flow numbers.




Good luck!

Tim

[William C.]

Re: 62 340 rebuild thoughts and advice. PICS!

How many miles since the rebuild? Pistons look very good, how are the bores?

[Duke W.]

Re: 62 340 rebuild thoughts and advice. PICS!

Okay, let me say this before a dozen others chime in. Replacing a Duntov or 30-30 cam with a LT-1 cam is heresy and cause for excommunication from the church!

Bill emailed me before he started this thread, so I gave him some input, and I agree that he is on the right track.

The Federal Mogul LF-2166-XX pistons are available in 30 and 60 over. The installed pistons are clearly the LF-2165-030. If there is no taper or out of round at the tops for the cylinders I would recommend a hone and the 30 over versions, even if the the clearance ends up a little over the nominal .0035" recommended clearance.

And Bill, I would like to know the deck clearances of all eight cylinders when you get the data, and flow test numbers that I highly encourage you to have done to verify that head massaging was done properly.

The crankshaft should be Magaflux inspected, checked for straightness and dimensional conformity. Most will pass, which means just a nice journal polish is all that's required. Turning the crankshaft removes the thin surface Tufftride treatment, which can reduce crankshaft durabililty, so this should NOT be done unless the above tests fail. Unfortunately many machine shops turn cranks as SOP, so GET IT IN WRITING, that your approval is needed to turn the crank if the above inspections fail.

If you do everything right, you'll have a 7000-rev screamer with all around OE reliability and durability that will make about 280-290 SAE corrected RWHP with the off-road mufflers. With good rods about the only way you can hurt the engine is oil starvation from too low oil level with high revs and/or high dynamic chassis loading, so always keep that five-quart pan full, if not a little over.

Duke

[Steven B.]

Re: 62 340 rebuild thoughts and advice. PICS!

Bill, you are getting some good ideas. When I plan my street and comp engines I always do heads, balance, blue print, and ignition mapping whether 100% factory parts or aftermarket. Have fun! Steve

[William C.]

Re: 62 340 rebuild thoughts and advice. PICS!

Duke and I are headed in Exactly the same direction!

[Bill O.]

Re: 62 340 rebuild thoughts and advice. PICS!

Guys, thanks for the thoughts. I told Duke, I spent at least 4 hours yesterday reading the archives here and because of that I feel pretty prepared to tackle this. Duke has given me some good advice and after reading all the old threads he contributed to, I am definitely more educated.

Tim, glad to know the LT-1 cam worked great for you. I am definitely going to use it too.

Bill, I am not sure when the rebuild was done. I have owned the car since 2005. Sadly, I have only put about 2000 miles on it in that time. That will change when I get this engine back in the car.

Steve, thanks, and I too feel the advice I have gotten here puts me in a can't lose situation. Knowledge is power, right?

I am also going to give the heads the full treatment that Duke recommends. My 461's are Sept. 61 castings so I assume that means they have the 2.02 intakes?

Duke,I am going to give you a call later. All, thanks again.

[William C.]

Re: 62 340 rebuild thoughts and advice. PICS!

Bill, if the original heads they will NOT have 2.02 valves, 1.94 was the largest size for '62 and it is unwise to try to put 2.02 valves in the early "X" configuration '461 heads as the casting is thin in the water jacket area surrounding the valves. Also you will lose some compression when the chamber is cut to allow the 2.02 valves to fit. For all practical purposes, the 1.94 will run the same on an engine with a stock exhaust as one with a 2.02 head thru the same exhaust. Your Sept '61 castings are a frightfully rare set of the "461 X" castings that at one time were extremely sought after by stock class drag racers, (think Bill Jenkins and friends) Remember "tricks are for Kids" and you are dealing with a very rare piece of cast iron in your possession, and accept the fact it will never outrun a C-5 or C-6 Corvette, Much different technology. If you look, you will see the "X" cast into the bottom side of the recessed unmachined area of the head, about 1/4 inch in height.

[Duke W.]

Re: 62 340 rebuild thoughts and advice. PICS!

Clup - I also recommended that Bill retain the OE 1.94/1.50" valve sizes, but I did recommend that the heads have the unshrouding cut centered on the inlet valve guide. I recall that Chevrolet initially recommended a 2.40" diameter cutter, but later reduced it to 2.34". Does that sound familiar?

My concern is that with the nominal 60-61 cc 461X chambers, the cut will both unshroud the inlet valve and reduce the amount of hand grinding to bring the side of the chamber to the edge of the bore and add a couple of cc to the chambers so a thinner head gasket can be used to keep the final CR at no more than 10.5:1 using approprate measurements and the online compression ratio calculator.

However, if you think that this cut could possibly hit the cooling jacket or leave too little material thickness between the chambers and cooling jacket I withdraw my recommendation.

What do you think?

Duke

[Bill O.]

Re: 62 340 rebuild thoughts and advice. PICS!

Thanks guys. Duke, I am going to do as you suggested and delay taking the engine to the machinest and measure the deck clearance so I know better what I have got here.

Bill, both of my heads have the casting date of Sept. 11, 61. The block casting date is Sept. 28, 61 and the build date of my car, serial #1243 is around Oct. 8th I believe. The engine pad shows an assembly date of Oct. 4th. Unfortunately I have no history on the car before 95 or so, which is when the guy I bought it from got it. So who knows what is original or not. It is interesting that these heads are considered rare, I had no idea. I will look for the "X" you mentioned and measure an intake valve. Good stuff!

Bill

[William C.]

Re: 62 340 rebuild thoughts and advice. PICS!

I had a good buddy back in my racing days who ran a very successful porting shop in the 70's, he was the one who tipped me off on being careful with the valve size in the early heads, If the date is correct, they are "X" heads, and larger valves given the stock exhaust aren't really helpful (2.02 vs 1.94) on a street engine thru mufflers. My '62 is very close to yours, 1843, 360hp fuelie...

[Duke W.]

Re: 62 340 rebuild thoughts and advice. PICS!

I'm glad you're going to measure deck clearance before the block is disassembled. It's very important to get the numbers so you can determine if the decks are parallel to the crankshaft and start the compression ratio management process.

Deck clearance can be a little tough to measure on SHP engines. The piston crown is the machined area around the circumference of the piston. Also, because forged pistons are fit at about .003." clearance they may have noticeable "rock", so it's best to have two feeler gage sets, and the piston is upright in the bore if the same size feeler gage fits between the straight edge and crown on both sides.

The above, except the rock issue, won't apply in your case until the engine is reassembled with domed pistons. The installed LF-2165s are easy because they are flat. Also, the LF-2165 compression height is 1.671", which is .004" less than OE pistons. So if you deck heights are the nominal 9.025", the clearance with these pistons will be .029" rather than .025" with OE pistons.

Since it's a tricky measurement, a first timer or one who doesn't do it every day should do the measurements at least two times and look for data consistency. If all measurements are within a thou or two, then you've probably got it.

You should also clean up any carbon deposits at the tops of the bores, and if you can come up with a dial bore gage measure for taper and out of round. You can also usually detect any significant taper with your finger nail or a tool like a dental currette.

Your machinist should be able to accurately measure for taper and out of round and help determine if a rebore is necessary, but I recommend you not bore unless absolutely necessary. My bet is that since the engine was rebuilt it doesn't have that many miles and may not have enough taper to justify reboring to .060" over.

Another alternative to consider is using the KB157 hypereutectic piston, which has a 0.5 cc dome. 1.678" compression height, and they are available in .040" over.

Once you have the deck clearance measurements you can immediately go to the CR calculator and quickly run various piston-head gasket combinations using nominal head chamber volume. I highly recommend that you measure final chamber volumes, especially if the chambers are modified, even slightly. Then upon reassembly you measure deck clearance a final time to make the final head gasket selection in order to achieve your NTE number of 10.5:1

Duke

[Duke W.]

Re: 62 340 rebuild thoughts and advice. PICS!

I had a good buddy back in my racing days who ran a very successful porting shop in the 70's, he was the one who tipped me off on being careful with the valve size in the early heads, If the date is correct, they are "X" heads, and larger valves given the stock exhaust aren't really helpful (2.02 vs 1.94) on a street engine thru mufflers. My '62 is very close to yours, 1843, 360hp fuelie...

What about the unshrouding cut I mentioned in post #9? Is that risky on 461X heads?

I agree that increasing valve size is of little value, and I don't recommend it, even on later heads. The best flow data I have is for a set of 462 heads with 1.94/1.50" valves, but the owner went to extremes having the heads tested three times after incremental modifications were made.

The larger valve size, even on later heads that were designed for both size sets increases the likelyhood of a crack developing between the inlet and exhaust seats.

BTW, it's my understanding that ALL '61-'63 heads are 461X, and the port volume is in the 170-175 cc range versus 461 (1964) 160-165 cc, and 461X utilization was '61 275/315 HP FI engines and all '62-'63 300/340/360 HP engines.

I recall that back in the seventies sprint car guys liked to start out with a set of 461x heads even after Chevrolet began introducting the off-road heads. That's why 461X heads are getting rare. They were used up by racers. In addition to the larger ports, the 461X heads supposedly have a higher nickel content that made the material tougher and more resistant to cracking. I know from my own experience that they are a bear to grind.

And I've always been interesting in knowing if the 461X heads flow better than later heads in both OE and massaged forms, but I don't have any data.

Duke

[Duke W.]

Re: 62 340 rebuild thoughts and advice. PICS!

I ran some numbers through the CR calculator and it shows why GM began adding a second .018" production head gasket during the 1962 model year due to customer detonation complaints.

Using nominal .025" deck clearance, 5.3 cc dome piston, 60.5cc head chamber volume, and the currently available .015" gasket, the CR comes out to a whopping 11.67, and a .038" head gasket only cuts it down to 10.90 - still too high.

Substituting the 0.5 cc dome KB157 pistons drops the numbers down to 10.93 and 10.26 respectively, which gets the CR into the correct range.

Getting the CR into the correct range with these small chamber 461X heads and the OE replacement 5.3 cc dome pistons may not be an option unless the chambers are opened up, a thick head gasket is used or piston dome volume is less than OE or some combination of the three.

Deck clearance is the dimension that varies most, and that's why it comes down to taking measurements on each individual engine. And I don't have any actual measurement for 461X chamber volume, but 60-61 cc is what I've always understood for Flint machined heads.

Duke

[Bill O.]

Re: 62 340 rebuild thoughts and advice. PICS!

Ok here are my measurements for deck clearance.

1) .033 2) .027
3) .032 4) .027
5) .030 6) .028
7) .030 8) .032

I measured around all 4 sides of the piston and worked the piston around until all 4 spots measured the same. I tried to very careful and used the go, no go approach. It seemed as if the #8 piston could be rocked in its bore more than the others but maybe just my imagination.

If I do need to bore, wondering if a custom piston might be the way to go. Not sure how much more that will cost?