Rebuild my 65 365hp motor

[Craig F.]

I have been an NCRS member for 25 years, just after I bought my 65 roadster, and this forum along with the driveline is the best place to find parts, services and get questions answered. My goal has been to get my car back to stock and NCRS has been a great help in doing so.
I am getting ready to rebuild my 365hp motor that has been sitting for 20+ years while I have enjoyed my 65 with a 406 small block. It is a factory 365 car so I want the motor to be as correct as possible. I have read most all of the posts about this motor rebuild which has been extremely helpful in figuring out what choices to make. It seems as though the popular choice for the bottom end is to use the Eagle rods, after you figure the costs to R&R the stock rods, the $150 more to upgrade to good rods is cheap insurance. I was all set to put a 30-30 cam in it but from what I have also read, the LT-1 cam seems to offer equal power and still give me the solid cam that this car has to have. I have run my 406 with that cam for a while and it is a great street cam. My engine builder says it is too small but that is just his opinion and most builders are used to putting race motors out there so I am going to try to go the more stock route.
The questions that I still have are: with the stock 461 heads (that have some light porting already done to them) what pistons should I use? I like the idea of putting a dome 11:1 in it but want to be able to run it on premium pump gas, I assume flat tops would be a safe route. Next, the stock 2818-1 carb was long gone when I got the car and I have never spent the time to hunt one down. My car is a driver, not a show car so is a new 600 Holley going to perform any different than a correctly (and costly) rebuilt 2818? I have seen many 2818's for sale on ebay that look fantastic but at a pretty high price.
If anyone reads this and has an opinion I would really be interested in hearing it. Nothing has been done yet, I am just in the planning stages and really want to make sure that I don't screw this up.

Thanks!

[Duke W.]

Re: Rebuild my 65 365hp motor

Search this forum "327LT-1" under my name, and it will lead you to all the system engineering and tests that were reported on The Corvette Forum.

Since these engines were assembled and tested, the Eagle SIR5700P rod has become available, and it appears to be essentially as good as the Crower Sportsman, at half the price.

If your "engine builder" thinks the LT-1 cam is "too small", I highly recommend that you ditch him and find a guy who understands the difference between a race engine - or his version of a hot rod motor - and a vintage SHP Corvette engine that's going to spend 99.999 percent of its time below 4000 revs.

Don't leave CR on the table. It will cost torque and fuel economy. Use the OE domed pistons. Find your Fall 2009 Corvette Restorer and read the "Compression Ratio Explained" article to learn how to manage your CR. Then educate whomever you choose to do the machine work. Target 10.5:1 as the not-to-exceed level and you should be able to get close. I doubt if any 365 HP engine left Flint with a true 11:1. That was just advertising copy. They probably average about 10.5, and by the time you do the requisite chamber grinding, you will probably be close to 10.5 depending on how high the decks are with a moderate thickness head gasket, and you raise or lower it a few tens either way with your head gasket thickness choice.

The more you educate yourself and plan your project the better the result will be. Of course, you will have to closely manage whatever "engine builder" you chose. If not, you could end up with a POS. Many others before you have - big aftermarket cam that requires gorilla valve springs, low compression resulting in lousy torque and fuel economy - a cantankerous stone regardless of how much power it has at the top end on a lab dyno test with headers and open exhaust, which is usually not that impressive, anyway, and by the time it gets into your car with manifolds and mufflers...

I think Holley offers a generic 600 CFM vacuum secondary carb that will bolt on, but I don't know if it is calibrated properly. I'm sure some experienced Holley guys can offer advice on this issue.

Duke

[Craig F.]

Re: Rebuild my 65 365hp motor

Duke,
Thanks for the information. I will go out and read those posts, that should be very helpful. Don't happen to know a good engine builder in the KC area do you?

[Duke W.]

Re: Rebuild my 65 365hp motor

Kansas City? No.

Most of the guys I work with on engine restorations do their own "forensic" disassembly and assembly making all my recommended inspections, tests, and measurements along the way. That way they know exactly what measurements and machining operations need to be conducted on both the block and heads by the machine shop. No more, no less.

Machine shops generally want to cut more metal than necessary. For example - main bearing align boring or honing. On most blocks this is unecessary. How can you tell? Once the block is striped down to the crankshaft simply give the crank a spin. If it spins freely and the bearings so no distress upon inspection after the crankshaft is removed then the crankshaft is "straight" (although it should be measured for runnout), and the main bearing alignment is fine and should not be touched. The biggest "problem" is deck height variation, which is critical to achieving the correct CR range and consistency across all cylinders, and this can be determined by measuring deck clearance of all eight cylinders prior to removing the piston/rod assemblies.

Contact me via the email function and I'll send you the "Special 300 HP" technical support paper. (Also see the Fall 2010 Corvette Restorer article "A Tale of Two Camshafts".) Certain parts and dimensions are different for a SHP engine restoration, but the basic processes are the same if you want to achieve maximum torque bandwidth, maximum power, and maximum useable revs while maintaining original appearance and general operating characteristics including idle behavior.

One other note. The "327 LT-1" will probably make similar if not more power than your 406 with the LT-1 cam depending on how much more, if any, head flow you can obtain, but there will be a big difference in torque, so the 327 will be weaker across most of the rev range until the very top portion of the rev range - 6500 to 7200. The 327 will be much less "torquey", but it will want to rev forever, which is what 327s were always all about, and the "327 LT-1" configuration makes useable power to about 7200 with OE reliability. That's beyond the rev limiter of a lot of modern DOHC V-8s!

Duke