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Jim - Boring a 396 out by .060 shouldn't be a problem but just to be on the safe side, a sonic check of the cylinder wall thickness would be a good idea.
As far as horsepower gain for 'just' the .060-overbore, that takes the 396 out to around 407 cubic inches so not sure the horsepower improvement would really be noticeable.
Is this 396 already bored out and needs additional cleanup?\
Mike T - Prescott AZ
Jim - Boring a 396 out by .060 shouldn't be a problem but just to be on the safe side, a sonic check of the cylinder wall thickness would be a good idea.
As far as horsepower gain for 'just' the .060-overbore, that takes the 396 out to around 407 cubic inches so not sure the horsepower improvement would really be noticeable.
Is this 396 already bored out and needs additional cleanup?\
Mike T - Prescott AZ
Thanks for the answer.
So, it's actually a car I've been looking at and considering buying. The engine was re-built about 12 years ago and was finally placed into a new restomod build about 7 years ago. There's actually already about 10K miles put onto this engine. I just kind of wanted to hear others' opinions and whether I should be aware of anything else.
Jim - What year is the engine and other than any overbore that was done, what are the rest of the specs like cylinder head work, cam specs, compression etc? Also, what year is the Car?
The 65 L78 396 had high(er) compression and a hot solid lifter cam and ran great. A bone stock mild hydrualic cammed 396 is okay but kinda sedate. My 66 L72
Roadster is running a '68 vintage 396 but with the original #3247 carb and aluminum intake. The engine runs fine, is super clean under the valve covers and has very good oil pressure and after some small adjustments
the plugs are clean but for performance, it's just okay. The 325 horse hydraulic cammed 396 had a very very mild cam from the factory. A step up performance wise would be the higher lift cam they used in the 350 horse 396s.
If you're asking about 396's in general, there are no issues to be aware of, basically just a smaller inch Bigblock than the 427s or 454s.
Is it a 4-bolt block or 2-bolt?
Mike T - Prescott AZ
It's a Frankenstein car from all different pieces, but the engine is from a 68 Camaro SS. It's in a 65 Corvette BB frame.
Here's some of the info from the engine re-build, if that helps. Thank you!
Camshaft: Lunati Hydraulic SPB1-276-290
Lifters: Speed-Pro Hydraulic HT617R
Valve Springs: GM L88
Rocker Arms: GM Type "H"
It's a Frankenstein car from all different pieces, but the engine is from a 68 Camaro SS. It's in a 65 Corvette BB frame. Here's some of the info from the engine re-build, if that helps. Thank you! Camshaft: Lunati Hydraulic SPB1-276-290 Lifters: Speed-Pro Hydraulic HT617R Valve Springs: GM L88 Rocker Arms: GM Type "H"
I looked up that cam number on Lunati's site, Summit and Jegs and couldn't find it. Maybe it is an older part number that's no longer produced.
The Speed Pro Lifters I have used and still find on those sites are actually listed as HT817R, not 617.
Rockers with the H are what I believe to be Bigblock versions with a slightly longer slot, maybe not. I have a couple sets, pic attached.
A bit surprised they are using L88 valve springs on what I suspect might be a hydraulic flat tappet cam but again, not sure since I can't dig up that Lunati part number.
Back to your original inquiry, if the block is already .060 over and that's your concern, you'd think if it really does have 10K miles on it, any issues like overheating would have popped up by now.
But, for most bigblocks, overboring to .060 isn't really that extreme.
By the way, you said it was a 65 Bigblock Frame...how did you determine that? If it's due to seeing that depression in the front crossmember, all 65's came that way, regardless of engine selection.
And, what year is the body on this car?
Mike T - Prescott AZ
.060" over on a 396 is near nothing. Certainly always good to ck wall thickness..but they are thick and many go .100'-.125" without issue. Early 396's were even punched out to 4.250 to make 427's and 454's way back when. Folks also put 4.25" cranks in them for added cubes.
I've personally built quite a few relatively mild versions that ran killer with little effort. Some were 396/325's with stock bottom ends...cast pistons etc. Using oval port iron GM heads, the L72 cam and a decent intake/carb and headers they would all run high 11's in a typical Camaro with a set of 4.10's r 4.56's. Some pocket porting and more compression gets mid/low 11's without much work. My old Nova with a 396/375 using an L-88 cam and tunnel ram with a 4 speed and serious gear ran 10.60's with untouched rectangular port heads and no real trick stuff at all. These are basic "screw together" solid flat tappet engines with no expensive work or parts. Still using thick stock rings etc.
A basic oval port 396 with a cam can make 500 HP all day long. Much more if you start paying attention to detail.
I looked up that cam number on Lunati's site, Summit and Jegs and couldn't find it. Maybe it is an older part number that's no longer produced.
The Speed Pro Lifters I have used and still find on those sites are actually listed as HT817R, not 617.
Rockers with the H are what I believe to be Bigblock versions with a slightly longer slot, maybe not. I have a couple sets, pic attached.
A bit surprised they are using L88 valve springs on what I suspect might be a hydraulic flat tappet cam but again, not sure since I can't dig up that Lunati part number.
Back to your original inquiry, if the block is already .060 over and that's your concern, you'd think if it really does have 10K miles on it, any issues like overheating would have popped up by now.
But, for most bigblocks, overboring to .060 isn't really that extreme.
By the way, you said it was a 65 Bigblock Frame...how did you determine that? If it's due to seeing that depression in the front crossmember, all 65's came that way, regardless of engine selection.
And, what year is the body on this car?
Mike T - Prescott AZ
I know the owner. The frame was 100% from a 65 BB corvette, and the body is/was a 1966 BB corvette.
A Forum Member and I have been collecting VINs from any 65 396 Corvettes we come across. We have 334 of the original 2157 made in 65. Long shot but by chance does anyone happen to know what the VIN was on that 65 BB frame?
Mike T - Prescott AZ
