overbore 396 max? - Team Camaro Tech
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post #1 of 26 (permalink) Old Oct 8th, 05, 07:51 AM Thread Starter
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overbore 396 max?

My 396 is bored .60 over right now, and needs an overbore....can I go to .90 with no problems? and are flat top pistons in that size availible readily? I have not driven the car in 15 years, and have 12 1/2 to one compression right now...no good. Am trying to make it so I can drive it. Also if the overbore is going to cause problems I am thinking 502?????? Joe
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post #2 of 26 (permalink) Old Oct 8th, 05, 09:10 AM
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Re: overbore 396 max?

Quote:
Originally Posted by Joes_68
My 396 is bored .60 over right now, and needs an overbore....can I go to .90 with no problems? and are flat top pistons in that size availible readily? I have not driven the car in 15 years, and have 12 1/2 to one compression right now...no good. Am trying to make it so I can drive it. Also if the overbore is going to cause problems I am thinking 502?????? Joe
The only way to tell how far you can bore a block is to have it sonic tested, for the 40 bucks it cost its a good peice of mind
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post #3 of 26 (permalink) Old Oct 8th, 05, 09:17 AM
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Smile Re: overbore 396 max?

It is known that some early 396 blocks can swallow a 454 rotating assembly fine AND with NO grinding!

One old-fashioned, "shade-tree" test is to try to stick a wooden pencil between the cylinders through the freeze-plug holes and if it doesn't slide between them, chances are it will bore to .155" over!!

BUT like said, sonic testing your cylinder walls is cheap insurance b/c then you will know for sure.

pdq67
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post #4 of 26 (permalink) Old Oct 8th, 05, 11:49 AM Thread Starter
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Re: overbore 396 max?

Ok my machine shop can do sonic testing. Friends have told me a 402 is a 396 bored .030, and boring a 402 .060 over is no problem......I was just trying to avoid a step I guess. I was hoping someone would say duhhhhh of course you can. Are 090 over flat tops availible? Joe
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post #5 of 26 (permalink) Old Oct 8th, 05, 01:42 PM
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Re: overbore 396 max?

Check the taper on the bore. If you only need a .001 or two to clean up the bore, might get away with the L2328F30 (+.030 402) that is listed as 4.155. I was able to pick through several sets, and came up with 8 that were 4.156, enough to clean the taper on one 396 block I had. The +.060 402 is 4.185.

Silvolite also makes a +.040, that measures 4.164. Sonic testing is the only way to tell for sure. I've taken an early 396 all the way out +.100 without a problem. On the other hand, I just had a '67 fail a sonic inspection, and it is at +.030 right now. The expert told me I would have heating problems if I tried +.040! That hurts. Then you start thinking about honing and re-ringing until the denial phase passes, and then you reach acceptance...and move on.

Let us know what pistons you decide on.
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post #6 of 26 (permalink) Old Oct 11th, 05, 06:04 PM
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Re: overbore 396 max?

Quote:
Originally Posted by pdq67
It is known that some early 396 blocks can swallow a 454 rotating assembly fine AND with NO grinding!

One old-fashioned, "shade-tree" test is to try to stick a wooden pencil between the cylinders through the freeze-plug holes and if it doesn't slide between them, chances are it will bore to .155" over!!

BUT like said, sonic testing your cylinder walls is cheap insurance b/c then you will know for sure.

pdq67
Yep, you can tell by sticking your fingers in the freeze plug hole. It's been a while, but if you put a thick wall 396 next to a thin walled one. You can see the difference.
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post #7 of 26 (permalink) Old Oct 11th, 05, 06:18 PM
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Smile Re: overbore 396 max?

Ah, yes, "fingering" is "shade-tree" all the way!!

That's how I set my lash, rotate my lifters in grease, etc... "Fingering"!!

pdq67
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post #8 of 26 (permalink) Old Oct 11th, 05, 08:05 PM
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Re: overbore 396 max?

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Originally Posted by dragsterman
Yep, you can tell by sticking your fingers in the freeze plug hole. It's been a while, but if you put a thick wall 396 next to a thin walled one. You can see the difference.
Wish I could get a way with doing that it would have saved me 1200 dollars on a sonic tester.
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post #9 of 26 (permalink) Old Oct 17th, 05, 08:24 PM
 
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Re: overbore 396 max?

I must be real bored or very drunk to be out here doing this,but why is some of the most incorrect information I have ever seen,being offered by people with "senior tech" under their names.That would lead me to beleive that they actually know what their talking about.I'm sorry ,I can't take it anymore, all these threads I've been reading for the last half hour are driving me nuts.The "pencil" test only shows a thick wall casting 396 and the ONLY one that will pass this test is the #962 casting.Even though it can be safely bored to 427/454 bore you still have to clearance the bottoms of the cylinders for the crank to clear.As a matter of fact the 69' 427 even needs to be clearanced for a 454 crank and they are even the same casting #512.Dennis 518-234-2480
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post #10 of 26 (permalink) Old Oct 18th, 05, 06:16 AM
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Smile Re: overbore 396 max?

Carl,

There is a BIG difference between your shop AND my "shade-tree" ways!

You do things 100 percent by the book right, where, if I think it will get me by, I "shade-tree" it, is all..

AND I am so glad you post here to give me, AND the other guys that don't do this professionally, a reality check!

If I was to build a "balls-out" motor that had to do it right the first time for a LONG time, I would do like you suggest! But for my "grocery-getter", daily driver, what the hey! I know I am not going to beat on it so I "shade-tree" is all..

And my gut feeling will tell me how much I can beat on one when I decide to spin a tire.

I guess I took to heart the saying when the old Machinist that helped me with my old junk301 said, "It'l be OK, boy!".. AND the old pos jobber was almost indestructable. BUT then again, it wasn't put together like these 450hp/302's are that we have been yammering about recently.

He also said a couple a times, "no, don't think so"....

pdq67
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post #11 of 26 (permalink) Old Oct 18th, 05, 06:52 AM
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Re: overbore 396 max?

Quote:
Originally Posted by pdq67
Carl,

There is a BIG difference between your shop AND my "shade-tree" ways!

You do things 100 percent by the book right, where, if I think it will get me by, I "shade-tree" it, is all..

AND I am so glad you post here to give me, AND the other guys that don't do this professionally, a reality check!

If I was to build a "balls-out" motor that had to do it right the first time for a LONG time, I would do like you suggest! But for my "grocery-getter", daily driver, what the hey! I know I am not going to beat on it so I "shade-tree" is all..

And my gut feeling will tell me how much I can beat on one when I decide to spin a tire.

I guess I took to heart the saying when the old Machinist that helped me with my old junk301 said, "It'l be OK, boy!".. AND the old pos jobber was almost indestructable. BUT then again, it wasn't put together like these 450hp/302's are that we have been yammering about recently.

He also said a couple a times, "no, don't think so"....

pdq67
I understand what your saying. But I know guys out there spend all the money they have and want it done right and it takes the guess work out and you have a good running peice when its done. As most guys can't afford to do it twice ( I was one of those guys years ago and I wish I had some one to tell me how to do it right the first time.)

Every block we machine we do them all the same as we don't want some one to fit things up and the block end back at the shop cause the crank don't spin freely cause it was not line honed or the engine is using oil or has a lot of blowby cause it was not plate honed or the engines vibrates cause we didn't balance the assembley ETC.

We fit up a lot of assemblys for customers that assemble ther own engines they have us machine there block, Balance the rotator size the rods, fit the wrist pins in the pistons and pin end or the rods, fit rings ETC. And so far everybody is happy and the engines run fine.
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post #12 of 26 (permalink) Old Oct 18th, 05, 05:48 PM
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Smile Re: overbore 396 max?

Right you are Carl,

I'm not arguing with you at all, b/c to me it's just that my low buck ways have worked for me.

AND phaque,

Per Ed Staffel's book, "How to Build Max Performance Chevy Rat Motors", a -961, 1966, 396 block will swallow a stock 454 P/U motor's rotating assembly with NO grinding!

AND I do know that my '75 454 P/U block swallowed my 496's rotating assembly using thumb rods with NO grinding!

AND I figure it probably would swallow a 4.375" stroked crank with minimal grinding using 6.385" long rods....

pdq67

PS., page 34!
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post #13 of 26 (permalink) Old Oct 18th, 05, 10:13 PM
 
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Re: overbore 396 max?

Well pdq67,I'll tell you what.You are the one that gave someone else false info that this could be done with no grinding which is total BS.I have been doing this muscle car stuff for over 30 years and better than half of the publications and info out there is so inaccurate it'll make you head spin.Even Colvins book;Chevrolet by the #'s (which is a Very accurate book)Is still not a hundred percent accurate,and I invite him to come and look at my 30 year collection(125 early small blocks and over 50 big blocks),so that I could proove to him that some of the info in his book is inaccurate also by showing him things he can see with his own eyes.As for your hero Ed Staffel he's probably working at Walmart now,because ALL #961 castings are thin wall and couldn't swallow a Chipmunk,let alone a full size Rat.I'll bet you $1000 and supply the Parts ,Hell ,I'll even fly you here so I can see it with my own eyes just like Colvin should.Don't beleive everthing you read .Dennis Hidden Valley Performance Ctr. 518-234-2480 feel free to call
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post #14 of 26 (permalink) Old Oct 19th, 05, 06:25 AM
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Smile Re: overbore 396 max?

No problem here,. All I am saying is that some can do it.

AND if I tell guys on the Boards something wrong, TELL all of us quick so that WE all will learn from it.

Thanks for the heads up!

BUT did you notice I ALSO said this several posts back??

"BUT like said, sonic testing your cylinder walls is cheap insurance b/c then you will know for sure."..................

B/c I would first use the pencil test to pick a block to even start considering for a big overbore!!!!! AND also look the cam bosses over to see if the holes are bored centered too...........

AND I do stand behind my poor "shade-tree" ways...

Have a nice day.

pdq67
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post #15 of 26 (permalink) Old Oct 21st, 05, 02:39 AM
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Re: overbore 396 max?

Quote:
Originally Posted by CNC BLOCKS N/E
Wish I could get a way with doing that it would have saved me 1200 dollars on a sonic tester.
Ha ha, you guys are funny. That's how an old timer showed me a long time ago. They didn't always have sonic testers. Back in the day, you bored it and if it didn't make it, it went in the garbage! Thank god for technology!
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