overbore 396 max? [Archive] - Team Camaro Tech

: overbore 396 max?


Joes_68
Oct 8th, 05, 06:51 AM
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

CNC BLOCKS N/E
Oct 8th, 05, 08:10 AM
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

pdq67
Oct 8th, 05, 08:17 AM
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

Joes_68
Oct 8th, 05, 10:49 AM
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

PL7481
Oct 8th, 05, 12:42 PM
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.

dragsterman
Oct 11th, 05, 05:04 PM
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.

pdq67
Oct 11th, 05, 05:18 PM
Ah, yes, "fingering" is "shade-tree" all the way!!

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

pdq67

CNC BLOCKS N/E
Oct 11th, 05, 07:05 PM
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.

phaque
Oct 17th, 05, 07:24 PM
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

pdq67
Oct 18th, 05, 05:16 AM
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

CNC BLOCKS N/E
Oct 18th, 05, 05:52 AM
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.

pdq67
Oct 18th, 05, 04:48 PM
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!

phaque
Oct 18th, 05, 09:13 PM
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

pdq67
Oct 19th, 05, 05:25 AM
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

dragsterman
Oct 21st, 05, 01:39 AM
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!

TexasPerfProd
Oct 23rd, 05, 09:05 AM
Hey guys I was just reading and noticed that one point that wasnt mentioned was core shift. Even if one casting # was able to handle a certain stroke or overbore that does not necessarly mean that every last one of those casting #s would be able to.

Core shift occurs at the foundry when the blocks are being cast. The internal core will shift from the external core during casting, resulting in an “off center” block. The biggest problem with this is an un-uniform cylinder bore thickness. It is of utmost concern when using large overbores or very high horsepower.

The easiest way (not necessarly the cheapest or best) to check for core shift is to look at the cam and lifter bores. If they are in the center of the cast bulkhead in the block, the core didn’t shift too much, if they are way off center the core did shift. A block with a moderate amount of core shift will still be okay for performance use. I dont mean they will be good for a 1500hp build but your standard factory block isnt the best idea for over 5-600hp anyway.

I just felt that was some good info for the average builder not taking any shots at anyone here.

pdq67
Oct 23rd, 05, 12:53 PM
Tex,

I mentioned core shift later. AND thanks for chiming in! Good point again...

pdq67

PS., are we square here phaque? Hope we are....

TexasPerfProd
Oct 23rd, 05, 06:22 PM
Sorry ther if I repeated you. :clonk: I must have missed it. I'll try to be more careful before I coment. :D

pdq67
Oct 23rd, 05, 08:19 PM
phaque,

Where are you at guy?

Come on back and join in on the thread.

pdq67

blackvi
Oct 24th, 05, 08:32 AM
PDQ,

I think the man is REALLY missing the point. You know from experience that some things WILL work. Other things WONT work! If you don’t have a mass of money sitting around but a whole lot of parts, OF COURSE you can afford to experiment! Some folks were not able or did not have the same resources to develop years of “shad tree” mechanics.

Many inventions, skills and ideas have been initially forged with a single thought.... "What if..."

On the opposite side of the coin, of course a sonic tester was and is cheap insurance. But I don’t think there were too many shops around town in the 60’s 70’s and 80’s with that type of technology, as affordable as it is today…

Poor form indeed Phaque!

Am I correct that the 396 was the most manufactured block GM produced! I bet you ALOT of junk motors were built with the 396's "finger / pencil" test.

PDQ... If not for you, there would be no recollection of shade tree magnificence.... Guys saying "what if....."

Hats off!!!!!

pdq67
Oct 24th, 05, 04:43 PM
Thanks guy,

I try to pass along to the younger guys what the older guys showed me as a kid when I didn't know squat is all.

Onna the older guys even made a two cylinder out of a four cylinder just so he could use it on a welder/generator that he made out of a bunch of used Army Surplus stuff. That's the kind of "shade-tree" stuff I have seen old Country Mechanics do!

I watched the middle Brother of the three that ran the DX Station try to used a used in-motor crank journal grinder for like two days before he gave up on it b/c he wanted to be able to fix bad rod motors in their Garage. Because the closest machine Shop was two towns away, the place that did my junk301 motor for me!!

Heck, I figure it woulda worked slick if he woulda got a new machine instead of one that was half worn out... BUT as usual, they had no extra money for a new one..

I saw the guy last summer at my 40th year Class Reunion and I asked him about his brothers and they are both gone now. His little Brother helped me stuff the Stude V-8 motor and trans in my old '52 Willis Areo Eagle H/T car WAY back then when I was either still in or just out of highschool.

pdq67

namz111
Oct 25th, 05, 06:10 PM
Whats the worse thing that could happen??? put it in the car and have to rip it out because it wasnt done right...3 things i have learned at my age is
1. You get what you pay for
2.Never try to not do it the right way
3. measure twice cut once

pdq67
Oct 25th, 05, 06:36 PM
Right you are.

I am talking about daily driver stuff that will get a guy that is low on bucks by until he can afford better!

I generally DON'T beat on a shade-tree motor! BUT I sure did my old junk301!

MANY times!!

pdq67

dragsterman
Oct 26th, 05, 02:47 AM
A good friend of mine that is in his 70s is an old hot rodder. That's who taught me about the thick walled blocks and so fourth. He has another buddy that was a heavy hard core boat drag racer back in the day before all these inventions. He would buy new ls6-7 blocks and bore 125 over. Some would hang and some would bore through. He had money and wanted the largest cubic inches possible. Some may not go by shade tree now days. But, at one time. That was all that was around! I am sure most of us are used to the modern machine shops by now!

PL7481
Oct 26th, 05, 04:25 AM
I just completed an 18,000 sq ft building project for a longtime local machine shop owner. He was the grandson of the original owner, and his dad was still involved in the operation on a very cursery level. The new facility is very well equipped, with modern CNC machines, clean rooms, loading docks, mezzanine offices, stainless work surfaces, seperate welding facilities, etc. VERY nice.

The old facility was on the same property. It was constructed of wood and tin in the late thirties, and after the war, two Quanset were errected end to end for additional space. By the time I started hanging around the place in the 70's, the grandfather had died, and the dad had taken over. His son (current owner) was off at college. The trees on the property were huge, and it was not uncommon for all us kids to pull our vehicles under the trees, pop the hood, have the shop R&R the heads, and be back on the road by nightfall. The shop was very good at working within ones budget, and this many times meant compromise. I blew every paycheck on my 67 Chevelle, and my buds did the same.

Not many of the machine tools from the old shop made it to the new facilities. I got one of the Jhead bridgeports, and a 60's Rockwell manual. The rest were scrapped out, and the buildings will be demolished in a few weeks to make way for parking. A dispute has come about over the disposition of all the trees on the property. The dad would like to work the parking around the trees, as they are a reminder to him of the rich history of the business. The son, and person with the ultimate say so, wants to distance the new operation from it's "shade tree" past. His exact words.

I had to laugh when I read this thread, even though it morphed into a ****ing mean spirited slugfest. I'm not at all ashamed that I grew up under a shade tree. I had much more time than money back then, and did everything possible to stretch my paycheck. Perhaps it was a false sense of economy, but it gave me the $5 I needed to fill my tank for Friday night!

pdq67
Oct 26th, 05, 05:26 AM
Yes, I installed my junk301 using a big Crab Apple tree in my F-i-L's side yard just off the street! Had to jump the curb to get to it and roll my car in and out by hand to get the 301 out of the back of his old '50's Chevy P/U sorta deal..

I wonder how many trees have been used vs cherry-pickers since the dawn of motor time?? He, He!!

pdq67