Help need some tech advice on my 396 build
Thread Starter
Racer
Joined: Sep 2012
Posts: 366
Likes: 0
From: washington
Help need some tech advice on my 396 build
I'll try to get to the point and add lots of pictures for my questions
(not to many)
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i have a 1969 L71 vert i've had for over 23 yrs when i first saw it it had a tree growing throw it and in lots of boxes...
Now its a runing driving car
non big block....
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Fast fowards 23 yrs I just bought a cheap parts car (78 corvette)
for the big block it has a 66 chevelle 396 I will be putting in my vert
here are the casting numbers
Can you guys tell me what 396 it is ? 340hp 375hp.?
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the heads had a casting number 3866781.? (E18-74)
1974 113cc?
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here is a picture of the inside dome pistons hash marks on the cylinder walls
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looks like a rebuilt .?
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under side looks clean newer pistons .?
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now here is it gets diffrent for me
i noticed this ..?
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weights .?
balanced assembly.?
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so my question is were do i go from here.?
Plastic gage the bearing set.?
Hone the cylinder walls throw in a new set of rings.?
Aluminum heads.?
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.thanks for your imput .......s
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(not to many)
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i have a 1969 L71 vert i've had for over 23 yrs when i first saw it it had a tree growing throw it and in lots of boxes...
Now its a runing driving car
non big block....
.
.
.
.
Fast fowards 23 yrs I just bought a cheap parts car (78 corvette)
for the big block it has a 66 chevelle 396 I will be putting in my vert
here are the casting numbers
Can you guys tell me what 396 it is ? 340hp 375hp.?
.
.
.
.
.
.
.
.
.
.
.
the heads had a casting number 3866781.? (E18-74)
1974 113cc?
.
here is a picture of the inside dome pistons hash marks on the cylinder walls
.
.
.
.
looks like a rebuilt .?
.
under side looks clean newer pistons .?
.
.
.
.
now here is it gets diffrent for me
i noticed this ..?
.
.
.
weights .?
balanced assembly.?
.
so my question is were do i go from here.?
Plastic gage the bearing set.?
Hone the cylinder walls throw in a new set of rings.?
Aluminum heads.?
.
.thanks for your imput .......s
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Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Most of the 5961 blocks, as a matter of fact all of that casting number I've had to this point will go standard bore 427. That might be a cool move with that engine. Have it sonic tested.
It's been ballanced at sometime in the past. Check the bore, it may ave been over bored some already. Clean off the pistons and see if they show an oversize stamped on them.
It's been ballanced at sometime in the past. Check the bore, it may ave been over bored some already. Clean off the pistons and see if they show an oversize stamped on them.
Thread Starter
Racer
Joined: Sep 2012
Posts: 366
Likes: 0
From: washington
thanks for the reply and info
i will pull the slugs out next after I get a reading on the bearings with
the plasta-gage
would you know right off hand what the troq spec
for the main & rod caps .?
45 lb for rods and
80lb for mains sound right.?....thanks again .....s
i will pull the slugs out next after I get a reading on the bearings with
the plasta-gage
would you know right off hand what the troq spec
for the main & rod caps .?
45 lb for rods and
80lb for mains sound right.?....thanks again .....s
Thread Starter
Racer
Joined: Sep 2012
Posts: 366
Likes: 0
From: washington
couple of more question
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I did the bearing gage I think they need replacing
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cylinders messured 4.09 so that is stock for 396.?
but what I'm wondering is the crankshaft has some spot like it got realy hot in the pictures it around #5 #6.?
should i just throw a set of ring and new bearing and go with it.?
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and the numbers on the rods don't match the holes they came out of
I pulled the #3 out of #1 hole there just put in any hole no rime or reason.?
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I did the bearing gage I think they need replacing
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cylinders messured 4.09 so that is stock for 396.?
but what I'm wondering is the crankshaft has some spot like it got realy hot in the pictures it around #5 #6.?
should i just throw a set of ring and new bearing and go with it.?
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and the numbers on the rods don't match the holes they came out of
I pulled the #3 out of #1 hole there just put in any hole no rime or reason.?
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Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Could be mistaken but the discoloring on those counterweights looks like something got real hot. Might wanna take it in to a machinist and get it checked, mic eveyrthing. Maybe a simple polish/bearing job can get you by maybe not
Race Director
Joined: Jan 2000
Posts: 13,022
Likes: 2,265
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Yeah...I'd want to look at that throw on the crank closely also. Definitely some heat there. Maybe it spun a bearing in the past and it was ground undersized? What size are the bearings? Read the numbers on the back of them. The only pic I could see of the rod bearing didn't look too bad really...had some trash go through it...but not terrible. Either way you polish things up and replace bearings/rings at least.
With all the silicone on the gasket It's been into before. Rods were likely re-sized or replaced during the crank issue so it doesn't really matter where they go except pistons might have got mixed up too. But again, they could have pressed rebuilt rods on old pistons. Are any of the small ends of the rods *blue* looking also? That's usually from a rod heater when they are assembled outside of the factory and doesn't hurt anything.
I'd throw a tack weld on the oil pump pickup tube while I had it apart to make sure it didn't fall off later.
JIM
With all the silicone on the gasket It's been into before. Rods were likely re-sized or replaced during the crank issue so it doesn't really matter where they go except pistons might have got mixed up too. But again, they could have pressed rebuilt rods on old pistons. Are any of the small ends of the rods *blue* looking also? That's usually from a rod heater when they are assembled outside of the factory and doesn't hurt anything.
I'd throw a tack weld on the oil pump pickup tube while I had it apart to make sure it didn't fall off later.
JIM
Thread Starter
Racer
Joined: Sep 2012
Posts: 366
Likes: 0
From: washington
Yeah...I'd want to look at that throw on the crank closely also. Definitely some heat there. Maybe it spun a bearing in the past and it was ground undersized? What size are the bearings? Read the numbers on the back of them. The only pic I could see of the rod bearing didn't look too bad really...had some trash go through it...but not terrible. Either way you polish things up and replace bearings/rings at least.
With all the silicone on the gasket It's been into before. Rods were likely re-sized or replaced during the crank issue so it doesn't really matter where they go except pistons might have got mixed up too. But again, they could have pressed rebuilt rods on old pistons. Are any of the small ends of the rods *blue* looking also? That's usually from a rod heater when they are assembled outside of the factory and doesn't hurt anything.
I'd throw a tack weld on the oil pump pickup tube while I had it apart to make sure it didn't fall off later.
JIM
With all the silicone on the gasket It's been into before. Rods were likely re-sized or replaced during the crank issue so it doesn't really matter where they go except pistons might have got mixed up too. But again, they could have pressed rebuilt rods on old pistons. Are any of the small ends of the rods *blue* looking also? That's usually from a rod heater when they are assembled outside of the factory and doesn't hurt anything.
I'd throw a tack weld on the oil pump pickup tube while I had it apart to make sure it didn't fall off later.
JIM
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.no the con rods look good ...
no blue-ing ....
only thing is the extra weight added to the #6 con -rod
But it has 31 stamped on it .? wrong hole.?
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I was going to ask about the oil pump pick up tube
weld it or braze it.?
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the numbers on the con-rod bearing (clevett) have a date 92
I could try to get a better pictures .?
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and the pistons have minamal skirt wear and look realy clean
underneith Like there new-ish
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the motor ran strong ..compression was 170-185
cross hatching looks good rings and oil ring look good No crome ring
Reason I broke this motor down was to fresh'n up
till i saw the miss-holed pistons and the blueing on the crank counter weights
I'm not feeling that warm and fuzzy feeling about this motor.
It does look like it has run for a few miles after it's last rebuild
thank you guys for the response
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Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
It's been apart before, it looks like. Are the bearings oversized, and by how much? Bluing is most likely from a prior spun bearing. Explaining the rod shuffling. Which if reconditioned, means nothing.
Thread Starter
Racer
Joined: Sep 2012
Posts: 366
Likes: 0
From: washington
I was thinking a spun bearing
I miked most of the bearing #5#6 & #1#2
and they all seem standard bore but i don't claim to be a machinest (or a great spel'r)
the numbers on the bearing all seem the same
( Clevite 77)
(9 92 )
(CB743P)
( B )
................I can't find were they are stamp {STD} or {10} or {20}
what do you think beside the hot spot It looks stock bore 4.09
bearing too stock...what do you think.?
I miked most of the bearing #5#6 & #1#2
and they all seem standard bore but i don't claim to be a machinest (or a great spel'r)
the numbers on the bearing all seem the same
( Clevite 77)
(9 92 )
(CB743P)
( B )
................I can't find were they are stamp {STD} or {10} or {20}
what do you think beside the hot spot It looks stock bore 4.09
bearing too stock...what do you think.?
Last edited by L71Ragtop; Sep 19, 2012 at 11:00 PM. Reason: spelling errors
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
I can't imagine getting hot enough to be blue and still be in condition to be standard. I suspect it's been turned. Get a mic reading on the rod journal and see what it is.
A little scuffing on the bearing surface. As long as it's that far apart, I'd clean it the best I could and replace the bearings while you're there.
A little scuffing on the bearing surface. As long as it's that far apart, I'd clean it the best I could and replace the bearings while you're there.
Thread Starter
Racer
Joined: Sep 2012
Posts: 366
Likes: 0
From: washington
I can't imagine getting hot enough to be blue and still be in condition to be standard. I suspect it's been turned. Get a mic reading on the rod journal and see what it is.
A little scuffing on the bearing surface. As long as it's that far apart, I'd clean it the best I could and replace the bearings while you're there.
A little scuffing on the bearing surface. As long as it's that far apart, I'd clean it the best I could and replace the bearings while you're there.
very perplexed .??
then it hit me the reason for the weight add is they replaced that rod with another and added weight to make the rotating assmbly ballanced
or that rod or any of those rods would be just as blue as that crank journal
no marking on the bearing but I'm with you definitely been turned
and its a "steel" crank not cast... so the blueing is EZR to sleep with I'm not pushing alot of HP maybe 350 if I'm lucky
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mic'd the journal it came up just shy 2.089(sorry)
then I spotted this
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Weighted rod #6
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forged Steel Crankshaft .?
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what grit crocus cloth can i use to clean the journal .?
thanks for the help.....s
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Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
We have to have a nay sayer, years ago I had the high performance 396 375 hp or something and I had it on an engine stand for a rebuild. The day i took it down to the motor shop for boring and blue printing the shop owner looked me straight in eye and said: "Are you sure you want to?"
Then he guided me out back and he had a pile of 454 long blocks and he said take your pick. They do a certain amount of GM crate motor swap outs and end up with the rebuildables.
So for basically the same money as a high performance rebuild I did the 4.250 stroker 4340 forged crank with the max bore and got 100 more ci 496 ci
Then he guided me out back and he had a pile of 454 long blocks and he said take your pick. They do a certain amount of GM crate motor swap outs and end up with the rebuildables.
So for basically the same money as a high performance rebuild I did the 4.250 stroker 4340 forged crank with the max bore and got 100 more ci 496 ci
Burning Brakes
Joined: Sep 2012
Posts: 818
Likes: 0
From: coon rapids mn
for the lowest cost maybe get new bearings ,cam,springs and rings.some shops can do a mild hone.look at a comp cams extreme cam line if you are going with hydraulic flat tappet.maybe bead blast the pistons .consider a valve job.I like boring it out for a new rotating assembly.check the comp cam catalog for a cam of your liking .what rear end half shafts do you have ?a 496 or bigger is the best if the rest of the drive line can handle the power.
Thread Starter
Racer
Joined: Sep 2012
Posts: 366
Likes: 0
From: washington
ok no question.....
but feedback is very welcome (maybe someone sees something i will miss)
this rebuild is full on ......
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There was only one place I could get a Rering kit for a 396 with malloy rings for an affordable
is ...summit
and a free hat to boot
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had to get a 4.1/2" hone and started to zip the cylinders with a cordless drill & starting fluid for lube
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checking ring gaps....
thought it was to much... but when i checked the gap on the used ring it was realy close
.
.
.
.
.
but feedback is very welcome (maybe someone sees something i will miss)
this rebuild is full on ......
.
There was only one place I could get a Rering kit for a 396 with malloy rings for an affordable
is ...summit
and a free hat to boot
.
.
.
had to get a 4.1/2" hone and started to zip the cylinders with a cordless drill & starting fluid for lube
.
.
.
.
.
.
.
checking ring gaps....
thought it was to much... but when i checked the gap on the used ring it was realy close
.
.
.
.
.