| [GMCnet] Interesting note on the 403 piston bore size [message #336547] |
Thu, 30 August 2018 23:22  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
|
Senior Member |
|
|
On the top of the main block. Next to each cylinder bore hole. GM stamped a letter code as to the bore size of that cylinder. The 403 was Olds first use of Siamese cylinder blocks. ( No water could pass between the adjoining cylinders.) They may have been concerned about cylinder expansion. I don't know. Chevy did the Siamese design with their small block 400 at the same time as Olds did. Chevy also had a big block 400. That didn't have the Siamese cylinders. Bob Dunahugh
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336549 is a reply to message #336547] |
Fri, 31 August 2018 07:02  |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
|
Senior Member |
|
|
Interesting. Did they make any effort to select pistons for fit?
Someone I used to know worked for olds in the late 60s early 70s said they had an in house 'Blueprinting" effort on certain engines on a separate line
THe chevy SB 400s [esp the 70 4bolt mains ] are popular in the Hi po world- Ive runa few but they tend to overheat
Didnt know the 403s were siamesed bore. Dont really hear about overheating problems with them. Different cooling flow?
76 Glenbrook
|
|
|
|
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336561 is a reply to message #336547] |
Fri, 31 August 2018 12:51 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Not seen the 403 large block chev, what did it fit when? Many many 400 small blocks because Back When, one class of racing allowed the 350 with a 4BBL but limited the 400 to a two BBL. The move was to get the huge two bbl fitted to some trucks, which will flow 600cfm or so. And eat the 350 on a dirt track.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336566 is a reply to message #336561] |
Fri, 31 August 2018 15:23 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
|
Senior Member |
|
|
Hi Johnny, you saw a 403 bb Chevy on the engine stand in the barn. It came out in 1970, it is a .30 over 396. Was still called a 396 in Camaro's and Chevelles but in trucks and Monte Carlos was called a 400. The 70 - 71 4 bolt main 400 small block had 2 bbl carbs then in73 the 400 went to 2 bolt mains and4 bbl q-jets.
Johnny Bridges wrote on Fri, 31 August 2018 13:51Not seen the 403 large block chev, what did it fit when? Many many 400 small blocks because Back When, one class of racing allowed the 350 with a 4BBL but limited the 400 to a two BBL. The move was to get the huge two bbl fitted to some trucks, which will flow 600cfm or so. And eat the 350 on a dirt track.
--johnny
C. Boyd
76 Crestmont
East Tennessee
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336570 is a reply to message #336566] |
Fri, 31 August 2018 16:16 |
Rob
Messages: 651
Registered: November 2013
Location: Victoria, BC
Karma: 3
|
Senior Member |
|
|
If being picky - a 0.030” over Chevy 396 is a 402!
Rob
Victoria, BC
76 Royale - Rear Twins/Dry Bath
> On Aug 31, 2018, at 5:53 PM, Charles Boyd wrote:
>
> Hi Johnny, you saw a 403 bb Chevy on the engine stand in the barn. It came out in 1970, it is a .30 over 396. Was still called a 396 in Camaro's and
> Chevelles but in trucks and Monte Carlos was called a 400. The 70 - 71 4 bolt main 400 small block had 2 bbl carbs then in73 the 400 went to 2 bolt
> mains and4 bbl q-jets.
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Rob -
Victoria, BC -
76 Royale - Rear Twins/Dry Bath
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336572 is a reply to message #336570] |
Fri, 31 August 2018 17:38 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
Main reason siamese cylinders did not work well for Chevy and they did for
OLDS was the metallurgy involved. Olds used high nickel alloy in their
blocks, Chev used graphite (carbon) alloy. One wears well, the other wears
out quickly but is cheaper to cast and machine. All about the benjamins.
Jim Hupy
On Fri, Aug 31, 2018, 2:17 PM Rob wrote:
> If being picky - a 0.030” over Chevy 396 is a 402!
>
> Rob
> Victoria, BC
> 76 Royale - Rear Twins/Dry Bath
>
>> On Aug 31, 2018, at 5:53 PM, Charles Boyd
> wrote:
>>
>> Hi Johnny, you saw a 403 bb Chevy on the engine stand in the barn. It
> came out in 1970, it is a .30 over 396. Was still called a 396 in Camaro's
> and
>> Chevelles but in trucks and Monte Carlos was called a 400. The 70 - 71
> 4 bolt main 400 small block had 2 bbl carbs then in73 the 400 went to 2 bolt
>> mains and4 bbl q-jets.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336586 is a reply to message #336581] |
Sat, 01 September 2018 06:21 |
Rob
Messages: 651
Registered: November 2013
Location: Victoria, BC
Karma: 3
|
Senior Member |
|
|
I was referring to the fact that the 0.030” over 396 BBC is a 402, NOT a 403. The small block 400 is really a 401 (which, if used - would just confuse things even more!).
I agree that GM did some very odd stuff at times. I still occasionally come across a Trans Am owner that think their 403 is a Pontiac engine...
Rob
Victoria, BC
76 Royale - Rear Twins/Dry Bath
> On Sep 1, 2018, at 1:52 AM, Bob Dunahugh wrote:
>
> Rob. Not picky. Just a fact on what went on back then. Never understood why Chevy had a big block, and small block that were both referred to as 400's. Remember. Figures don't lie. But liars can figure. We see this same thing now with ALTERNITIVE FACTS.
>
> Bob Dunahugh
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Rob -
Victoria, BC -
76 Royale - Rear Twins/Dry Bath
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336590 is a reply to message #336586] |
Sat, 01 September 2018 09:33 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
GM and many other domestic and foreign manufacturers have selectively
fitted pistons into cylinder boxes since the 1940's and perhaps earlier
than that. Production lines being what they are, emphathis has always been
on assembling the most units at the lowest cost.
Is that bad? Depends on who you ask. Automobile manufacturers have
always used offsite suppliers for components that are used to manufacture
their products. Castings, forgings, fasteners, difficult to manufacture
stuff like pistons and rings, it is a big list. Trying to get all those
pieces to fit each other and hold up longer than the warranty period, with
your competition breathing down your neck, has and is challenging. Lots of
steps involved. Same for automotive rebuilders. They have to know many
brands, not just one. Keeps you on your toes. Just ask Dick Paterson.
Jim Hupy
Salem, Or
On Sat, Sep 1, 2018, 4:22 AM Rob wrote:
> I was referring to the fact that the 0.030” over 396 BBC is a 402, NOT a
> 403. The small block 400 is really a 401 (which, if used - would just
> confuse things even more!).
>
> I agree that GM did some very odd stuff at times. I still occasionally
> come across a Trans Am owner that think their 403 is a Pontiac engine...
>
> Rob
> Victoria, BC
> 76 Royale - Rear Twins/Dry Bath
>
>> On Sep 1, 2018, at 1:52 AM, Bob Dunahugh wrote:
>>
>> Rob. Not picky. Just a fact on what went on back then. Never
> understood why Chevy had a big block, and small block that were both
> referred to as 400's. Remember. Figures don't lie. But liars can figure. We
> see this same thing now with ALTERNITIVE FACTS.
>>
>> Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: [GMCnet] Interesting note on the 403 piston bore size [message #336647 is a reply to message #336547] |
Sun, 02 September 2018 14:46 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Thanks for the clarification, Chuck. I'm not a gint chev fan - usually want something to outrun them  Cummins didn't siamese the cylinders in the Big Cam motors so the could rebuild with liners and new pistons. Unfortunately they came out too close together and would boiled the water between pairs which led to erosion of the liner steel. Their solution was water filters numbered one to five which related to the amount of chemical in the filter to lessen the erosion wit5hout eroding the radiator with it according to my long term Cummins/Onan tech. There was a test kit to determine the amount of the stuff in the coolant, and the proper filter was selected based on the test. Ours made it 22 years that way until one pinholed. OIl in the water, coolant in the oil, gimme a short block.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
