| FAQ |
| Members List |
| Social Groups |
| Calendar |
| Search |
| Today's Posts |
|
|
|
#1
03-08-2005, 03:25 AM
|
|||
|
|||
I have here a 78? 400 block that has the odd layout for the mounts. I was told it was a 78 peice. From the looks of it, it dont look as strong as the older blocks. Has anyone had any luck with these things or should i try to find another older block? its for a bracket motor that will be about 600 HP. Thanks
Rex Caroll |
|
#2
03-08-2005, 01:29 PM
|
||||
|
||||
|
What would be the top rpm, for the thinner blocks.
__________________
NHRA tech. "Its just a 412, I swear it". Pontiac tip of the year, quit those damn cigarettes. 
|
|
#3
03-09-2005, 01:08 AM
|
||||
|
||||
|
so what would be consiseded the best (strongest) or one of the best castings then #481988? or what?
rob 67 lemans
__________________
-Rob 67 LE MANS in pieces... 68 gto 84 grand prix twin turbo 496 pontiac 25.3 cage |
|
#4
03-09-2005, 10:33 AM
|
||||
|
||||
|
Back in the 80's, a Pontiac Engineer told me before 70 something, Pontiac used a stronger metal composition. In the early 70's, they used a softer? metal. Thicker main webb blocks were used in the HD applications when they changed metal strength. The 400ci cast# 481988 blocks are the HD's. Not sure of early 70 useage. In 78 & 79, Pontiac used alot of these in TA's (X7 & WC). They have xx on both sides of block, top rear of blk, and in the valley. I dont have the cast # for the 455 blocks.
__________________
If you cant drive from gas pump to gas pump across the map, its not a street car. http://s207.photobucket.com/albums/b...hop/?start=100 |
|
#5
03-08-2005, 03:25 AM
|
|||
|
|||
|
I have here a 78? 400 block that has the odd layout for the mounts. I was told it was a 78 peice. From the looks of it, it dont look as strong as the older blocks. Has anyone had any luck with these things or should i try to find another older block? its for a bracket motor that will be about 600 HP. Thanks
Rex Caroll |
|
#6
03-08-2005, 05:37 AM
|
||||
|
||||
|
No, keep it for a stock or mild/medium build. Weak around the lower main support area. These blocks have a tendency to crack from the dowel pins to the cam journal.
Have converted to a 455, but still has to be a rather mild/medium combo. |
|
#7
03-08-2005, 08:53 AM
|
||||
|
||||
|
1970-1973 400 blocks seam to be the ticket.
__________________
When people tell me they HAD to sell their car when they started a family, I show them the three car seats in the back of my 69Trans-Am..............and we didn't even use car seats back then!! |
|
#8
03-09-2005, 10:51 AM
|
|||
|
|||
|
A few years back we tried "455ing" a 76" 400" block. .680" roller cam and 14-1cr. Wound up having the most CATASROPHIC engine explosion ever seen at Milan dragway out side of top fuel!!!- Block was in 8 pieces, crank in 4,EVERY piston in the pan, and a main cap with part of block attached went through a Vega's windshield in the next lane!! Happened in the traps at 133mph! Scariest thing I had seen to that date, Glad Jeff was driving, not me! To this day, neither one of us know how he kept from rolling it. I hope this answered your question!-Bob.
|
|
#9
03-08-2005, 11:56 AM
|
||||
|
||||
|
The better 400 blocks are before mid-1975 which is when the 481988 casting was discontinued and replaced with thinner castings beginning with 500xxx.
__________________
http://www.pontiacpower.org/ |
|
#10
03-09-2005, 09:19 AM
|
||||
|
||||
|
I've heard that for the 2-bolt main 400 block all '67 to mid-'75 are pretty much the same. Someone also posted saying they thought the 67 block was meatier. You would have to line up all the casting numbers and check them, or talk to someone who has built hundreds of motors and knows the ins and outs of certain castings.
For example, Dan Whitmore told me '66 blocks tend to crack in the lifter valley region and quite a few 76 455 block have some of the lifter bores drilled crooked.
__________________
http://www.pontiacpower.org/ |
| Reply |
|
|
The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.
Hybrid Mode
