Building a GMC 702 V-12
From Crankshaft Coalition Wiki
m (Minor clean up; add category) |
|||
| Line 1: | Line 1: | ||
== GMC 702 == | == GMC 702 == | ||
| − | This is perhaps on the obscure side of hotrodding, but nevertheless the 1960-1965 GMC V-12 702 cubic inch motor affords the | + | This is perhaps on the obscure side of hotrodding, but nevertheless the 1960-1965 GMC V-12 702 cubic inch motor affords the purist an opportunity to live the glory days of hotrodding. With ZERO aftermarket items for this 1800 lb behemoth that measures roughly 41 inches from the front timing cover motor mount to the engine flange on the rear of the block, you will need to apply your creativity to the chassis and metal design aside from how you are going to make this unique motor hum. |
I will continue to add as my progress continues. This engine is going into a 1926 International Speed Truck. The truck was chosen because I had it for one, and because it is relatively simple to move the cab back and radiator forward. | I will continue to add as my progress continues. This engine is going into a 1926 International Speed Truck. The truck was chosen because I had it for one, and because it is relatively simple to move the cab back and radiator forward. | ||
| Line 160: | Line 160: | ||
The basic V12 heads have large stem diameter valves which are sodium filled. The associated intakes have all the right cylinder numbers on them so you get the cool 1-12 numbering on the rear manifold. I went to magnum because the port sizes are significantly larger and to me that means better flow. According to those in the know, a good ported standard head will flow as well as a magnum. I believe this has a lot to do with the magnum exhaust port design (I have a neighbor who has been porting heads since Harvey Crane opened shop in Orlando and Daytona was still run on sand) and the fact that the runner is flat and almost in the same plane as the exhaust valve. I will take some time here to document what I have collected as I am by no means in a position to recommend what will be best for you other than how to be cheap. | The basic V12 heads have large stem diameter valves which are sodium filled. The associated intakes have all the right cylinder numbers on them so you get the cool 1-12 numbering on the rear manifold. I went to magnum because the port sizes are significantly larger and to me that means better flow. According to those in the know, a good ported standard head will flow as well as a magnum. I believe this has a lot to do with the magnum exhaust port design (I have a neighbor who has been porting heads since Harvey Crane opened shop in Orlando and Daytona was still run on sand) and the fact that the runner is flat and almost in the same plane as the exhaust valve. I will take some time here to document what I have collected as I am by no means in a position to recommend what will be best for you other than how to be cheap. | ||
| + | |||
| + | |||
| + | == OK Time for the "ache" == | ||
| + | I am back and have a bunch to share; '''FIRST (PAY ATTENTION), though all the BB v-6 heads will work ONLY the V-12 intake manifolds work'''. As I don't have a V-6 apart to measure the bank to bank spacing, I can not explain why but the V-6 has a greater left and right bank offset that the V-12. This results in the V-6 intake manifolds having a different port and bolt spacing between the odd and even bank sides when compared to the V-12. It means that you can FORGET using magnum heads unless you are going to fab your own intake. So, I will walk you through this in a series of pictures and document what the differences are as well just in case any V-6 builders wander onto this and want to swap to magnum heads. | ||
[[Category:Engine]] | [[Category:Engine]] | ||
| − | + | ||
[[Category:GM]] | [[Category:GM]] | ||
Your Privacy Choices