455

[pneumonic]

I have a 455 from a 1976 grand prix I would like to put it in my 1976 firebird.The firebird has a 350 with 6x-4 heads so i want to take the stock heads off of the 350 and put them on the 455 but i would also want to put a crane blueprinted ram air 4 cam in there .Does anyone know if there will bevalve train issues

 

[melsg5]

I believe the 350 may have combustion chambers that are way to small resulting in way too high a compression. Have you checked online what the volume of those heads are? A 455 typically has a volume over 100cc. The cam requires lots of clearance where the pushrods go through the head if you use the 1.65 rockers with the cam. Also it is high lift so you have to check the compressed height of the valve springs for clearance.

 

[pneumonic]

The 6x-4 heads are 91 to 94 cc.

 

[melsg5]

there are formulas on the internet to figure out compression ratio using the swept volume of a cylinder and the cc of the head. The bore is 4.15" and the stroke is 4.21". That makes a swept volume of 54.86051. You have to add in the volume occupied by the head gasket you intend to use. You then divide that volume by the head cc after converting to inches and you have the compression ratio.

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['51 delivery]

check out this article...501 horsepower..

http://www.carcraft.com/techarticles/116_0101_501hp_455_pontiac/index.html

 

[pneumonic]

According to Jim hands book the engine will be making about 9.25 to 9.5 compression ratio no greater.I wanted to use stock rocker arms ratio 1.5 to 1 with new lifters. I will physically check piston to valve clearance before starting motor.If that comes up good will the stock valve springs survive with the ram 4 cam? Thanks

 

[melsg5]

I had a Ram Air IV cam in my 71 455 HO and I took it out and went back to the Ram Air III cam. I have an automatic transmission and I do not think you should put it in a car that does not have a manual. In addition if you do not have a rear end ratio of at least 3:55 the car will fall on it's face when you nail it. The Ram Air IV cam was the most radical factory cam that Ponitac ever made and it is made for steep gears and not an automatic. If you still want to go with that cam you have to get the matching valve springs and the proper lifters. Pontiac used a higher leak down lifter than with any other motor plus they used splash shields on the valve train to keep the rocker balls lubricated. You probably, if going with an automatic, would need a higher stall torque convertor.

 

[pneumonic]

Thanks for everything.I have been doing some homework and will go for ram 3 cam.ram 4 may be too aggressive at this time.

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