This is for my pro-touring build. Thanks to blowing all my budget on suspension, I need to do a cheap 455 build to have fun this season before spending the money on a new motor. Fortunately, my buddy Lou (thanks again!!) hooked me up on a low mileage stockish rebuild. Unfortunately, we have no documentation on what was done to this motor. Here is what I think I know: 73 455. Rebuilt with a few thousand miles on it Stock style replacement cam, new bearings, etc Balanced crank Double roller timing chain Stock timing cover B4B M/T Headers 800 CFM Q-jet 4.3425 bore Sealed power?? I think. .030 L2353 pistons 3.900 stroke Decked 69 CC 70 heads Stock rockers .055 piston clearence to deck .156 dish Felpro 8494 head gaskets .040 compressed My calculations show around 9.0 : 1 compression. Am I way off? I used summit’s calculator, so I would assume it’s static. If I am correct, would it be better to just stay with the stock replacement cam? I would like to run a used Lunati 230/240 112 LC hydraulic cam w/ matching lifters. Is that too radical for the rest of the engine? Any help is appreciated! I tried to get everything as close as I can before posting. Let me know if there is something that looks off.
You're definitely in the area and if no cam specs were added it is static compression. It wouldn't hurt to try a dynamic checker with 9:1 as your base compression and cam specs. If it was decked then it shouldn't have .055" deck clearance. IMO that would be worst case non-decked so it should have something less than that which would raise your compression by a bit. The spec for that piston is 27.8cc so the dish depth means nothing. Maybe you mean the heads were milled to get 69cc and the deck of the block is stock? I came up with 8.87 using a 4.43" gasket diameter. If the block was actually decked then the usual minimum would be around .010" bringing your deck height to .045" which gives you 9.03". Check your deck for machining marks on the flat between the 5/7 exhaust ports. If the block ID letters are gone then you will know if it was decked at least something so your deck height at that point would have to be less than .055". With 9:1 that cam is going to have a weaker bottom end. I'd recommend something smaller for some snappy bottom end but if you already have it figure on getting at least a mild higher stall converter to help it out. I'd degree it in to +6* 0r +8* to perk up the bottom end. If it is a +/-4* set and you just stab it in make sure it is at +4* and you'll be about as good as you can get even if the cam has +4* already built in. I'd consider some oil control baffles in the oil pan if hard cornering/braking/acceleration is expected. Hopefully the oil pump has been improved with at least a thrust plate upgrade. That cam will really make the M/T headers "tic-a-tack".
Thank you for the detailed response. It’s much appreciated!! The block was definitely decked. It has no stamping on it. In talking with Lou, the original pair of 73 heads were also milled, but I will be using a set of 70 heads. The deck clearence measurement I got wasn’t probably inaccurate, to your point. I’ll habe to remeasure. So the cam I have is not ideal for the application. I might just keep the current cam in it then. I’m already behind schedule so...
The cam you have will work until you are ready to build another one. I wouldn't bother swapping cams until you have a motor built specifically to handle it. Pistons .055 down in the hole is not an ideal quench.
Thanks guys, I’ll remeasure and see what the actual reading is. So is it even worth the time to swap the cam if there isn’t going to be a big return? Again, the purpose of the car is to accelerate quickly from corner to corner, and make a highway trip at 70mph up to 2 hours each way. I want to assemble and install this week. As far as the headgaskets, I’ll probably stick with the .040 felpro blues because of the 70 heads
The short answer is “lol”.... 2:56 posi and stock converter with a rebuilt TH350 that has a shift kit. I’m hoping to upgrade the rear at some point this season, but we’ll see. My silver lining thought is a slow car will help me learn how to control the car correctly through the course
