462 build, cam questions

[ToddK]

I'm putting together a new engine for my 63 Galaxie, and I'm after some educated opinions or advice.

The short engine I bought was built to run in NSS, but was never used. It is a 406 block that has been crossbolted, 4.16" bore, with a Scat 4.25" stroke crank, Scat 6.7 H-beams and JE custom pistons. The pistons have a small dome and were designed to give 12.0 to 1 comp with 76cc Edelbrock heads. The rotating assembly has been balanced. I will be using a pair of Barry R's heads that have been worked over by Joe C. Not sure what the chamber size is yet, but Joe did open up the chambers a bit to unshroud the valves and pick up more flow. I'll also be using a 3x2 intake that Joe has worked his magic on, using 500cfm Holleys.

The car is a full weight 63 500XL, wide ratio toploader, 4.11 rear gears, no power options. It is mostly street driven, but I do like some 1/4 mile action.

The question I am facing is regarding to the cam and compression. I have the cam that came with the engine, it is a solid flat lifter Comp custom. It is using their High RPM lobes, 304/314 advert, 266/276 dur at 0.050", 0.626"/0.653" lift, 108LSA and 108ICL. The other cam I have is also a Comp custom solid flat lifter using their Xtreme Energy lobes, 290/298 adver, 252/260 dur at 0.050", 0.635"/0.656" lift, also ground on 108/108. I'm tempted to leave the domed pistons as they are, which should give around 12 to 1 comp, and use the 304/314 cam. The other option is to have the domes on the pistons milled off to give me compression around 11.2 to 1, have the rotating assembly rebalanced, and use the 290/298 cam.

The hot rodder in me is saying go with the big compression/cam combo, but the sensible, street driving guy is saying mill the pistons now while it is all apart and use the smaller cam. Especially in a big, heavy, street driven Galaxie. Fuel is not a problem with either combo, I can get 100 octane at a nearby pump.

I'm after opinions or advice as to where the hp is likely to peak with either combo, how well would the High RPM lobes perform on the street, and which way would you go? I sort of know the answer, but I've never driven a snotty, high comp engine on the street and am wondering how much a pain in the but it would be in the real world. Any advice is welcome.

[plovett]

Here's a thought.   I certainly like the smaller cam better.  It has less duration, more lift, and more aggressive lobes.   That's all to the good in my opinion. 

But could you run the smaller cam along with the high compression?   You mentioned you have high octane gas available. Would it be enough octane to work with that combination?   Less duration and high compression would be the best for a heavy Galaxie in my opinion.

I bet the smaller cam would peak around 5900-6100 rpm with good heads and intake.   I'm not sure about the bigger one.

paulie

[66FAIRLANE]

Listen to the hot rod guy! If you don't you will always wonder. Then later you can listen to Mr. Sensible (if you call that cam sensible). I know its a pain to pull the engine again but at least you won't die wondering. You may even get a couple of years (or more if you can keep Mr. Sensible in his box) out of the nasty set up and your gunna want to tinker in a few years anyway. Easier to mill and decompress later than recompress.

Good luck with your choice. I am sure it will be super cool either way.

[ScotiaFE]

How is the 100 pump measured?
RON or AKI?
I ran the yours numbers through the configulator and got 12.77 to 1 with a 6 cc piston dome and a Fel Pro 1020 gasket at zero deck.
Even with a 2cc positive dome I'm getting 12.22 to 1 comp.
The big cam DCR is 8.837 to 1.
The little cam is at 9.48 to 1. A tad high.
So then I lopped off the dome and gave you a flat top with a -6cc valve notch.
This gave you a 11.24 to 1 comp.
The big cam DCR is 7.82 to 1
Small cam DCR 8.38 to 1

Without all the actual measurements this only a guess.

[lovehamr]

Only one question from me.  If fuel is no problem then why would you kill the compression?

[ToddK]

The pump fuel rating is advertised as R+M/2. I haven't used it yet as I currently don't require it, but a few guys I've spoken to who have used it say it's good.

I'll have a go at measuring the piston domes in the next day or so, but won't know the chamber volumes until I get hold of the heads.

I'm thinking the hot rod guy might win out at this stage. As Andy said, unless I give it a try, I'll never know.

[ToddK]

Okay, I just went out and measured the piston domes, and I get 11cc. The pistons sit 0.003" above the deck, so I plan on using a Cometic head gasket that has the 4.25" bore and 0.051" compressed thickness. Even if I use a conservative figure of 80cc for the head chambers, I get a static compression ratio of 12.6 to 1. That's calculated using the Diamond pistons calculator from Barry R's website. I could use the head gaskets with the 4.4" bore, but that would only drop it down to about 12.5 to 1. Mmmm, decisions, decisions.

[lovehamr]

Oh that puppy would pop with that though!