Gramma's Car: the new project!

[njsteve]

Got the block update this morning. It needs a little cleaning up of the .030 bore, so it will be bored to .040. The machinist said, "yeah you could leave it at the existing .030, hone it, and slap it together, but if it was mine I'd make it perfect at .040 and start from there."

Since I have to order a set of forged pistons anyway, I went for the .040 (same price as the .030).

$312 for http://www.summitracing.com/parts/slp-l2359nf40

[scuncio]

Love to see your progress. I will be going through a low-mile 0.030-over 455 short block and 6X-8 heads very soon.

Which begs the question...what will your CR be with the 6X-4 heads?

[njsteve]

With the 6X-4 heads off a 350, around 9.5 to 9.75 to 1. They are the 93 cc heads but have been cleaned up to get them flat. The block will be surfaced flat as well. So it should make them a wee bit smaller. I will CC the heads once I get them off the 350 in the car now where they currently have 7.5 to 1 compression. (BTW, the 6x-8 heads off of a 400 are 100 cc)

Here is the chart info from the pistons

Pontiac 455 L2359NF

72cc = 11.5 1 to 1

87cc = 10.01 to 1

96cc = 9.3 to 1

111cc = 8.34 to 1

114cc = 8.17 to 1

[scuncio]

Thanks! I'm using the same pistons. I keep hearing about Pontiacs being detonation sensitive so I was leaning toward a 9.1 CR...what do you think?

[njsteve]

The detonation is really a function of camshaft centerline in these cars. You need a wide centerline on a big Pontiac to avoid detonation and get the most power. That was the nightmare of the engine in my black '72 455HO. Back in the 1970's an "expert" engine builder slapped in some domed pistons (which Pontiacs don't take kindly to) and a crappy cam choice. The thing would detonate under any load, even with the timing backed off 20 degrees! It had around 11.5 to 1 compression. When I did a compression check it showed 225 PSI!!!

A lot of guys swear by the Summit Racing 2802 cam (if they are not going the rollercam route). And you can't beat the price! That is what is going into this motor. - The Melling SPC7 reproduction RAIII/455HO 068 cam I had just installed in the 350 is too mild for the 455 with these heads. So I guess I'll save that for the next project.

http://www.summitracing.com/parts/sum-2802

There are some very informative discussions on cams on the PY site by some of the better engine builders. Here's one:

http://forums.maxperformanceinc.com/...d.php?t=775018

[cook_dw]

That is a great cam choice. I would run the almost same specs in a mild sbc but I would tighten up the LSA to 112.. Also impressed by how great the crank turned out.. Gotta love Evaporust.. Any time a new engine is being built and before the oil pump goes on I always pull them apart.. Something inside of me makes me not want to trust a machined part like that to go in an engine without inspection.. Excellent work! [img]<<GRAEMLIN_URL>>/biggthumpup.gif[/img]

[scuncio]

Thanks, great advice! I am going for a relatively tame street engine so the Summit cam may be a good choice.

What are your plans for the heads - valve size, porting, etc?

[njsteve]

The heads were just done 1,500 miles ago, when we rebuilt the 350, so they are getting bolted onto the 455 short-block as is.

[scuncio]

I may do some basic port cleanup to the 6X-8 heads I have here on the shelf. I believe these have the larger valves factory installed, so I hope it runs well.

[njsteve]

Look what showed up today! Oooooh shiny new parts!