Help me with some engine build decisions, please............

Now, I see. The main component that contributes to DCR between your motor and my proposed build is that 30cc piston dish. Looks like I'll have to drop the piston about .020 into the hole to get the compression I want. That will give about a .060 quench distance. I think I can live with that. Or, order the pistons with a deeper dish.

 

Should talk with Jim about rods and pistons them you can bump it up to a 470. Only real cost difference is mostly the rods.I was going with a .030 455 but I actually saved money on rods using his combo since I needed better rods. Now I am going roller on cam.

 

Talked with Jim but, price on his 470 was way over the .040 455 mainly because I have my own running 455 motor and the builder I chose is very close to my home. Buying all the core parts plus shipping from TSP to Florida and transportation for me to witness the dyno runs made the project cost prohibitive.

 

I would only take a minimum cut off the decks on your block to square it up so the heads and manifold line up properly down the road. Since you are considering forged pistons you should mock the short block up and order custom pistons with the proper compression height to yield the desired deck height and dish volume for your calculated static compression ratio. The way to go would probably be a zero deck and required valve relief/dish volume and use a .040 compressed thickness head gasket.
Doug Jones

 

Thanks, Doug. Makes sense. So, we're just cleaning up the deck and then ordering the pistons with compression height to achieve zero deck as opposed to buying the pistons first and then, milling the block to achieve the zero deck?

Will my machinist be able to measure the deck height of the block before we order the pistons?

 

Hopefully you have a stock piston/rod/pin assembly that you can mock up in your block. Have your machinist install the crankshaft with front and rear main bearings and install the piston/rod assembly in the block (after the deck has been machined with minimum cut). Measure the deck height and then have the machinist measure the compression height of the piston which is the distance from the center of the wrist pin bore to the top of the piston. You would then add that number to the deck height to calculate your new piston compression height number.
Doug Jones

 

What I found over the years is that most Buick 455 blocks require .020 to be removed from the deck to clean up all the corrosion around the water jackets. That 10.550 is the deck height the 470 is built around.

This does not adversely affect intake manifold fit, because the original motor was designed for a .020 steel shim gasket.

We all use a .040 composition gasket, these days, so the clean up cut makes it very close to blueprint for fit.

Assuming a nominal 6.600 rod length, you would need a 2.00 compression distance on your custom forged pistons.

I can make 2 changes to the 470 piston, for a $8 charge, per piston, per change..

I could change to the Buick Pin size of 1" and to that 2" compression distance for you. The 25cc spherical dish and .300 deep valve reliefs will put you right around the optimum static compression ratio for the combination your talking about.

Those pistons are $899 to your door.. use that when you price out piston options.

My pistons are the superior 2618 material, with offset pins for low noise when cold. Do your research on piston alloys so your informed about what your buying.




JW

 

Oops, I guess I should have read your post more thoroughly, I "assumed" that you were using the stock stroke.

 

I am using the stock stroke of 3.900 and the stock crank. What did you read that said otherwise?

 

He is using the stock stroke Doug.

My input was only to help save him the trouble of going thru all the pre-piston ordering work.

And to give him an idea what the low end pricing will be on a custom piston.

It's the forging I use for the 470, but changed for this application. I do that quite often for folks that are building custom stuff.

JW

 

Cam choices......thoughts?

I've got my cam choice narrowed down to two different sources and basically two similar grinds. Here they are:

TA (Schneider) - 288-98H
adv duration - 288/298
.050 duration - 230/245
lobe lift - .323/.323
overlap - 61
LSA - 116*
install 4* advance
intake closes - 76*
SCR - 10.4:1
DCR - 7.5:1

Comp Cams - custom Magnum grind
adv duration - 280/292
.050 duration - 232/244
lobe lift - .322/.3235
overlap - 54
LSA - 116* ( I can order any LSA I want)
install 4* advance
intake closes - 72*
SCR - 10.4:1
DCR - 7.8:1

While these cams seem very close at .050 durations and lift data, the advertized durations are quite different. Both companies say they measure advertized duration at .006 lift so, why such a big difference? It seems to matter when it comes to overlap and DCR. I'd like to keep the DCR up close to 8 so the Comp Cam seems to get that but, am I missing something? Is it ramp velocity?

Just to refresh my build, the motor will be a 464 with TA SE Stg 1 heads with bowl and runner porting, Performer and ported iron exhausts, & built quadrajet. Car is a '71 GS with A/C P/B etc and 95% street use. Converter will be in the 2200 - 2500 range.

 

Re: Cam choices......thoughts?

The Comp cam will indeed give you a higher DCR and a little better idle and manifold vacuum.
As you observed, the lobe intensity (ramp velocity) is greater on the Comp cam where they are trying for more "area under the curve" to make better power.
The down side is there is more stress on the valve train.

 

Re: Cam choices......thoughts?

So, if I stay with my stock stamped 1.55 rockers and shafts, and keep the RPM below say, 5800, should I be OK? Or, should I get the heavier duty aftermarket shafts to add a bit of safety?

 

Re: Cam choices......thoughts?

You should be ok.

The addition force is also seen between the lifter and the cam lobe making cam break-in more important along with the choosing a good oil for flat tappet cam use.

If you were to spend the money on a roller rocker set then I would suggest also going to a roller cam and eliminating the flat tappet cam breakin procedure along with the chance of a flat tappet cam lobe going flat.

Also consider that a ported TA head works well with valve lifts closer to .550"