I'm building a .030" 406 engine- below is what I currently have

2 bolt block, will use ARP main studs
Stock crank
6" Scat H-beam rods
SRP flat top forged 416 gram pistons
Edelbrock Performer RPM heads, 70cc angle plug

I need a 400 flex plate, am undecided on balancer choice- to use a stocker or go with a more expensive but better one.
I'm undecided on the cam, but it will be hydraulic flat tappet and I am leaning towards a Comp XE-274, and will probably need a reduced base circle due to the rods.

I am shooting for 10 to 10.5:1 CR with this.

The machinist (nothing has been done yet but hot tanking and magnafluxing) asked if I needed the block decked. I said that I woud trial assemble, measure the true deck clearance, and then determine what needed to be milled off to give me the desired CR with the head gasket I will be using etc.

He insists I don't need to do that, that if I give him the head cc, the piston dish volume (5cc according to SRP) he can figure it out exactly and mill accordingly.

The engine is going in a 3200lb S10, with a dual plane intake, 750CFM Q-jet, mild stall converter, 700R4 and currently 3.73 gears. The truck gets used "as a truck" for daily driving and spends lots of time idling in traffic.

So, does anyone think I should have it decked or trial assemble after boring and honing to see what it is and if it's needed? What deck clearance should I have?

 

i'd have it zero decked and optomize the squish more than worry about finial compression ratio

 

If you're aiming for a true zero deck, I would trial fit it and measure it.
Sometimes factory blocks can be a bit off from the std deck height, either from one bank of cyls to the other or from front to back.
Miking it is the only way to be sure.
It would be tragic to get your block back from the machinist and discover that the right side is zero and the left is .005 above the deck.
Although it could be compensated for by using a thicker gasket, that isn't what you want.
There's a machinist in my area who likes to try to talk guys out of doing stuff the right way, I quit going to him.

 

are you using the "cap screw" rods?if so a small base circle cam will probably not be needed.the 274xe will idle choppy but give you enough vaccum for power accesories.i got 11-12"in a 357 with that cam but it was touchy with a stock converter at lights.
the 700r4 and 3.73 gears are right on in my opinion,and in a 3200lb truck,the main problem you will have will be traction!
your c/r should be right on for 89-92 octane if you shoot for .035 -.040 quench whis optimal.quench is the total distance between the piston top and head (including head gasket).
as i see it you are on the right track!the rpm heads flow about 180cc (if i remember correctly!)so the only thing i could reccomend might be a slightly longer duration cam(xs282solid?)or a roller($$$),but i am gonna try my good old 274xein a very similar combo before i change anything!by the way,since you are using aluminum heads(i just noticed)you can probably push 11:1 without detonation problems,but are the gains of 5-7 hp worth the risks?
i would stick with the 274 and if your springs can handle it,maybe 1.6:1 rockers on both sides.
Eric

 

Thank you for the replies! I think I will just have him bore and hone, then I'll take it home and do the trial assembley and measure.

I spoke with Richard at SRP today (GREAT tech support BTW) and he said they want a minimum of .040" piston to head clearance, weather you zero-deck and use a .040" gasket or what ever method you want to use.

I got the rods (and pistons) from www.dirttrackthunder.com, they are the Scat 6" 4130 I-beams, I have them at the machine shop right now but I believe they have 12 point nuts- there is a picture of them on the site.

As far as the cam goes, my mind isn't completely made up, but I do know I can't see the justification of the higher cost to go hydraulic roller.

I got the heads with less than 3000 miles on them from a guy who was building a stroker and had 220cc heads on order so he needed the cash- I got a set of barely used Crane Gold 1.5 roller rockers for $100 off a friend.

I still need rings, a balancer and flex plate, bearings, push rods, gaskets and about $500 more dollars worth of machining and balancing. Donations accepted!

 

You're building this"daily use truck motor" with way way too much compression.

I get 10.9:1 with what you have on a " 0 decked block"

Either open up the combustion chambers to lower the cr or get reverse (D dish) domed pistons.

A true 9.8--- 10:1 is much more practical for a daily use motor in a truck. 10.9 is definatly too much.
You will always have to run the best ( most expensive) fuel available and you'll still be too close to the edge.
may have to compromise timing to avoid pinging in daily useage.

Unless your machinst has a block deck height measureing fixture, presassembling the motor and measureing before cutting the decks is the only way to end up with
an exact 0 decked block. And as RB said one side may not be the same as the other.

the cam is too big for daily use truck too.
(poor fuel mileage)
a cam like this one

Will be better with a over drive trans in OD , better with the 2200stall converter that yu have, better with a Qjet and better overall for a "daily driver" and last longer.
(easier on the valve train)
Will give up little or nothing in *actual quarter mile performance (in the car....er truck)* and pass alot more gas stations.

My friend built a simular motor for a customer's truck like yours with the same purpose. Tried several cams after the initial build was just not quite what they were looking for. This cam worked the best of all tried. A noticable difference. it was so nice some one stole the truck ..

 

You have made some valid points F-bird, as far as the CR, I'm probably going to end up closer to 10:1 then over it. I am going to have it decked only if needed to true the thing.

As far as fuel, I'm already using 93 octane in the thing, the cast piston 355 in there now with 882 heads and about 8.3:1 will ping on 87 octane, likely due to a crappy combustion chamber design, so I'm used to paying for it.

As far as the cam, I'm going to call several companies and get advice. That Crane is close to the cam I currently have in the 355 still in the truck.

What balancer would you use?

 

Don;t try to evaluate that cam (or a simular one) in your edelbrock headed 400 based on a 350 with crappy 882's. It will be like night and day. One of the reasons why your 350 pings is because it has no quench.

I use a PowerBond balancer on my 400. Nicer than a factory balancer. Degree marks too from TDC to 40*BTC
Seems like a nice piece.

If you want to build a better mousetrap, getting the cr and quench clearance right instead of "close enough"
is one important thing to work on.
Will make much, much more difference than say the 6" rods. If you don;t deck the block you'll end up with about .065/.070" total quench clearance. too much.

 

F-Bird,

If you were putting this together, what type of quench would you shoot for?

I am aware I stuck my big old foot in my mouth with that comarison of the cams, and you are correct about the poor quench on that 355 I have.

Could it be said my current engine leaves my thirst for power "unquenched", hence I am looking into the 406?

 

are you getting this engine balanced.i might be wrong but a light piston and long rod may throw the balance of that stock crank way out.

 

Absolutely! I still have to get a balancer, flexplate, rod bearings and rings so the machinist can start balancing it.

 

1. .040" total qench clearance at TDC including the gasket. no less than .038" no more than .050"

Mine is .040" The block is "0decked" so the pistons come right up to the top at TDC.

2. your 355 probabily is making between 310 and 325 gross bhp .

your new 400 will make about 425-440 gross bhp and feel like 500hp compared to what you have now.

there are a few ways to get the quench and compression ratio right on your 406 using what you have.
i would look into properly machining the block decks
to ge the quench clearance right and do some deshrouding on the combustion chambers on the 70cc heads to gain some flow and increase the chamber size to get the cr to something reasonable that will work every day. aim for something between 9.8- 10.3:1 finished.

there is lots of meat in those heads for carving the combustion chambers. won;t take much to open 'em up a bit.

Find the compression ratio calc on this page and plug in the numbers for yourself and see what you need to do.

 

I'd be happy if my 355 made 310 to 325 gross. I dynoed at 201 RWHP and 248 fl/lbs. More like 240 Flywheel.

The thing has flat top cast Speed-Pros, .045" down in the hole, probably thick rebuilder type fel pro gaskets and stock 76cc heads, COMP 268XE (way too much cam for it) wieand dual plane and Heman headers.

I found a machine shop more reasonable, $140- to bore AND torque plate hone.