I think you would be waaay better off with a single carb intake and a 850 cfm carb!

what would be the difference between the 2?

The two 600 will equal 1200 cfm cubic feet per minute more gas   and the 850 will be a lot easier to tune and better on gas and one less carb to buy also keep in mind the daul carb setup will cost a little more on pluming.   by all means say away from the 660 center squirters if your worried about fuel.

what heads do you have?

stock crank & rods?

heres a question for you ford guys out there

me and pops are gunna be building a new motor for the centurian and have most of the parts to put it together besides the pistons

so here it goes.....what would be a resonably priced fored piston that would give good performance with the parts i already have.....parts are as follows


stock block 40 over  (30 over right now but gunna go 40 over to match new pistons)
stock heads
stock rockers
comp cams timing kit
comp cams push rods
comp cams lifters
comp cams camshaft- .530 lift .230 duration 110 lobe seperation .3060 lobe lift
offenhauser tunnel ram (dual carb)
pertronix ignitor 2 ignition with flame thrower coil
and im thinkin of goin with 2 600 holleys unless you guys think its gunna need more

A flat top piston will put you at about 9.5:1, which would be a good pump gas friendly compression ratio. It would be wise to zero-deck the block while the engine is apart so as to help control detonation. You could go with a Probe flat top (which we have in stock), or a Speed-Pro flat top for about the same price but slightly lesser piston (still up to the job), or a much more expensive piston such as a Diamond, Ross, Venolia, etc.  Depending how frugal you are, you might even consider an OEM replacement cast piston for a 1998-1992 460FI engine; this piston would put you at about 9:1 and you'd definitely have to deck your block.

The only individual that I know of that can bore a block 0.010" (from 0.030" to 0.040") is god, and god does not bore blocks. Power-hone to 0.040" or bore to 0.060"; your block is fine at +0.060" overbore and likely much further than that for such a build.

Regardless of induction and/or exhaust, you should port your heads. This is true even if you don't install oversize valves.  This is especially true based on the camshaft you have presumably (<---based on your post) already purchased.  We can port the heads for you if you prefer.  Or you had better go with a different camshaft profile.

600 vaccum secondaries on a tunnel ram will get pretty decent fuel economy on such an engine, compared to other tunnel ram carbs.

LO

Hey Lakes Only...How's biz...Hope Good

Anyhay, not knowing the condition of this gentlemans  cyl. bores now at  .030   

Based on the piston, he may be able to stay at .030, given the desired piston to wall/marine application clear.

Don't ya think.

Also  given the correct conditions, Boring / honing  from  .030  to .040 over is do-able...U know how much time it takes to power hone that much...Yet u end up with a killer hone by honing only.  IMO only 

X2..

BTW, pretty close to God I guess   

http://www.rottlermfg.com/machine_info.php?cPath=25&products_id=41

Saw this machine in action, fell in love with it immediately 

Bored over 7 cylinders and sleeve cut one on the same block during my lunch break ('bout 40 min.), needless to say, impressive....

Beats the hell out of standing in front of a CK10 with your willy in one hand and a cup of coffee in the other....They had their honing machine too....More money then they knew what to do with I guess....(Private shop).

GT

The block we picked up was recently bored to 30 over. The guy had the pistons it was bored to, but sold them before it got to us. Our local machine shop, Rancho Machine, checked out the block/crank/rods and said everything was OK (previous machine work) and he recommended going with the 40 over pistons and he would bore it to them after we get them. The listed items on 78's first post are the parts we already have. We also have a single aluminum intake, a new polished 750 Holley dual feed with vacuum secondaries (courtesy of our failed attempt to join the AVI trip, and soon to be possibly posted for sale at $350.00) and a 780 double pumper with manual secondaries.  

60 over at this point would not be a problem. Just looking to put together a decent motor with the parts we have that will be dependable, and run on pump gas.

IMHO no need for .060", if anything, would rather see you stay .030", but if you already own nice .040" slugs, I am very "run what ya brung"....But....If those pistons are cast or will not provide the CR you are looking for, then I would say buy some .030" forged pieces and go with a slight overbore and save the block for future rebuilds (just the way I was brought up).

I have actually had blocks go a bit too far over and had the pistons Knurled (OK so how many of you machinists just cringed?) just to get one or two more runs out of them(not recommended), also had the pistons coated by Jet Hot.

GT

We don't have any slugs right now, and were told by our local machine shop that checked the block, that it is best to have it machined to match the pistons that are going in it. That is why 78 posted which pistons would be recommended (there are several choices on Summit and we were not certain what to get.

We would like them to be compatible with the parts we already acquired. Is our local machine shop correct that the bore needs to match the pistons, or can we get a set of 30 over and be done with it?

Well, here is my take...The people that do this for a living will better answer your intelligent question, but IMO, a jetboat engine typically gets bored with larger piston to cylinder wall clearances than that of an automotive type (the amount varies). That being said, a .030" oversize piston is .030" over that of an OEM bore size...That's .030" over a known bore size...So it could stand to reason that you could use .030" slugs and get the machine work adjusted for the new pistons, I think you would be GTG.

Your machinist could just be trying to cover all his bases and make sure to not put you in a spot...definately have the machine work checked/done before you hang the pistons......they are almost always returnable depending on where you buy them from.

I have literally taken a junkyard motor (running) and done a hone to just clean up the walls after a hot tank, throw in some used forgies with new bearings and a cam and let her buck.....We called them "Grenades"  I can't remember ever puking one....

My advice on engine building is sort of the "Redneck way" so use with caution...

GT