I think I've dropped the 496 idea and will just stick with 468. I'd love to have a few extra dollars for other things on my car or just for my own use than in the engine, if I don't need a new crank. I don't really want to upgrade suspension tooo much to take the low torque of the 496, and frankly don't want anything that has a chance of killing myself...well, not a high chance, anyway. A few things I have to ask:

Will a Q-jet (800 cfm) be enough to feed the 468?

I would like to be building with oval aluminum heads. What size intake runners are best? I'm pretty sure I've read that bigger isn't always better in this case.

Are the cheap pistons (cast, I think?) fine holding up under compression of running 93, as long as the engine isn't blown or NOSed?

Thanks.

Q-Jet will be fine.
Edelbrock aluminum ovals have 265 cc intake runners I believe.
You'll need at least a piston with .100 dome minmum to get some compression,actually more like .270 if you are running 110 cc's or more for combustion chamber size.

Taylor, killing yourself is not knowing the physical limits and not paying attention. These cars require respect for what they can do. 0-60 in 4 seconds is rippin' quick. Any one of us could die driving a 85 bhp econobox. If one is acutely aware of one's surroundings, I'd rather have 500 hp on tap so 1.5 seconds of acceleration gets it out of harm's way.

Cast or hyper pistons are fine if you keep rpms mild, say 5500 rpm max.

If it were me, I'd use SRP slugs and forgo the fancy alum heads, since you already have great castings.

Taylor,
In my opinion i think it would be wise of you to spend you're money on a nice set of pistons, and go for Closed Chamber Iron oval port heads, rather then Open chamber Aluminum heads.

Since you're a few years younger then me, i know how long you need to work to be able to buy a set of heads.

The Qjet would be fine, but i think you'll like the ease of tuning, and ease of available parts that Holley offers.

What kind of power can the '781s make and what does it take to get them there?

Also, the current intake I have is squarebore aluminum Edelbrock Performer RPM, but I've got a Q-jet. Should I just buy a spreadbore intake on eBay or are adapter plates OK, or do those hurt performance.

Sorry for all the questions, I just want to learn and make sure I'm getting things straight.

Originally posted by soccerguy045:

Sorry for all the questions, I just want to learn and make sure I'm getting things straight. If we got in trouble for asking questions, I'd be in a 55 gallon drum at the bottom of the atlantic..
Thats what we are here for..

I think if you are content with 500hp @ the crank, engine dyno style, 781's, forged SRPs, GM rods with ARP bolts, even a cast crank would be suitable here I bet, nice solid flat tappet or if you have the $$ handy a hyd roller, would set you up with an off-idle to 6000 (the solid would keep revving, but pick a grind that keeps the RPMs down low for longevity) 500hp rat that should be plenty of fun, especially if your car isn't a tub.
I think you can pick apart the old BSE combo and work from there and tailor it to your needs. Don't listen to what I say very loud though, I'm new to this too, and I went about everything the hard way- big this, big that, high cost this, hight cost that, new this, new that, and it got me nowhere fast (well, actually, nowhere slow :D ). There are plenty of ways to skin the cat though, and no matter what you do unless its just plain mismatched, a 10:1 468 with a good cam, decent carb, correctly sized headers should do you just fine. Its when you get power hungry that things can get ugly..

Matt

What kind of power can the '781s make and what does it take to get them there? I've got a friend running a 468 with a cast crank and 781's in his '69 Camaro. It has a best of 6.26 in the 1/8th (no nitrous). They of course have big valves and he ported them. Just thought you's like to know.

I might be a little power hungry..but that's the fun of it! Part of a petty goal of mine is to beat my friend's Camaro who is all talk and money. Hopefully I could come up with something that could make my Chevelle run 12ish with 3.31 rear?

ask Todd "10secbu" about the 781's...mid 10's with 414 cubic inches.

Originally posted by Rapid Robert:
ask Todd "10secbu" about the 781's...mid 10's with 414 cubic inches. Also at 3600 lbs race weight, through full exhaust out the back, on 93 octane pump gas, on BFG drag radial DOT tires, yadda, yadda, yadda ;) :D :rolleyes: .

Seriously, the 781 head is an excellent street strip performance head with minimal mods. Mine have 2.19/1.88 valves, throat cut in the bowl to open that area up, then bowl blended, 3 angle valve job, short turn radius gently rounded, and the intake runner opening matched to the intake manifold (not really needed for power, but lines things up well and looks purty). That's all that's needed to be done to these heads to support 600+ hp.

Sounds pretty cool. Seems everyday I learn something new that changes what I want to do on my combo, but that's a good thing! graemlins/thumbsup.gif

I guess in order to get as high compression with open chamber heads, all that is really needed is bigger dome, correct? Will that impede flame front in any way, or is that still fine?

Yes, a bigger dome is all that is needed. They say a dome can affect the flame travel, but IMO, I'd rather have some compression and work the dome shape or combustion chamber to tweak the flame travel.

Don't forget the zero deck the block, or maybe .005 or .010 down in the hole at most. Proper quench distance is very important to efficient combustion. This "tight" deck height also helps keep from losing too much static compression.

What kind of CR is pushing it with iron heads to run 93? I mean I know that's a very general question to ask, but around 10.5:1-ish? 11:1ish?

Closed chamber heads are less susceptable to detonation, then Open chamber, by design.

Don't bother with closed chamber, again, you have good heads use them. Buy the medium dome SRP piston. THey are superb. That's the aluminum you should spend money on.

Brian is right that smaller chambers/smaller domes are better, but it isn't a big deal at this level at all.

I pushed the envelope at 8.6:1 dynamic compression. I would recommend you leave yourself more room than that. shoot for 8.2 tops if you don't mind buying 93 octane. I know oc closed chamber mills running 8.4-8.5, but they don;t use vaccum advance and are leaving 2-3 mpg on the table for highway use.

Your final compression ratio depends on cam selection, which is why I speak of dynamic compression above. To be rough about it, shoot for 10:1 which should be right toi match a cam designed to work with 3.31s ( which isn't a huge cam btw), but visit Pat Kelley's pages and learn about dynamic, or run searches here. Your cam choice affects where you want the motor's compression.

Well right now I'm looking at some cams to toy with what would be good in the combo to at least run compression numbers and stuff. I was just looking at some Comp cams, though I think when I get there I'll be contacting UDHarold for a cam. Anyway, I'm having trouble identifying the ICL. The LSA is listed but not the ICL and I'm not sure how to derive that. The reason I need it is to find the degree when the intake is closing to work the calculator.

Just curious why headgasket bore is important on this calculator and if it's the same as the regular cylinder bore? Thanks.