VE, MPG, and ported heads. Keith?

[navyblue2000]

I was talkin to a guy locally who has a lot of experience porting heads. In fact he does it for a living. I asked him to take a look at the supersix heads, and he said they were done very conservatively, and he was suprised that they left the small intake valve alone. in fact, lemme bring up the email he sent me in my response:

Those numbers arent great for cam and heads. Seems about right for either or. I wonder why they left the small intake valves alone. Leads me to believe they didnt get too aggressive.
I dont do rear gears anymore, but Tracey ( Badassbird88@aol.com ) would probably be glad to do them for you.
Your probably going to invest about 850.00 in just the heads with porting and parts for an ALL OUT- high end race port job, plus install if you need it. Your car will be down for about 2 weeks. I can work you up a complete price for the job if your interested. Just let me know
THanks
Dave

Then, when I had asked him about gas mileage and what not:-
Ok Ill work you up a price on a max set of heads installed. Just an FYI, you will improve your gas milage with ported heads due to the greatly improved Volometric Eff., not the other way around.

SO, I know that the cam does adverse things to gas mileage, but is this guy right that it helps MPG? i don't doubt this guys abilities, everyone that has had their heads done from this guy love the work he does.

[Magnus]

Higher VE can utilize a leaner mixture to make power. If your PCM remains unchanged though, it will still shoot for the same richness levels I believe so I'm guessing MPG will remain unchanged.

I'm not totally certain on that though.

I think the stock intake valve is fine. I don't think its worth the $$$ to put in a new valve.

For now I'm sticking with stock valves and stock rockers.

We don't have huge cylinders, so there isn't much space to fill.. So a cam like a 224/224 is rather agressive on an LS1.. think of what it would be like on OUR cars.. overkill imho.

If you want, you should drop Tom @ Supersix an e-mail and ask him about his porting, ask him if he could step it up a little bit for you.

Tom has done several 3.8 heads, how many has your guy done? The thing here is... as you do more and more of a certain head, you learn its limits.. you know how far you can port to be safe.

I'm sure in time Tom will be coming out with even better port jobs for us.. we just need to keep sending him heads.

[navyblue2000]

i had a thought. i priced up a pair of heads from gmpartsdirect.com
660 shipped to a door.
think i could just ship a pair over to tom at supersix? i'd hate to ship them twice.

[Magnus]

why buy new heads?..

Order heads from Tom... pay the core charge... then get yoru $$$ when you ship your stock heads back to him.

[navyblue2000]

well, does it even out?
i'm paying for heads and labor, or just labor?

[Magnus]

You pay for labor.. and pay a CORE charge...

You get your core back when you ship him your STOCK heads..

its a switch off program get it?

You pay for labor.. and a core.. and you get a set of heads in the mail.. so now you have to...

but your supposed to send your stock heads back... so the NEXT guy can do the same.. follow?

Thats a core.

[navyblue2000]

ah, i get it. say labor costs X, and core costs Y. you pay X and Y, but you send your heads back, and get Y money back?

[Magnus]

Exactly. [img]smile.gif[/img]

[Patrick Javert]

As far as ve goes, yes, your friend should be right, but, as with anything having to do with an engine, the more air that can get in, the more fuel has to go in to match what the computer has set for optimum mixture. The car has to put out x amount of fuel for every y amount of air going in. The way you really get better mileage is if you can lighten the car. First, all unessesary stuff in the car itself. Then, parts of the car you can buy that are lighter than the stock pieces. Now the powertrain. Lighter heads, block, ect. will help. In order to make more horsepower and lose weight, buy a forged/billet crank, forged/billet/titanium rods, forged pistons, billet flywheel, alluminum/carbon fiber driveshaft, lightweight/titanium axles, forged rims as big as you can get and tires with as little sidewall as possible. Also, less weight/car load=less octane needed to prevent detonation.

[Pro Stock John]

Too big of a valve might not show a gain since the stock 3.8 bore is rather small, what was the size again Magnus? You can end up with shrouding.

Might see a gain by going with a slightly bigger intake valve, nobody can argue that there would be zero gain unless someone has actual data to support that.

There are other factor at work when selecting valve sizes and cam specs.

For example, COST is a factor. Once you get to a certain size, you would need to have different valve seats installed. That can be expensive.

If you want to get really serious with this stuff, you would want to get a stock head flowed and a ported head flowed.

Magnus, I know someone locally who could do that for a small fee. You can also flow the head with the intake bolted on to see how restrictive it is.

My stage III ARE LS1 heads flow about 305cfm at 600 lift, but with my LS6 intake bolted on, it's probably more like 280cfm.

I am running 2.08/1.60 valves which are significantly bigger than stock but I am running a big bore, 4.060 vs 3.900 stock. I am running a Silverado LQ4 block.

[Pro Stock John]

I just wanted to add, that I see that the stock bore is 3.800. To the guy who is talking about using a different guy, ask him how big he would go with a 3.800 bore motor.

A traditional SBC or 93-97 LT1 is a 4.000 bore. That is the standard for the industry.

An LS1 is a 3.900 bore. But it has more stroke, 3.62 vs the traditional 3.48 stroke of an SBC / LT1.

Another motor to compare, is the 3rd gen 305ci motor. That is either a 3.800 bore or a 3.85 bore. Find out what size valves those folks do maybe that would be interesting for comparisons sake.