Timing with Hypereutectic pistons
Back up the bus, there young fellow.
I'm assuming;
this is for a street car?(2400TC)That you have an Early A,(3000lbs),
that you have limited mechanical knowledge,and
That for some as yet unstated reason,you are targeting 320hp,
So......................computer controlled ignition timing can break an engine every bit as quick as a regular distributor. Maybe even quicker.
And, IMO, at your power level, EFI is just bragging rights. What I mean is;A carb is just fine with an XE268 cam. The 2400 is probably gonna have to go, unless you are thinking of running big-number rear gears, like 3.91s, or if you don't mind coming outta the gate a bit soft, or are running skinny tires, or real crappy street suspension.What I mean is; if it hooks, the 2400 will drag the revs down into the soft part of the engine's powerband. If it spins and the revs get up to mid to high 3000s, where the torque starts, then it don't matter much what stall you run.
But then I'm thinking; if you are targeting 320hp, you will not be wanting to just spin skinny 245s;heck you can do that with a stock teener. So, I got to thinking, I wonder what this guy(you) are thinking? Then I thought, I wonder what his plans really are? He (you) seems to be all over the place.
On the one hand, he says 320 hp; but he's confusing ignition timing with cam timing.Then, he's concerned about skirt clearances, but the machinist hasn't asked for the pistons to "hone the cylinders out .040". And he wants to run a 2400TC with an XE268.
Ok, a picture is starting to form in my head. I think this guy is a little "green".Am I right? That's ok, we all started out green. So, how about you tell us a little about yourself and your car, and how you intend to drive it, before you spend your life-savings on a disappointing combo.
I guess I should've elaborated. It is a 1966 VC Valiant. Stock diff ratio is 3.23, which is what it has.
The 318 I have has already been bored .030". The machinist has my short motor. He found .003" cylinder wear and suggested taking it out .040". Without doing this, he was concerned there may be an issue with blow by.
We discussed pistons, I mentioned the KB167, he asked for a few figures, including compression height of the pistons and was able to tell me how much the block needed to be milled as well as what was required in terms of machining the stock 318 heads. He has asked for the new pistons also.
As recently as yesterday, I have found an aftermarket option for the heads which I will be purchasing
http://www.ebay.com.au/itm/Mopar-Ch...225767?hash=item1eac450ea7:g:XCkAAOSwezVW06YY
With the chamber volume of 65cc, it should put me in the 9.4:1 range just by using the heads with the KB167 pistons, without even factoring in the work done to the block.
Since finding these heads available, with the valve sizing (which i think is a typo on the ad) I may even be able to run an xe274 cam, and according to the CamQuest program, that needs a 2200rpm+ stall.
How much the cam and valve sizing does/doesn't hurt vacuum with that compression ratio, I'll see. But there are options to work around this.
I also have an Edelbrock LD4B I am using.
Car is 100% a street car, it will run 98 Octane fuel, it's not a daily driver, it's a weekend cruiser/whenever I wanna take it out for a thrash.
I agree that Fuel Injection won't make it immune to detonation or hurting the engine, or even make it have greater HP, but the Fitech system is so cheap, it makes sense to use it, with all the benefits of correct AFR's in correlation to coolant temp, cold starting and constant self tuning of the AFRs for near perfect combustion under all engine loads. Why spend $$$ building this motor to only run it with a carb? Definitely not for "bragging rights". Why should how much power you have dictate whether or not you use fuel injection??
I'm using this motor because it's free and 360s, 340's are expensive and hard to come by in Aus. Forget stroker motors, too much needs to be done in terms of getting it street legal here. The year of this vehicle does not need to meet emissions in Australia.
I trust what the machinist recommends, he has been in the industry since 1975 building street and race motors. He didn't laugh at my ideas or what I have planned, he explained how MY goals can be achieved. He thinks its great that I'm going to build the motor myself.
And he certainly isn't sitting behind a computer screen taking the piss out of people and their ideas.
I appreciate the help other users have given in the thread. Thankyou.
There may be some other people out there that had the same questions I had hence starting this topic but lets not ASSume that.
Andrew