help on performance decision

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duster731

duster731

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I'm in a tight spot and need some help on which part I should get... :angel9:

I'm gonna be yanking my 318 back out to redo my combo.
It's 40 over stock bottom end and on the top I'm adding a air gap int, 302 head gaskets matched, 650 or 670 holley, my question is should I get kb pistons or a stall converter from cope racing both about the same price but what would be better. Would the pistons be good upgrade I have only found the kb 167 is there any other ones... I also have a 904 and 3.91 s.g rear.......

Pistons or stall thanks any opinions would help
 
lots of other stuff to think about.

any work done to the heads?

headers?

whats it got for a cam? lifters? rockers? valves? and so on...

whats your ultimate goal? to build a peppy 318 and keep it or to make the 318 a little quicker to tide you over until you can snag a different engine?

I personally think an air gap might be a little much for a mostly stock 318 but ill let someone else chime in on that.

I run an eddy performer dual plane intake with an eddy 1406 600 carb and it runs great.

also you have to consider that if your going to toss new pistons in that you should probably take it to a machine shop and have it balanced out which will add to the cost.....(not sure if your working on a budget or not).

I personally would probably poke money into the bolt ons and get as many ponies out of it that you can with a basically stock internals.

maybe a little bit of porting and polishing and gasket matching with heads and intake,a nice performing intake and carb set up,cam,some headers and a good exhaust system and probably a stall converter,nice rear gearing a tire set up and a shift kit would not hurt either.
 
Goal= make it quicker

I have headers and about 3,000 miles on the engine, just the bottom end is stock I have a performer and 600 now but I'm putting the 302 swirl port heads on with a bigger valves and intake and port/gaskets match em I already have a new cam for it as well its the comp 268 with 488 lift and 225@50 dur... I have everything else covered its just a toss up on those too parts

I built thks engine with all brand new parts and machine work I'm just redoing the combo to get more horses..

o ya I do have a shift kit,lower gears, deep pan trans, 8 3/4 rear 3.91 s.g, 40 series flowmasters dual exhaust

That's the pic of my set up I have right now in my Sig
 
You better figure compression with the pistons you have now and adding those 302 heads FIRST. If you get the KBs, you may end up with an engine that doesn't like pump premium. That would SUCK. I'd be willing to bet the compression with stock 318 pistons and those 302 heads will be in the 9:1 + range. That's just right for a street engine. But do the math and find out for sure.
 
So get the converter and whatever bolt ons bigger carb or headers etc. that you can and then save up for a new shortblock or stroker for later.
good luck

are you going to run that cam with the new heads? GREAT cam and Comp specs recommended a 2000 stall converter but will work with stock piece

My opinion I would get converter and a Transgo 2 kit for your 904
you will be better off.
 
67Signet said:
So get the converter and whatever bolt ons bigger carb or headers etc. that you can and then save up for a new shortblock or stroker for later.
good luck

are you going to run that cam with the new heads? GREAT cam and Comp specs .
Click to expand...

As mentioned above I'm getting a new carb and already have headers and shift kit

I'm going to run that comp cam with my redo I thought since the engine will be back out probably for the last time I should do the pistons...... How would I figure what compression I'm putting out and wouldn't 10-1 or 10.5-1 be good also on 91 pump gas if the kb even bump me up to that..

I can always add a stall later so my Q is are pistons a nice upgrade.... And which carb should I get the street avenger 670 or a dp holley 650
 
Those 302 heads will up your compression ratio a bit. Like Stroker said you better do the math. If it won't run on pump premium you won't be happy.

I think I'd go for the stall, that will help you get off the line faster. If you do, get a good one, I have done a lot of studying on the converters and a good quality converter built to your combo is the way to go.
 
There's a company called cope racing that would build one to your combo for about 320$ shipped
 
Do your homework. If you elect to do the converter make sure to install a trans cooler and temp gauge.
 
Temp gauge for engine or trans?

What do Aftermarket pistons do really? Do the just bump up my cr
 
If you're just going for some street performance I would not spend money on a new manifold or carb as both are adequate for a 318. Here is where you can figure you CR http://kb-silvolite.com/calc.php?action=comp
The stock pistons are probably dished so the KB 167 would help bring the CR up. Save the money on the carb and manifold and you can have pistons and a 2k-2.5K converter
 
1 fst Dart said:
If you're just going for some street performance I would not spend money on a new manifold or carb as both are adequate for a 318. Here is where you can figure you CR http://kb-silvolite.com/calc.php?action=comp
The stock pistons are probably dished so the KB 167 would help bring the CR up. Save the money on the carb and manifold and you can have pistons and a 2k-2.5K converter
Click to expand...


im upping my intake for more and better flow because of the heads im doing plus the bigger vavles in the heads and i also need a bigger carb like the ones mentioned above
 
I think the 302 heads and those pistons would make it pretty high compression. my personal choice would be the converter. gas is not getting cheaper.
 
Ok thanks for the help now how about the carb any thoughts probably new or if I can find a good one on cl
 
Converter, no question about it. Reason is, as mentioned the heads will bump up the compression already so if you add high compression pistons to the mix you'll have an engine that may want race fuel. Even if you bump up the compression from 9 to 1 to 10.5 to 1 your not going to see a huge improvement. Plus as was also mentioned you just can't slap a set of pistons in there. I didn't check the weights but my guess is the KB's weight is quite a bit different than your stock pistons so the whole assy. will need taken to a shop and balanced. Another reason I'd go with the converter is that is a pretty hefty cam for a 318, no matter what anybody says. It needs more than factory stall or it'll be a slug out of the hole, even with the gears you have. Personally I'd use a smaller cam than that unless the heads have been worked over a lot. JMHO

The air-gap is a great intake but the ports are way bigger than the intake ports on 302 heads so they'll need a lot of porting to match them. I'm not sure you'll gain much using an Air-gap. I'd use a 600 carb on a teen. I have a 360 built up considerable over what your wanting to do with your teen and a 670 Avenger ran just as good as anything else I tried (750 Holley, 770 Holley, 850 Holley) on it.
 
I'd go with the converter, I've had a number of converters in my car and for your setup a worked set of the closed chamber 302 heads will do well with a stock piston. If your adding fresh heads you may want to use a cheapo hone and re-ring the motor, having a new good seal up top will make the rings feel old QUICK lol and nobody likes a smokey motor, just tires. I vote converter and maybe like a 700cfm carb.
 
Gears before convertor.imo

KYB Pistons weigh less and will lighten the rotating assembly, but will require a re balance.

The pistons will also give you more compression compared to stock=torque/hp improvement.

the closed chambered heads will allow higher compression, like up to around 185-195 cranking and live on 91 octane no issue, it's when you get over 175 cranking with 'open chambered' heads that u will run into issues.

you could


Consider what room you have 'cylinder pressure wise' for a cam up grade before actually doing so.

The 302 heads are an actually 64cc chamber, the open '675 318 heads are 68cc, not a huge diff comp wise.....and stock 318 w/ 302 heads might raise the cranking 'for instance' a whole 5 psi to 'maybe' 10 psi, it's only 4 cc's diff.

jmo
 
Already have 3.91 gears and I'm not changing them

So my 302 heads are closed 64 cc heads ?
 
One thing, inspect those heads carefully before you install them, they can be prone to cracking between the valves. Just a heads up.

I think your money would be better spent on a converter. I desperately need one too, and will get one as finances allow, probably a winter project.

I would call and talk to Kenny at PTC, he is a Mopar guy and they will build one to fit your combo.

Carb, Thermoquad. I love mine. Getting ready to rebuild another from a 72 340 to try out.
 
Badsport said:
Carb, Thermoquad. I love mine. Getting ready to rebuild another from a 72 340 to try out.
Click to expand...

I knew I would get you hooked. That first one is always a learnin curve but then it's downhill from there.
 
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