One thing leads to another... mean 318?

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cawcislo

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I bought my duster last year with longer term plans to build a 408 for it. I was going to live with the 318 It came with (Not original to the car) but I didn’t know anything about the engine. So I dig in a bit check the timing chain, pretty sloppy. No worries, pull the heads to check them out, looks like some porting has been done to 360 open chamber heads with 1.95 intake valves. Cc’d the chambers 63 cc not too bad, they’ve been milled. Found out I have a Crower 224/224 cam, but one cam bearing looked a little suspect. Check pistons 0.106 in the hole means low compression about 7.8:1 pistons are 0.030 oversized. Well I’m in this far might as well go deeper.... pull engine, tear it down. Crank has had journals machined 0.010. Mains looked okay, rod bearings down to copper and a couple have some more significant scratches not sure if they will polish out or if it needs to be ground. Cylinders look alright but if I want more compression with kb167’s which travel higher up the cylinder we will need some machine work. So I took it to the machine shop today. We will see if 0.040 will work on the overbore of if I have to go more.
I’ll wait to see what they say about the cylinders and crank and pricing...I also have to consider the rods which have now been in and out a few times and reusing the rod bolts might not be a good idea if I plan on running the motor hard and this isn’t going to be A grocery getter. So with the time and or cost of pressing on and off the pistons, Buying and replacing rod bolts,, resizing I may be better off just buying Aftermarket rods such as eagle which cuts labour down, but adds to the amount of machining needed to bring crank back to balance as aftermarket rods are lighter then factory.
So what started off as a look see may have turned into a full rebuild... but I may be leaning towards building a mean 318... we will see.
 
Best to 408 it now rather than dump a boatload of cabbage into a teener unless it’s a 72 or earlier block.
 
The Chevy 327 is nine cubes bigger than the 318 and we all know how mean some of those were.
 
if you were going to go 408 then why not stroke the 318 to 390. the money you'd have put into rods, pistons and a crank' grind will get you a good way into the stroker kit with a new crank to boot not a regrind.
neil.
 
If you're planning on replacing the pistons you would want to have the rotating assembly balanced anyway. As far as the rods are concerned, take a look at the SCAT rods. There some of the nicest forged aftermarket rods on the market. IMO 65'
 
Yes I hear the 390 strokers run like a scalded dog!
 
I also have to consider the rods which have now been in and out a few times and reusing the rod bolts might not be a good idea if I plan on running the motor hard and this isn’t going to be A grocery getter. So with the time and or cost of pressing on and off the pistons, Buying and replacing rod bolts,, resizing I may be better off just buying Aftermarket rods such as eagle which cuts labour down, but adds to the amount of machining needed to bring crank back to balance as aftermarket rods are lighter then factory.
So what started off as a look see may have turned into a full rebuild... but I may be leaning towards building a mean 318... we will see.
That's the way it goes...... I tried to salvage an Opel 4 banger last fall.... nope, full rebuild with better parts.

SCAT rods and KB's will drop the bobweight a bit over 300 grams. From doing a similar thing, this is probably one hole drilled in each large end counterweight in the crank to get it to balance. The nice part of the SCAT rods (and probably Eagles) and the KB's is that everything is well weight matched, and you can get a pretty good balance with no mods to the parts. So all you do is weigh a few parts, work up the bobweight, balance the crank. Saves dough.

Now the 390 suggestion saves crank work. But looks like the only CR choices with the milled heads will leave you with low 9's or low 11's for Static CR. I can only see forged piston options. Not cheap. But then again you are almost to that 408.... same 4" stroke.
 
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sure grumpy's 331
but bottom line larger bore is free horsepower
see rumbles posts today or yesterday
 
A larger bore has a direct impact on power. It’s not a lot though. Save the cylinder boring to keep the cylinder sleeve thick and strong. Bore as needed.

Me? I’m a retard wasting money. I’d check it out and see if I can get to a 4.00 bore and go there. Then build it like a 340. Them kill 327’s and 350 and 383’s all day long.

OH! Put the car on a diet. Under 2900 (with you in it) is a good thing!
 
figure an .125 over bore equals the same amount of horsepower as an increase of 1"of stroke.
 
A larger bore has a direct impact on power. It’s not a lot though. Save the cylinder boring to keep the cylinder sleeve thick and strong. Bore as needed.

Me? I’m a retard wasting money. I’d check it out and see if I can get to a 4.00 bore and go there. Then build it like a 340. Them kill 327’s and 350 and 383’s all day long.

OH! Put the car on a diet. Under 2900 (with you in it) is a good thing!


All true. Any time you can make the bore bigger, you can run a bigger intake valve. A bigger intake valve means you can port for more air flow. More air flow means more horse power.

Obviously, it’s a deep, dark rabbit hole to travel down if you ain’t careful because you can only get the port as big as the casting allows. And you have to have port cross section to feed the bigger valves. And so it goes.

And then, we decide more RPM is more power (it always is IF you have the induction system to feed the RPM) so we slam big honking valve springs on the heads to get that awesome RPM, and the pushrods act like wet noodles in there. So you have to upgrade them to baseball bat sized pushrods. Then the cheaper, small diameter wheel lifters start to fail with RPM so we update those and now we are ready to make some steam. Except the oiling system is lacking and BOOM...out come the rods.

And so it goes. There is more than one rabbit hole. And most of them are deep. And dark. And dirty. Trying to find the bottom of them is $$$$$$.
 
Lots of work for a teen. have you looked into a Jasper or board sponsored reman 360? Cam it and go. IDK if a stroker 318 will run like a 'scalded dog' but it will pull like a pit bull. gotta watch your piston speed.....400 HP 360 Mags with carbs are not uncommon with just cams , intakes and headers. sounds like you already got those! (Maybe not the mag carb intake......)
 
If I was doing a big bore teen, I’d stay with a solid cam and see if a bigger than 3/8 pushrod will fit. Mildly worked Edelbrock heads would get the nod since I have a set sitting. Though a well done 340/360 would do really well also.

IF I could actually get to a 4.0 bore size, that would be a 332/333 IIRC. Even at a .060 over bore, it would be 327/328 cubes. I call that my minimum CID I want to play with just for the fun challenge of a small cube engine.
 
IF you can get a .125 overbore!!! Most OE blocks won’t even come close to that without hitting air.

its a comparison, Doc.
so for the way critical that tend to over think things, an .04 over bore equals the same amount of horsepower as an increase of .32 of stroke.
 
Lots of work for a teen. have you looked into a Jasper or board sponsored reman 360? Cam it and go. IDK if a stroker 318 will run like a 'scalded dog' but it will pull like a pit bull. gotta watch your piston speed.....400 HP 360 Mags with carbs are not uncommon with just cams , intakes and headers. sounds like you already got those! (Maybe not the mag carb intake......)

https://www.amazon.com/dp/1934709476/?tag=fabo03-20
https://www.amazon.com/dp/1557885540/?tag=fabo03-20

Check these oit. The first linked book has easy calculations for piston speed like kim mentioned.
Toss them in your bathroom magazine rack. Makes the time go by faster.
 
How did you come to this conclusion?


I was trying to point out not many OE blocks are even close to capable of a .125 overbore and ch’s panties caught fire. I just didn’t want someone to think .125 over was a viable option on almost anything.

BTW...I’m not sure where he got that number. You can calculate power increase from bore size if you know the cylinder pressure etc. I just don’t have that info in front of me, and I’ve never seen that particular math. Doesn’t mean it’s wrong. Just means I’ve never seen it.
 
I was trying to point out not many OE blocks are even close to capable of a .125 overbore and ch’s panties caught fire. I just didn’t want someone to think .125 over was a viable option on almost anything.

BTW...I’m not sure where he got that number. You can calculate power increase from bore size if you know the cylinder pressure etc. I just don’t have that info in front of me, and I’ve never seen that particular math. Doesn’t mean it’s wrong. Just means I’ve never seen it.

My question was directed @ch1ll though I do appreciate your reply. I certainly get the cylinder displacement issue as well as adding compression and figuring out timing events effects.
(Over rated or general street hot rodding but it does pay nice dividends when you do. AKA - AJ

Id like to know how or where ch1ll received that information and how the math works. It is an interesting though. How does one compare power between stroke and bore increases against each other?
 
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