First engine build question

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The difference between 9:1 and 9.5:1 is 5-10 hp not enough to worry over.
 
273 said:
The difference between 9:1 and 9.5:1 is 5-10 hp not enough to worry over.
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LOL! On a good day but true enough that’s for sure. You only need the compression to keep the cam and engine in the efficient way of the dynamic workings. Since the bigger the cam is the more pressure it bleeds off this the need to raise the static ratio.
 
MOPAROFFICIAL said:
Just make sure the dynamic isnt lower than 8.1 and not higher than 8.4.

Static compression can be 10. Or 9.5, just get a good dynamic=cranking psi.
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This right here is the answer all of us 318 guys have been asking !! Lol thanks MO!
You are referring to pump gas correct?
 
According to my calculations with a 10:1 scr and your cam xe268h, engine bored .030 over. The DRC will be 8.21 so according to mopar officials info your right on the money.
 
273 said:
The difference between 9:1 and 9.5:1 is 5-10 hp not enough to worry over.
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It is not in the peak HP which is all that number means; I sure wish folks would get away from that stupid HP vs CR Wallace calculator (which is not accurate anyway). It is totally misleading as to the outcome of SCR/DCR changes.

The operating difference for DCR shows up in the low RPM torque. Anyone with hot rod sense will indeed feel a difference of .25 point of DCR in everyday driving, in terms of throttle response. 0.5 point will be noticeably quicker taking off. A full point of DCR makes the engine a very different animal.

So, for a street engine, CR IS quite worth worrying over, as well as forsome racing disciplines. Drag racers just work around it with high stall torque converters, etc., but that is not what works well for a road race car or rally car, where the wider torque band, extended down to the lower RPM's, is very much needed.... or for some street usage if you don't want to rev to 2500+ RPM just to move away from a stop sign. (Though some people may like that LOL)
 
wow, this is being made WAY more difficult than it needs to be, than it has to be, than it should be. It takes pages to discuss DCR/static, what's correct, altitude, longitude, full moon, on a Septober night! LOL.
 
318willrun said:
wow, this is being made WAY more difficult than it needs to be, than it has to be, than it should be. It takes pages to discuss DCR/static, what's correct, altitude, longitude, full moon, on a Septober night! LOL.
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IKR? All the forum geniuses have to come out to show how smart they are. Just measure what you have, and put it together. It will be fine.
 
A RRR said, just put it together, and if it ends up being fussy on pump gas, run the premium, pull about 5* or so out of ignition timing, and if it ends up in the dump for compression, grab the timing by the leash and yank it up over 40* full advance. I've ran a lot of "no compression" engines around 44*, I couldn't care less because if it has flow she'll run like a rabbit with the dogs on the trail.
 
I'm still learning so I appreciate all these drown out threads. I want to understand the whole process. I know alot of you guys have been there done that a million times it it's annoying to answer the same questions over and over but for the guys like me who havent build 100 engines and don't know we are still learning and need answers to the little question. There are 2 types of car ppl.
1) the ones that drop there engines and cars off at a shop and let someone else do the work
2)the diy that does all that he can himself
I fall into 2 I'm trying to learn all I can I know alot of the learning process is trial and error. But with all the wealth of knowledge here alot of error can be avoided.
 
dartfreak75 said:
I'm still learning so I appreciate all these drown out threads. I want to understand the whole process. I know alot of you guys have been there done that a million times it it's annoying to answer the same questions over and over but for the guys like me who havent build 100 engines and don't know we are still learning and need answers to the little question. There are 2 types of car ppl.
1) the ones that drop there engines and cars off at a shop and let someone else do the work
2)the diy that does all that he can himself
I fall into 2 I'm trying to learn all I can I know alot of the learning process is trial and error. But with all the wealth of knowledge here alot of error can be avoided.
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I get what your saying and understand. My point is, the "experts" will conflict/contradict each other on something that really isn't a deal breaker at all for the OP's build. Tell me, do you feel "more wiser" when somebody says "static of no more than 8.1" and the next says "naw, I run 8.8 all the time and no issues". You can read this and you know which one is right? Look, the OP wants to throw some freshened 360 heads on a 318 with a mild cam, 4bbl, and some street pistons. Put it together, and if she's a little fussy on todays gas (i'm betting not), pull a few degrees of timing out. If she is doing great, pull the timing up till it's happy! this isn't that difficult. When some of the "experts" get done, it don't seem safe to build an engine. You think Chrysler cc'd every head, measured every piston in the hole and every deck height? I'm not saying these things aren't good, i'm saying don't spend 1189 dollars and 27 cents to go from a 7.9 to ones "opinion" of a desired 8.2... LOL.
 
318willrun said:
I get what your saying and understand. My point is, the "experts" will conflict/contradict each other on something that really isn't a deal breaker at all for the OP's build. Tell me, do you feel "more wiser" when somebody says "static of no more than 8.1" and the next says "naw, I run 8.8 all the time and no issues". You can read this and you know which one is right? Look, the OP wants to throw some freshened 360 heads on a 318 with a mild cam, 4bbl, and some street pistons. Put it together, and if she's a little fussy on todays gas (i'm betting not), pull a few degrees of timing out. If she is doing great, pull the timing up till it's happy! this isn't that difficult. When some of the "experts" get done, it don't seem safe to build an engine. You think Chrysler cc'd every head, measured every piston in the hole and every deck height? I'm not saying these things aren't good, i'm saying don't spend 1189 dollars and 27 cents to go from a 7.9 to ones "opinion" of a desired 8.2... LOL.
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Oh absolutely I get what you are saying. I get confused alot on here by the different opinions. One guy says this another says that. And honestly I dont know any difference between the two. Haha
 
I would NOT deck the block or mill the heads . this causes sooo many fitment issues with intakes , pushrods and rockers . I suggest messing around with different head gasket thicknesses . this is a much easier way to achieve your goals than milling a bunch of cast iron . I also suggest very strongly to have the entire rotating assembly precision balanced . The expense of balancing pays of in smooth operation and engine life downthe road .
 
nm9stheham said:
It is not in the peak HP which is all that number means; I sure wish folks would get away from that stupid HP vs CR Wallace calculator (which is not accurate anyway). It is totally misleading as to the outcome of SCR/DCR changes.

The operating difference for DCR shows up in the low RPM torque. Anyone with hot rod sense will indeed feel a difference of .25 point of DCR in everyday driving, in terms of throttle response. 0.5 point will be noticeably quicker taking off. A full point of DCR makes the engine a very different animal.

So, for a street engine, CR IS quite worth worrying over, as well as forsome racing disciplines. Drag racers just work around it with high stall torque converters, etc., but that is not what works well for a road race car or rally car, where the wider torque band, extended down to the lower RPM's, is very much needed.... or for some street usage if you don't want to rev to 2500+ RPM just to move away from a stop sign. (Though some people may like that LOL)
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My point is most just want hassle free performance. They just want car they can just put gas in cruise and burn some rubber.
Their better off being on the low side of acceptable CR. Especially when the gains of a .5:1 is relatively small. His build is gonna be about twice the stock 318 hp Im sure he'll be happy with 9:1 performance.
 
RustyRatRod said:
I understand. Be careful is the number 1 rule. "I" would not go much past 7.5 DCR.
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Where does one learn such rule?

Nothing less than, perhaps.
@ 8.88889 seems to be the max near sea level with some quench. He has none "to my knowledge" so anything under 8.1 would be absolutely safe, basing that on my repeated experience.
My .030 kb hyoer 340 ran 160psi @9.5 compression 69cc heads pistons and around .020 out of the hole. Valve closed iirr 58*

In other words 130-140 PSI is kind of like stock territory... we need to be 150 or better if we're really trying to build any kind of performance or even stock performance motor.

There are engines out there that dont fit the above, but we'll stick to this 340 for now.
 
MOPAROFFICIAL said:
Where does one learn such rule?

Nothing less than, perhaps.
@ 8.88889 seems to be the max near sea level with some quench. He has none "to my knowledge" so anything under 8.1 would be absolutely safe, basing that on my repeated experience.
My .030 kb hyoer 340 ran 160psi @9.5 compression 69cc heads pistons and around .020 out of the hole. Valve closed iirr 58*

In other words 130-140 PSI is kind of like stock territory... we need to be 150 or better if we're really trying to build any kind of performance or even stock performance motor.

There are engines out there that dont fit the above, but we'll stick to this 340 for now.
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Why 150 or better? You can take a stone stock engine and add bolt ons and add a good bit, you know that. Good intake, carburetor, headers and distributor you can adjust mechanical advance on. Come on man, he's not building something to go racing here. He may not have the budget to do what you're talkin about. I haven't read every post, so maybe he does, but I try to approach it like someone is on a budget until they say otherwise.

I completely do agree with you though that if his budget allows he should get cylinder pressure up there. Does he have to? Not in my opinion.

And where did I learn that rule? Trial and error doin stupid **** as a kid.
 
RustyRatRod said:
Why 150 or better? You can take a stone stock engine and add bolt ons and add a good bit, you know that. Good intake, carburetor, headers and distributor you can adjust mechanical advance on. Come on man, he's not building something to go racing here. He may not have the budget to do what you're talkin about. I haven't read every post, so maybe he does, but I try to approach it like someone is on a budget until they say otherwise.

I completely do agree with you though that if his budget allows he should get cylinder pressure up there. Does he have to? Not in my opinion.

And where did I learn that rule? Trial and error doin stupid **** as a kid.
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If it were me....That's all each of us can say "depending on the perspective"...either of us are right.
For all he knows.. the heads are already 68-69cc and it cranks 160 after its together.lol

Short stroke engines can really use the extra snap. Stock is around 145psi. Not terrible, but not what I'd call high performance.
Happy Thanksgiving btw
 
MOPAROFFICIAL said:
If it were me....That's all each of us can say "depending on the perspective"...either of us are right.

Short stroke engines can really use the extra snap. Stock is around 145psi. Not terrible, but not what I'd call high performance.
Happy Thanksgiving btw
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Right back at ya! Hope you feasted good!
 
For the OP, if he is still here, just be advised that using the KB167 pistons will typically require a re-balance of the crank to match the lighter piston weights. There looks to be a trick to avoid this with your earlier crank and rods; let me know if interested.
 
nm9stheham said:
For the OP, if he is still here, just be advised that using the KB167 pistons will typically require a re-balance of the crank to match the lighter piston weights. There looks to be a trick to avoid this with your earlier crank and rods; let me know if interested.
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Yeah bottom end balance is something I plan to have done on this engine, and all this is definitely a lot but I read it all and I’m just tryna learn what I can.
 
Good for you to have that planned already! The good news is that you are going to lighter overall weights, and so the balance shop will take off the crankshaft weight by drilling into the end counterweights. They won't have add weight to the counterweights by drilling and installing heavy metal; that process would be more expensive.

And, your early 318 should have floating piston pins (retained in place by wire clips) and bushed connecting rods already. So that is a plus for you.
 
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