318 (275 Hp)

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LJS30

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I know numerous threads have been created in regards to this topic. However I want a no nonsense assessment as to what it takes to build a 275 HP 318.
 
LJS30 said:
I know numerous threads have been created in regards to this topic. However I want a no nonsense assessment as to what it takes to build a 275 HP 318.
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4bbl, manifold and headers did it for me in 1969
 
What year 318?

If your starting with a 250 HP model, the above would do well with a minor bump in cam timing.

Take notes from this page. http://www.geocities.com/alwest_83/318 (Bottom right has the dyno test results. Read the whole section titled (DYNO TESTED 318.)
 
OK, I don't not have a book infront of my tired eyes and brain, what the listed Compresion ratio and advertised HP for that year engine?
 
rumblefish360 said:
OK, I don't not have a book infront of my tired eyes and brain, what the listed Compresion ratio and advertised HP for that year engine?
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If my memory serves me correct the compression ratio was 8:5:1 with the advertised HP being around 175.
 
A performer RPM 318 port size, and a cam change, with a set of good manifolds or cheap headers, and you will exceed that number, as long as the engine is in good shape now.
 
moper said:
A performer RPM 318 port size, and a cam change, with a set of good manifolds or cheap headers, and you will exceed that number, as long as the engine is in good shape now.
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Cool, very cool. The engine had a complete rebuild and only has about 10,000 miles or so on the rebuild. The heads were ported, an RV camshaft type grind was installed with a Thermoquad 650 on top. I kept the stock manifolds but did install a complete dual exhaust with Dynomax Super Turbo's and a crossover pipe. I ask this question because I simply want more power out of this motor.
 
Stick a better cam in, and if the intake is stock, you could do better with a small port intake. That one will have 340/360 ports. Also, Thermoquads only come in 800 and 850 cfm versions. But are great on a mild build. I'd go XE268 and stick an Edelbrock 650 on it for ease of tuning. Also, headers will make a big improvement over any 318 type manifolds in power and weight. The 340 type exh manifolds prior to '72 would also be good, but more $$. Lots more.
 
moper said:
Stick a better cam in, and if the intake is stock, you could do better with a small port intake. That one will have 340/360 ports. Also, Thermoquads only come in 800 and 850 cfm versions. But are great on a mild build. I'd go XE268 and stick an Edelbrock 650 on it for ease of tuning. Also, headers will make a big improvement over any 318 type manifolds in power and weight. The 340 type exh manifolds prior to '72 would also be good, but more $$. Lots more.
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So do I have too much carb for my motor right now? What headers are recommended especially in regards to clearance and durability?
 
You have enuff carb. Not to much. Even with the larger T-Q your fine. A possible re-jetting or rod change will fix up the primarys. Tighten up the air door spring to tune the secondarys timing of opening and a possible rejetting of the secondarys apon W.O.T.

Header wise, the best are the tti for fit finish and durabilty. I have a set of Hooker comp's in my Duster and I have no complaints. Very hard to get in though.
 
I will definately look into the suggestions you guys have given me. A bigger cam and carb tuning will be the first step. After that I will go with some headers very soon.
 
Finally, what Mopar Performance grind should I use for my cam upgrade? I was perusing their site last night looking through the grinds and saw alot of nice possibilities. However, I still want to run power brakes and have an idle.
 
As a good first step..look anywhere else besides Mopar Performance. Much better available now.
 
Oh yea, if nothing goes wrong I am looking at purchasing a Comp Cams XE268H for my 318!!!!!!!!!!! Come on good luck, please hold on!!!!!!!!!!! It seems like everytime I am close to making a purchase some BS happens in my life.
 
The Mopar grinds are 30 years old single pattern cams more ment for the track rather than the street.
Single pattern cams work well with heavy ported heads.
Split pattern cams help squeeze out a few RPM and HP. This is due to the extra exhaust duration. You can have to much exhaust duration. This is why there generally limited in the amount. Cranes have more exhaust duration and work ratherly well with stock or mildly preped heads.

I also agree with post #18. I know what you mean. The last year has been rotten for me. Last few months have been unbelieveably bad.
 
LJS30 said:
So Mopar doesn't make very good grinds?
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No, they have soem good grinds. The problem is they aren't made very well. They are older designs, but they work fine. But the last few I tried were between 10 and 8° off in the manufacturing process (centerlines of the lobes were off that far). I think if they cant get the basics right, the rest of the work and degree of accuracy can't be much better. "Low bidder" mindset gets lowest quality every time.
 
You say you want more power.. Is this because the car seems like it is slow??? You want more get up and go? You may just need to change your gear ratio.... Even with a really good build up on that 318 if you have some highway gears in there its going to be a dog!!! Gears are a cheap way to go fast!!! Just my $0.02....
 
SleeperScamp said:
You say you want more power.. Is this because the car seems like it is slow??? You want more get up and go? You may just need to change your gear ratio.... Even with a really good build up on that 318 if you have some highway gears in there its going to be a dog!!! Gears are a cheap way to go fast!!! Just my $0.02....
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Have to agree I had a 74 a body that my mom bought new and the gears were way too high. In my 89 m body I just switched from 2.3 to 2.9 and the 318 is a LOT faster ( not saying much but I only take it yarding and .. ) so thats my 2c.

Now if I were building the motor I would have put more compression in it. RV cam and ported heads and low compression also not a good combo. When the motor was built did they tell you what the static compression ratio is? B4 you buy any new parts check the compression for me.
 
Roberson_Tech said:
Have to agree I had a 74 a body that my mom bought new and the gears were way too high. In my 89 m body I just switched from 2.3 to 2.9 and the 318 is a LOT faster ( not saying much but I only take it yarding and .. ) so thats my 2c.

Now if I were building the motor I would have put more compression in it. RV cam and ported heads and low compression also not a good combo. When the motor was built did they tell you what the static compression ratio is? B4 you buy any new parts check the compression for me.
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As far as I know my compression was 8:5:1. As for gears I want this car to be a street machine so I can't go too crazy. However I believe I have 3.55's on right now.
 
moper said:
Thermoquads only come in 800 and 850 cfm versions.
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This would be correct for stock Thermoquads. Carter did build Thermquads for the aftermarket that were 1000cfm. I ran one in the early '80s on a Buick Stage 1.


Chuck
 
340mopar said:
This would be correct for stock Thermoquads. Carter did build Thermquads for the aftermarket that were 1000cfm. I ran one in the early '80s on a Buick Stage 1.


Chuck
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Yeah, the Comp9000 versions. I'd love to get my hands on a couple of them...lol. I havent seen a single one in almost 14 years.
 
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