Mild budget build on an original 318

[907mopar]

Hey guys, this is my first post on the forum.

I'm looking for some advice on adding a little pep to my wife car. It's a 74 barracuda with a 318 and an automatic. She has had the car since she was 18 she bought it from her grandpa with 60,000 miles on the clock. Now it sits at 67,000 the motor runs good, but has a terrible bog down low. Her grandpa had some do some work to it and for some reason they threw on a Mopar Performance high rise single plane intake manifold and a holley 750 cfm carb. This combo kinda leaves me scratching my head for an otherwise stock top end??? either way it is a complete DOG down low!

Ok so my question to you is, she wants a mild build and kinda likes the low miles 318. Ive been told to put 360 heads on it but it already has low compression so they would need to be milled. Just wondering if i would be better off porting the 318 heads myself and going with an edlebrock performer intake and 600cfm carb and headers, possibly a small cam???

Thanks in advance everyone!

 

[Steve340]

If the motor runs good why not just do the manifold, carb and headers.
Easier just to bolt on a few parts.

 

[907mopar]

I thought the heads were the big choke point with there small ports? Just figured if I was gunna do the intake manifold exhaust and carb might as well bolt on heads or port these to take advantage of the better flowing manifold. Unless it won’t make that big of difference???

 

[Rob C]

To keep it simple with decent results;

Upgrade the ignition.
Dual plane intake
Carb of choice
Basic headers into a 2-1/2 exhaust
Cam that works with the stock stall converter and gear ratio. I’d recommend a cam, but you tell me the gear ratio first.
Don’t worry about the heads.

 

[Steve340]

a 318 is never going to be a tyre fryer so if it is a driver keep it simple.
Plenty of crate engines out there if you want power and have the budget.

 

[Rob C]

a 318 is never going to be a tyre fryer so if it is a driver keep it simple.
Plenty of crate engines out there if you want power and have the budget.

Totally disagree in a huge way. That quote above comes from (IMO) someone who never built one up in anyway. But I do agree that a bigger engine is better to do for good power.
I love ( sarcasm!!! ) the way he spends your money in trashing the engine and making mention that you should throw away a perfectly good engine in favor of spending THOUSANDS on a different engine when your request was “Help the 318.”

While his suggestion makes sense on most levels, it didn’t really help or answer your question now did it?

Enhancing the 318 with basic bolt on parts can produce good results from the cubically challenged. A nice driver is obtainable and a mild hit rod can be produced without braking the bank or swapping cylinder heads.

The ‘74-318 has a low compression problem. Swapping to a 360 head hurts it. Even though the additional air flow helps it. It is a catch 22. But yes, it will gain in power. Air flow over compression every time. It is always a winner.

IF you decide to put 360 heads on top, have them milled for a reasonable compression ratio. (9.0-1is just fine)

The Performer and 750 are good to go. (I’d use a smaller carb myself, 600-650cfm, but you use what you have, right?)
I don’t know if summit racing still has the header exhaust kit for the car, it it is worth checking out to couple it with the standard 1 size fits all headers.
(But I suggest not getting the 1 size fits all header and use Hooker Super Comp headers that fit freakin GREAT! And cobble your own pipes to fit the Summit racing exhaust set up.)

If you have extra coin to spend, I would suggest the entire exhaust system from tti. Headers and exhaust.
There system fit my wife’s A body Cuda really really well.

What is the gear ratio in the car now?

 

[Steve340]

Dear 907mopar.
I apologise if my comments caused any offence that was not my intention.
Steve

 

[70Hardtop]

I agree fully with RF360 about the 318 work and also his comments on the previous poster. The 318 was never a performance motor in the sense of the 340 and was not even as good an engine as the venerable high revving 273, however it is still a Chrysler LA engine with many of the great and bullet proof design features and still better than a SB Chev right? And any LA engine responds very well to any help in the breathing / flow department. First thing is to get rid of the single plane (sell or swap etc) and use a good dual plane. The Performer is a good manifold but there are now some other great dual plane designs being offered that also allow the engine to rev easier up higher as well as give the torque down low (Eg Weiand). If you are talking about "porting heads yourself" that means you are confident with a die grinder and if so, then it would be a good idea to port match the intake manifold to the heads. It's not that much extra work really and the 318 really responds to the improved flow. I don't think a new ignition system will dramatically improve things if the current one is in good order, (although an Orange ECU would be a good cheap addition) however if you were spending money on getting the existing distributor recurved and rebuilt then that money might be better spend on a new and better dizzy and new better spark leads (called ignition wires in the USA). Also, along with the dual plane, a set of headers will really improve flow, as the 318 in stock form with stock exhaust system is a bit choked and under-exhausted. As RF360 mentioned, a complete new twin system 2 1/2". with TTi headers would be a great improvement.

After these easy things, if you wanted to go further, the next thing to look at would be increasing compression and doing head work. Then comes the new torque converter (a "more-stall", or modified stock converter works great) and diff ratio. If it is a 74 Ebody it should have a 742 8.75 axle and depending on what ratio her father may have chosen, it would have either a 2.76, 2.93 or 3.23. If it is a 3.23 you are in luck as this is a really desirable 'all round' street ratio. If it is a 2.76 (often chosen to improve cruise economy), then this will not help low down torque or driveability and a higher ratio would be recommended.

 

[aussiemark]

I rebuilt a tired 318 (original engine) in a 68 Charger and it ran great. I reconditioned the std heads with larger exh valves, rebuilt the original carb, used the std manifolds, polished the crank and installed .001"bearings and used a 340 auto trans camshaft. It ran and sounded sweet (even with a single exhaust) you could put a glass of water on the air cleaner when running and not spill any and it had great acceleration for such a heavy car. The guy who I sold it to loved it and even wanted me to do the engine in one of his other cars.

 

[907mopar]

Thanks for all the info guys I appreciate it.

I am fully aware of the 318’s limitations but I am going to go ahead and throw some bolt ons at it and see if it will pick up some pep. I might get be getting my hands on some spare 318 heads to try my hand at porting. Other than that I am trading some diesel parts for an offenhauser intake manifold. It’s a dual plane so it should do better than the single plane. Also getting headers( not tti unfortunately) exhaust and a new 600cfm carb. We’ll see what that does. Also no idea on the gearing but I’ll check.

Thanks again

 

[907mopar]

What are your opinions on the offenhauser dual port manifold?

Seems like it gets mixed reviews.

 

[Rob C]

I would t touch it.

Mild builds = OE 4bbl., M1 dual plane, Performer or Action plus.

Muscular build = RPM, 6 pack or M1 single plane.

Older intakes are fine as well like the LD-340, Port-O-sonic, Strip Dominator

 

[aussiemark]

The 318 has smaller ports then the larger engines if you put a manifold off a 340 on it there will be a step where the manifold and cylinder head ports meet this will disturb the airflow. It is ok to put a manifold with small ports on an engine with large port heads but not the other way around. Check the Offenhauser manifold ports using a 318 gasket and see if it will be ok, if not you will have to open up the cylinder head ports to suit but it would be easier to get the correct manifold There is nothing wrong with using it if the ports match up it is aluminium so it saves weight, it is dual plane so it will give you good response and four barrel for power just don't go too big with the carb. I know edelbrock make a performer manifold for the 273/318 and another for the 340/360. Even if you install an original cast iron 2 barrel manifold and carb it will go better then the single plane/750 combo that set up will make it sound good but kill all the low down power.

 

[Rob C]

The 318 has smaller ports then the larger engines if you put a manifold off a 340 on it there will be a step where the manifold and cylinder head ports meet this will disturb the airflow. It is ok to put a manifold with small ports on an engine with large port heads but not the other way around.

While this is mostly true it is also dependent of what your doing and how far your going with the modifications with speed as the goal.
Installing a larger window/port intake on a smaller head does disturb air flow but it is not a big HP killer when your not making a lot.
It can be argued to death but the proof is in the pudding. It will still work, operate and creat more power.

Best intakes for the 318 are the smaller port window sizes.
Edelbrock Performer, LD4B, Action Plus, etc...

I know edelbrock make a performer manifold for the 273/318 and another for the 340/360.

Not any more. Once the Performer came out, it replaced the earlier intakes. (LD-340 & the LD4B)

Currently, Edelbrock offers the Performer for any size small block and the RPM series for more muscular builds with the recommendation of a bigger head for maximum results.

There is no Performer for the 273/318 & then another Performer for the 340/360. Nor is there a (Edelbrock) specific intake manifold for the 340/360 only.

The port sizes of these and past intakes do not always meet the supposed sizes of the engine because they constantly change year to year and aren’t even consistent from the factory.

Pick up a Victor and note that the ports are close to a 318 size than a 360 size. This intake was made for porting.

 

[73Barracuda]

Totally disagree in a huge way. That quote above comes from (IMO) someone who never built one up in anyway. But I do agree that a bigger engine is better to do for good power.
I love ( sarcasm!!! ) the way he spends your money in trashing the engine and making mention that you should throw away a perfectly good engine in favor of spending THOUSANDS on a different engine when your request was “Help the 318.”

While his suggestion makes sense on most levels, it didn’t really help or answer your question now did it?

Enhancing the 318 with basic bolt on parts can produce good results from the cubically challenged. A nice driver is obtainable and a mild hit rod can be produced without braking the bank or swapping cylinder heads.

The ‘74-318 has a low compression problem. Swapping to a 360 head hurts it. Even though the additional air flow helps it. It is a catch 22. But yes, it will gain in power. Air flow over compression every time. It is always a winner.

IF you decide to put 360 heads on top, have them milled for a reasonable compression ratio. (9.0-1is just fine)

The Performer and 750 are good to go. (I’d use a smaller carb myself, 600-650cfm, but you use what you have, right?)
I don’t know if summit racing still has the header exhaust kit for the car, it it is worth checking out to couple it with the standard 1 size fits all headers.
(But I suggest not getting the 1 size fits all header and use Hooker Super Comp headers that fit freakin GREAT! And cobble your own pipes to fit the Summit racing exhaust set up.)

If you have extra coin to spend, I would suggest the entire exhaust system from tti. Headers and exhaust.
There system fit my wife’s A body Cuda really really well.

What is the gear ratio in the car now?

a 318 is never going to be a tyre fryer so if it is a driver keep it simple.
Plenty of crate engines out there if you want power and have the budget.

I agree with rumblefish, I’m building a moderate 318 now and have no doubt it’s gna Smoke tires. Modified 302 heads, aftermarket cam, Fitech, headers, and upgraded rear end gears. It’s got a EB650 ld340 now and it screams. All though I wouldn’t call heads the choke point of a 318, their early 70’s heads combined with below deck piston are not compression makers.... heads are. I agree that 360 heads can make compression but so can the late 80’s 302 stamped 318 head. Lol argument begins ... now....