Offenhuaser dual port intake and Holley 550 on 318

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74swingerlover

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As the title says..... I am thinking of throwing on a Offenhuaser dual port intake and a Holley 550 onto a 2 barrel 318 motor. Any pro or cons to doing this?

These are just some extras i have lying around. Not spending any money on the 318
 
the theory is a good one my experiences with them were on a 440 and the stock manifold made more power and mileage was even higher but i never tried to tune the carb when i put it on so there may something there too but on your 318 over a stock 2 barrel might be alright. the idea of the manifold is to keep air speed very high giving good throttle response and good economy at cruise or part throttle the same time giving you good 4 barrel hp ill just say this im not a fan of these manifolds but im with ya when you dont want to spend money and you have something laying around its like free beer you dont complain. id use it/at least try it... carb size sound fine
 
I know it sounds like alot of trouble, but without upgrading the camshaft it will not perform like you want it to. On a scale of 1 to 10 you may get a mushy 4. Remember longer duration and higher lift is what gives you better compression and power. New lifters and timing set will give you a worry free motor you will be much happier with.
 
. On a scale of 1 to 10 you may get a mushy 4. Remember longer duration and higher lift is what gives you better compression and power. New lifters and timing set will give you a worry free motor you will be much happier with.

i agree that the cam will help. good advice, but i disagree, long duration cams do not give better compression
 
I know it sounds like alot of trouble, but without upgrading the camshaft it will not perform like you want it to. On a scale of 1 to 10 you may get a mushy 4. Remember longer duration and higher lift is what gives you better compression and power. New lifters and timing set will give you a worry free motor you will be much happier with.


ok, but where does a 2 barrel 318 sit in that scale?
 
ok, but where does a 2 barrel 318 sit in that scale?
it will run better with a properly tuned 4 barrel carb,the 2 barrels are not as good at fuel metering.my 18 got 3 more miles per gallon and ran stronger,and that was an eddy 1406 from pick n pull $25.00 and stock 80s truck manifold.and i;m a holley kind of guy,but it was cheap lol
 
I totally disagree on the hate for Offenhauser intakes. I use one on my 318 along with a Edelbrock 600 carb. It does well on my engine and I wouldn't heistate to use another one. YMMV...

I am a Holley fan but have no experience with the Holley 550 at all.
 
i agree that the cam will help. good advice, but i disagree, long duration cams do not give better compression

This is the truth. To big of a cam can lower cylinder pressure but a larger cam can also be used to bleed off some compression with a higher compression engine. To big of a cam in a low compression engine *almost always equals
dissapointing bottom end performance. Overall combination and the cubic inches are the major factor here. For example, a 440 can handle quite a bit of cam due to it's cubic inches....
 
Yeah, I figured I would lose a bit of bottom end torque, but I live ibn the country and do most of my driving on the high way.

Not touching a cam at all for this engine. I am in the middle of a 408 build, that will take all my extra cash but that won't be done for a while. so just trying to get what I can for free since these are just sitting there
 
If you ever get tired of that Offy Dual Port, send me a pm please. If it's similar to the one on my 318's anyways. I don't think they made to many types of them really...
 
Not busting your balls are starting anything with you, but....


I totally disagree on the hate for Offenhauser intakes. I use one on my 318 along with a Edelbrock 600 carb. It does well on my engine and I wouldn't heistate to use another one. YMMV...

I am a Holley fan but have no experience with the Holley 550 at all.

I don't wanna fall into the "HATE" for the Offy intakes, but, the dual port intake never was "all that."


If you ever get tired of that Offy Dual Port, send me a pm please. If it's similar to the one on my 318's anyways. I don't think they made to many types of them really...

Do you have the dual port?


This is the truth. To big of a cam can lower cylinder pressure but a larger cam can also be used to bleed off some compression with a higher compression engine. To big of a cam in a low compression engine *almost always equals
dissapointing bottom end performance. Overall combination and the cubic inches are the major factor here. For example, a 440 can handle quite a bit of cam due to it's cubic inches....

On the cam topic, I agree, unless the cam is ground specific like for example, the Hugesengines cam(s) ground with low compresion engines in mind. Granted, there not a big cam, but the idea is there and that idea can also be applied to larger cams.

On cubic inchs, while your statement of the 440 handleing "quite a bit of cam due to it's cubic inches...." is only true to a point since the same could be said about the 273 vs 360.

It's not that the 440 can handle more cam, just a sizeable amount more vs the smaller engine. It's an unfare apples to apple comparo. The larger engine produces a sizeble amount of torque over the smaller engine and stroke has alot to do with it.

Change the perameters around while still keeping the displacement the same and you have a totally diferent engine in operating charicter (SP! OUCH! Sory cant think now)

Imagine a 440 CID engine with a stroke of only 3.30 vs the 3.75 or with a stroke of 4.5 inchs.

3.30, major top end screamer
3.75, what were all used to
4.5 major low end torque, like pulling houses down for breakfest.

The current engine of discussion is a 318. The short stroke and small-ish bore lacks torque. I beileve the Performer will out perform the Off dual port.


IMO, not that it means much in this world,
The Offy ha a limited window of operation. It could be useful to the OP. I, myself, would rather use a Edelbrock Performer for daily useage with the 550 carb.

The Offy could bring in enuff money or a possible trade for the Performer, in which that intake can be found on here for a realitivly good price and even under a $100.

On the scale mentioned before, I'd give the Performer and Holley combo a nice upgrade status of a 5 for power and if well tuned, a 8 for economy. Power possiblity without piston or head change(s) or mods, would rate a 10 for a economy/low level build.

I'm soory, I'd just simply give the Offy a "F."
 
In other words dont even bother with it. BTW I meant a higher lift and shorter duration cam, duh. ](*,)
 
ok, but where does a 2 barrel 318 sit in that scale?

The cam would be specd at the factory to the 2 bbl setup. Increasing the fuel supply would do little in the way of performance if the valvetrain is unable to keep up with the airflow thru the motor. I have seen 2bbl setups run better without any mockup, for both performance and economy. A rebuilt carb will surprise you and so will a little porting here and there.
 
Rumblefish360...

All points that you mentioned are well agreed upon for sure. I have an old as dirt Offy Dual Port on the 318 that is in my '71 Duster Twister and I am very pleased with it.
 
I had one of those Duel ports on my 360........Not sure i would have given it a (F).......well maybe.......It only lasted a couple mouths before i put the stock cast iron 4 barrel back on.
 
Well if I did go and put a cam in, I do have a cam also lying around...... .443 intake, .465 exhaust. I guess the question then is will the 318 heads be able to take that?
 
It's not the heads that are in question but the valve springs.
 
i agree with rumble
i put some 273 heads on a 318 once to pick up the compression the engine would start and die with in a few seconds, then when you cranked it the compression was down in all but a couple cylinders as i cranked it more cylinders would come back and it would try to start and crap out again. problem was the spring were too weak and the lifter would pump up. didn't have this problem on the 273 because it had solid lifters they don't pump up. this wont be your problem here but it reminded me of it so i put it down. i don't think the springs can handle the lift without coil bind that's were i think the problem will be but im not sure. also so they wont handle much rpm if they don't bind. just a guess though
 
I had one of those Duel ports on my 360........Not sure i would have given it a (F).......well maybe.......It only lasted a couple mouths before i put the stock cast iron 4 barrel back on.

I here you man I had a Edelbrock torker 340 on a 340 and had nothing but problems, changed back to a stock 340 cast intake and my life was so much better. Now I have a Edel. Performer on my new 360 and I'm back to the same ol same ol. I guess I should have learned the first time.
 

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