318 Port match heads to Performer RPM Intake

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C2ndLTpigeon

C2ndLTpigeon

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So I'm at the point where I need to gasket match my cylinder heads on the 318.
It looks like alot and I would like to just taper the ports on the heads. Can this be done without issues? I know many will suggest 360 heads and as much as they would be better I'm not sure if they would affect the whiplash cam I've already purchased since it relies on stock low compression. If the heads will not affect compression I might search for a set so if someone knows please let me know.

My build is Stock lower end with windage tray, Cam is a huges Whiplash 318 cam with matching springs and lifters. Intake manifold is a Edelbrock Performer RPM Airgap, topped with a edelbrock 600 CFM carb. Distributor is a Pertronix gen III ignition timing matched to my Whiplash cam. Headers are a set of hookers 3in reduced to 2 1/2.

Seems my week point is the heads, like I said if I can taper port match them to the manifold I will stick with that, if someone knows what other heads will work and keep compression low so that it works correctly with my cam kit im open ears.

Yes I know this is a 318 build and I am not looking for tons of HP, I am not looking for a 10 Sec 1/4 car. I just want something that will sound good, fun to build (unlike my other 4 cyl cars) and gets up a little better than stock.

Thanks!

Intake manifold Ports
103605226_2431559820467620_5684475464552342031_n.jpg

Head Ports obviously smaller
104204520_737013943701085_4029432587457408116_n.jpg
104423065_821077795089702_8153263444467374944_n.jpg
 
I wouldn’t worry about it. U may be better off with an intake with smaller ports such as a regular performer. 360 heads will lower ur compression about 1 point. I’m sure someone will start talking about reversion. Nothing of significance in ur build. Kim
 
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The reg performer would of worked better but I went with the air gap to get rid of heat cross over, not to mention the performer has a slot for the choke heat riser, way to many ports that need block off plugs, and if I ever do change to a 360 down the line I can reuse this manifold instead of buying another. Since I already purchased it would like to port it to match the best I can even if its just a slight taper if this is possible.
 
A long time ago....in a galaxy far far away.....I port matched a set of 302's to sorta match up to a performer RPM intake (not pretty). Basically all I did was round off the edges a bit on the port so the air was not slamming into a wall as it entered the head....again, it was not ideal, but it ran OK for what it was. As you can see from the picture, the parts you selected are severely mismatched...best choice would be get a performer intake (which is a 318 intake), or get 360 heads and keep the Air-gap.......but since you said that is not an option, you can also just bolt it up and run it. It should run about the same as anything else on a stock-ish rebuild such as this.
 
Don't sweat it. I've put 340/360 sized ports on 318 heads a ton of times. In fact, just did it about a month ago to my truck. Runs Perfect.
 
C2ndLTpigeon said:
So I'm at the point where I need to gasket match my cylinder heads on the 318.
It looks like alot and I would like to just taper the ports on the heads. Can this be done without issues? I know many will suggest 360 heads and as much as they would be better I'm not sure if they would affect the whiplash cam I've already purchased since it relies on stock low compression. If the heads will not affect compression I might search for a set so if someone knows please let me know.

My build is Stock lower end with windage tray, Cam is a huges Whiplash 318 cam with matching springs and lifters. Intake manifold is a Edelbrock Performer RPM Airgap, topped with a edelbrock 600 CFM carb. Distributor is a Pertronix gen III ignition timing matched to my Whiplash cam. Headers are a set of hookers 3in reduced to 2 1/2.

Seems my week point is the heads, like I said if I can taper port match them to the manifold I will stick with that, if someone knows what other heads will work and keep compression low so that it works correctly with my cam kit im open ears.

Yes I know this is a 318 build and I am not looking for tons of HP, I am not looking for a 10 Sec 1/4 car. I just want something that will sound good, fun to build (unlike my other 4 cyl cars) and gets up a little better than stock.

Thanks!

Intake manifold Ports
View attachment 1715547630
Head Ports obviously smaller
View attachment 1715547631 View attachment 1715547632[/QUOTE
Click to expand...


Port match if you want but you or your engine will never know if you don't.
 
Round the sharp edges back on the 318 heads and go.

Just port matched 302 heads to stock 318 manifold and 318 Felpro 1243 gaskets, there was a little to take out too. Would be interested to see how close a 318 gasket comes to your new intake ports for the fun of it ?

302s before port match
20200614_111858.jpg


After port match
20200614_194409.jpg
 
George Jets said:
Round the sharp edges back on the 318 heads and go.

Just port matched 302 heads to stock 318 manifold and 318 Felpro 1243 gaskets, there was a little to take out too. Would be interested to see how close a 318 gasket comes to your new intake ports for the fun of it ?

302s before port match
View attachment 1715547682

After port match
View attachment 1715547683
Click to expand...
Nicely done. It makes for a smoother transition but not a big increase in flow. It would be interesting to see a before and after on a flow bench.
 
toolmanmike said:
Nicely done. It makes for a smoother transition but not a big increase in flow. It would be interesting to see a before and after on a flow bench.
Click to expand...

Seems like smooth port flow is one of the secrets to the small port 318s, and big 2.5" exhaust system all the way to the back to help suck the hot gasses out.

Interesting how it works out even with stock exhaust manifolds.

IMG952019030995103236847.jpg
 
I've read that the only time it matter is when rpms exceed 6k ish and hp race applications.
 
Nice work. This type of port matching does little in cfm and power gains but what it helps in most is helping the air and fuel get into the head/cylinder without puddling which means a quality air and fuel charge rather than the fuel puddling and then dripping in.
 
toolmanmike said:
That's pretty! TTI?
Click to expand...

Yes TTI

That is Brian's '72 Duster, with a nicely port matched small port LD4B 318 intake on 302 closed chambered heads. 340 Cam, thin Mr Gasket head gaskets, 9.5 :1 Compression with a stock '69 block and pistons (9.2:1 pistons factory in 69).

For being built with Mopar Components, that one goes . .

I believe in the 318 port flow after riding along in that one, just smiling . . .
 
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If you really do some digging, there are examples out there where this type of mismatch....... where the intake is bigger than the heads........ and after being corrected........ has actually resulted in a loss of power(before and after test on the dyno).

And some of the mismatches are way more extreme than what you get with 318 heads and a 360 manifold.
Like...... oval port BBC heads with a rectangle port intake(about a 3/4” mismatch).......or a BB ford cobra jet intake on std port heads.

MP used to sell an iron 2bbl intake manifold for w2 heads.
It was nothing but a non-egr 360 manifold with relocated bolt holes.
The ports were still std 360....... which is a horrible mismatch with w2 heads.
The instructions stated to not bother trying to match the intake to the heads, as it would make no difference in power.

It “seems” like blending makes sense, but a lot of what goes on there isn’t intuitively clear.
 
Just dont create a pond in the middle of the stream 'so to speak' and you should be fine.

You obviously see the smaller 318 gasket is a hair smaller than the existing intake port windows...so that idea is out, if that's right.

Open it to the intake, make the heads port windows look like the intake 'manifold' port windows with the gasket in place. Theres the middle.lol
If you use the stock composite that comes in a stock kit... the intake port window on those gaskets are smaller than the HP felpro you have in the pic...

Imo... you are approaching this with the WRONG 360 intake gasket. You want the #MS9..something. cant remember. Hold on..
Fel-Pro Intake Manifold Gaskets MS90109

2.188x1.00 vs 2.27x 1.160
You can 'in the end' use the larger window gasket after port matching with the slightly smaller one.
 
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PRH said:
bigger than the heads........ and after being corrected has actually resulted in a loss of power.
Click to expand...

Absolutely.
The flow capacity of the stock 318 heads is a major mismatch to the manifold. Signal to the manifold will be very lazy in the bottom end, killing torque.
I would be sceptical even with ported 318 heads..
 
The factory even used the 360 intake on 318s in the mid to late 70s and early 80s. Even in a 2 bbl application on a 4x4 Ramcharger they used a 360 intake on a 318. Almost everytime someone upgrades to a 4 bbl on a 318 the mismatch isn’t even given any thought. Kim
 
Thanks for all the info guys, I will try to clean up the ports and open them a little see what it does. If I dont like it I can always swap them out.

Are these 302 318 heads hard to find that I keep hearing about? Obviously there better than the ones I have.
 
oldkimmer said:
The factory even used the 360 intake on 318s in the mid to late 70s and early 80s. Even in a 2 bbl application on a 4x4 Ramcharger they used a 360 intake on a 318. Almost everytime someone upgrades to a 4 bbl on a 318 the mismatch isn’t even given any thought. Kim
Click to expand...

Yes, you're right about that... not that I was a fan.
My Dad bought an '87 Fifth Avenue, back when, and you could outrun that thing on foot across an intersection.
 
x2 what kim just said
302 heads at your local pick a part
all late 318s had them
better cores to start with than earlier heads
 
The air gap manifold seems to be a mismatch to the rest of the combination. That’s a higher rpm manifold on an engine that Likes low end torque.

the air gap seems to be more of a manifold for high compression, higher duration cams, 360 heads, and makes power more at the top end. You can’t really have this well without over 9:1 compression at least

A performer manifold if fine but I would like to see the ld4b or it’s copy cat weind action plus. The performer seems to be like a stock 4 barrel

In my research of building the 318 and my current build I find that
Whiplash or xe262 or similar with low compression
4 barrel
Dual 2.5 exhaust
Ported heads matched to intake
Action plus or ld4b

that’s close to the best combination a low compression motor can get

also the thin head gaskets and .030-.040 taken off the head.

I’ve wondered lately if the stock 68 318 heads are as good as the 302 Heart shoes heads for low compression engines
 
What is the rpm range of your cam? Those heads look to be open chambered so why not just get some 360 heads?
 
LOL... just did a air gap swap on my 318 2bbl..... :)

And here's the results...
 
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