Manifold Port Matching Question

[D52E]

I posted this on the 510realm but no answers yet...

 

Does anyone know if a Cannon side draft manifold can be ported to 1.5"? I am concerned that too much material will be removed if I try to open it up and port match it with the head. Can it result in manifold breakage due to thinning the runners too much? Should i look for an alternative brand manifold?

 

 

Additional info:

L20B Engine

Datsun W53 Head

Head machined about 0.040"

Cannon Manifold

Weber DCOE 45's with 36mm Chokes

Cam is about 0.471" lift I think (don't know duration)

 

Manifold/Carb setup:

 

Manifold Ports:

 

Head Ports:

[datzenmike]

 

Looks a little thin on the right side. Hold the gasket up to it and align the bolt holes. Sure looks like the sand shifted during casting.

 

 

 

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[datsunfish]

Yeah,check the gasket,that one side might be on the far side of th gasket port. if it is you can certainly open the rest to match. Either way if the head ports are bigger it wont make much difference. Never seen a mani that was perfect. They never go in and correct small flaws.

[Skib]

 

Looks a little thin on the right side. Hold the gasket up to it and align the bolt holes. Sure looks like the sand shifted during casting.

 

 

ditto.

 

even if you cant get it exactly the air is flowing down the "step" and not up it so its totally fine.

[D52E]

Here is a picture of the manifold with the gasket:

 

The head and gasket:

[Skib]

use the gasket as your template.

[RoadRace]

going by your measurements, you have .071" of material to remove if you were expanding the port from the center out, equally.

 

this is where you have take 2 things into consideration:

1) am i willing to match and pin the gasket, head and intake manifold to achieve true gasket alignment, and is it worth it $, time for results.

 

2) do i know enough about flow charachteristics to attempt offset porting the 1 suspect runner, and matching the cylinder head and gasket to that as alternative to the above method?

 

gaskets will move, when there is a small amount of material holding them down, they move more. thats why you pin the gasket/head/intake manifold to ensure 100% accurate alignment and consistent results.

 

now, in the big picture, are you even going to notice the port matching after all that work? probably not on a street car that does not live its life searching for that last 1/10th of second per lap. in fact, the reversion effect that will occur in your ports will probably even help your low end power curve as the air will slow slightly in the middle of the port while still bringing in more air/fuel at the front, helping the torque curve. - top end results will differ, but you wouldn't notice it unless you spent alot of time there.

[hang_510]

I posted this on the 510realm but no answers yet...

same answer, ill measure tonight to confirm.

[79D50]

I ran into the same problem with my 2.6 build. RoadRace is correct in his statements. There will not be a noticeable difference in performance removing .050" + of material to match up the gaskets and port openings. In your particular case I would be wary of removing too much material on the outer runner. You could develope weak spots and leaks over time. I would also however be wary of the gasket being misaligned to the degree thats shown in your pic. Yes, you can apply a very liberal, thin coat of RTV to compenstae but that looks to be a bit extreme.

 

During my build I was fortunate to discover the misalignment at my machinist while I was port matching the header and intake. We took more material out of the head and the intake to compensate and only ended up .10" off. I had to modify my gasket a little bit but nothing a steady hand and a very sharp exacto knife cannot solve.

 

Looking at your pic of the intake it seems that the quality of the casting mold might have been crap. It there a variance on the other side as well? It just doesn't look right. Nice setup though man!!

[banzai510(hainz)]

You might want to use 1/4 inch pipe plugs to seal up those hot water ports so you dont have to worry about water leaks.

 

Thats a a 471lift Cam (regrind) might need .200 lash pads or so.

They really had to cut the back side lobe to get .471

 

I would have got new core Isky or a webcamshft. best to have bigger lobe centers