JMF manifolds/ smim larger plenums

[zilo900]

I still have a 2g motor right now, but have plans within the next 1 year to go to a built 6 bolt.

I am looking to order the JMF smim, but for 2g's they only have their "street" version, which has a smaller plenum than the 1g "race" version.

I already talked with jmf and they said the 1g race version will fit on a 2g, but of course I would need to port match the head.

At first I was looking to buy the race version for the purpose of not having to sell a 2g manifold down the road, and pick up a 1g.

However now I am wondering how much of a difference the size of the plenum will make?
Basically I know either will be a great improvment over the stock manifold, but What about that larger plenum, where would that be helping out mostly, high rpms/high boost?

 

[90blacktsiawd]

I dont have any info on your main question. But i've got to ask. Why can't you just tell him you want the race version for a 2g and he'll make it for you. Jim builds those manifolds all day long. I'm certian if you wanted something he didn't happen to have sitting on the shelf, he'd make it for you. Jim is one of the most accomodating vendors we've got these days.

 

[zilo900]

O for sure.

Its not a problem of getting the race version for my car, I just got to wondering with there would even be such a difference in plenum design

For instance, the AMS VSR manifold uses a large plenum,

the Magnus uses the smaller plenum.

and then JMF makes one of each....

So what does a larger plenum actually aid in?

 

[CanadianTSi]

High Boost/ High RPM...basically if your building an all out track car than get the Larger Plenum.

 

[zilo900]

well....yeah

But what exactly does it help by having a larger area by the #1 and #2 intake runners?

 

[my98GST]

I dont have any info on your main question. But i've got to ask. Why can't you just tell him you want the race version for a 2g and he'll make it for you. Jim builds those manifolds all day long. I'm certian if you wanted something he didn't happen to have sitting on the shelf, he'd make it for you. Jim is one of the most accomodating vendors we've got these days.

+84 on that one! I'm extremely happy with my JMF Race manifold!

 

[sbcxtreme]

Jmf said that they could make the 2g with the 1g race plenum, but it has not been tested yet. He suggested that i go with the regular 2g smim if my head had not been heavily ported.

 

[90blacktsiawd]

well....yeah

But what exactly does it help by having a larger area by the #1 and #2 intake runners?

It's not larger just by runners 1 & 2. It's larger all the way through short of the actual TB flange. That's just where the difference is most noticable.