Explorer Manifold porting?

[b2tf]

Has anybody looked into explorer manifold porting, Im just after a bit of info as to what extent it can be done. I have a workshop up here that can do it for me, but they can only do the lower, they reckon they cant do much with the upper cos of its design.

They suggested extrude honing it but that would be damn expensive, so Im just wondering if it would be worthwhile going fairly nuts with the lower, and just doing what can be done on the upper? I dont wanna end up with a bottleneck is all, and I know there's only so much you can do with the explorer, but for the cost it might be a good option for me (for now at least).

Shaun I know youve done it so speak up :hihi:, but has anybody else done it/looked into it? And what sort of gains are there to be had?

[BLACKAUXR8]

yeah i went pretty nuts on my lower. I took the gt40p heads out as far as they would go. SO far they break through into the push rod hole then you get the push rod holes sleeved and you have a set of heads that flow awsome. Any way back to the manifold. once i did the heads we took the lower out and port matched with the heads. It did make a big differnce to the accelaration which the au xr's seem to lag a bit until about 3000rpm so it id deffinitly worth doing it.

[xr8ute]

The lower is the bottleneck by far. There is a bunch of information on Tmoss' porting site... http://tmossporting.com

[honer]

I might of dreamt this

But I pretty sure I seen some upper porting jobs where they have cut the side of the upper off, ported, then welded back on.

[NeishaXR8_347]

When i did mine i took a heap of material out of the lower, where the ports meet the heads there can be lots that can be done to match the heads, but i also opened the heads up so every case will be differant. Around the injector can be played with aswell to help it spray a better pattern but you have to be careful. Runner number 1 and 5 are the worst flowing runner and need some straightening work done to help it almost match the other 6 runners, it needs welding and grinding then welding again and more grinding in runner 1 and 5.

With the upper there isn't really much that can be done other then a clean up of the casting that you can see and a light polish, where the throttle body is there is the bolt that holds the upper down it has a hump into the Air path, i also took a heap off that area aswell but i had a thickness tested so it was all safe. Extrude honing is well worth it on the upper and have seen the upper flow up to 35% more volume but for the cost (around $800) its not worth it unless you have to run the factory manifold for reasons.

[b2tf]

so it sounds like even just a basic cleanup of the lower would be worthwhile. I do want to put a cam in this thing (jeez how long have I been saying that now), so while she's in bits I might get it done depending on price. The GT40P's will be on for a while and Id like to see what they can do with a little bit of a tickle.

[xr8ute]

I dont think a basic "cleanup" would achieve much, as the shape of the runners really need to be re-worked.

The front runners (numbers 1 and 5), need work to straighten them up so they flow like the others, and all runners need to be opened up where the manifold joins the cylinder head. The cross section of the runners at this point is much smaller than the cross section of the runners in the upper (and much smaller than even the std GT40P intake port)

[Stav]

You will gain around 7 to 10 rwkws through the rev range by porting the whole manifold.

[BLACKAUXR8]

Neisha has hit the nail on the head here. It sounds like you've done exactly what i have done. And with the right work on the gt40ps they are a realy good head. Although just porting the lower you can as said above gain nearly 10 rwkws. I portmatched mine to the heads and then re did the lower when i did the heads. I didnt realise about the bolt in the upper though neisha so thanks for that it will be coming of this weekend now. :evil3: : :evil3: