Would matching the inlet manifold alone make a big difference on a 172?

[len_beach]

I have picked up a 172 inlet manifold for practically nothing. Firstly, I need to clarify that they are interchangeable between phase 1, 2 and 182?

Secondly, I only have the inlet manifold, not a replacement plenham and have never liked modding any part of my car without a standard replacement ready for sale time. If I was just to match the inlet manifold, what sort of a gain would I see or is the plenham matching integral?

 

[Fred@BTM]

172 and 182 inlet manifolds are all the same, its the plenhams that are different

 

[edde]

Theres 3 types of plebhams
172 phase 1
172 phase 2
182.

You can swop the last two the first is different best drop BenR a message

I think BenR/Hill power have exchange units they send you there modified one you send your old one back when you've swopped it.

 

[len_beach]

Cheers fellas, that clears things up nicely.

So will a DIY match of the inlet have an effect or will I need to fettle the plenham as well?

 

[RichMcc]

The gain relates to how bad the original cast was. If the cast was really bad you'll get a good gain by opnening it up. The worst bit is where the manifold joins the head.

Correct me if Im wrong but ideally you would need your fueling adjusted so its not running lean afterwards.

 

[len_beach]

The gain relates to how bad the original cast was. If the cast was really bad you'll get a good gain by opnening it up. The worst bit is where the manifold joins the head.

Correct me if Im wrong but ideally you would need your fueling adjusted so its not running lean afterwards.

Superb, just what I needed Rich. My main grey area is wether it is the inlet alone that gives the gains or a matching of the plenham as well. I know where to start now in respect of the head side.

I've already had an RStuning remap but if things need adjusting, i'm sure Paul will oblige.

Thanks again.

 

[Fred@BTM]

Theres 3 types of plebhams
172 phase 1
172 phase 2
182.

You can swop the last two the first is different best drop BenR a message

I think BenR/Hill power have exchange units they send you there modified one you send your old one back when you've swopped it.

sorry edde, incorrect, 172 mk2 and 182 plenhams are different

 

[The Hoff]

Indeed, different bolt spacing Edde, it will 'fit' as such, but you canny bolt it on afaik.

 

[RichMcc]

If you want to do a DIY job use a perminent marker or engineers blue and a spare gasket. Put the gasket on and score around the inlet ports. You'll see the difference between the gasket size and the smaller port size. Thats what you would have to remove. Use grinding stones to remove the worst of it and cartridge rolls to smooth it all. You will need to leave a rough surface inside, dont polish it.

Ive been thinking about doing this myself for a long time but I started thinking I didn't want some ports flowing better than others and what if one had more material removed than another... I'll probably get mine done properly now.

Dont think of using anything crazy like a dremel or drill either you need a propper grinder and compressor.

 

[len_beach]

^^^Cheers Rich, am I right in saying you remove material around 1.5'' into the ports?

 

[RichMcc]

Yeah, I would remove just the length of your grinding stone all the way around then blend the rest in but Im no expert mate but Ive only dabbled i the dark arts of grinding

People like BenR can do magical things with inlets, Im sure 13bhp was mentioned on one he cut open and worked on.

p.s. dont expect 13bhp lol

 

[len_beach]

I'd love 13bhp lol. In all fairness, having read posts from both BenR and Stan, I may well just leave it to the pro's instead of dabbling in the very dark arts of grinding.

 

[RichMcc]

Yeah thats the conclusion I came to. I know its reletivly simple to do but I would prefer to have it done by some one that "really" knows they're shiznitz

 

[len_beach]

That's the one mate, I would want to start screwing with flow rates and AFR's etc. In theory, it could do some serious damage if done badly. Thanks for the info' though Rich, much appreciated.
Now where's BenR?

 

[BenR]

Yeah, I would remove just the length of your grinding stone all the way around then blend the rest in but Im no expert mate but Ive only dabbled i the dark arts of grinding

People like BenR can do magical things with inlets, Im sure 13bhp was mentioned on one he cut open and worked on.

p.s. dont expect 13bhp lol

13bhp was on a non cut up plenum, direct swap, no tuning.