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thelynx
22-11-2006, 12:27
Hey

Just picked up a cheap 1.8 head with bent valves, if I were to get it fixed, would it be best to go with bigger valves? If so what size are bigger than standard ?

Cheers

stan
22-11-2006, 12:56
williams inlets can be cut onto the existing seats, tho they are a renault only part.

megane f7r inlets will require larger seat inserts to be fitted/cut...more expensive.

in either case you would want to fettle the bowl area to get it to flow properly.

you could just send it to me and i'll sort it :D

summeh
22-11-2006, 20:42
When Ben put megane inlets in mine I think it was just the seats cut larger to suit ?? :?: :?

stan
22-11-2006, 20:52
yeah...thats the nasty way...FAR better fitting new inserts.

stan
22-11-2006, 20:52
yeah...thats the nasty way...FAR better fitting new inserts.

BenR
22-11-2006, 22:54
nasty lol.

its 'better' to run a new insert as your right on the edge of the std insert with 33mm valves.

But if you've got the equipment and know how its not detrimential :wink:

stan
22-11-2006, 22:58
I disagree :D

2 live
23-11-2006, 08:44
thin seats have more of a tendancy to get dropped ...in my experience....would always go with larger seats to accomodate the larger valves....recuttin is the cheap/easy way out.

BenR
23-11-2006, 11:25
thin seats dont.........thin inserts do, but even recut std inserts do not become 'thin', just the seat margin is moved to the edges where the top cut is part of the parent ally.

TBH i have never seen a renault drop a seat in any form or stage of modification.

Its an option for people who dont want to spend the large amount of money to add larger inserts for the propriety percentage point gain.

Its a wiser idea to add larger inserts, but as many customers see it.......if its not going to gain any bhp, and its not going to be any less reliable in the grand scheme, why spent the extra wad......and its not a small one. Customers thing ££££££££........not engineering ideal, so you have to blend the two.

stan
23-11-2006, 19:07
thin seats dont.........thin inserts do

but by taking the internal diameter close to the external, you are making it a thin seat insert.

tho i agree it likely wont fall out...its a risk especially if your using uprated camshafts.

also the lack of meat to play with, means by nature of the profile left, you WILL get increased shear/flow seperation...no matter how good you are or what tools you have :D

Daz.
23-11-2006, 22:11
Out of curiousity while your bickering :wink:

Good strong willy engine on 75k + Cams + head played with = Roughly how much increase in bhp and cost? "Roughly" 8)

Obviously a Chipwizards session to follow

stan
23-11-2006, 22:25
who's bickering?!

depends on spec of cam and timing etc and state of engine in the first place, aswell as how good the headwork is.

anything from 160-180bhp at a guess.

Daz.
23-11-2006, 22:32
who's bickering?!


You are now! :lol:

No only joking - Ok say quite mild ish catcams (anything that works well with the willy - not bothered if its a rough idle) and your quality headwork...

BenR
24-11-2006, 00:08
Well, like i said............new inserts are better, but it isnt the dire engine blowing situation that you are all making it out to be. We run thinner inserts, in higher rpm engines, with significantly larger valves (upto 48mm), much wilder cams with appropriately high poundage springs. If they dont worry me, then these setups dont.

And in terms of 'lack of meat'..........There never was a lack of meat......the ID previously was small so you had massive ammounts of meat, the only issue is that the seat margin sits on the outer extreems of the instert, so the bottom cut becomes part of the ally.......as it is on many stock and heavily modified engines. The top cut you can do what you want with it.......if you leave it generous for a substantial top cut or radii......then you have a small throat.

What am i trying to say? lol

That you dont have to have a thin inset with big valve, just that the seat margin sits on the outside of the seat.

Anyway, we all know ultra flowing race heads only run single angle seats :wink:



thin seats dont.........thin inserts do

but by taking the internal diameter close to the external, you are making it a thin seat insert.

tho i agree it likely wont fall out...its a risk especially if your using uprated camshafts.

also the lack of meat to play with, means by nature of the profile left, you WILL get increased shear/flow seperation...no matter how good you are or what tools you have :D

cliolord
24-11-2006, 21:18
who's bickering?!

depends on spec of cam and timing etc and state of engine in the first place, aswell as how good the headwork is.

anything from 160-180bhp at a guess.

craig is there anyway to get abit more power than 175 using the same plenum? I have looked into high compression pistons (domed) I just can't help myself :roll: Knife edge crank, stronger rods. But all this is still going to cost around 100quid per bhp :cry: I'm going to go mad if I search around any more.

stan
24-11-2006, 21:44
no point in knife edge crank, and no point in "proper" rods unless you have proper pistons, and cams to warrant the increased rpm.

big-valve head would have been the one step further, but im sure you'll see nice gains with the head ive done you.