GTR Forum banner

Should the exhaust hump be removed or not?


  • Total voters
    20
1 - 19 of 19 Posts

·
Registered
Joined
·
675 Posts
Discussion Starter #1 (Edited)
Hey guys.

The guy I bought my replacement engine from was recommending removing the exhaust hump from the head of the new rb26 to improve spool up etc. Is this a worthwhile mod and would it have to be done in a machine shop or would any mechanic be able to do it with a dremmel?

Also I read on one of the other threads that this is not a good thing to do

Hi there.
Right i got a new head and took the time to use a rotary burr on the old head .
My findings are not good, i always wondered what the big exhaust hump was for and i ground it right down.
And i found a water jacket that comes fromt he cylinder.
So for a everyday car and for a car that is going to be used as a track car i would advise that you do this .
Not only that but you can also loose coolant if you grind the exhaust port too much ...
I dont think its worth the risk the water jacket sits about 2mm below the circlular surface if you had to grind down the hump to match the ark of the whole port .
Now this would also affect the water temps as the Egts are very hot (Exhaust Gas Temps) so if you grind down the hump it would mean the hot exhaust gases pasing by going to the turbo where there is a little restriction from the turbo would mean that there would a be a heat build up on the whole length of the exhaust port including the smoothed off section of the hump, and heat transfer would occur into the water jacket increasing water temps so know that this is not ideal if you are running a standard radiator .
i have not done this mod and have just sanded down hard corner edges and smoothed of the exhaust chambers with the hump left inside and used a smooth sand paper to get the exhaust ports like glass . (Gas Flowing )
I was wondering what the main tuners reckon on this and if anyone else has it done and what they noticed after?

Thanks guys
Steve
 

·
Registered
Joined
·
675 Posts
Discussion Starter #3
It's an opinion poll because from what I've read people have different opinions on whether or not it should be done..... But going by the condescending nature of most of your posts I wouldn't expect you to value other people's opinion anyway
 

·
Registered
Joined
·
8,540 Posts
But going by the condescending nature of most of your posts I wouldn't expect you to value other people's opinion anyway
PMSL...

TT
 

·
Registered
Joined
·
6,560 Posts
going by the condescending nature of most of your posts I wouldn't expect you to value other people's opinion anyway
Awe....come on, Glens great to have around in times of need, here's some of my favorites:

Yes I still know, and no I'm not going to tell you
I just walked over to the window to check if there were any pigs flying past...
all those dumbass stupid questions repeditively asked by stupid dumbass's that cant be *****'d looking first
This is like dejavu
sigh... sometimes you might as well save your breath
One thing is for damn sure, alot of people get alot of entertainment from Glens posts, be a boring forum without him I reckon.
 

·
Registered
Joined
·
614 Posts
Well personally,

Glenn seriusly chill out there... not everyone been around since 2002..
instead of posting meaningless crap on the forum just ignore it?

There is no way you can have any forum, without allmost dayly repost by "newbies"

All imo..


As for the topic! ill say leave them in, unless your going quite high power engine.
there is not that mutch meterial between the exhaust port, and the waterchannel, wich properly is why nissan chose to put this supid hump in there.

The guy who made my head, left the humps in place, and just did some tutchups to smooth it a bit.

You have 2 very different heatranges on eatch side, and if you have a thin wall between, a crack might accur.

All the stuff about higher watertemp, im not buying though.

Ron
 

·
Registered
Joined
·
4,429 Posts
Ronnie, seriously I am chilled
What exactly is the point in a poll if you need a question answered ?
If he said, I have x engine, with x turbo's,and are wanting to use the car for x, and I would be expect x hp etc: ...

But IMO starting a poll with ZERO background info in the form of a question is stupid...
 

·
Registered
Joined
·
4,586 Posts
Surely you are better off picking a well respected engine builder/head specialist that has had good results with an RB engine and follow his advice/send the head to him.

Not a lot of point mixing and matching head ideas....stick to one guy and do that!

From what I have read (and I'm far from an expert on this) that the humps are very close to water channels.....So unless you are and expert on heads, I wouldn't go anywhere near it with a die grinder!
 

·
Registered
Joined
·
359 Posts
I ground them exhaust lumps of flush with a 'die' gringer (on my rb25det head) over 2 yeras ago, also removed the inlet 'squish' pad, no other work on head appart from tomei cams.
My car has seen a LOT of high-speed full load/power time since then, multiple track-days, ran mid 12's at the 'pod with 'ludders' driving, makes say 450-500bhp.
NO ISSUSES, runs better now than the day it was assembled. period.
And that must be at least an hour in total in those 2 years I'd guess flat in 5th.
So how does that work?
Lol.
 

·
Registered
Joined
·
6,560 Posts
we always remove them, never had an issue.
 

·
Banned
Joined
·
686 Posts
Hytech, you have had alot of experience and know how much material to remove and in doing so manage to not eat to thin into the head pocket, and there fore leave enough wall between the exhaust port and the water jacket.
Its an art and something i wasnt going to risk as i wasnt aiming for high power, but if you are experienced like yourself then worth every drop in removing the hump as then performance will be increased :)
 

·
Registered
Joined
·
2,507 Posts
i/we removed them on my last two heads with NO problems at all. used a dremel type thingy and ground them flat`ish...
and yes,i did notice the difference as it weas the exact same set up as before, just had bearings. i noticed the pick up was better and boost came on just slightly sooner.
 

·
Registered
Joined
·
675 Posts
Discussion Starter #19
Thanks for the feedback guys, I think I might just leave em where they are, I don't wanna take the risk of having to go looking for ANOTHER engine :)
 
1 - 19 of 19 Posts
Top