Javascript Disabled Detected

You currently have javascript disabled. Several functions may not work. Please re-enable javascript to access full functionality.

Yella Terra Head vs 186!

Started by _glennhailstone_ , Mar 13 2012 06:06 PM

Please log in to reply

11 replies to this topic

#1 _glennhailstone_

Guests

Posted 13 March 2012 - 06:06 PM

Hi everyone,

Can somebody tell me, what the story is with yella terra heads and holden 6 cylinder engines, more specifically 186.
I was looking on ebay and the heads just look like standard holden heads. If somebody could tell me how it works and where the best place to buy them from would be nice.
Also, can I buy a yella terra head with roller rockers new and bolt it straight on to my block.

Thanks Glenn

Back to top

#2 _stretchlc_

Guests

Posted 13 March 2012 - 07:15 PM

Inlet port head bolt bosses are removed and thinner steel tubes placed instead of them, larger inlet and exhaust valves, mild porting on the ports and double valve springs

Back to top

#3 _stretchlc_

Guests

Posted 13 March 2012 - 07:20 PM

!B02gk2wBWk~$(KGrHqUOKiEE)TJ1vJQ2BMcIPBERK!~~_35.jpg 13.52K 14 downloads

!BmD+w+wCGk~$(KGrHqUOKjkEtlzbdzEcBLeMPIoCkg~~_14.jpg 1.2K 28 downloads

Back to top

#4 _glennhailstone_

Guests

Posted 14 March 2012 - 06:10 AM

thanks

Back to top

#5 _glennhailstone_

Guests

Posted 14 March 2012 - 06:46 AM

so is it a holden head modified by yella terra, is there any markings or dimensions you can give me so I know Im not just getting a standard holden head, I only just found out what a port and polish is! haha
Thanks again

Back to top

#6 orangeLJ

Yes, yes I do post alot!

Members
10,261 posts

Joined: 02-May 06

Posted 14 March 2012 - 07:24 AM

Most of the original YT heads had "YT" stamped on the face of the valve.

obviously over the years they have had valves replaced etc, so chances are, they wont have those markings on every valve in every YT head.

I think people place too much importance on buying a "yella terra head"

Have a good look at any head, if it has had the inlet bosses removed and replaced, chances are its had some minor work done (atleast a stage 3 holden head) check the valve springs (you want double valve springs)

Buy a head that suits what you want, dont go specifically looking for a YT one as every asshole and his dog thinks they are worth a million dollars, when realisitically, starting with a cheaper modified holden head and having it tickled, is probably cheaper and a better option.

Back to top

#7 _glennhailstone_

Guests

Posted 14 March 2012 - 08:53 AM

Thanks a lot mate, very helpful

Back to top

#8 _glennhailstone_

Guests

Posted 14 March 2012 - 08:56 AM

Why do they replace the inlet bosses, and if I just want to use my head, whats the thing they do to the valve seats for unleaded gas.

Thanks again

Back to top

#9 S pack

Scrivet Counter

Members
15,736 posts

Name:Dave
Location:Luggage Point
Car:73 LJ
Joined: 25-January 10

Posted 14 March 2012 - 09:43 AM

Why do they replace the inlet bosses, and if I just want to use my head, whats the thing they do to the valve seats for unleaded gas.

Thanks again

The cast bolt bosses in the inlet ports are removed and replaced with steel tubes to open up the port for better breathing.
Hardened steel valve seat inserts are fitted to the head for the exhaust valves.

Back to top

#10 orangeLJ

Yes, yes I do post alot!

Members
10,261 posts

Joined: 02-May 06

Posted 14 March 2012 - 09:44 AM

one of our long time members has his own site with tonnes of VERY good information-

this page specifically talks about the inlet ports and bosses-

http://oldjohnno.id.au/page14.html

The main reason they remove the inlet bosses is that they restrict flow!

they are very large and right in the middle of the port opening. By replacing it with a steel tube insert it removes most of the restriction.