Hi recently sent an enquiry through your website about a possible yella terra i removed from my car. Here is the reply i got:
Unless it is one of our own castings there is no way of telling if it’s a YT modified head. Unless you are familiar with them.
The XT5 3300 had 1.740” inlet valves; 1.550” exhaust valves, dbl springs, chamber and port mods.
Was that you tappethead? or just coincidence that his name is also mark?
Anyway measured the valves which are stamped yella terra and they are indeed the size listed above. It's a 12 port head blue motor by the looks. Now mine also had double valve springs and port mods but no chamber modification. It also had 30" approximately machined off (3.137").
Now questions are would the spring seats/base on the head been machined down? (mine have been in comparison to other heads)
Also when they are assembled which style exhaust retainers did they use? red or the blue/black rotary retainer style?
Any further info to help me ascertain if its a YT head would be much appreciated
Yeah that would have been me. Doing 20 or 30 per day they are often short and sweet.
The spring pads would have to be machined to fit double springs and likewise the chambers would have to be opened up to fit the bigger valves.
We used to use V8 retainers on the Blue heads to get a bit more spring installed height, and we never re-used slow rotors "hate em".
Thanks Mark ok now i understand by what you meant by chamber porting and mine has been done. Ok now i'm almost positive its a yella terra head.
If i recut the valve seats maybe put in hardened inserts is there much depth and width before i'd hit water?
The original ones look good with no recession should i just leave them like that?
Thanks in advance Mark for helping me out
It's very risky to fit seats to a GM casting that has the big exhuast valves, you have to use very shallow seats and hope it's a straight casting with no core shift. That's one of the reasons we made our own head in the end.
Yeah thats what i thought i ve seen a couply at work that they've cut and gone into water and they were standard ports. Thanks Mark you've been a big help