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OK guys a mate of mine has a real nice HR van and he has an issue,

I gave my yella terra head to a dude at work who's mate is a pretty switched on engine guy, and he is saying that the head is a 161, and not suitable for a 202. Do you think the ports could be too small?

My old red 202 ran a 149 Yella terra head and had high comp (10.7 to 1) but went on fine as far as I was aware. I did have the motor built by Quick 6 in Dandenong and that it was, just didn't enjoy standard fuel too much.

Now I'm not sure if he has a later blue/black block or if there is indeed a difference. I thought they were all fairly interchangeable? Is this guy speaking BS or truth?

*edit* Just found out it is a red 202......

As far as I know the port sizes were all the same for 9 port heads.

Combustion chamber sizes were the only difference.

I've got a 161 Yella Terra head here with casting number 7438296 ( casting number was confirmed as 161 head by Dr Terry ).

Your workdudes mate is probably referring to the combustion chamber volume being too small and increasing the compression by too much on a 202.

I can't see why he couldn't use the smaller chamber head on a 202 as long as he used premium fuel.The engine would have to be in good nick though as a tired motor may not take the extra compression too well.

I guess the compression ratio would at least be around the 10 to 1 mark.

Werent the small combustion chamber heads from a 149 ??
I used to run one on my speedway rocket years ago.

They used them on 138 red's, 149's and 161's definately.

Not real sure whether 173's used them or the larger chamber heads.

I'd guess low compression 173 may have been large chamber head,and high compression 173 may have had the small chamber head??

i was told the smaller chamber heads had smaller ports but i've never really looked or noticed, this shouldn't matter in this case being a YT head as the ports would be modded, my 202 has small chamber head and flat top pistons and runs fine also has a 138 engine No if that makes a difference
i would say his mate is full 'o' sh!t

I've got a 138 and 149 head here at home so can have a look at port sizes on them versus port sizes on 202 but won't be able to have the time to do it 'till next week.

If they are different it would only be by a poofteenth of an inch as side by side they look the same to me.

I'll measure and let you know.

Unless DR Terry on the forum can add to this question as he would be the one that would know exactly.

Terry, how big exactly is a poofteenth ??
Is it as big as a mickeywhisker or smaller than a tad

even if the head does have really small combustion chambers you can always put a decompression plate in there ... they arn't dear and from what i've seen you can get them in .032 and .060 thou thicknesses.

i put one on my engine after the compression was around 11.2:1 and with a .060 it dropped it to a more friendly 9.4:1 from memory...

Thanks guys you confirmed my thoughts, comp would be up but realistically that would be all. Sounds like he's sproutin BS...

Hey guys I'm the fool who owns the HR mucking around with red motor stuff still
Thanks for your tips, have decided to get the head cleaned up and decked, may put a new cam in it but will see how the current stuff holds together.
Will post a couple pics of the car in the appropriate section.
Cheers!

Blacky

as long as you have larger valves fitted yella terra size the xu1 torana used this combination it is valves that are smaller not ports