Heads up

[BlueRex]

Just fishing ATM, but what is the general feeling about the legality of swapping heads between engine models/capacities (providing original displacement, number and angles of valves and number of camshafts are maintined). Specifically I have the option of using an 1800 head which has better flow and larger valves in place of my existing 1600. This is for a pre-86 1600, the book states that modifications are allowed, but the use of the word "original" may be the killer.

C

This is as I said, hypothetical and not an issue for current engine, just sorting options for the re-build of the spare 1600 sitting on the trolly in the corner.

[BlueRex]

Hmm, I may have answered my own question after reading Mick's Evo thread. If the pre-86 1600 thing makes any diff please comment, otherwise I will accept the wisdom expressed in the other thread.

c

[tortfeaser]

Bah. The datsun crowd seem to swap head castings at will. But it is illegal.

If they're so similar it would be easy to swap the 1800 (or bigger still) valves to the 1600 head and do all the porting you like. End up with a better result than the basic 1800 head anyway.

[BlueRex]

Damn those dirty Datsun owners!!!
The 1800 head would be so much easier.... oh well, might look at how much the 1600 can be worked.

C

[rowdytoot]

Gemini crowd does something similar- swapping late model heads for early model big valve heads- the combustion chamber design is rather different as well...

I dunno whether it's legal or not considering the blocks they are off are identical...

Rowds

[tortfeaser]

Depends if the late model is the same model as the early model. I think this is a big grey area.

I've got a JD Camira which came with an 1800cc motor only. The JE Camira came with a 2000cc engine, same block (identical a la Ric but for different bores). My motor is bored to 2000cc as allowed under pre-86 PRC, but could I just use the 2l block? Is it the same model car? The only mention of model is in the pre-86 bit of the PRC rules - everywhere else mentions series production. Is a JD Camira the same series as a JE Camira? They're both Camiras. Both same underlying shell, both J series GM products with Family II engines.

But then the Vauxhall Cavalier was also a J series GM product with a Family II motor, with the same underlying shell. Can I use the Vauxhall 2l twin cam head?

What makes a model a model. When does series production become a different car.

Part of the problem is that different manufacturers have different standards - a Datsun P510 might have come with lots of part variations, for Toyota an AE82 Corolla came with either the 4AGE or 4AFE (one twin cam, the other single cam), the JE Camira only came with the C20LET single cam 2l. Can an AE82 use either motor? Or is the Corolla AE82 Twin Cam model designation what matters.

And who has the knowledge to sort this out at scrutineering.

Maybe its all about the recognition document. If you can find a manual that's got your shape Gemini in it with the head you want mentioned you're probably good to go.

[DaveTrees]

Originally Posted by tortfeaser

And who has the knowledge to sort this out at scrutineering.

They shouldn't have to .... scrutes can't all be expected to be "eligibility experts" on all cars.

It's the entrant's responsibility to present a legal car. If you think someone's car is illegal, and you believe they have gained an unfair advantage over you because of it* , then stump up the fee & lodge a protest against them.

Otherwise say nothing.

*IMHO, a protest in any other circumstance is frivolous and should be treated accordingly

[Swill]

use the 1800 head. If your worried grind all casting marks and numbers off it. Or if your real worried get Mark B to port one out for you

[rowdytoot]

Tort- I know I'm all good - I have the early shell- so the early head is the right one

I was more curious about the techicalities of it than anything..

Rowds

[smee]

Originally Posted by rowdytoot

Tort- I know I'm all good - I have the early shell- so the early head is the right one

I was more curious about the techicalities of it than anything..

Rowds

Fine Print of Gemini series regs.

Parts from any model may be used as long as the parts can be clearly identified as a standard gemini replacement part.

[Spac]

Doesn't matter, because they've still gotta meet the PRC regs.

[Matt Dyne]

Interesting...using Marc's strict interpretation of the regs, the Gemini Series cars are potentially ineligible?

[Spac]

Absolutely.
Strict interpretation makes 99.99% of PRC cars ineligible for PRC...

Edit: I should clarify... the Gemini Series cars can make them selves illegal for PRC, IF they use this freedom in the Gemini series regs where it contradicts the PRC regs.

Stuff like fitting a TX exhaust manifold to a TG is OK, because that's free for old NA 2WD cars in PRC.
On the other hand, fitting a TG front sheet metal to a TD is not OK, unless you also fit the TG rear panels and call it a TG (and even that's probably not 100% lega).l

[BlueRex]

Originally Posted by YRALLY

use the 1800 head. If your worried grind all casting marks and numbers off it. Or if your real worried get Mark B to port one out for you

Hehe good idea
Good thing no-one else reads these posts hey?

C