Cool head dome ID

[iwallace]

hiya. Could anyone tell me what size coolhead dome I have please. Tri z 250 . Brought when first came out. Just can't remember what I had planned for it. Thanks ian254217

[iwallace]

For a tri z if it makes any difference

[El Camexican]

Not sure what this might tell you, but this is what a "Pump Gas" dome looks like. Sorry, no numbers, it's in use at the moment.

254218

[iwallace]

Cheers mate. Looks similar to me. But I can't remember what the others look like

[christph]

Measure the volume. Put a plug in it, top it off with water, and measure the volume. I have a Sprock head for my Z. I think he only made stock and 50/50 domes. The range is probably around 20 to 22cc.

[iwallace]

If I'm remembering right. He made 3 different domes at the start

[christph]

If I'm remembering right. He made 3 different domes at the start

Yeah, but I think he had a problem with the full race dome, so that was a limited run. When I got mine the highest compression available was 50/50.

[yaegerb]

If its a sprock run race gas.

[Tri-Z 250]

I have had both the BigBore and stock bore domes relieved to allow for pump gas to run. This is on the advise of my motor builder to smooth down the hit and vibration related to the flat high compression of Sprocks domes.

[christph]

I run 50/50 in mine, around 100 octane.

[iwallace]

Hi.just filled the dome with water.it measures 16ml on my syringe. I take it . It's not for pump gas.

[iwallace]

I only filled the inner dome piece. ..should I fill it to the first edge. Inner o ring....think I've answered my own question

[iwallace]

I should of looked more closely befor I asked the question...just found a number stamped on it..25. Cheers for all your help anyway.ian

[iwallace]

I should of looked more closely befor I asked the question...just found a number stamped on it..25. Cheers for all your help anyway.ian

Am i right thinking my 25cc dome wont be no good for my standard engine, also can i still buy the sprock domes anywhere ,if so what size should i go for.
Willbe giving the engine a rebuild soon. Its still on its original piston and rings. Thanks ian

[El Camexican]

Try Off-road Innovations for any Sprock products you’re looking for. If anyone has parts it will be them.

Do you have the stock head? Just shaving .020” or .030” of it might be your best option if you want to run pump gas.

[iwallace]

Try Off-road Innovations for any Sprock products you’re looking for. If anyone has parts it will be them.

Do you have the stock head? Just shaving .020” or .030” of it might be your best option if you want to run pump gas.

Thanks for the reply.Think ive tried everywhere looking for sprock domes.Even looked for file program for the domes,no joy.
Put me right please.
Surely if i take offmore ali it would increase the cc in the dome.Thanks

[El Camexican]

Thanks for the reply.Think ive tried everywhere looking for sprock domes.Even looked for file program for the domes,no joy.
Put me right please.
Surely if i take offmore ali it would increase the cc in the dome.Thanks

Not sure I understand your last line or what is it you want to accomplish in the end. If it is to use race gas and have a peppier Tri-Z, then put the Cool Head on and run it. (I believe the advertised cc for the "pump gas" Sprock dome was 26cc, so that's likely what you have, but contact Greg at Off-Road Innovations and ask. There are rumors that a second, more pump gas friendly version of the dome was produced, but I have no way to know if that's true.

If you just want to keep your engine stock and run pump gas, use the stock head, but do make sure that it's flat as they are known to warp.

If you want a little more power and don't want to run race fuel, you should be able to get away with removing .020" to .030" of material from the mounting surface of your head which will reduce the cc's in the dome and increase your static cylinder pressure to between 165 and 170psi on a stock engine.

Do keep in mind that there are many variables from engine to engine. The height of your cylinder, the height of your exhaust port, the thickness of your base and head gaskets and the shape of your piston can all change your static compression ratio.

Once you pick what it is you want to go with, assemble your engine and do a compression test. Anything under 175psi should allow you to run pump gas (at least that has been my experience), but if you find it's higher, or that it's detonating a lot, you can pull the cylinder off and add a base gasket, or raise your exhaust port a mm or two.

If you start making major changes, like cutting your cylinder you'll want to check your squish band for clearance. Here's some reading that may help confuse your issue ;)

http://www.3wheelerworld.com/showthread.php/172195-Tri-Z-Engine-Build?highlight=triz+engine+build

[iwallace]

Here's some reading that may help confuse your issue...that made me laugh..After reading what you wrote . I read it properly this time..You said stock head. I read it as sprock. Sorry mate..I will email that company just incase they have something.
My plan is to try and use the SPROCK head. But try and find a dome suitable for pump gas. Off I go for the confusing read. Thanks for taking the time to get back to me.

[yaegerb]

Here's some reading that may help confuse your issue...that made me laugh..After reading what you wrote . I read it properly this time..You said stock head. I read it as sprock. Sorry mate..I will email that company just incase they have something.
My plan is to try and use the SPROCK head. But try and find a dome suitable for pump gas. Off I go for the confusing read. Thanks for taking the time to get back to me.

Personally I would put the motor together and run a UCCR test (tons of articles on this on the web) then get your dome cut to run pump if that’s what you want to do. I have it on good authority that none of the sprock heads were ever cut correctly for pump gas. I just built a tri z for a customer and he bought the pump gas dome sprock Head. After performing the uccr test I confirmed that the Head was set up to run 110 race gas. It has since been sold and we cut . 030 off the OEM head and it runs happily on 93 with 174lbs of compression.

[ironchop]

Some good info in here on Sprock Tri Z head...

https://r.tapatalk.com/shareLink?url=http%3A%2F%2Fwww%2E3wheelerworld%2Ec om%2Fshowthread%2Ephp%3Ft%3D155587&share_tid=155587&share_fid=192465&share_type=t


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