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-   -   VVT head question (https://www.miataturbo.net/general-miata-chat-9/vvt-head-question-105515/)

joe morreale 07-08-2021 07:18 AM

VVT head question
 
I bought a "built" vvt head from someone a few years ago. He said the combustion chambers were opened up to drop compression, allowing him to run more boost. Can a hamfisted guy, who has a hard time understanding stuff, figure out how much it drops compression? I got it cheap and it had 1500 miles on it. He dropped a thrust bearing. Cams don't have any scoring, so I'm assuming that it's a good head. I'm trying to decide if I want to keep it for a forged build or sell it. I just want to know what I have. Original owner is out of the picture.

HarryB 07-08-2021 07:59 AM

You can measure the combustion chamber volume quite easily. From there, static CR calculation is straighforward.

Blkbrd69 07-08-2021 07:37 PM

https://motoiq.com/how-to-measure-yo...n-chamber-ccs/

https://auto.jepistons.com/blog/how-...d-displacement

joe morreale 07-13-2021 08:44 AM

Thanks for the link. I can get my head around that and figure out what I have.

joe morreale 07-25-2021 03:29 PM

Hate to sound dumb but if the cams are still in the head can you just close the valves to measure the volume with the oil. I would think if it holds compression it should hold oil.

Blkbrd69 07-27-2021 07:31 PM

Correct.


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