The Mantalorian Posted Tuesday at 00:04 Share Posted Tuesday at 00:04 (edited) I've been slowly rebuilding a 2.4 CIH over the summer and things are finally starting to come together. The bottom end is freshly rebuilt now and wrapped up patiently waiting for the head. I stripped the head a few weeks ago and checked that all looked okay then took down to my local engine shop for a rebuild - Crack tested, pressure tested, ported and Beryllium copper vales guides fited with 3 angle valve seats. I popped down today to see how he was getting on, and was excited to see the head looking quite different to when I took it in! It needs a final clean and finishing the valve seats but it should be home soon and then we can get it on the engine stand, and crack on. Progress at last! Project images are available to Club Members Only, Click to become an OMOC Member. Project images are available to Club Members Only, Click to become an OMOC Member. Project images are available to Club Members Only, Click to become an OMOC Member. Edited Tuesday at 00:05 by The Mantalorian 4 Quote Link to comment Share on other sites More sharing options...
Jessopia74 Posted Tuesday at 08:30 Share Posted Tuesday at 08:30 Looking good, as the ports have been fettled a little, I would be nice to have the insert edges blended more into the throat of the inlet port. As that is where the initial flow at low lift gains will be, really helps with cylinder fill. Does not take much to just blend this, just a gentle carbide burr on the lowest 2mm, think of it like a thinner valve seat but on the other edge as such. Can even be done with a round stone, just takes a while longer. Other tiny bit and arguably more important is clean up the really rough points in the orange highlights, just take the really rough castings off as these are now potential detonation points. the 3mm shank smaller dremmel cone stone is ideal for these and will take very little time. Project images are available to Club Members Only, Click to become an OMOC Member. Project images are available to Club Members Only, Click to become an OMOC Member. 1 Quote Link to comment Share on other sites More sharing options...
The Mantalorian Posted Wednesday at 13:40 Author Share Posted Wednesday at 13:40 Thankyou Jessopia74, that is really useful. I know there is some work to do on the head, so will mention it to my guy and see what he reckons. I know he has been working on the CIH engine for a long time and did all the engine work on a few race/rally cars back in the 80's, so I trust his knowledge. I know he mentioned that there's a bity more tidying up to do, so we shall see. 1 Quote Link to comment Share on other sites More sharing options...
Jessopia74 Posted Wednesday at 23:34 Share Posted Wednesday at 23:34 9 hours ago, The Mantalorian said: Thankyou Jessopia74, that is really useful. I know there is some work to do on the head, so will mention it to my guy and see what he reckons. I know he has been working on the CIH engine for a long time and did all the engine work on a few race/rally cars back in the 80's, so I trust his knowledge. I know he mentioned that there's a bity more tidying up to do, so we shall see. Ah, cool indeed. Then for sure he’s going to finish the little bits 👍 Interestingly, what we used to focus on (port size rather than bowl design, valve seat angles etc) yield far more than originally know since testing, dyno results and modelling. So lots to be learned from modern engines that is still relevant to the old lumps, but most of what I apply to engines is based on info gained from the bmw M12 development as that even in the N/A guise was about cylinder fill at the lower lift. CIH engine is a great design, it just suffers from the crap (think 50bhp per L) design of ports in the head. Hence why the the special Crossflow head (still 8v, pre Cosworth) gave great results even in the low efficiency era . Read https://www.opelgt.com/threads/cross-flow-head-cih-engine.10420/ Quote Link to comment Share on other sites More sharing options...
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