PART 10 - Compression Ratio - How to Build a CB Performance 2017cc Builder’s Choice VW Engine

Here I'm checking the compression ratio to see if it's close to the kit's spec of 8.7:1. I'm measuring the head capacity and the deck height to check it's in the ballpark.

[@charliemessenger6537]

Another great vid. Was getting worried. It’s been awhile. Always worth the wait. Simple and straight forward.

[@aircooledanything2415]

Thanks Charlie. More to follow in a few days.

[@charliemessenger6537]

@@aircooledanything2415 You still breathing, mate? Hope everything is well. I get worried when I don't see any updates. Actually I'm greedy and impatient and I need my fix!

[@aircooledanything2415]

@@charliemessenger6537 Hey Cahrlie. Hahahahah, yeah still at it. Uploading a new clip right now. It's taking an age to process.

[@masbeetleboy9169]

This is shaping up to be a nice motor. I had something similar built for my Ghia, a 2007cc motor, that is now in my beetle. My compression is a bit lower than yours, closer to 7.5 to 1 because I used "B" pistons. These have a relocated wrist pin that allows the piston to sit lower in the cylinder and requires no shims for my motor. This may sound very low in comparison to your 8.5 to 1 but I lived in the mid west when I had the motor built and now live in southern Texas. Summers in both places can be brutally hot and I happily make my power through my displacement, heads, cam, carbs, and exhaust. Keep up the good work.

[@aircooledanything2415]

Thanks. How's your motor working out? Sounds like you've had it some time.

[@masbeetleboy9169]

Well, My beetle is in the shop right now getting the 2007installed, getting new front disc brakes and patching up a couple of rust holes. I haven't driven the motor since it was in my Ghia about 5 years ago. Just last year decided to put this motor into my beetle, bought new carbs, 44 IDF clones, a Magnaspark II dizzy, a new clutch and pressure plate, and awaiting word from my mechanic. The motor was very responsive and strong with a 009 and 40mm Webers in a heavy Ghia, so it should be a blast in a lighter beetle with the newer parts.

[@aircooledanything2415]

@@masbeetleboy9169 That Beet;e is gonna be a whole lot of fun. Good luck with it. Keep me posted on progress.

[@masbeetleboy9169]

@@aircooledanything2415 You bet I will. Are you going to install a deep sump and extra external oil cooler?

[@aircooledanything2415]

@@masbeetleboy9169 yeah. I have a slimline sump and external cooler lined up.

[@vintage76vipergreenBeetle]

I would put the pistons and cylinders with the highest deck height # on the number 1&2 side. Number 3 cylinder always runs a little hotter than the other 3.

[@bwm999]

For dynamic compression, you need the rod length & the degrees when the intake valve closes. Google “dynamic compression calculator” and look for the link to UEMpistons website, near the top of the search list.

[@aircooledanything2415]

Wow, that's some very handy information right there. Thanks for that.

[@bwm999]

The crank bore machining can be slightly off centre, even on the original cases back in the day. Using the original under cylinder paper gaskets on one side only will add 0.15mm to the deck on that side. Anything less than 0.1mm is not worth it, unless a blueprinted motor (when you’d get the piston tops machined to match perfectly).

[@aircooledanything2415]

Yeah, I reckon that's exactly what has happened. The bore is slightly off centre. That or the machining of the cyclinder seat on one side,but the bore error makes WAY more sense.

[@bwm999]

@@aircooledanything2415 it’s worth having a depth mic for next time because you want a fairly accurate measurement & the end of a vernier caliper is too easy to lean over etc. I have some ancient hefty apprentice made mic from eBay but it does the job. You can get a digital depth gauge for about a fiver from eBay. Sold as a tyre depth gauge but that could work with the usual TDC plate bolted in place, if it measures to 0.01mm

[@aircooledanything2415]

@@bwm999 A tyre depth guage is a genius idea, but a Depth Mic is definitely on my list of tools along with a digital dial guage indicator.

[@bedlamite42]

You would be much better off with 60-61cc heads, and drop the deck height to .040"-.045"/1-1.1mm. That would still get you an 8.5:1 compression ratio, but the better squish would be more efficient, more power with less heat.

[@aircooledanything2415]

Yeah. That would have been a better idea. I'm still learning and I'll know for next time. Thanks for the advice.

[@cgip1220]

Whats going on? Need more videos.

[@aircooledanything2415]

Update on its way.

[@mikehammer4546]

Are you planning on lapping in the cylinders to the heads?

[@aircooledanything2415]

That would have been a good idea right. I didn't though. Pretty straight forward thing to do and I really should have. Damn. Next time.

[@patrickmclaughlin6013]

I've kinda thought that wasn't a good idea. It could change the seat between the two cylinders and stress the block and the head. If you had those split heads it would might be a good idea. It might change the deck height too. Not sure. I know many builders do lap the heads. I'll have to check thesamba for a discussion on it.

[@charlestait5303]

How long did this build actually take please?

[@aircooledanything2415]

I started in February I think. Still not finished. Should be done end of July.

[@patrickmclaughlin6013]

Without a full machine shop and the skills, at some point you just have to go with what you got.

[@aircooledanything2415]

Ain’t that the truth. 😂