How to Calculate Compression on Volkswagen Aircooled Engines - Part 1

Todays video, we will be tearing down the top end of this 1835cc Volkswagen type 1 engine to determine compression ratio for the installed cam that's inside.
We will cover how to check deck height, cc the heads and use the CB Performance engine calculator to determine the compression ratio.
I'll also cover how to correct the compression ratio.
This is part 1, part 2 will show the correction.
Thank you for watching.
Please like, comment, share and follow along!
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[@zimms-world]

Good information. I would like to see a video where you put in the shims. I think it would helpful for guys like me that have never done anything like that before

[@VWJawbreaker]

Thank you sir and that’ll be next weeks video!

[@backyardkombi5466]

Much cleaner than the engines I am accustomed to tearing down.

[@VWJawbreaker]

Some are better than others…. Yours have been well used.

[@paulchristiansen7014]

been watching your videos, look the old VW as they have soo much soul to them..plus very easy to work on..

[@VWJawbreaker]

They are very easy to work on as long as you understand how finicky they can be. I appreciate you watching him for the support!

[@bluecarlos65]

Thank you I enjoyed and learn something new. Please do next step Thanks Chuck Chicago.

[@VWJawbreaker]

Thank you sir, next step will be next weeks video.

[@SladesVWBeetle]

Great video! This will help many people for sure.

[@VWJawbreaker]

Thanks brother, hope it helps at least one person at some point.

[@SladesVWBeetle]

@@VWJawbreaker oh it will!!

[@adamgray2720]

Thanks for the video. I needed to see this. Very helpful.

[@VWJawbreaker]

I’m glad you found it helpful!

[@douglasbarnhart3324]

Great video Gary thanks see ya on the next one.

[@VWJawbreaker]

Thank you sir and I hope you have a great week.

[@HubertusSchaper]

Hi, Garry nice vid. surely informative for those who follow you🔧, Have a great week🌞.greetings🇺🇸 ☮️🙏🍀🇳🇴Hubertus.

[@VWJawbreaker]

Thank you Hubertus and hope you have a great weekend.

[@jamesquintana9137]

Yes Gary...please make a video of you installing the shims! I did this job once on a 1965 Bus 1776cc engine, and just want to make sure that I did it right - for the next engine I get. Thanks!

[@VWJawbreaker]

Good thing I recorded anyway… video will be out next week!

[@jamesquintana9137]

@@VWJawbreaker Awesome! Thank you Sir!

[@richpeacock5768]

Good stuff to know! When I bought mellow yellow, my dad made special note to tell me never to use silicone on a Volkswagen engine. I used gasket sinch. It's now made by Edelbrock.

[@VWJawbreaker]

Silicone on the engine half’s isn’t a great idea imo but anywhere else isn’t an issue. Gasket sinch is some good stuff though, forgot they are now making it.

[@WolfHausMotorwerks]

Another great video!

[@VWJawbreaker]

Thank you!

[@bigboardfun]

I love the stuff you show us. Thank you.

[@VWJawbreaker]

Thank you for being here.

[@patrickmcneil2911]

Thanks for sharing, I always learn something from your videos and would love to see you install the shims! Thanks again

[@VWJawbreaker]

Thank you sir, part 2 will be out next week!

[@VWRICH23]

AHHHH, i needed a engine video, thank you !!

[@VWJawbreaker]

You’re welcome…. Part 2 next week!

[@DesertRatFabrication]

Great calculations Gary, and another great video, yes we want to see it all

[@VWJawbreaker]

Thank you sir. Part 2 will be out Wednesday 👍

[@DesertRatFabrication]

@@VWJawbreaker I will be there 👍

[@FixinBugsNStuff]

Great video. Keep up the good work!

[@VWJawbreaker]

Thank you sir. Hope all is well on your end.

[@Tikicar]

Great information, thank you.

[@VWJawbreaker]

Thank you for being here.

[@jimlester5003]

Great info Gary! I haven't seen many videos on lapping the cylinders to match the heads. Letting people know that it can be the simple things that can help keep the compression chamber tight. Jist a thought. I was amazed at how clean the rocker area was. Thanks for your tech savvy Have a great day! Jim

[@VWJawbreaker]

Thank you sir! I’ve put lapping in a few of my older videos but figured it would be a good refresh for some. This engine has maybe a few hundred miles on it so it better be clean 😂 Appreciate you as always Jim!

[@mikehammer4546]

Great info. Much appreciated.

[@VWJawbreaker]

Just explaining what I’m doing… right or wrong lol

[@michaelnagy4603]

Love your videos ❤

[@VWJawbreaker]

Appreciate you being here 🤙

[@eduardorodriguez3262]

I just got schooled Maybe I too one day can rebuild my own engine👍🌴

[@VWJawbreaker]

Nah man, we all have different strengths and weaknesses and I am by no means an expert!

[@48busman]

Gary, I really can't see this kind of stuff to much. Hope you show it being put back together. I assume it's a universal case. Thank you fovideo! great vids!

[@VWJawbreaker]

Thank you, I appreciate that. Part 2 will be out next week 👍

[@johnflynn9463]

View #98 at 1:42PM on 3/23/22 - NJ.....VW "The Doctor" Jawbreaker

[@VWJawbreaker]

Thank you sir but I’m far from it. Plenty of other great ones out there!

[@teddyallen6338]

Would like to see the installation of the shims and replacement of the cylinders

[@VWJawbreaker]

Thanks for the input. Part 2 will be out next week!

[@1fastbuggy502]

Great job Garry. I seen no one mention, you will need to make the correct length push rods now. Make sure you check the rocker arm geometry.

[@VWJawbreaker]

Yea sir, good point. I did check the rocker geometry and it was good with the stock push rods.

[@JMKGarage]

Good info here… had to do this on my build last year, and took me a little while to properly figure out… was calculating it wrong at first and couldn’t understand why my compression was so low 🤦‍♂️

[@VWJawbreaker]

Thanks man. I’ve done the same before, inputting wrong numbers caused a ton of headaches… that’s when I learned to slow down and write down my info on a spreadsheet… just fill the info out as I move along. As long as you find a process that works for you, you’ll be good.

[@vayabroder729]

Brazilian 041 heads; old school. You can either shim at the barrel bases or between the barrel and the head. In my case I put bronze (or brass?) shims between the head and the barrel. Also, if the barrel are thick wall you should be all set. Earlier 92s were not very reliable because they were thin walled. For a Bus this is very important.

[@VWJawbreaker]

Yes sir, don’t see these heads very often. I took them apart off camera and everything was in great shape. I’m personally not a fan of the copper gaskets between the heads and the jugs as I’ve seen the heads constantly work loose on a regular driver vehicle. Those are meant more for the racers who are constantly pulling things apart or re torquing the heads.

[@patar7999]

Damn Gary … are you sure your not tearing down my Baja motor… 😂 damn near same specs even th rocker shafts lol good stuff sir!

[@VWJawbreaker]

Haha, pretty sure I know where this engine belongs 😂😂

[@reyes3972]

Si men.. sube el video donde pones los separadores... excelente información

[@ahernandez9860]

Glad you make this content! Helpful in understanding more about the vw powerplant. I too learned I have a 110 cam after I had a local shop smash my heads getting them off to install 88 thick wall piston/ cylinder kit. He stated my compression was 8.75:1 sold me a 38 gas empi crap carb manifold and said good luck. Never was able to get carb dialed right so put it where it belonged in the trash. Proceeded buy several empi 34 clones and engine still not right. I've been told get dual carbs but am reluctant as money is low along with my patience. If I did, which would you recommend?

[@VWJawbreaker]

Well, you can run a single carb with the 100 cam and it runs well with dual 34’s. You don’t need dual 2bbl carbs for the 110 cam. Sounds like there’s something else going on and not just a carb issue if you’ve been through that many carbs and still having issues.

[@TheEZGZ]

Nice job! I am interested in how the cam lobes and lifter bases look after 500 miles. How much of the parkerized stuff came off.

[@VWJawbreaker]

I would have loved to split the case on this one but he wanted to leave it alone. I suggested swapping for 90.5’s, a W100 or C25 cam and a 74 stroke crank…. He would have loved that combo in that early bus.

[@TheEZGZ]

I agree! Maybe shine a light inside the case and look inside without splitting. Thanks

[@VWJawbreaker]

@@TheEZGZ I did look inside and it all looked good… didn’t film it though 🙄

[@teonthevwwhisperer7316]

Would like to see you put it back together

[@VWJawbreaker]

Thanks for the input. Part 2 will be out next week!

[@teonthevwwhisperer7316]

Great can't wait

[@jonathanl4691]

Liked the video, agree static compression ratio is a bit high. Have you factored in the Dynamic or running compression ratio. The closing time of the intake valve @.050 will affect the compression ratio depending on your camshaft. Just something to consider. Thank you again for an informative and educational video.

[@VWJawbreaker]

I’ve ran the numbers with this cam before and the dynamic doesn’t drop that much due to a small overlap compared to bigger cams like the FK8 in jawbreaker. Good thinking and looking out!

[@Mtbeaver9]

Hi Gary . Need to backup a bit. I am installing cylinder head studs in a new aluminum case with stud savers. I was curious what should I use to seal the studs in the case savers. Do you use blue lock tight or gray silicone ?

[@VWJawbreaker]

All depends on if they are blind case savers or not. If you can not see through the case saver, there’s no need for sealant on the studs. If you can see through the case savers into the engine, then a thin layer of aviation sealant is all you need or permitex #2 non hardening. I don’t like to use locktite on case studs.

[@deanrobinson3717]

Please do the shims Gary, it would be awesome to know the next step, and can you also show building back up without leaking oil, mines pissing out everywhere lol

[@VWJawbreaker]

I’ll go over it on next weeks video…. As for the oil leaks, if it’s not leaking it’s out of oil! 😂

[@deanrobinson3717]

@@VWJawbreaker that’s my theory on both types of motors too 😂

[@Slick56]

It would be interesting to know if the heads were still torqued to spec or how loose they were. those 50cc chambers are pretty small. You could go old school and have them hemi cut to gain back chamber volume. I would do shims under the barrels to get more deck .035 is too tight in my opinion. I like this motor build stuff, but hey I like all your videos . Cheers

[@VWJawbreaker]

Hey buddy! Seems the builder put something on the threads to keep the heads torqued down, that’s why the studs pulled from the case. Easy enough to clean up. Wish someone near by could hdmi cut the heads, I would have rather gone that route and yes, .035” deck is too tight for me. I prefer a minimum of .040-.050 depending on the chamber size.

[@Paulman50]

Is it nessisary to seal the inner head bolts and washers. I'm putting my jugs and heads on tomorrow morning. Would have done it today but don't own sir clip pliers.

[@VWJawbreaker]

Yes sir, I prefer to put a little sealant on the washers only on the 4 inside head studs.

[@williamtanner1372]

More stuff I didn't know. Well explained. Now how is the engine going to be adapted for the mustache bar?

[@VWJawbreaker]

Thank you sir. They sell a plate that bolts into the oil pump to accommodate a mustache bar. I haven’t seen his bud but he said he thought it didn’t take a mustache bar in his ‘69 bay…. I beg to differ though.

[@goldentrunnell7450]

I'm curious if you know of any calculations of compression ratios for elevation changes? Say if you have 9:1 at 1000 ft would you raise compression a certain % as you go up in elevation? It's 5700 ft above where I live, they lower the octane levels here so maybe raising compression isn't a good idea, any thoughts?

[@VWJawbreaker]

I’m at sea level so I’ve never really dug too deep into this. My thoughts are this, and I could be wrong… A normal vehicle doesn’t change their compression ratio for altitude, it’s only the computer that keeps the afr’s in check by adding more fuel for the thinner air at higher altitude. At least I’m pretty sure it’s adding more fuel, can’t remember off hand now lol I wouldn’t go crazy with a high compression air cooled engine but as long as it was timed and tuned properly, I wouldn’t see any issues.

[@jimmywilkinson9190]

Hey Gary was that motor getting carb. washed . some thing dont look right there . For a bus what works good is a 32/36 and messing with the jets you can get rid of the soot . Then does it have a brake servo . you will need plenty of vacuum. The 110 is so close to a W100 lift wise .and a W100 works on a bus . Its all good . later.

[@VWJawbreaker]

Considering I hadn’t ran the engine prior to me digging into it I’m not sure what carbs were on it or how it was jetted. All I know is that it was a very low Milage, rebuilt engine. He didn’t want me to split the case and put a smaller cam in jt, he wanted to leave the W110 in it.

[@jimmywilkinson9190]

@@VWJawbreaker 110 aint much bigger than a 100.

[@vayabroder729]

@@VWJawbreaker the 110 is a highly regarded VW performance cam. Should be good.

[@VWJawbreaker]

@@vayabroder729 I actually prefer the C35 over the 110… nicer profile imo.

[@VWJawbreaker]

@@jimmywilkinson9190 yes sir.

[@monchy25]

I am going to try to do this quick question, the carbon build up on top of the piston will not give you a false reason, when using the feeler gages?

[@VWJawbreaker]

If the carbon build up is thick, yes. In this situation it was more of a discoloration.

[@monchy25]

@@VWJawbreaker *reading

[@ropadoped]

Please show us deck shims install sir.

[@VWJawbreaker]

Part 2 will show that 👍

[@jkh8350]

What is the reason for reducing compression

[@VWJawbreaker]

The more compression the more heat it produces. There’s an optimal range for the given aftermarket camshaft chosen, outside that you make too much heat and the additional compression is not effective. Too much heat, no radiator to cool things down, short lived engine.

[@pekacasper7194]

Hi Gary.....040 deck height in a stock 1600cc is a good idea??

[@VWJawbreaker]

I’ve always been told that .040” is the minimum for any build. If it’s a bone stock build, keep the static compression down in the low to mid 7’s.

[@anrescue]

Hi. have you ever tried building a zero deck with a copper head gasket? In this case you could of put a .040 copper and only had .035 deck in the cylinder. I built a 1904 with zero deck and a 0.040 copper head gasket on the recommendation from AJ Simms, It is supposedly better all around to keep the burn in the head, I never had a problem and I personally think copper between the cylinder and head will seal better than cylinder to head. That was 10 yrs ago and I only kept it for a few years maby 1-2k miles but I actually found 2 owners later... 5 years later on the Samba and he drove it from Tampa Florida to California with no problems and got 25-28 MPG, 74mm x 90.5 Mahle, Had AJ Simms ported heads, his Kadrons, SVDA, hyfire ignition box, bugpack 4062-10 ( basically a 110), 1.1 rockers, about 8.5-8.-75-1 & one of Tigers first SS Sidewinder exhaust with thing fan shroud, all vw factory tin and working thermostat in a 1959 Single cab. Ran real good, sound reminded me of a crotch rocket. Would spin 1st & 2nd in the rain.

[@VWJawbreaker]

Sounds like a stellar setup for sure. I personally don’t run the copper gaskets as you tend to retorque the head snore than normal…. From my experience and understanding from other more knowledgeable people. However what you say does make really good sense. Might be an upcoming experiment down the road.

[@anrescue]

@@VWJawbreaker yeah, that seems to be a lot of mixed opinions about that but I might’ve done the first retorque while it was still out of the car after break in If you try it, you should do it on an existing motor where you change nothing but that to see if it makes any performance difference and or cooling. It’s supposed to keep heat out of the cylinders also.

[@VWJawbreaker]

@@anrescue as I’ve said many times on my channel, there’s many ways to skin a cat…. Pick whatever way works best for you. We all don’t do things the same exact way, sometimes there’s more than one right way to do something. I’d like to do this to my current engine however the head area is kinda small so I’m running .070 shims to get .080 deck. I could run the .060 copper shims and still be within the specified compression ratio range….. Hmmm…. Maybe that’s something for a ways down the road.

[@triariicat8448]

what determines setting the compression ratio? is it the size of your camshaft?

[@VWJawbreaker]

Yes mostly but also no. It all depends on the complete engine combination and what it’s going into, used for, etc. Heads will only breath so much so a cam needs to be paired with the heads.

[@triariicat8448]

i've been watching your vids, trying to learn all i can, I'm about to put 1776 together with a engle w90 (cheater cam) in it and I think ill just run 8.250 to 1 CR with my stock dual port 500 series heads, maybe it'll work @@VWJawbreaker

[@VWJawbreaker]

@@triariicat8448 I’d run closer to 7.9-8.0 imo

[@vintage76vipergreenBeetle]

Shims video please. 👍

[@VWJawbreaker]

Next week sir!

[@ropadoped]

Does anybody know what would be a good cam size for a 1915cc?

[@VWJawbreaker]

Cam choice needs to match the heads you’re running on the engine. What’s re the specs of the 1915?

[@ropadoped]

@@VWJawbreaker it's not built yet sir. I have an 1835cc that was under water I'm waiting for my floor jack to be repaired so I can tear into so I assume (I could be wrong) it has 90mm jugs,stock 69mm crank and stock cam. 041 heads in which the ports are the size of quarters. This was my first car(1963 Karmann Ghia) paid $1500 for the engine back in the day (1988ish) with the duel 44 idf carbs. I know now the carbs were probably to big for the engine but I was a kid...they simply looked cool.

[@VWJawbreaker]

@@ropadoped if you’re going to run the same heads and if they have stock size valves I’d recommend a scat c35 cam. Good all around cam

[@ropadoped]

@@VWJawbreaker good to kwow, what are your thoughts on going with 84jugs keeping the 60mm crank or stroking with 90.5mm b jugs and going with a 76mm crank I know 74mm will drop in but I don't know what the difference is here...to many choices.

[@ropadoped]

69mm crank I mean

[@prkid424]

Would the 9.2:1 be good for a Bug or Ghia?

[@VWJawbreaker]

It would probably be ok however that high of a compression is kind of a waste considering it’s higher than the cam needs. Always match the compression to the cam specs.

[@vayabroder729]

Higher compression is more power but can lead to overheating if not properly combined; especially street driven cars. To give you an idea; stock cars are between 6.6:1 to 7:1.

[@prkid424]

@@VWJawbreaker I’m in the process of building an 1835 with a W110 (go figure) what carb set up would be recommended. This would be going on a street driven Ghia

[@VWBEETLEOVAL1955]

Hi Gary, great video and learned again. With a stock engine (1200cc) is that a 6:1 ratio or higher and do you have to do this with a stock engine?

[@VWJawbreaker]

@@prkid424 what heads are you planning on running? You could run dual 40 IDF’s or a single 38 egas.

[@ChipsAndSparksGarage]

Great information, Gary. That seemed like an awful lot of gook leaking out of that head. What compression ratio do you run in Jawbreaker? 👍

[@VWJawbreaker]

Yes, the heads were leaking some. Lapping the heads and the jugs together will stop that. Jawbreaker not having a stock engine is running 10.0:1

[@VWJawbreaker]

@@Joesrustbuckets thanks buddy! Several ways to skin a cat, this is the way I chose for this situation. Part 2 will be out this week.