Need help with compression ratio setup

[Samtracing]

Basically it's a 92mm bore with stock 69mm crankshaft and I've added the following:
-130 camshaft
-ported and polished cillinder head
-chromoly push rods
-stock rocker arms
-high pressure oil pump
-straight cut gears
-bigger valves were added

I also have some doubts about the fuel system, is it possible to adapt a carb from another vehicle? For example, the dual Motorcraft carburetor that ford 6 cillinder engines use.
As for the compression ratio, I believe it's a 1835cc engine but what I'm having trouble with is how to measure the ideal comp. Ratio

[glutamodo]

I think just about any carb(s) you can imagine have been adapted at some point for a VW engine. Now, is that a good thing? I think in many cases, no, not really.

But then again, I think many of the usual suspect high performance carb setups for Bugs are often overkill. (sometimes I get asked HOW CAN I POSSIBLY run OK with a teeny-weeny 30PICT-1 on my 1600DP Baja? Well, it does run and runs fine. I have traded it's matching carb/distributor combo out for a matching 74-ish 34PICT-3 and 043905205 dizzy more than once, and with that, it runs much the same and never noticed any boost in top end.)


Compression ratio: you need specific raw data to compute it. You need to know the distance between the top of a piston at TDC and the top edge of the cylinder. You need to know the volume, in cubic inches or centimeters, of the combustion chamber of the cylinder head. Oh, you have to know the bore and stroke of the engine as well, which it sounds like you do not know for sure. And, you have to have the cylinder heads off the engine to get these numbers.

As for what is ideal, well part of that depends on what grade of fuel you want to be buying. Stock VW was 7.3:1 in the 72-74 era which is usually fine on cheap pump gas. Go above that and you will want to be running mid or premium fuel. Most people don't like to go beyond 8:1.
_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[Bashr52]

Wow a 130 cam in an 1835? That is on the large size. You are going to need some higher compression and a decent set of carbs to keep up with that. Don't expect a ton of power down low, you will likely have to ring it out to get into the power band (depending on heads, carbs, exhaust, etc).

Where did you get the heads from? Did the specify how many CC's the chambers were? Did you check your deck height?

[Zundfolge1432]

Your CR is set during build up. There are dozens of free calculators online you simply plug in the numbers and it does the rest. You can buy a CCing tool from CIP1 and follow the simple instructions I’d also take a peek at the numerous YouTube videos showing exactly how to. Just my opinion but I’d err on the conservative side and use a stock or cheater cam to have off idle and low end grunt all in by about 4000 rpm. It will take some work to adapt that water cooled carb to an air cooled engine.

[glutamodo]

yeah, as far as exotic cams I'd rather not have them either.
_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[VW_Jimbo]

That stock crank will not allow that cam to work its magic. Instead, the crank will kill the number 2 main bearing. You need to get a counter weighted forged crankshaft, H beam rods and be very meticulous when building it. Stock crank is good up to 4500rpm or so. Counter weighted cast good for 6500rpm or so. Forged up to 8500. But you need it to be built to spin that fast. Needs to be balanced, dynamically. Compression ratio needs to get into the low 10s or it will feel flat.
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[Samtracing]

So the cam is too big for the engine? What cam do you recomend? I'm currently figuring out the math to know exactly how many cc I have in each individual cilinder, but once I have those numbers, how can I use it set an ideal compression ratio or what is the safe range?

I also have some 1:40 ratio rockers but I couldn't install them due to the cam.

[theKbStockpiler]

The 130 starts to make power at 2500 RPMs which is going to make a terrible street car and to get the benefits of that cam you have to support the higher RPMs by upgrading most of the entire engine.

With a big duration cam, the compression stroke starts when the intake valve is fully closed and not at top dead center. I'm not sure how to convert dynamic compression to static.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[Lingwendil]

Maybe a good idea to bring this thread over to the performance section? likely to get some much better visibility over there. Maybe send a mod a message?

I'm building a street 1776 and I'm going with a CB2239, sort of like an Engle 100 but a bit better all-around. Going for 8.5-8.7 compression.



I've diven an 1835 with a 130 cam and dual 40IDF carbs, it was gross. Definitely change the cam! Otherwise it wont wake up until pretty high up in RPM and feel weird, and have pretty poor street manners.
_________________
73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!

Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884

Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087!

[Samtracing]

The engine was rebuilt from zero, there is no axial movement so I believe it is in good condition, so would a 110 or 120 cam work?

[theKbStockpiler]

What RPM range is the engine usually going to be in? Do you want to be able to slip out the clutch at 750 RPMs and start from a stand still?
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[Lingwendil]

Those valves are huge
_________________
73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!

Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884

Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087!

[glutamodo]

Yeah, they are, and it looks like the chamber volume is tiny! Time for some thick spacers?
_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[Samtracing]

I want it to have power from the start but still have some power when the engine is high reved, it's an off road build so I'm trying to make my engine more reliable, I assume it's going to be between 2000-4500 RPM
What"s the max RPM these engines can handle?

[theKbStockpiler]

If you use a cam with more duration , it creates more power but at a higher RPM range and at lower RPMs it falls on it's face.



http://vwparts.aircooled.net/Engle-W110-Type-1-Camshaft-1-1-or-1-25-Rockers-p/e6110.htm

I would recommend something that's range starts at 1600 RPMs and under. A stock VW crank will sustain high RPMs on it's own ,but if you push your expectations too far the engine is not going to last without making a lot of upgrades.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[VW_Jimbo]

Engle 110, kicks in right off the line and typically falls out around 4500. I love that cam. It works great in my combo. I run 1.25 rockers and it extends the top end of the cam out to 5500 plus. So, you get another 1000rpm for a few bucks. If you are in the dirt, that probably where you want to be. Wouldnt think the higher rpm range, above 5000, would be of value.

You should get over to the performance section. The guys there all eat and breathe compression, timing and gear ratios! And most importantly, how do I squeeze another horsey out of this combo!
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[ach60]

Read about your cam here
http://vwparts.aircooled.net/Engle-W130-Type-1-Camshaft-1-1-or-1-25-Rockers-p/e6130.htm
Then buy the Engle W110, John even tells you what compression ratio to set it at.
http://vwparts.aircooled.net/Engle-W110-Type-1-Camshaft-1-1-or-1-25-Rockers-p/e6110.htm
_________________
Good Luck
Al