Building a 74 mm Stroke by 88 mm bore with 042 or 044 heads?

[[email protected]]

depends on what size you want. You linked to the 1 5/8" ones.

http://vwparts.aircooled.net/Bugpack-1-1-2-Street-Max-Heater-Box-Right-p/2507-11-2507-14.htm
and
http://vwparts.aircooled.net/Bugpack-1-1-2-Street-Max-Heater-Box-Left-p/2507-10-2507-13.htm

are 1 1/2" for a lot less $.

[Danwvw]

Ok then when you said 1 5/8" a couple of replies up then you were taking about Extractors?
Ok Strike the above in italics, I think someone said that then took it out.
I was out looking at the Intake manifolds I have from a 1974 Bug and man, they seem little, not much point on bolting them onto ported heads, so guess I should also consider finding some bigger ones or going ahead with Dual 40 mm IDF carbs and manifolds now.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[David Wayne]

[mightymouse]

[Danwvw]

[Quokka42]

Yes, I am sorry. It is semantics, but the important thing is you are correct as far as I am aware - the volume created by the step is included in the head volume. The deck is always calculated the same way, but an engine with this type of head and stock CR would only require about 10 thou of deck, not the 40 thou clearance you will often hear quoted.

Deck volume is calculated and added to the chamber volume to calculate CR, but an engine with such heads could run zero or even negative deck with little worry as the piston will still have clearance to the head at TDC.

I've never had the step with the heads left in place and even on a stock build it would probably be a good idea to have it cut out and then set the deck yourself. As far as I am aware any head cut for a larger bore will have the step removed, including if you are running "slip-ins" but someone suggested this was not the case.
_________________
There has only ever been one man who was perfect, and they nailed Him to a cross.

[mightymouse]

[Danwvw]

Ok I haven't gotten this far yet but for example take the CB Performance 2232 Camshaft here: 2232 With
adv. dur. 262 deg.
valve lift .396" No recommended CR is given.
CB Performance Calculator.
This head for Example: Los-Panchito CNC-Ported 40X35 with 59cc of volume,
Deck Height: .015"
The CR comes out to be 8.3 to 1
A MoFoco head with 53cc of head volume like this: Super Street 35.5X32 would give a 9.1 to 1 CR with the same .015" Deck Height.
_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[[email protected]]

this is why we veterans can't stand the "step".

You have to be sure you account for it, and also don't account for it twice, when doing your math.

The ONLY time the step should come into play is if you have a 85.5mm bore engine. This is because anything larger and the piston can hit the step on the edges. So if you are running 87mm or larger P&Cs, you should cut the step out of the head ANYWAYS.

Running with the step adds .060" to your piston/head clearance IF you measure from the top of the piston to the top of the cylinder. IF you have a 85.5mm bore engine, you can simply run the piston flush with the cylinder, and the head step gives you the piston/head clearance you need. If you have .060" from piston to top of cylinder, and are also running a stepped head, the CR will be too low and it's going to run horrible.

The example above with .015" deck height, the engine won't last 2k miles.

If you are trying to figure out what works best, you MUST set the Deck Height to .060" or so, and do all calculations from that. To figure out what CR you have with what head CCs, or to figure out what head CCs are needed to get a target CR. Then if during assembly, you are off by .010-.015", it's not a big deal and you can just make that minor adjustment and run with it.
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[mightymouse]

[Danwvw]

Did the calculations again using the .060 Deck Height recommended for the two heads in the Example above and got these results.
Los-Panchito CNC-Ported 40X35

Super Street 35.5X32

Looks like the small valve head get's me closer to the compression Ratio I wanted which was 8.5:1 interesting! I guess this means that the larger valve head would need to be fly-cut a little more for it to give a little more compression. Any thoughts or comments about the CB-2232 Cam with 262 deg. advertised duration and .396" lift at the valves with 1.1 Rockers for this build. CB-2232.
_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[Danwvw]

Any Thoughts on what effect running the Shorter Rods 5.325" Porsche 356 and 912 Length will have on "Dynamic Compression"? Perhaps Up it a Little?
_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[mightymouse]

Well you have to remember, panchitos have the step and it needs cut out. Last 2 sets i did, they were exactly 55 cc once the step was cut.
So redo your calcs.

And when you do the dynamic it calcs the rod length and tells you. So yeah you could put both in there. but i wouldnt shorten the rod. Id leave it at 5.4
_________________
Nothing can stop the man with the right mental attitude from achieving his goal; nothing on earth can help the man with the wrong mental attitude.
Thomas Jefferson


Note to EVERYONE.
Know your ZDDP levels or you WILL lose a cam and lifters.

[mightymouse]

OH! and remember.. CB is retarded and if you buy panchitos and tell them to cut them for your 88s... you HAVE TO specify to cut out the step. They wont do it.
Im lucky to have a machinist local who is also a samba member. so i just handle stuff like that.
_________________
Nothing can stop the man with the right mental attitude from achieving his goal; nothing on earth can help the man with the wrong mental attitude.
Thomas Jefferson


Note to EVERYONE.
Know your ZDDP levels or you WILL lose a cam and lifters.

[Danwvw]

[Quokka42]

I believe Eagle cams are ground straight up on 107LC so intake closing will be 107+131-180 = 58 degrees ABDC

That was the lobe centre plus half the lobe minus 180 degrees for BDC
_________________
There has only ever been one man who was perfect, and they nailed Him to a cross.

[mightymouse]

yeah but 2 things. Dont use the 59cc volume number. since the step must be cut out of the panchito.
AND you must put in your target altitude.

You are on the right track. You are good with anything between 7 and 8 dynamic CR for pump gas. I try to stay out of the 8s if i can. This is not a very efficient chamber and was designed when leaded gas was 103-110 octane.
So i consider 91 as a MINIMUM for these engines.
But if you did want to run 87 you would stay between 6 and 7 dynamic and youd be doin alright.


if someone lives at extreme altitude i try and set them up so they make decent power for their every day use and can still travel down to sea level without any changes. So they are a tad on the high side for sea level travel, but for their constant daily use at 4 or 6k elevation they have the proper squish goin on.
_________________
Nothing can stop the man with the right mental attitude from achieving his goal; nothing on earth can help the man with the wrong mental attitude.
Thomas Jefferson


Note to EVERYONE.
Know your ZDDP levels or you WILL lose a cam and lifters.

[Danwvw]

Thanks, Just typed in 9000 feet and got a Dynamic CR of 5 something to 1. I live on the coast at about sea level but plan on driving the bus to Colorado in the future. Still thinking about the Mofoco 42's. I think they are 53 cc heads I think that is what they will be when fit for 88 mm Thick wall cylinders, Probably the same as for 90.5 or 92's would be, Not sure.
Also thanks Quokka42 for the bit about the CB-Performance 2232 Camshaft figuring to have a 58 Degree ABDC Intake Closure. I will run that and see how it changes the results.
Results here:
Static compression ratio of 7.6:1.
Effective stroke is 2.37 inches.
Your dynamic compression ratio is 6.37:1 .
Your dynamic cranking pressure is 117.81 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 6.37 :1.
V/P (Volume to Pressure Index) is 32
Interesting the Web-Cam 86 increases the compression and effective stroke a little.
_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[mightymouse]

I always use whats on the cam card for the ABDC measurement.
_________________
Nothing can stop the man with the right mental attitude from achieving his goal; nothing on earth can help the man with the wrong mental attitude.
Thomas Jefferson


Note to EVERYONE.
Know your ZDDP levels or you WILL lose a cam and lifters.

[Danwvw]