Anyone used a GB315 cam

getgeoff · Posted: Wed May 20, 2009 8:07 pm Post subject: Anyone used a GB315 cam

Has anyone ran this Gene Berg cam before. I am building a 2275 and it came with the used block that I picked up. It seems like a fairly wild cam.

Glenn · Posted: Wed May 20, 2009 8:08 pm Post subject:

It's similar to a FK-87.

Not a street cam.
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getgeoff · Posted: Thu May 21, 2009 7:18 am Post subject:

That was what I was afraid of. I guess I will have to tone it down cause I am building a semi daily driver.

neil68 · Posted: Thu May 21, 2009 5:45 pm Post subject: cam

I've used the FK8 and Web 86C in my street/strip 2332 cc and liked them both. The FK8 was very smooth and streetable...definitely a great cam!

The 86C is "between" an FK8 and an FK87, so not too bad...but definitely leaning more to the race side of performance.

I have family in Vernon and visit a few times each summer. Maybe I'll send you a PM next time, if you don't mind showing your motor and VW to me some time Wink

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‘68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 108 mph
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Alexander_Monday · Posted: Fri May 22, 2009 7:47 am Post subject:

I have in a 2110, dual 44's, ported heads 40X37.5, 1 5/8 header.

Depends on your definition of a "semi daily driver".

It will idle down to 850 if you want, but 900 to 1000 seems better.
Over comes reversion and starts waking up around 2000.
Comes alive around 3000.
Loves 4000 to 7500.
Solid 13 second combination.
Makes carb setup touchy, but doable.

I would consider it a weekend warrior cam that can be used as a semi daily driver, however that is kind of like asking what muffler sounds best.

If you are looking for a grocery getter, or are afraid to see 7500 to 8000 on the tach, forget it.
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mightymouse · Posted: Fri May 22, 2009 8:58 am Post subject:

MinamiKotaro · Posted: Fri May 22, 2009 10:41 am Post subject:

Alan_U · Posted: Sat May 23, 2009 8:05 am Post subject:

No mention of CR, heads valve combo, size of intake ports cc, transmission gearing, carburation, venturi size, distributor advance curve, weight of vehicle etc etc.

lighter car with shorter gears can be more driveable than a heavy beetle with taller stock gears.
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MinamiKotaro · Posted: Sat May 23, 2009 8:33 am Post subject:

Alan_U · Posted: Sat May 23, 2009 8:53 am Post subject:

MinamiKotaro · Posted: Sat May 23, 2009 10:02 am Post subject:

getgeoff · Posted: Sat May 23, 2009 10:18 am Post subject:

Okay, I see I need to give you guys some more info
2275
82 mm crank
5.5 rods
Steve Tims stage 2 42x37
48 ida
GB 1.4 rockers
1 5/8 exhaust
comp ratio not determined yet but think min 8.5 to 9.5 max
Tall big beef intakes
No ignition yet

Going into a 57 oval with p205/60/15 wheels
Getting a Rancho tranny ( will select gear ratio ) note Gene Berg recomended for this cam close ratio 3 and 4 or 5 speed.

As far as my definition for a semi daily driver is a car that goes like stink to work from May thru to Oct and if requires maint to fix then have dependable transportion for back up. Brought out on nice days but not stormy ones and will put in premium gas but not racing fuel.

mightymouse · Posted: Sat May 23, 2009 11:22 am Post subject:

Id say set your compression mid 10s. i did the calcs using the wallace calculator for dynamic compression. I set your motor at .050 deck, with 50cc chambers and started with 10.7 to 1 static CR. Yes for pump gas. Using an 87 for cam, this is what you end up with.

Static compression ratio of 10.7:1.
Effective stroke is 2.47 inches.
Your dynamic compression ratio is 8.17:1 .
Your dynamic cranking pressure is 163.37 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.17 :1.
V/P (Volume to Pressure Index) is 52

Pretty much right on the money. Any lower and your gonna have a soggy motor. I usually shoot for about a point over stock on dynamic compression, and thats where they seem happiest. Any higher and the heads cant shed the heat fast enough. If you have a stock shroud that is. If you have say, a DTM...ohoh.. now your talkin. no problems at all.
_________________
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.

getgeoff · Posted: Sat May 23, 2009 12:09 pm Post subject:

I think that this cam might be more trouble than it's worth. I think that if I got the GB310 or GB311 I would get more out of it. If I have to go the high end of the compression ratio chart and have close ratio gears then I don't know if it's worth it in the end.
Is the static compression ratio the calculated or set up compression ratio based on deck height and head cc? And what does 87 for cam mean. I was hoping to shoot for 0 deck height as I read that the most effective combustion chamber cooling is in the head and not at the top of the cylinder.

mightymouse · Posted: Sat May 23, 2009 12:28 pm Post subject:

by 87 i meant FK87 cam. (gb315)
gb310 is a bit smaller. like a k8. so, youd wanna drop cr a bit to go with that cam. 9.5-10 to 1. id have to calc it.

Cant run zero deck. if the crank flexes, the piston will hit the head. So either you have a safe deck in the top of the barrel, or you run zero deck there, and have the safe zone in the head. Via a step, or my suggestion is use a copper head gasket, crushed .040-.050. (just FYI)
10s on the compression chart isnt high. 13, 14, 17 to 1, thats where it starts to get fun.
If you gear it with stock gears and 3.88 its gonna be perf. You can hop on the highway if you want, and roll 70 mph, and it will still rail when you need. Stock super beetle gearing was made for 50-60 hp. You throw 170-200 at it, and its a rocket.
Honestly half an inch of lift is childs play. IMO its perfect for a big 2 liter.

Also, remember, its 6 of one, half a dozen of the other. You can run a smaller cam, and less compression, and still have same cylinder pressure. Make more heat, and less power.
You have to find a good balance of cam, then run the compression to match it.
Reason most novices will say a cam "wont work" is because they tried tossing it into something they had that was setup for a smaller cam. They dont run enough CR (scared) and then claim its the cams fault, or its NOT streetable.
Age old mistake.
And while aircooleds are a tad less forgiving than say a small block chevy, and engine is an engine. You can apply basic performance principles to it, and it will respond. You have to ask yourself, what do i really want out of it, and build from there.
You have already made it clear, this isnt going to be a car you drive thousands of miles on road trips, and your not looking to haul 4 people in your bug lugging around in high gear all the time.
So build it to haul ass. Smile

_________________
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.

getgeoff · Posted: Sat May 23, 2009 12:59 pm Post subject:

So what you are saying is run with this cam, build it to have 10.1 compressing ratio, get proper gearing and have fun with it! To me the cam is the brains of the engine and I just want to make sure.

mightymouse · Posted: Sat May 23, 2009 2:06 pm Post subject:

Yup. Thats what id do. You may have to eyebrow those pistons for valve clearance also.
Who is building your engine?
_________________
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.

getgeoff · Posted: Sat May 23, 2009 10:33 pm Post subject:

Alan_U · Posted: Sat May 23, 2009 11:28 pm Post subject:

mightymouse · Posted: Sun May 24, 2009 2:59 am Post subject:

Remember, everyone has their own recipes. What your suggesting to the OP alan, IMO is no good. short rods have no place on a stroke that big.
A short rod needs a better cyl head to produce same peak power as a longer rod. So of course in your recipe he wouldnt want to run such a big cam, because with your recipe the engine works itself and the head as hard as it can. Shorter rod = more force on the crank pin, and more side load on the cyl walls than a longer rod. One benefit though, is with the shorter rod, the piston dwells at tdc for a shorter period, so its less likely to detonate, and you can often get away with higher CR and more timing. On the adverse side of that is, with a longer rod the piston moves past tdc slower, leaving the charge a longer time to burn. SO you need less timing for peak power. Using less timing decreases the chance youll detontate, so you can run higher CR. But like i said, every builder does stuff different. ( 6 of one, half dozen of the other) Wink

As long as the tims heads have decent work on the exhaust side, and he has a good collector to go with it, that cam and a long rod will be fine.
2.3 is a BIG motor for a bug. And with IDA's.. i doubt hell have any driveability issues at all. Smile

_________________
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.


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