cam selection help.

[advinnie]

Hi all I have two cams but not to sure on what one to use so any help and advice would be great. The engine is a 1800cc lump in a street vw beetle here's the engine spec. 
Dual relief case 
CW 74mm crank 
Lightened flywheel 
Stock dual port heads with stock size valves 
Stock heat exchanges 
4 into 1 header with a hideaway exhaust 
A pair of dellorto 36 carbs 
Running a gearbox from a 1200 vw beetle 
The cams I have are 
1 - gene berg 307 cam with 1.4 rockers. 477 lift at valves and 278 degrees duration 
2 - bugpack 4062-10 cam with 1.1 bolt up rockers with .425 lift at valves and 284 degrees duration 
Any advice on what one to go fir and why would be great cheers. 
Adam

[Marc]

Doing any intake port work? Any idea of what your compression ratio will end up at?
You'll need dual valve springs for either cam.
The GB307 (compares to an Engle FK-65) is actually the milder of the two; should work well up to the point where you become port-limited, say 5000 or so.
The 4062 pulls strong up to 6000+ and the one I'd choose (with some moderate porting, say a "mini-D" job on the intakes and some bigger heater boxes). Nothing comes for free, though, you'd give up some low-end grunt...probably not an issue with the 4.37 trans...
I guess the 307 would be the more sensible choice, especially if your climate makes stock heater boxes desirable. Do you have the correct-length HD pushrods for it? If I had them for the Bugpack but needed to buy them for the 307, I might just decide to put that money towards bigger heater boxes and a sweater instead.

[advinnie]

Hi mate heads are stock at the moment but I was not sure if I should or should have them ported.
The compression ratio will end up very close to 9.1:1.
The Gene Berg 307 cam is in use at the moment as well as the 74mm crank in my 1699cc engine and that pull hard from idle all the way up but the engine rpm falls flat at 5000rpm and that's all it will give but again that engine is just using stock heads. I don't know if it the cam or the heads holding it back cause it seems to want to go higher?
I'm only running single HD springs at the moment with the gene berg cam and 1.4 rockers and all seems good.
I'm in the UK and I use the car as much as possible so soon cabin heat would be good but are you saying the stock heat exchanges are to small? If they are what size should I go for?
By the way thanks for the reply

[advinnie]

PS what I'm after is the fastest 0 to 60mph time possible with this engine not to bothered about the top end speed 80mph is more than fast enough.

[Marc]

...the engine rpm falls flat at 5000rpm...I'm only running single HD springs at the moment...and all seems good.

Yes, you can get away with HD singles on the 307 - the cam is represented as "idle to 5000" and it's working as advertised.
The 4062, though, is marketed as "Moderate idle good up to 6500 rpm" - A fresh set of singles, perhaps shimmed up some, might work (for a while, anyway) but duals are advisable (and don't forget that bigger valves are also heavier valves, which require stiffer springs at the same RPM)...better IMO to just fit them now and not have to pull the heads to do it later.

Seriously, though, if you'll be using the 307 on an even larger displacement you can expect it to run out of breath even sooner - bigger valves don't offer much improvement in stock ports. 9:1 is steeper than I'd choose for it (around 8:1 would be my target) but you have better gas available, so while it may be spendy you should at least be able to feed it right.

Around 1800cc is the cutoff point IMO for stock heat exchangers - it should be obvious that RPM's a factor too, they'll need to flow as much at ~4700 on an 1800 as they do at 5000 on a 1700. The only readily-available/affordable replacement option is the Dansk sold as 1½" (around $300 a pair) - they have the larger pipes you'd want for a 6500 RPM 1800, but they lack any heat-exchange extrusion. With just a pipe in a jacket you'll get good airflow but not as much actual cabin heat.

[advinnie]

Thanks for the reply. So if I run the bugpack cam I will need dual springs?
I've also been doing some research and I was under the impression I had stock heat exchanges but I don't. What I have is basically a 1 3/8 J tube with a piece of tin raped around it. I don't know if that will make any difference compared to a true stock heat exchange?

[Marc]

Sounds like what CBPerformance sold as "racing" heater boxes - much lighter in weight than stock, but no significant performance advantage. I didn't mention that the "1½"" have flanged outlets so the header must have flanges welded on also.

While it's possible to run 6000+ RPM with singles, they need to be shimmed up fairly stiff. By their nature, duals can be set up with lighter seat pressure and achieve the same or greater RPM since the harmonic weak spots of the inner & outer springs come at different speeds - they also enjoy some inherent self-damping by virtue of the friction between the springs. As I said, you may be able to get away with singles on the 307 but IMO it would be folly to try with the 4062.

[advinnie]

Cheers for that mate. I'm looking into dual springs now but I thought it was just a case of take the. Out the packing and fit them but it looks like everyone is saying you have to machine the heads to get them to fit is this true

[Marc]

Which cylinders did you decide upon?
88s come in 4 sizes. One requires no machining to the case or heads, two require both, and the AA "slip-in thickwalls" require that only the heads be machined - but to the diameter that was once used only for classic 92s and late 90.5s.
Nominal diameters of the bores in the heads are, respectively: 93.8, ~95.5, 97, and 98mm...what do your new heads measure?
If the new heads are already cut for dual springs it'll be obvious, the bosses around the valve guides will be whittled down considerably. It's a simple job if you have the right tools (the cutter, an angle plate to tilt the head so the guides are vertical, and a drill press). Ideally the bosses should be cut down only enough to allow the inner springs to just fit.
Whether you go dual or single, be sure to use steel shims under the springs to keep them from gnawing into the aluminum of the head. For duals that's really all the shims are for in your application, so .015-.030" should be thick enough (and get the correct ones with a smaller I.D.) For the singles I'd plan on needing at least .060" to establish seat pressures in the ~150-lb ballpark (most HD singles are around 135 at 1.550" installed height, entry-level duals are typically 150-180). A machine shop should have the equipment needed to measure spring pressures; you can actually achieve reasonably good results with a bathroom scale, ruler, and a hydraulic press (or even a drill press). A second set of eyeballs, and maybe a third hand, makes it easier.

[advinnie]

The pistons ive gone/going with are the AA thick wall cylinders where the heads only need machining. Now the heads are only 45cc cambers so running 88mm pistons with a deck height of 1.5mm / 0.059" will give me a static compression ratio of 9.1 : 1. Now if I have this right, if I do NO work to the heads using the gene berg 307 cam would be pointless because it gives to much lift cause for stock unsorted heads so the bugpack cam would be better because it gives less lift ( but more than enough for stick heads) and be kinder to the valve train? But if I do get the heads ported and polished the gene berg cam would be the best because the heads can now flow more with the extra lift? Now I thought that if I kept the rpm down below 6000rpm I would of be fine with single HD springs and that dual springs were only for very high reving/high lift cams so if the bugpack cam has less lift why would I need dual springs with that cam and not with the higher lift gene berg cam?
PS im still learning here so any information would be great
Cheers

[Marc]

Actually those numbers result in a C.R. of 9.3:1.

If anything, the 4062 would be hampered more in reaching its full potential by the stock ports - if you aren't going to do any work to the heads the 307 would be more appropriate.

Lift is only one factor; even if peak lift may exceed what the port can use to full effect, what's more important is the amount of time the valve is open. The GB307 is actually a very mild cam as regards the effective duration, the lobes have long and gentle ramps.
Same thing goes for spring selection - the acceleration rate as the valve opens, and how harshly it's set back onto the seat, affect the spring requirement at least as much as the lift does.

[advinnie]

Right I think i'm slowly getting it.
The 307 cam may have more lift but the duration is less and lifts and drops the valves gentler so single HD springs can can handle it but the bugpack cam may not lift as much witch would suit unsorted heads but the duration is longer moving the power band up the rev range but also lifts and drops the valve harder and allows the engine to rev higher hence why I would need dual springs.
But if I was to get the heads worked on ( I've just spoken to a vw garage who said for £250 they could get the heads to flow 20% more) the gene berg 307 cam would be the better option although it has less duration the power band will be lower and that would suit what I'm after witch is off the line acceleration/street racing.
Have i got this right?

[Marc]

You're getting it. If you'll be staying with the 1⅜" heater boxes the 307 would be the better choice between those two. The 4062 still has plenty of low end (especially with the stroker crank) and I'd predict it to be quicker IF the heads and exhaust were both upgraded.
It's always a challenge figuring out where your perfomance dollar is best spent, since most of the time it's not an either/or proposition - one improvement compliments the next until you run out of money ....If you're settled on the 307 cam and smallish exhaust, it's probably not going to be worth sinking £250 into porting. But I'd still "spring" for new valvesprings (and shims) even if you aren't going to step up to duals.
If you don't port the heads, do at least port-match the intakes to your manifolds (and make sure the gaskets don't overhang)...you can do that yourself with a Dremel.

Now, let's hope that the cam still looks good when you tear into this project. If it's tired, there are other cams for 1.4 rockers to consider - another 5° or so of effective duration would be nice IMO.

[advinnie]

Got an email from a vw machine shop saying
" with stock size valves and a port job the valve will flow 20% more at .420 lift but above this lift with stock size valves even with the best port job going, will not flow anymore. To get more flow at a higher lift you need larger valves. Max flow is valve size x 0.3 so 35mm x 0.3 equals max flow at 10.5mm/.413" so lifting the valve above this is pointless. The Gene berg 307 cam was designed to be use with 40mm inlet valves where max flow will be around .472" lift so the bugpack cam would with the head work would still be the better cam to use with stock size valves. Now on to the exhaust system 1 3/8 header will restricted the max/ higher rpm causing heat to build in the heads but will increase torque In the lower rpm range. Therefore no to stock heater boxes and the 1 1/2 heater boxes are crap you might as well run 1 1/2 J tubes. The 1 5/8 header is way to big and that's all I will say on that.
So the best combo I would run is
88mm pistons
74mm crank
Lightened flywheel
Dual Dell 36 ccarbs
Stock heads with some work on them
Bugpack 4062-10 cam
1.1:1 rockers ( allows you to use single HD springs)
1 1/2 J tubes
1 1/2 merged header ( not a 4 into 1 header)
Hope this has helped you with this combination you should be about 75 to 80 BHP and dam close to 100 lbs torque. "

Does this sound good to you lot?

[Marc]

That's one combination to consider, but you'll lose all heat & defrost (dunno about your M.O.T. regs, but in my home state a functional windshield defroster is required by law); so factor in the cost and hassle of installing a gas heater if you want heat. It is possible to cobble up a non-freshair heating system similar to what was used on pre`63 1200s if you're only after a minimalist way to satisfy the law.
I've used the Dansk 1½" heater boxes and been unimpressed with their quality-control as regards flange placement, and as I said above they don't put out as much heat as stockers - but your present unfinned 1⅜" boxes are no better. At least you get some warm air flowing to the windshield to defog it on a damp morning, I wouldn't classify them as "crap" (just a bit overpriced) and maintain that you should get some if your intention is to set this engine up for >5000RPM.

There's nothing inherently wrong with opening a valve further than necessary to achieve the maximum flow that the port or valve allows, and in fact it's common to do so since it's impractical to design a flat-tappet cam lobe that's flat on top - the valvetrain motion needs to decelerate, change direction, and accelerate as the nose of the lobe comes by so the lifter doesn't fly off the end and slam back down, if you limit max lift to what the port/valve are capable of you're giving up more time spent near the top of the useful flow curve.
This family of Bugpack cams was designed for 1.1:1 rockers only (there'd be no harm in using 1:1 if it was necessary to reduce the lift, but 1.25:1 or greater were never considered when the lobes were designed.)
The 4061 grind can just get away with shimmed-up, fresh stock 1600 springs with aluminum pushrods; for the 4063 entry-level duals and HD pushrods are mandatory. The 4062 is, as one would expect, right in the middle - stock springs are out of the question and duals may be overkill, but it depends upon the peak RPM and the overall valvetrain weight (lifters/pushrods/adjusters/valves/retainers) - just going from stock adjusters to swivelfeet could add enough mass to make HD singles inadequate. IMO, now's the time to machine the heads and install duals to be done with it - if you choose to stick with singles, I reserve the right to say "told you so"

"Merged-collector" headers are a subgroup of 4-into-1 designs, the terms are not mutually exclusive. A true merged system will typically benefit top-end power over the more compact style of "street" header, but protrudes out the back of the car several inches more which can present a ground-clearance problem, especially if the rear is lowered - they also need a muffler designed specifically to tuck back forward unless you want it hanging out in space behind you. MOST merged systems have the pipes from #1 &3 tucked a couple of inches inboard from where heater boxes or typical "J-tubes" are routed, so they don't clear a thermostat and don't allow the option of using heater boxes - to run the "sled" tins (which you want to do, to duct the spent cooling air rearwards) you'll need to do some custom fitting...but there do exist specialized merged-collector systems which retain the stock width. Didn't you just buy a new "street" system of some kind?