V-26, trapping and mileage

[FreeBug]

Hi, I've been reading all the mileage threads, and have made a few stabs at it, a 69 x 88 with CB Cheater in a bus, 76 x 85.5 with CB 2229 in a beetle.

Now I want to rebuild a 78 x 90.5 I had years back as a 78 x 88, with heavily ported stock valved heads, 8.5 C/R

I'm using B pistons, 40 x 35 ported-but-tight -ports (low volume) stock heads, a 1 1/2 4-to-1 with single quietpack, 44 mm throttle bodies, longer manifolds, 9:1 C/R or maybe even 9.5... looking to run euro 95 unleaded.

I really liked the V-26 in the 78 x 88, but I'm thinking that I should think about changing in the 2007 configuration? With the old engine, max torque was around 3500, and it pulled to 6-6500. I don't need to pull that high, would be happy with it pulling strong to 5500-6000.

I'm wondering if anyone has experienced this cam and found something better in regards to "area under the curve", I'm looking at power between 1200-5500 rpm... Thanks! I also plan on getting ACN's alloy pushrods, I'm looking for something quiet, too...

Any input is welcome and appreciated. Thanks!

[Alstrup]

Quiet, and V cams do not compute
Personally I have never figured out why people are so fond of the V series, unless we are talking all out off road or something. The engines have to be built VERY specific to actually gain from using those compared to many other solutions.
I have rebuilt quite a few engines with bashed lifters and valve train, where a V cam was hidden inside, and GAINED power by switching to different "softer" cams in the same range, along with getting a valve train that is much more quiet and durable.

That said. If you are looking at a cam in the same range as the V26 which pulls a wide power band, you might want to consider a Web 110/163 on 108 LC. Or if you want it more spirited above 5000 the 109/110.

T

[Dan Ruddock]

[modok]

If you are looking for that powerband and good MPG then consider the web 218, or 218/119 split.

On the other hand if the heads are good then IMo you would have more "area under the curve" and be able to run more CR with a more radical cam.
Not the RPM range you want tho.

[stealth67vw]

V-26 is a ratio rocker cam between the FK-7 and FK-8.

_________________
John Bates
JB Machining Services
1967 street Bug 2276 w/ 48 IDAs, 2020lbs with driver
7.76 @ 89.55mph 1/8 mile
12.34 and 108.10 mph 1/4 mile

[Alstrup]

[FreeBug]

I have the Berg version, the GB 309. It's not advanced, like the engle :

IO: 19° BTDC
IC: 54° ABDC

EO: 54° BBDC
EC: 19° ATDC

It's for 1.4:1 rockers, and I already have them, and was hoping to keep them.
Would there be any advantage to the Web 86A over this cam? It seems to have been popular "back in the day", but obviously a dated design... I was wondering if there was some new-fangled computer designed modern alternative?

I think cam design has come along, in some circles, in better design of ramps and whatnot to allow better tracking with less spring. Anything out there?

I'm also concerned about how much mileage will take a hit from the 38° overlap at TDC... I read a post recently where Mr. Alstrup was getting 400 ppm at power, which I want to see as proof that one can run a "hotter" cam without all the gas going straight out the exhaust. I have to go back and see which cam it was, how much overlap.

No, I don't know I/E flow ratios for my heads or anything useful like that, but I am wondering if I can arrive at a more educated guess at which cam to choose.

It's a heavy 1303, with low gearing for now, will step up to a 3.88 when I can, mostly for mileage reasons, as well as cruising comfort. I think. Thanks for the replies.

[FreeBug]

I have the Berg version, the GB 309. It's not advanced, like the engle :

IO: 19° BTDC
IC: 54° ABDC

EO: 54° BBDC
EC: 19° ATDC

It's for 1.4:1 rockers, and I already have them, and was hoping to keep them.
Would there be any advantage to the Web 86A over this cam? It seems to have been popular "back in the day", but obviously a dated design... I was wondering if there was some new-fangled computer designed modern alternative?

I think cam design has come along, in some circles, in better design of ramps and whatnot to allow better tracking with less spring. Anything out there?

I'm also concerned about how much mileage will take a hit from the 38° overlap at TDC... I read a post recently where Mr. Alstrup was getting 400 ppm at power, which I want to see as proof that one can run a "hotter" cam without all the gas going straight out the exhaust. I have to go back and see which cam it was, how much overlap.

No, I don't know I/E flow ratios for my heads or anything useful like that, but I am wondering if I can arrive at a more educated guess at which cam to choose.

It's a heavy 1303, with low gearing for now, will step up to a 3.88 when I can, mostly for mileage reasons, as well as cruising comfort. I think. Thanks for the replies.

[Alstrup]

You most likely will not see any advantages switching to a 86a. Personally I was never really impressed with that one. It has its place in a few combo´s though
If you are after low emission you have to think slightly different.

But erhmm, if you like the V26 and the cam and lifters are good, I´d say reuse it and upgrade the heads according to the increased displacement.

T

[FreeBug]

Thanks!

I am looking for mileage, not emissions, necessarily.. I used the example of ppm of HC because I thought it would e a good indication that the exhaust is not over-scavenging and taking out too much incoming mixture.

Heads are getting upgraded from 35.5 x 32 over-ported to 40 x 35.5 with mildly ported intakes, exhausts ports left mostly unmolested. 1 3/8 and single quiet pack is being replaced by a 1 1/2 heater boxes and header, still single quiet pack. Hope to gt a BAS oneday...

How much overlap before mileage drops off? would I be better off advancing te cam? When I used to plug this into DeskTopDyno, and ask it for best area under the curve 1000-500 rpm, it would come up with split duation cams, at 115° lobe separations... I know it's a poor model for the vw engine, but still, it has me thinking... web 119/218 on 112-115° LC? anyone ever run something like that? Thinkig out loud...

[modok]

It might be a good idea in some cases. If aiming for a wide powerband in a lowish rpm range...... a split with more on the exhaust could be best, BUT only if the headflow balance is right, as in 70-75% ex flow ratio.
With a 35.5 valve on that size engine you will be on the side of too much exhaust flow. ANd since you have IR carbs there is no reason to be shy opening the intake early. These reasons are why we're thinking split with more on intake.

IMO you should run 40 degrees overlap or 20, reason being if you want to employ scavenging you should run enough overlap that it works strongly, or less overlap so it isn't critical.
How much it will overscavenge will depend a lot on the header and where in the rpms you are. For instance might overscavenge at 3200 rpm but not at 4000. Depends on the harmonics of the header.

I think the web 218 would be good if you want to run 8.5-1 compression, This cam is soft ramps but does move the valve quite fast once lifted over .100" thus can make good torque.
I'd be tempted to run higher and use a bit more duration to bleed it off......... "dynamic compression" as they call it.

[FreeBug]

Sorry, yes I meant 218/119, 218 intake lobe, 119 lobe on exhaust...

The higher-compression-bleed-off is what I was thinking running the V-26 and closing the intake 54° ABDC, with 9-9.5:1, but...

I've had so many detonation probs on an engine with 8,75:1, with intake closing at 48° ABDC, Same fuel. I'm kinda hesitant and confused, thinking there must be more to it..lack of exhaust dilution of incoming charge? I'm just guessing here.

The cam was a CB 2229, 236° intake duration, 224° exhaust duration, 112° L.C.

[modok]

I am confused about that cam. the #29 cam is a stock cam according to cb.

Did you degree it? is that closing at 48 measured at .050" lift?

[FreeBug]

Sorry, Modok, my bad, I meant the 2228. Yes, the 2229 i think has less duration than stock! It's past my bedtime, can't find the cam card, but will try to post it tomorrow.

Yes, 48° @ 0.050" , at least on the cam card... IIRC, I didn't index the cam, just installed straight up. I should check that, too

Thanks for your thoughts.

[FreeBug]

Again, in my head it doesn't make sense, the stock vw closes the intake around 1mm off the seat at 37°, with as much as 8.5 C/R for 98 Ron, as stock, 7,7:1 C/R with 95 Ron.

I want to run 8.75:1 C/R, clsing valve 1.27 mm off seat @ 48° ABDC, on 95 Ron, and everything goes to hell! (Detonation)

I want to know what's happening before I make the same mistake(s) on the more expensive 2007...

[modok]

I see. That is the "cheater" on a wide LC i think.

half the duration plus the lobe center is where the closing point is. 112+112=224 ATDC, or 44 abdc, and that is with no advance at all

I believe the closing point of that cam would be 41-44, not 48. Could be wrong but you won't know for sure unless you degree the cam

[Alstrup]

Hello.
Its rather interesting that you had detonation problems at 8,75-1 CR. Do I understand it correct that it happened with using 95 RON. If yes, I know where the problem is. - Octane. With that cam anything over 8,5 - 1 requires 98 Ron or Vpower fuel. The reason is roughly spoken that the cam makes more DCR than the cam card tells you if the intake is good.

Powerwise I have noticed that an ILC on 106 is generally where the best overall performance is.

It is correct that an I/E ratio of about 73-75% is good for engines that peak before 5500 rpm. At this ratio there is normally a good relation and the gasses are burnt reasonably well. High reving engines can benefit from a higher I/E ratio.
The Web 218/119 can make loads of torque if needed. 9-1 on 95 octane is good. Fuel efficiency is good. But compared to the V26 you will loose some upper end power I think. The 218/119 typically peaks in the 5300 - 5700 rpm area dependant on the set up.

T

[FreeBug]

Wow, ok, thanks!

Still looking for the cam cards, I had them right where I could find them, on a pile of stuff.. now she-who-must-be-obeyed asked me to clean up, and I carefully put them away... I'll probably never see them again.

Thanks for all the thoughts, I guess I'll be sticking to the V-26, with 9.5:1 C/R

I'll rebuild the heads for the 2228 cammed engine and drop the C/R to 8.5, or even 8.3 if I'm feelin' scared!

Still would love to understand how the 2228 "traps" so much of the incoming charge. As far as induction, it was not exactly stellar, just a pair of CB's 34 PDSITs, with 28 vents, on a 1750. I did try 98 Ron, mileage went up, making me think that octane was better suited to the engine, but I still had intermittent detonation issues, and concentrated, unsuccessfully, on the timing curve. Now I have a black box, so that may help, too.

Thanks again for your words of wisdom, you guys rock!

Now, I'm off for a while where the Net don't shine, so don't take my silence for disinterest, I'll get back to cams when I find the cards...

[Dan Ruddock]

With dual one barrels I would go with less cam by at least 10 degrees. I would keep the cam with dual dual's. Dan

[modok]

I had a 1776 with the cb cheater cam 8-1 CR seemed just about right, but that was with dellorto DRLA 36 carbs.

With dual one barrel carbs the engine does not run equally on all four, especially at part throttle. When you have that one apart try lowering the CR on cylinders #1 and #3, as I think those are the ones knocking. This is odd advice but IMO engines that run unevenly may run better with "split CR", if you are trying to push the limits of octane.

The v-26 is a classic. I cannot think of another grind that is better overall.