1641cc tuning - whats your thoughts???

[Lee.C]

well a few of you on here will remember this thread from last year - http://cal-look.no/lounge/index.php/topic,6900.0.html

After a few problems (read as incorrect set up by ME!) the motor is now running VERY WELL indeed and is making very good power

here are the spec's just to remind you :

- AS21 case - full flow oiling
- 69mm counterweighted crank
- 87mm barrells and pistons
- Stock balanced 311 Rods
- Engle 100 cam (giving 0.421" or 10.7mm lift at the valve)
- Stock dual port heads 040's with stock valves, cromoly retainers, hardened collets, matching spring pressures, mildly ported and set for CR of 9.0:1 
- 32mm oil pump (race trim)
- deep sump (race trim)
- Boosh 009 dizzy with electronic ignition kit (32degs)
- 8mm silicon leads
- Bosch W8 Plugs 
- Stock vw coil
- Power pulley (smaller 356 diameter)
- Lightened and balanced and 8 dowelled 200mm flywheel
- "Bolt up" rocker sharfts - 1.1:1 rockers 
- Porsche style swivel feet adjusters
- 3/8th Ali pushrods (282mm length)
- clearance set at "zero loose"
- Straight cut timing gears
- Stock fuel pump (no regulator )
- Dual weber 40dcn14 carbs on SHORT manifold (race trim)
- 28mm venturi's - 120mains - 50idles and 200 air corrections
- 4 into 1 merged header with single glasspack muffler (covered with exhaust wrap)

Now I have put a few miles on it and got used to how it drives and I am sure there is more to come, you see for a start it idles OK but it is a little RICH and does get a little chocked up and needs a little blip to keep it going  - Any thoughts 

Also the "powerband" has only moved UP by a few hundred revs and now it pulls alot harer at the top of the revs it still tops out around 5600rpm 

Now after talking with friends and doing some reading I am wondering weather to move UP to 32mm Venturi's and maybe some 130mains  Any thoughts   

[Jim Ratto]

32mm will "mathematically" get you 6200rpm.

[Lee.C]

32mm will "mathematically" get you 6200rpm.

Hmmmm please tell me more dude?

my main concerns are the stock sized valve  will they take the bigger 32mm venturi's and 130mains

[Jim Ratto]

32mm will "mathematically" get you 6200rpm.

Hmmmm please tell me more dude?

my main concerns are the stock sized valve  will they take the bigger 32mm venturi's and 130mains

yes, I know of more than a few motors with stock 35mm valves that spun to 7000+. Wenzel comes to mind first. He ran 88 x 69 with stock valves and 32mm vents, motor spun to 7200 like a super bike,
I think your cam is the limiting factor.

[Jim Ratto]

PS if you're running aluminum pushrods, you should open your valve lash up to .004". Running zero lash with aluminum p/r is a no no.

[Torben Alstrup]

More cam. THEN more venturi.
T

[Lee.C]

ok cool but you told different things by different people   you say zero is a no no but others say its totally cool  

They are the larger 3/8 thick wall type with ball ends, the gaps did open up a little after the first 50mile I reset them to zero/loose again and it seems perfect when its hot AND cold  

By the way I machined them all by myself on my own lathe  

Anyway just a couple of updates:

- it is running 200 air corrections
- it also has f24 emulsion tubes
- there are also 2 positions for the Accelerator pump arms - currently they are in the 2nd position which gives MORE  
- the carbs have 1.75 fuel inlet valves

Anyway back to the cam (engle 100) it has LOADS of low down torque but it still seems to be pulling at 5500rpm, what do you think it would be good for  

[Udo]

For your cam the venturies are big enough i think. What you first need is more cam and may be more head work.

Udo

[Zach Gomulka]

I also think the cam is your limiting factor, but you can make it think it's a little bigger by installing a set of 1.25's for .050"-.060" more lift at the valve. I'd definitely swap to 32 vents, as well. Your light buggy will like it!

[RMS Boxer Service]

Way too big oil pump, it will make too much pressure and open the oil control valves too early
so no oil is routed to the oil cooler. It will make the engine run HOT.  I would not use a 30 or
32 mm oil pump with out a pressure relief cover. With a 32 mm pump I would still reconsider
the pump even with the pressure relief cover.

Eagle W100 cam is very hard on lifter bores and make pretty much valve train noise, a W110
is much better in every matter.

Just my 2 cents


/Rolf

[Zach Gomulka]

Way too big oil pump, it will make too much pressure and open the oil control valves too early
so no oil is routed to the oil cooler. It will make the engine run HOT.  I would not use a 30 or
32 mm oil pump with out a pressure relief cover. With a 32 mm pump I would still reconsider
the pump even with the pressure relief cover.

Even if it was 50mm, it's Race-Trim, so it's staying!

[Lee.C]

Cool thanks for the input guys, Everything you have said makes perfect sence 

BUT,

- I don't really want to be spliting the case for a BIGGER cam so 1.25 MIGHT be a possibilty but that means ANOTHER set of push rods 
- The Oil Pump - you are not the first to say its "too big" but I have NEVER had a problem with it hot OR cold plus Zach is right it was a NOS Race Trim so its staying 
- Zach - are you saying only go up to 32's AFTER I install 1.25's 
- As for the heads - they are flowing 75cfm accross the manifold and are "Rated upto 130bhp" according to the FV shop that did the work 
- Also I mentioned the "accelerator pumps" on my carbs - they have 2 positions and they are currently in the MORE position  does anyone think I should move them to the LESS position

[pupjoint]

sorry to hijack, but if i were to build a similar engine, using 40 Dellortos instead , what cam is recommended since 100 is too small?

110 or equivalent?

sounds like good fun!

[Jim Ratto]

ok cool but you told different things by different people   you say zero is a no no but others say its totally cool  

They are the larger 3/8 thick wall type with ball ends, the gaps did open up a little after the first 50mile I reset them to zero/loose again and it seems perfect when its hot AND cold  

By the way I machined them all by myself on my own lathe  

Anyway just a couple of updates:

- it is running 200 air corrections
- it also has f24 emulsion tubes
- there are also 2 positions for the Accelerator pump arms - currently they are in the 2nd position which gives MORE  
- the carbs have 1.75 fuel inlet valves

Anyway back to the cam (engle 100) it has LOADS of low down torque but it still seems to be pulling at 5500rpm, what do you think it would be good for  

The 100Engle is made just for that running a small motor from idle to 5500. Without more overlap, it will be tough to get more rpm. If it runs well why rev the snot out of it?

[Lee.C]

Well after a day messing around scraping my nuckles etc it all seems good 

I was thinking there was not many more rev's to come from this cam - 5200rpm is about its MAX but I shift up at 5000rpm anyhow,

I have moved up to 32mm venturi's and 130 mains as well as moving the Accelerator pumps to the LESS position - this seems to have given me a MUCH broarder powerband 

oh yeah Jim I also opened up the clearences to 4thou 

It really does pull like a train! although there is a SLIGHT hesitation around 2k - Any ideas 

Oh yeah I can also pop the front wheels on the street much to the surprise of other road users 

[Zach Gomulka]

You wont need new pushrods with 1.25 rockers, you can shorten the ones you already have. But that will all be determined when you reset your rocker geometry.

Looks like you already have swapped to 32's with favorable results I would have done that first, just because it's easier than installing 1.25's. And since you already had them in stock, that's a bonus

Go stick some 1.25's in there and let us know the results!

[Lee.C]

You wont need new pushrods with 1.25 rockers, you can shorten the ones you already have. But that will all be determined when you reset your rocker geometry.

Looks like you already have swapped to 32's with favorable results I would have done that first, just because it's easier than installing 1.25's. And since you already had them in stock, that's a bonus

Go stick some 1.25's in there and let us know the results!

yep I had 4 32's in stock from my collection of old used dcn's  which is a shame as I spent $120.00 on the 28's 

With the 32's and 130 mains it pulls really really hard but as I mentioned there is a small hesitation around the 2k point  I am thinking maybe go up to 55 idles to go with the 130mains - Any thoughts 

I think I will get some "stock style" 1.25's and see what happens - I do have another set of 280mm pushrods already so I maybe lucky but if not then I'll shorten the current ones 

[Zach Gomulka]

In my experience bigger venturies will need a slightly larger idle jet, and richen up the mixture screws a little as well. But I'm no carb pro!

[dyno don]

     fyI >>>regarding engle 100 cam      >>>all engle w series cams made for 1:1 ratio are very gentle on the lifter bores...period..!!  the VZ series is another story due to the severe ramp of the cam. the only time a lifter bore has an issue with these w series cams would be from insufficient spring tension/improper valve train set up which will create valve float/which in turn hammers the lifter bore...     now ...where the hell is my beer..??

[Lee.C]

Thanks Zach - It just feels like it need a little more at the bottom end - we'll see 

And thanks Don that makes a lot more sence - I was wondering why such a mild cam would do this but it turns out it doesn't - Cheers dude 

[Jim Ratto]

you can determine if you need a bigger idle jet by how many turns from bottom the mixture screws cause a cylinder to fall off at.

[Lee.C]

you can determine if you need a bigger idle jet by how many turns from bottom the mixture screws cause a cylinder to fall off at.

Sounds very interesting - please tell me more dude 

[Jim Ratto]

Every Weber I can remember playing with, whether it was an IDA, DCNF, IDF or DCOE (I'm talking one barrel per cyl here), they all ran best when idle jetting was such that the idle was best at 3/4 to 1 full turn out from bottom. I'm not just talking VW motors either. I helped a friend do a big bore BMW 4 cyl about 10 years ago, with ported head, a "K8-ish" Schrick cam, and a pair of 45DCOEs with 38 chokes. We played hell trying to find right combination of idle air jet (F #) and idle fuel jet. But what made it easier was trying to set mixture screws. At one point, the car would idle nicely @ 1/4 out from bottom, but soon it would be limping along and loading up (too rich). We went bigger idle air and it cleaned up @ 1 turn out, with same fuel jet. But then driving it, as you tipped in off idle, it would stumble. So we went richer on fuel and bingo...3/4 turn out it idled nicely, stayed clean and pulled away smartly. I don't know if your DCN's have a separate air jet for idle (like IDA and DCOE). Those carburetors are from old Ferrari applications, right? Not sure where your float settings are calibrated, but you might experiment with changing float level specs. This can definitely cause stumbles, and/or hesitations under acceleration, and since the carb were originally designed to have their throttle shafts in same axis as axles of car (and not the crankshaft), they are probably more sensitive to float level inaccuracies. I went through hell with this when i first "bolted" my 48's to my car in 1991. The carbs insisted that the floats be "dead on" for the car to run well off idle and through the range. You might take some notes of where they are and what happens if you raise or lower them. I'd be interested to see what it does.
A note on selecting idle jets on smaller motors with generous venturi (at least from what I was taught by somebody that really schooled me on Webers, and by applying his knowledge and gaining my own experience)... contrary to what you might assume, sometimes a smaller cyl cc (again, when run with bigger vents) requires a LARGER idle jet than the same carbs on a bigger cc motor might use. Not always, but I've seen it on 1776 and under running 2 2bbl Webers. When I was younger, I thought in such a literal and linear fashion. I would think “smaller motor, smaller jets”, which would be true, if your vent size was optimized for the rpm each jet is “responsible” for. But the vents are at best a compromise (sometimes more so than others!) to get you a good crisp response when “under the cam” and to get you the high rpm pull. So if you err on the “high rpm” side of things (i.e. if YOU went 36mm for instance), you will have to realize, that under most conditions, you have severely “weakened” the message the motor is sending to the jet circuits. My old boss taught me this when I sold a kid a pair of 40IDFs to put on his 1600 in his bus. It was a total dog. It ran 50 idle jets, etc etc… and it bucked and stumbled off idle something horrible. Without “really” knowing, and of course, not asking somebody else, I just assumed the kid needed 45 idle jets. Guess what, it made it WORSE. Now Jerry got involved and taught me “small cyl cc and big vents means less pull on the jets, you need to give it more fuel” and it worked. We screwed in 55 idles and the thing was so much better. This same thing happened even on a 1904cc that was running 40IDFs on it, since my car had the motor out of it at the time (2276, FK10, 42 x 37, etc), and the 48’s were collecting dust, I let the guy borrow them. We bolted them on AS IS… 42mm vents, 60 idle, 165 mains, 205 air. His car seriously…would not run! Not run. It would fire up and die. Fire it up and blip throttle and it would rev, but put a load on it and the fire would go out. I remembered what Jerry told me and realized that we were really downsizing cyl cc vs. venturi and tried bigger idle and mains. It ended up running 70 idles (3/4 turn out on mixture) and 175 mains and the thing was a real tiger. Sure, the vents were WAY too big for the motor, but the lesson we learned was worth it. Had we had a set of 38mm, or even 40mm vents around (mine had been lent out at the time, not to return until 5yr later!), it would have jetted in with more “sensible” jets. I hope this makes sense.
And my opinion on cam for a seriously hot 1650-1700cc motor that you want to spin, would be something with around 255-262 degrees @ .050”. No it will not be torquey down low, and with big buggy tires probably makes no sense. But for a light car, with low final drive (including tires), I know from experience this cam timing will scream. If you were to bump cc to 1776, the K8 is incredible. See post somewhere about 86B we put in 1776 IDA motor,

Have fun doing wheelies.

[Lee.C]

Thanks Uncle Jim 

All of that makes ALOT of sence - for a start I have been doing all this tunning with the mixture screws 2 or more turns out

Anyway I am off out to the garage for another late nite tunning session and especially check those float levels (and yep they are old Ferrari carbs  )

There is more to come from this setup I am sure 

[Jim Ratto]

no prob. I think, if the mixture screws need to be 2 turns out to get a steady, hard idle, the idle jets need to be upped.

[Lee.C]

Well I only just realised the time so no tunning tonight (I think I have pissed the off the guys next door )

So I removed the carbs and checked the the float levels which were out  the problem is on these carbs it just relies on tabs on the float its self which you have to bend - not the best or easyist way but they are the same now (open & closed) 

I will also mention it has never idled that well even with the old vents (28's) and smaller idle & mains - which is confusing me, it always seems very rich at idle

anyway I am going back to basics in the morning with this combination:

- 32mm Venturi's
- 200 Air corrections
- 130 mains
- 55 idles
- 1 turn out on the mixture screws
- Accelerator pumps in the LESS position

Lets see what this combo gives 

[Lee.C]

Well after I put it back together - and re-balancing the carbs and reseting the idle/throttle stops everthing seems pretty good 

I actually went for 50idles in the end as I figured I was already richening it up via the mixture screws - once running I ended up moving the the screws out a little which helped smooth things out just off idle, one thing I am learning is that these carbs are VERY sensetive 

Now I have really "fine tunned" them and taken my time the motor is running/pulling VERY strong all the way through the rev range,

Right now I'm polishing my wheels before I go out Friday Night Cruzing - I will report back later 

[Lee.C]

Well guys I did approx 70 miles last night inc some very high speed highway stuff (90+mph!) it all seems cool - I took the plugs out this morning just to see what each cylinder was doing, 1+ 3 seemed a little rich so I backed out the mixture screws alittle more, clened the plugs and fired it and rebalanced everthing again, Inc the linkage which was ever so slightly out - it is now almost PERFECT, I have done another 60miles today inc some off roading and it has not missed a beat, Ok with these vents I have deffinetly lost some high end torque, it is now much more of a "Thrashy motor" it loves to be wound up and driven hard but it still has plenty of torque! I can now see what you guys mean about the sharft axis of the carbs (needing to be alined with the axles not the crank) They don't like HARD cornering BUT on the plus side she will pull 85+ in 3rd 

I am sure I still need to do some fine tunning (inc upping the mains maybe) but I now understand this motor ALOT more and I LOVE this new setup - Thanks for all your help guys