1680ccm basket case

[Mangokid]

Ok guys, so it might be OT, and it's not my engine, but it bugs the crap out of me, and perhaps some of you out there can solve my problem, even though it's got nothing to do with IDA's and low 11's.

Engine is:

AS21 case
std. 1600 heads, (mild porting but std. valves)
SCAT Valvesprings, retainers, caps etc.
2x Solex 40mm Carbs
SCAT c35 cam
Mahle sylinders
std. balanced crank, rods, 300gr lightened flywheel
32mm filter-oilpump
009
Bosch red-coil

Problem is, it won't run right. It seemes ok in the high revs, but when i hit 80km/h in 4th, 60km/h in 3rd  it runs like shit, shaking, tumbling goddammit.

It smells like it runs rich but it's hot like it runs very lean.

What's up?

My old man's preoccupied with gas mileage so that's why we didn't put together a 2110 in the first place.

[Lee.C]

just an idea but those 40mm solex's are well known for wearing on the sharfts - I had this problem when I rebuilt an old stock 356 motor that ran these carbs.

Might be worth whipping them off and checking for play/movement in the throttle sharfts - just an idea dude

[Zach Gomulka]

just an idea but those 40mm solex's are well known for wearing on the sharfts - I had this problem when I rebuilt an old stock 356 motor that ran these carbs.

Do you mean 40mm Kadrons or 40P11 Porsche carbs??
What do your spark plugs tell you?
Where is the timing set?
Are the points adjusted correctly?
Are the plug wires worn?
Are the carbs in synch?
Pull off the valve covers, check your clearences, and generally make sure everything is ok. Ive had those Scat lash caps fall off!

[Mangokid]

Ok, sorry for the lack of info guys, but here:

I mean 40mm Kadrons, and they are brand new, and seller told me they were jetted for 1600+, and that they were well suited for the c35 cam. Much more than that I don't know.

What do your spark plugs tell you?
They tell me that i got a bright and powerful spark on every turn, and they are just the right colour after being run for a couple of miles. I've tried several brands with identical results.

Where is the timing set?
12 degrees pre, but I've also tried everything from next to nothing up to 21 degrees pre. Marginal differences.

Are the points adjusted correctly?
yes, and I've tried a set up with WBX-ignition. Same result, crap.

Are the plug wires worn?
Brand new, and i've tried a couple of others too, all from bone stock to "hi-tech" bullshit wires.

Are the carbs in synch?
yes, both on idle and when it's revved up.

Valve covers have been off several times, and no clearances have changed.

Compression 8:1, equal on all four.

Thanks

[Zach Gomulka]

So if I read your post correctly, you are saying that it runs ok until about 80km/h, then it starts shaking, but when you get higher revs it cleans out and drives ok again? That sounds like the carbs are having a hard time transitioning from the idle to main circut. It wouldnt hurt to rebuild/clean the carbs, Kadrons are super easy!
Run the car up to the point where it starts to run like sh!t, then immediately shut it off, coast to a stop, and do a plug reading.
What jets are in the Kadrons? Factory is 55 idle and 130 main, these should work well on your motor. I would gauge the jets to make sure they havent been drilled out.
Good luck!

[Mangokid]

The Kadrons are brand new, as well as the manifoils, linkage etc etc.

Mains are 150 and idles are 60

I've done a few plug readings, and the answer is still the same. Like they should be, no matter where i cut the engine.

It sounds "ok" when I'm revving it up stillstanding, but when driving problems like the ones described above occur.

Still haven't figured out this one.

Anyone else? Thanks so far guys!

[SilverPig]

Aha..."seller told me they were jetted for 1600+, and that they were well suited for the c35 cam"

When did you start to listen to other peoples beliefs and thoughts?

[Mangokid]

Never, just for once thought i could trust someone, but hell, that sucker is out of business today...guess whom, hehe.