Twin Plug 1883 Advance Curve & Ignition System Advice Needed

[Martin Benade]

If you don't mind sharing, what cam, any head work, and do you think either the mains or rod bearings will have a hard time surviving? I expect the 6500 rpm will not be used that often. It sounds like a very nice engine- us Americans always liked low-end torque.

[C J Murray]

Hi Martin,
There are too many details to list and I might want to keep a few secrets but I can say that you don't need to do too much trick stuff. An engine this size needs larger intake valves and the stroke was achieved by using smaller rod journals but the same rod bearings are used in some ultra high hp drag race V8s without problems. The stock Porsche mains work well on 170hp 1600cc race engines that spin 7500rpm all the time without trouble. The combination of the small rod journals and the extra stroke may weaken the crank slightly but the extra strength of the modern Scat crank should make up for that. The car is going to be my "touring"(cross country) and daily driver(weather permitting) car and I didn't want to rev it much anyway. What I wanted was the 150+ torque from 3000-5700rpm.

The car that the engine goes in is close to you at Panelwerks in Mentor waiting to be picked up.
Cliff

[Craig Richter]

Vic, Ron, Jac, Mario, et al,
You guys are absolutely amazing! I would love toy pay $1,000 to hang-out with Ron for a dyno day! Only problem is that I totally agree with him...
So, my only point is that you guys have started some really fun and intriguing topics (including the Hirsch roller crank topic), which is the whole point of club interaction, and a lot more interesting than political/lawsuit stuff. Thanks for bringing us back to the club...
Craig

Cliff: Perfect! Maybe not "bragging rights", but perfect for street-driven, cost-effective fun.

Ernesto: Gene Berg has made heavy pulleys for decades, and very effective in certain uses.

[C J Murray]

Cliff: Perfect! Maybe not "bragging rights", but perfect for street-driven, cost-effective fun.

Thanks Craig. Bill Sargent started this thread asking about ignition systems and that is a question that comes up fairly often. Back then I tried to make a fairly simple point and that is that the basics must be done correctly first. The pistons, heads, and cam combined with careful assembly and attention to clearances is what makes the most difference for the smallest amount of money. Once the engine is built you have to address the issue of carbs and exhaust that work best on that engine. There are big improvements to be found with those. "Bling" ignition systems give very little improvement for the money spent. Crank fire is the best improvement but seems silly on a 356 antique farm implement. Fuel injection combined with programable ignition is effective but very expensive. First the cost of the system then programing time on the dyno. John Heinricy, racer and retired GM engineer, told me that GM spent millions of dollars programing each new model. You won't spend millions but you will spend a lot. For what we do with our antiques the stock fuel pump, points ignition, and carbs will work very well.
To give you an example of how important the correct carb and exhaust choice is here is my 2133 in 3 different modes. You can see that the small carbs stopped making power at 4100rpm and the small exhaust signed off at 4900rpm. They just couldn't keep up with the size of the engine. The exhaust and carbs from the race engine are good for more than 167hp so that is the limit of this engine with the cam and other choices made. It will make a bit less when the street carbs and exhaust are in place.

1201-crappy sport muffler-Solex 40 36 venturi
1203-crappy sport muffler-Solex 44 38 venturi
1204-Bursch stepped full race header-Solex 44 38 venturi

[Ernesto Cabrera]

Vic, Ron, Jac, Mario, et al,
You guys are absolutely amazing! I would love toy pay $1,000 to hang-out with Ron for a dyno day! Only problem is that I totally agree with him...
So, my only point is that you guys have started some really fun and intriguing topics (including the Hirsch roller crank topic), which is the whole point of club interaction, and a lot more interesting than political/lawsuit stuff. Thanks for bringing us back to the club...
Craig

Cliff: Perfect! Maybe not "bragging rights", but perfect for street-driven, cost-effective fun.

Ernesto: Gene Berg has made heavy pulleys for decades, and very effective in certain uses.

Craig, that's just not a "heavy Pulley" its a Fluid Damper harmonic balancer.

[Steve Proctor]

Allaway back to day one in the posts on this subject: Eric C. curious as to how big you went on your venturis on those 42mm Solex?? 1883, nominally 280* cam, similar to what I am building. Guessing I will give away some performance for aesthetics if I run my vintage Abarth exhaust and may wind up with a Bursch...

[Eric Cherneff]

Allaway back to day one in the posts on this subject: Eric C. curious as to how big you went on your venturis on those 42mm Solex?? 1883, nominally 280* cam, similar to what I am building. Guessing I will give away some performance for aesthetics if I run my vintage Abarth exhaust and may wind up with a Bursch...

I am running 34mm venturis. I tried 36mm and they greatly reduced drivability with no discernible advantage at higher RPMs.

[GregVandenbussche]

Resurrecting this thread;
Built a 10.5:1 1883, Wilhoit WR68 cam,, running a 123 programmable with twin cap and driving a simple msd with two coils: John advised 10deg static and 26 deg max all in at 3000, however I'm having hesitation around 2500-3000...anyway, trying to figure it out and was wondering if anyone ended up with a specific curve they are happy with?

[Ernesto Cabrera]

Resurrecting this thread;
Built a 10.5:1 1883, Wilhoit WR68 cam,, running a 123 programmable with twin cap and driving a simple msd with two coils: John advised 10deg static and 26 deg max all in at 3000, however I'm having hesitation around 2500-3000...anyway, trying to figure it out and was wondering if anyone ended up with a specific curve they are happy with?

Greg, are you triggering from two different distributors or just one? Is best to trigger just from one source, since you may be picking up some noise from the other trigger if you are using two. The other thing is, the MSD is very sensitive to induction from other wires and its best to use spiral wound plug wires and make sure to separate wires so that they are not adjacent to one thats next on the sequence.

[GregVandenbussche]

Hi Ernesto, thanks for your answer, pickup from one source, some of the spark plug wires are close to each other on the Mitsubishi twin plug cap which is innevitable

[Ron LaDow]

Greg,
If John can't tell you, you're pretty much looking for a dyno.
I can tell you a twin-plug with diametrically-opposed plugs and small domes in a 86mm bore likes 7* static, 25* all-in and the curve the springs give; not fiddling with asymmetric weights or such. I had a 'cough' early on at tip-in, but some A/P fiddling put that right. But I doubt that has anything to do with your combo.
Paul Hasselgren over in Berkeley has a well-instrumented dyno (or used to; it's been a while since I've dealt with them). He can run accel tests and get it straightened out. Not cheap, but you're dealing with expensive hardware already.

[GregVandenbussche]

Hi Ron,
Great thanks!! I'll try lowering the advance at idle and mimic a 031/022 curve 7-25, I'm a little worried about pinging that's the main reason

[Ernesto Cabrera]

Hi Ron,
Great thanks!! I'll try lowering the advance at idle and mimic a 031/022 curve 7-25, I'm a little worried about pinging that's the main reason

Greg, are you running Solex or Webers? What's your venturi seize?

[Ron LaDow]

Greg, are you running Solex or Webers? What's your venturi seize?

Greg, this is the point. What works on my combo is no better than a crap shoot for yours. To many dependent variables.

[GregVandenbussche]

Running dellorto 45 with 34 Venturi, I know it's a little large but I don't have 40 on hands, I'll try 36 ones tonight but I think it's probably too small
Running 75 idle jets made the transition better, and my Lm2 indicate that this is lean, but my eyes and nose indicate otherwise . I lowered the advance first from 10 to 7 and didn't really change anything start dying if I go to 5 degree at 1000rpm