Carbs for my 3.0L M20.... School me

[E30-TourZing]

Soooo I am back down the rabbit hole again.


My friend went to 'the vintage' car show, took some pictures and I saw all these beautiful inline 6's with webers and I am investigating again if that is the route I want to go.

By mid August I imagine I will have put together my block and cylinder head.

My build spec is...


Head-

- 885 head - machined and cleaned
- Reground valves
- Schrick 284/272 cam
- MM recommended valve springs - (Not beehives as they had issues and switched to the ones that I have purchased.)
- New Rockers
- (will buy) adjustable cam gear. Likely nukeproof

Block -

- 86' ETA block, single lock tang main bearings
- M52B28 Crank = Rods
- MM Sport/Rally pistons
- Molly Rings
- Coated bearings and such....


Conundrum....

- I still have to buy 24 lb injectors and SSSquid Chip. The total in parts will likely be somewhere in $700 range for me in Canada. Likely more with how much USD items cost arriving here.

- At some point soon I want to run RHD ITB. This comes at a cost off... $2500 before shipping and duty, so lets say $3000. Plus MS PNP $1200 CDN, I am looking at more then 4.5K+ for intake a fueling.

- My other option is to spent $3200 CDN and get triple webers with linkage and manifold. We have a performance shop in Vancouver who is willing to bring it all in for me at that rate.

- I am not building a race car, but I am certainly interested building my touring to be a emotional, quick and involving car. I would like something that makes me excited to drive. Two of my close friends are carb wizards with 60-years of experience between them specializing with Porsche's and I feel like I would learn the dying art of tuning.

So as you can tell, I am emotionally engaged in Webers.

I could eliminate the need for a costly chip, TPS sensor + plate, Larger AFM, by going directly to carbs.

- Logically though, a few people who are well educated in this craft have advised me not to do it. Jim from MM said my engine likely wouldn't last as long, and he just believes strongly in EFI.




- So this is where I need help from the greats of this site. By the end of the summer I would like to install the motor into my car and start driving in the fall.

The price difference is pretty big, what do all you people recommend I do and why?

Any first hand experience with carbed M20 Strokers or carbed stock M20's?




Also.... The weber guy in Vancouver said Spain made Webers have been more problematic in recent years and he recommends a carb that is half the price. Its made in China, but is completely interchangeable with original webers. The company name is FAJS. I cant seem to find a lot of info on them, but that would bring my price down considerably. Does anyone have experience with these instruments?


Thank you all in Advance!!!


P1011349 by Jan Willem Wilderom, on Flickr



P1011529 by Jan Willem Wilderom, on Flickr

[SkiFree]

Conundrum.....

So as you can tell, I am emotionally engaged in Webers.


The price difference is pretty big, what do all you people recommend I do and why?

Any first hand experience with carbed M20 Strokers or carbed stock M20's?



Also.... The weber guy in Vancouver said Spain made Webers have been more problematic in recent years and he recommends a carb that is half the price. Its made in China, but is completely interchangeable with original webers. The company name is FAJS. I cant seem to find a lot of info on them, but that would bring my price down considerably. Does anyone have experience with these instruments?

1) Carbs are not the logical choice (but neither doing this build in the first place). I much prefer them because of the analogue approach. Fiddling with jetting provides a nice break away from a digital world. The fact that you have a few weber friends in the fold is a huge plus in the viability of your ill-advised-but-awesome adventure.

2) Yes, a bit.

https://www.bmw2002faq.com/forums/topic/116731-m20-triple-weber-build-x2/?&page=9#comments

https://www.instagram.com/p/Bp2QIj2Hg8y/

https://www.instagram.com/p/ByJolhdACsh/

3) No...nonononooooo… The Chinese knock-off webers are NOT a viable alternative. I've dealt with random batches from present back to when they were throwing the first test samples at any hapless gentleman who unwittingly wandered into the side halls of SEMA. The tolerances are much worse on average than current real weber carbs. The Chinese jetting's don't follow any logical sense (stamped with random sizes that no way correlate to what the actual hole size is).


Overall, this is a bad decision, and you absolutely go for it.

[Jaxx_]

How fast do you want to spin it? What's the plan for ignition if you go carbs?

Personally I enjoy the "purity" of carbs, but for power under the curve, it's hard to beat an EFI setup. If you don't mind pumping the pedal a few times when it's cold, and don't plan on climbing mountains during long road trips, the carbs will perform fine. If you plan on storing the car during winter months, you'll likely also have to take the extra step of draining the gas and doing a little preventative maintenance to make sure you don't rebuild/clean them every season.

Do what you'll enjoy. No project is ever "done" anyway

[digger]

Do whatever you want. If everyone did the same builds it'd be boring

[SkiFree]

What's the plan for ignition if you go carbs?

Redline (US's weber importer) carries a dandy little TPS sensor adapter that fits on the end of one of the carbs. Couple that with the NoDiz wasted-spark system (like megajolt, but can read the M20's 60-2 wheel) and you have a slick programmable ignition setup.

https://www.instagram.com/p/BXgTyPUgBfC/

https://www.instagram.com/p/Ba4zLFMnGDT/

[ForcedFirebird]

The stock ECU could work for ignition - just tie the WOT switch wires together so it stays in the WOT map.

[E30-TourZing]

1) Carbs are not the logical choice (but neither doing this build in the first place). I much prefer them because of the analogue approach. Fiddling with jetting provides a nice break away from a digital world. The fact that you have a few weber friends in the fold is a huge plus in the viability of your ill-advised-but-awesome adventure.


2) Yes, a bit.

https://www.bmw2002faq.com/forums/topic/116731-m20-triple-weber-build-x2/?&page=9#comments

https://www.instagram.com/p/Bp2QIj2Hg8y/

https://www.instagram.com/p/ByJolhdACsh/

3) No...nonononooooo… The Chinese knock-off webers are NOT a viable alternative. I've dealt with random batches from present back to when they were throwing the first test samples at any hapless gentleman who unwittingly wandered into the side halls of SEMA. The tolerances are much worse on average than current real weber carbs. The Chinese jetting's don't follow any logical sense (stamped with random sizes that no way correlate to what the actual hole size is).




Overall, this is a bad decision, and you absolutely go for it.

- You are correct.. this engine build does not make sense. By the time this is done I wouldn't be to far away from the cost of a decent condition E36 M3

I very much agree with you about how nice mechanical tuning can be. I love the idea of a mechanical instrument, but a lot of this is also because I have never worked with a standalone tuning system, and it mildly seems a bit over my head. I also love the idea of being a student to these masters of vintage European cars. At our shop we specialize in body work, so it would be another step of learning I would appreciate deeply.

- Thank you for your input on FAJS. The carb man I was talking to is an old fella who has been selling webers for decades. His experience is with Datsun's inline 6's and has been selling more FAJS carbs in recent years then webers apparently.

I was stoked to see you have some old webers in photos. Did I read correctly you will be refurbishing them? I see on craigslist localish to me DCOE Weber 45's for sale often. They are almost always in pairs and for Datsun's, but there seem to be singles off of Lotus super 7's and such to. It would keep my costs down initially, but I would need to re-jet and perhaps ever refurbish them to get good results.

Do you recommend used carbs?

Do you recommend a 45 vs a 40? I am going more for torque then HP, and I am worried a 45 will affect the pull down lower.

Also.... I see you spend most of your time in photos with 2002's. Although, do the intake plenums cause issue with stock brake booster in E30's with your experience?

- Should I run an air-box vs plenum filters?


Thank you so much for your time Skifree. I wish I could bring over some beer, check out your cars and connect about this well accepted, yet invasive hobby.

[E30-TourZing]

How fast do you want to spin it? What's the plan for ignition if you go carbs?

Personally I enjoy the "purity" of carbs, but for power under the curve, it's hard to beat an EFI setup. If you don't mind pumping the pedal a few times when it's cold, and don't plan on climbing mountains during long road trips, the carbs will perform fine. If you plan on storing the car during winter months, you'll likely also have to take the extra step of draining the gas and doing a little preventative maintenance to make sure you don't rebuild/clean them every season.

Do what you'll enjoy. No project is ever "done" anyway

I super appreciate your quote of 'no project is ever "done".

I feel the same way, but I am trying to complete it 98% how I ultimately want it all in one go.

My issue is money, and I don't seem to make enough of it for such an extensive build. I am able to pull it all together how I want, but I cant do it all in one go as I am refusing to use my credit card for any purchases. Due to this I just want to make calculated decisions and not accumulate anything that I do not see myself keeping for the long haul.

I plan to spin the motor to 7K RPM. I want a reliable last me a lifetime motor, and I dont see myself needing to ring the motor out much more then 7K.

When you say 'under the curve' you mean torque? I have heard that carbs offer better torque then EFI. Perhaps my sources are ill informed?

[E30-TourZing]

Redline (US's weber importer) carries a dandy little TPS sensor adapter that fits on the end of one of the carbs. Couple that with the NoDiz wasted-spark system (like megajolt, but can read the M20's 60-2 wheel) and you have a slick programmable ignition setup.

https://www.instagram.com/p/BXgTyPUgBfC/

https://www.instagram.com/p/Ba4zLFMnGDT/

Neat! I was just planning to use an MSD ignition. Correct me if I am wrong, but the spark has a longer pulse if I am not mistaken. Thus causing better combustion.

Do you use the wasted spark setup?

[E30-TourZing]

Do whatever you want. If everyone did the same builds it'd be boring

Jim told me there is a racer in the US who has a 3.0L Rally spec M20, and he has tripple 45 webers. Jim said he puts down over 260 WHP and torque, but is unsure of the longevity of the motor with how much is being thrown its way.

Disclaimer.. I am not wanting to make 260WHP.... not even close. I would be satisfied with 200-220 WHP. I imagine thats all I would get without having a reworked head like you have going.

[Motheye99]

Look at how they do dual webers on a M10, I knew a guy with a 2L stroker M10 and Weber 40's. he bought hte car with 25K on the motor and it ran like shit. I think the Weber's needed a rebuild. He wad a MSD box for ignition.

[digger]

Jim told me there is a racer in the US who has a 3.0L Rally spec M20, and he has tripple 45 webers. Jim said he puts down over 260 WHP and torque, but is unsure of the longevity of the motor with how much is being thrown its way.

Disclaimer.. I am not wanting to make 260WHP.... not even close. I would be satisfied with 200-220 WHP. I imagine thats all I would get without having a reworked head like you have going.

There is one around this part of the world that put down 350rwhp although current spec is closer to 330 if I recall. On 42mm chokes

I don't think webers will cost you power, the stock head and mild cam will be more restrictive depending on what chokes are used.

[E30-TourZing]

My buds own a BMW wrecker local to me and I have advised them to buy this E23

https://vancouver.craigslist.org/bnc/pts/d/burnaby-1978-bmw-730-parts-car/6912406954.html?lang=fr&cc=ca

I wouldn't mind stealing the carbs from it... hahaha Tuned for a 3.0L as well ;)

I sent an email out, hoping they are what we need. Those euro bumpers and M30 manual trans are worth some coin. The wheels too it seems.