alexg89 Posted March 20, 2019 Report Share Posted March 20, 2019 Hello all Iv read my fair share of threads in here and i think iv got the majority of this down i have since located my webers, intake(which i had cerakoted and will be a 2 piece set up) , believe the correct Dizzy ,l28 shaft and an aeromotive 13301 regulator gonna also have to find a way to make a pedestal for the dizzy to sit on but i think i have that covered just want some quick insight on maybe jetting and anything to watch out for any help is appreciated, thanks guys 2 Quote Link to comment
Tom1200 Posted March 20, 2019 Report Share Posted March 20, 2019 While I have 0 knowledge of KAs getting the jetting in the ballpark should be easy enough; figure out your power output and RPM range, then simply find jetting recommendations for the same size webers running close to what you have. That should make it run well enough to either take it to a dyno place to fine tune it or if you have an A/F ratio gauge fine tune it that way. Even after you get it running well take it to a dyno place and pay for an hour. That extra fine tuning works wonders 2 Quote Link to comment
alexg89 Posted March 20, 2019 Author Report Share Posted March 20, 2019 yah i plan on trying to get it to a dyno.. hoping in the next week or so ill be able to start putting everything together and at least hear it run.. Another concern that i just kinda thought about is vacuum sources.. Power brakes and the vacuum advance.. what should i do for a vacuum source? Drill and add a nipple to each runner and bring them to a block? or whats the best approach on that 1 Quote Link to comment
Crashtd420 Posted March 20, 2019 Report Share Posted March 20, 2019 Make sure the dyno place knows webers..... If they dont they may not have jets on hand..... 2 Quote Link to comment
alexg89 Posted March 20, 2019 Author Report Share Posted March 20, 2019 6 minutes ago, Crashtd420 said: Make sure the dyno place knows webers..... If they dont they may not have jets on hand..... Ill be sure to keep this in mind.. i dont want to waste my time thats for sure lol 1 Quote Link to comment
wayno Posted March 20, 2019 Report Share Posted March 20, 2019 If you don't want to deal with tapping into your manifolds for a vacuum source for your power brakes, the 1981/82+ Datsun 720 diesel engines had an alternator with a vacuum pump on the back of it for power brakes in the 720, but you need an oil feed source and a way to pipe the oil back into the block/oil pan for the vacuum pump. 3 Quote Link to comment
alexg89 Posted March 20, 2019 Author Report Share Posted March 20, 2019 1 minute ago, wayno said: If you don't want to deal with tapping into your manifolds for a vacuum source for your power brakes, the 1981/82+ Datsun 720 diesel engines had an alternator with a vacuum pump on the back of it for power brakes in the 720, but you need an oil feed source and a way to pipe the oil back into the block/oil pan for the vacuum pump. This is quite interesting.. i may have to look into that now if i tap the manifolds, i would do it underneath so its not messy looking.. but how would i go about this? how would i combine them or would i have to ? 1 Quote Link to comment
wayno Posted March 20, 2019 Report Share Posted March 20, 2019 This is what I am talking about, I grabbed this off ebay, I am not saying buy it, I am just giving you options, you need the ones with the vacuum pump. https://www.ebay.com/itm/New-Alternator-For-Nissan-720-Pickup-2-2L-2-3L-2-5L-Diesel-1981-1985/301133299882?fits=Model%3A720|Make%3ANissan&hash=item461cf180aa:g:v00AAOSwugtZxA3G You need a oil source and a way getting it back into the block, I have a couple Nissan diesels so this is how I know about this option. 1 Quote Link to comment
alexg89 Posted March 20, 2019 Author Report Share Posted March 20, 2019 Thats pretty cool.. do i just run the booster vacuum straight to it ? 1 Quote Link to comment
Crashtd420 Posted March 20, 2019 Report Share Posted March 20, 2019 1 hour ago, alexg89 said: Ill be sure to keep this in mind.. i dont want to waste my time thats for sure lol If you can find one that deals with webers it will be cheaper they will have a variety of jets to try, and you would only buy a set that you needed.... Around me it all holley.... so I just installed a wide band o2 and air fuel gauge.... used that to give me a baseline , and compared to how the plugs look..... then started buying a few jets.... I also bought some on the small side and a drill bit set to make my own... And on the vacuum you could probably drill and tap for the power brakes, but I dont think it would be proper for the vacuum advance..... Usually with the dcoe you would make it mechanical only... no vacuum advance... 1 Quote Link to comment
wayno Posted March 21, 2019 Report Share Posted March 21, 2019 4 hours ago, alexg89 said: Thats pretty cool.. do i just run the booster vacuum straight to it ? That's what they do on the diesel trucks, straight to the booster with a one way valve, not sure why they have a valve on the diesel but they do, maybe to keep oil from being pumped into the booster from a vacuum pump failure of some kind. 2 Quote Link to comment
datzenmike Posted March 21, 2019 Report Share Posted March 21, 2019 Some GM vans and trucks have an electric vacuum pump on the booster that would be perfect for this. 1 Quote Link to comment
alexg89 Posted March 21, 2019 Author Report Share Posted March 21, 2019 14 hours ago, Crashtd420 said: mechanical only... no vacuum advance... What distributor would i look for in this instance? everything i read was about a matchbox set up and i figured this being the electric with vacuum it was the same.. so i presume i was incorrect 10 hours ago, datzenmike said: Some GM vans and trucks have an electric vacuum pump on the booster that would be perfect for this. Yah i was looking into this also, buddy has something similar on his 1937 chevy 1 Quote Link to comment
datzenmike Posted March 21, 2019 Report Share Posted March 21, 2019 It would be nice to have vacuum advance for part throttle use. There you could tap into each of the intake runners with a small fitting and pipe. Join all 4 together into one so it's more consistent. The thing is, the advance may be too much so an adjustable advance diaphragm is needed. 1 Quote Link to comment
alexg89 Posted March 21, 2019 Author Report Share Posted March 21, 2019 2 minutes ago, datzenmike said: It would be nice to have vacuum advance for part throttle use. There you could tap into each of the intake runners with a small fitting and pipe. The thing is the advance may be too much so an adjustable advance diaphragm is needed. that makes sense buttt unfortunately i dont know anything about it .. was there a particular model that came with something like that or would i have to source a different vacuum advance to put on? 1 Quote Link to comment
datzenmike Posted March 21, 2019 Report Share Posted March 21, 2019 All distributors from after the '60s are designed to have zero vacuum advance at idle. The signal is from a port on the side of the carb. Engines are deprived of the advance that the need at idle and if connected to the intake will rev up from the advance. You can adjust this out but the signal is too strong and it may ping as you accelerate. You can retard your distributor but then full throttle will be affected. NAPA used to sell an adjustable vacuum advance for chevys? Has a set screw you can turn down. Maybe the spring inside can be stiffened? 1 Quote Link to comment
Crashtd420 Posted March 21, 2019 Report Share Posted March 21, 2019 Mostly people eliminate the advance and recurve the distributor.... 2 Quote Link to comment
alexg89 Posted March 21, 2019 Author Report Share Posted March 21, 2019 16 minutes ago, datzenmike said: . NAPA used to sell an adjustable vacuum advance for chevys? Has a set screw you can turn down. Maybe the spring inside can be stiffened? i actually work at Ecklers and i believe you are on to something.. i will have to check on that , and i have yet to pull it apart so if i can stiffen it up a bit i may do so 6 minutes ago, Crashtd420 said: Mostly people eliminate the advance and recurve the distributor.... pardon my ignorance but im not familiar with this. 1 Quote Link to comment
datzenmike Posted March 21, 2019 Report Share Posted March 21, 2019 Which is great for full throttle driving where there is no vacuum advance to speak of. For best economy and throttle response there needs to be some extra advance at part throttle. Just look at it as the more gas and air you have in a cylinder the faster is burns so you light the fire as late as possible. As you reduce the cylinder filling the burn time increases so you need to start the fire sooner (advance) This is a very simplified explanation. 2 Quote Link to comment
Crashtd420 Posted March 21, 2019 Report Share Posted March 21, 2019 8 minutes ago, alexg89 said: pardon my ignorance but im not familiar with this. Im not either.... Mike explained it pretty good.... As far as the recurving and all that I'm really not sure, it's just what I read.... Something to do with the plates and springs inside... 1 Quote Link to comment
alexg89 Posted March 21, 2019 Author Report Share Posted March 21, 2019 I kind of have an idea with the springs stuff.. buddy and i stuck a Holley on his VG30 hard body and got a distributor form Performance distributors.. he went to a blow through design on it and he had to get lighter springs so it didn't advance as fast.. BUT it was a gm 6cyl hei set up.. so parts were easy to come by.. But as far as what i have i haven't the slightest idea.. 13 minutes ago, datzenmike said: This is a very simplified explanation. thank you , i understand it, just wonder if i have to run the advance to each intake runner or could i just plum it to 1? may have to do some tinkering when i get to that point .. like i said before, im new to this game so it is most definitely a learning curve 1 Quote Link to comment
Stoffregen Motorsports Posted March 21, 2019 Report Share Posted March 21, 2019 17 hours ago, wayno said: This is what I am talking about, I grabbed this off ebay, I am not saying buy it, I am just giving you options, you need the ones with the vacuum pump. https://www.ebay.com/itm/New-Alternator-For-Nissan-720-Pickup-2-2L-2-3L-2-5L-Diesel-1981-1985/301133299882?fits=Model%3A720|Make%3ANissan&hash=item461cf180aa:g:v00AAOSwugtZxA3G You need a oil source and a way getting it back into the block, I have a couple Nissan diesels so this is how I know about this option. Electric vacuum pumps with built in canisters are available too. They are popular in the hot rod world. - https://www.summitracing.com/search/product-line/summit-racing-electric-vacuum-pumps 1 Quote Link to comment
Stoffregen Motorsports Posted March 21, 2019 Report Share Posted March 21, 2019 53 minutes ago, datzenmike said: Which is great for full throttle driving where there is no vacuum advance to speak of. For best economy and throttle response there needs to be some extra advance at part throttle. Just look at it as the more gas and air you have in a cylinder the faster is burns so you light the fire as late as possible. As you reduce the cylinder filling the burn time increases so you need to start the fire sooner (advance) This is a very simplified explanation. We've gone over this many times before. A properly curved distributor will have better tip-in throttle response than any vacuum advance can deliver. Plus, the known and limited amount of advance set at predetermined speeds is the best way to keep your performance engine safe from breaking rings. I think once you've installed dual side drafts, the vacuum advance option is out the window. 2 Quote Link to comment
datzenmike Posted March 21, 2019 Report Share Posted March 21, 2019 Vacuum advance is for part throttle and cruise speeds. Yes, re-curved is fine for full throttle take offs and acceleration. At cruise, where a vacuum advance plus mechanical can run as high as 45-60 degrees total, your re-curved mechanical non vacuum distributor tops out at 32??? I asked questions that were never addressed.... If re-curving the mechanical (bringing in the advance sooner) gains so much why doesn't the factory take advantage of it??? Why is mechanical advance 'all in' by 3,000 when the engine continues to 6,000 and more? It would seem that as the time for the burn shortens you would need to keep advancing the start. 1 Quote Link to comment
alexg89 Posted March 21, 2019 Author Report Share Posted March 21, 2019 23 minutes ago, Stoffregen Motorsports said: I think once you've installed dual side drafts, the vacuum advance option is out the window. this is not what i was hoping for lol and what we have covered so far what are the options for a mechanical set up? unless i missed it previously, i dont remember reading about one to get Now the truck isnt going to be a road course truck or anything high performance but i will likely get a 89 240 cam or o&j cam and a header to spruce it up a little but its sole purpose will just be cursing and the occasional 1-3 pull around town 1 Quote Link to comment
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