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Holley carb on an L18


Joseph_change

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Carburetors force air through a venturi to produce a vacuum. The vacuum sucks fuel in and mixes it with the moving air. The jet size determines how much fuel is drawn in to mix with a certain amount of air. Carb 101.

 

You HAVE to have enough air moving through the carb for this to work. The Holly 500 is about 5X too big. Check it out and you'll see this carb would likely fit a 289 or 302 Ford engine (or larger)

 

Generally you ca can get a small power increase by running a (slightly) larger carb than needed, like a weber 32/36, (about 270 CFM) but this is because the opening is larger and the engine works less to suck air in. But you can't get something for nothing and the 32/36 has a slight bog at low speeds from being too big.

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Welcome to cars. Who doesn't want more power? I don't think there is an upper limit to wanting it. Your 32/36 is ideal for an L18 although slightly too large

 

Generally you can can get a small power increase by running a (slightly) larger carb than needed, like a weber 32/36, (about 270 CFM) but this is because the opening is larger and the engine works less to suck air in. But you can't get something for nothing and the 32/36 has a slight bog at low speeds from being too big.

 

Carbs mix gas and air and they all do about the same and get a 14 to 1 ratio with slightly richer under load. Bigger doesn't change this.

 

An engine is very basically a large air pump. The more air it pumps through it the more power it will make. To move more air you can simply rev it higher. Everyone knows that a engine pulls harder the higher it revs. Stock engines have to be drive able at low speeds so there is no need to rev much past 4,000 RPMs.

 

To get more power your engine needs to pump more air through it. This can be done by adding a 'larger' cam which opens the valves farther and for for longer allowing the engine to breath more air. This comes at the expense of good idle and low speed operation. Take note of this. An over cammed engine is hard to live with and in the extreme is practically undrivable on the street. The rule here is that it's better to have less cam and want more than to have more and want less.

 

Valve diameter can also be increased to get more air through them. A larger (heavier)valve and/or higher lift cam usually needs stiffer valve springs to force the valves closed at high RPMs

 

The intake and exhaust ports between the valves and their manifolds can also be ground put to a larger diameter to let more air through. Also known as porting.

 

A side draft carb is a more direct straight line into the combustion chamber and avoids a sharp bend as in a down draft carb. Any bend is a restriction to flow and the engine has to work harder to pump air in.

 

The exhaust should not be over looked as a restriction to flow either. Just changing the quiet muffler for a turbo one will reduce resistance to flow. Within reason, a small increase to pipe diameter (no NOT to 3") and mandrel bends or the elimination of bends will also reduce resistance to flow. BTW your L18 exhaust manifold has excellent flow.

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Hey all, just wonder if a Holley 500 2bbl will work with my engine (L18). Here is the link to what i'm thinking of. 

 

 

https://www.holley.com/products/fuel_systems/carburetors/performance_2_barrels/parts/0-4412S

Back in the 70s I had a 55 Chevy 2 door hardtop that I had a built 283 in it and I ran a Holley 600 2 barrel carb on it.  It did great hole shots.

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Offenhauser made a manifold to bolt a 4 barrel I believe it was a Holley to the L series engine.  I do not think that they designed these with the idea of putting them on a stock 30 to 40 year old, god only really knows the mileage Datsun L series motor. 

 

Page 11 in this link:

http://www.exeterautosupply.com/Docs/Offenhauser%20catalog.pdf

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Why would you buy that when you can go with a tried and confirmed Weber DGEV 32/36 or a Weber 38 Outlaw.  I quit running Holleys in the 80s.

 

Good luck finding an adapter for the Holley.

 

Offenhauser also made a manifold to fit the L motor and the Holley 2 barrel.

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Why would you buy that when you can go with a tried and confirmed Weber DGEV 32/36 or a Weber 38 Outlaw.  I quit running Holleys in the 80s.

 

Good luck finding an adapter for the Holley.

 

Offenhauser also made a manifold to fit the L motor and the Holley 2 barrel.

Never said i was going to buy, just asking. 

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Good power about double the L18's power. EFI reliability and smoothness, will even run upside down.

 

Type KA swap into 620 in the search engine top right of every page. I or someone else could write pages of info but you may not use it or want it. If curious do some research for yourself.. There were 10 pages of posts on 620 related KA swaps... http://community.ratsun.net/topic/48249-ka24de-datsun-620-swap/

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Sweet, I have access  to a weld shop, machine shop, and auto shop at the "high school tech school" thingy that i go to. I can easily fabricate engine mounts and modify the oil pan. I've heard those were the hardest things about the swap. Thanks all for the help!

 

While I admire your enthusiasm... I think you heard wrong. A lot more research is

needed first. Read everything about this, know everything involved, become an expert on this swap, ask questions.

 

Type KA swap into 620 in the search engine top right of every page. I or someone else could write pages of info but you may not use it or want it. If curious do some research for yourself.. There were 10 pages of posts on 620 related KA swaps... http://community.ratsun.net/topic/48249-ka24de-datsun-620-swap/

 

You will need money (the more the faster the swap) so having a job and no g/f is a plus.

 

A secure garage space close by to work on it. (auto shop ain't going to cut it)

 

Your truck will be off the road for weeks at least and months possible.

 

Assemble EVERYTHING needed before hand and more money.

 

A plus if you have done a swap before. Stuff does not have to be learned for the first time.

 

You will need to connect and convert your '74 over to electronic fuel injection (EFI) wiring. Probably a good idea to convert to internally regulated alternator now too. including a high pressure electric in line fuel pump.

 

Will this be a truck or car KA engine, and dual or single cam? advantages to each.

 

Will you use a KA or Z series 5 speed? Each have their advantages.

 

Things to research... rad replacement, drive shaft shortening and balance, exhaust piping, transmission mounts, speedometer....

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I wasn't implying that I was starting the swap. just saying that I have those things at my disposal. The only things that are keepig me from this swap are, a commuter car and a garage. And obviously the engine and tranny and everything else lol. Whats the best KA for a drift truck?

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Please do not let us kill your enthusiasm.  It is your truck do what you want.  Most of us personalize our Datsuns.

 

Here is some study material from Google search.  Good reading and a lot of information.  If you are truly going to do this take notes and copy pictures.  I do this on a regular basis copying and pasting into a word document. so I have it for future use.  You never know when picture links are going to stop working.

https://www.google.com/search?q=Datsun+620+KA+Swap&ie=utf-8&oe=utf-8

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I wasn't implying that I was starting the swap. just saying that I have those things at my disposal. The only things that are keepig me from this swap are, a commuter car and a garage. And obviously the engine and tranny and everything else lol. Whats the best KA for a drift truck?

 

So other than school shop, everything else is missing and preventing this swap. Well this is going no where soon, so enjoy your L18 truck for now. If you are asking what KA is best you haven't been reading those links provided.

 

Research and then research some more. Get an idea of what you want by weighing the pros and cons of the two KA engines and their two different uses in a car or truck. Start a build plan and list things to do and things to gather. Money will always fill any missed gaps.

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  • 1 year later...

The Motorcraft 2100 and 2150 carbs have the same flange as the Holley 500 but you can get them with much smaller venturi's.  Thats what I am trying to figure out, how to adapt the stock Datsun manifold/flange to the motorcraft/holley 2 barrel carb.  The Motorcrafts(poor mans efi) are also know as the best off road carb ever built and will run at any angle.  I think the .98 Motorcraft is around 250cfm, 1.08 is 300, and so on up to 4 or 500 cfm from the ones off big blocks.  I read that the Rochester/small 2 barrel to Holley/large 2 barrel adapter can be made to fit.  Or you might be able to get a Webber adapter and then a webber flange to Holley adapter and stack adapters.

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Stop looking to spend money on a different carb and spend the money on tuning the one you have.  The only guy I know in WA is 2 hours away at Bradley Restoration in Mt. Vernon.  I'm sure there are shops near Seattle who can tune a Weber properly.  My guess is that your float height is off for starters.  This is all the same tuning you'll need to do with a new carb, so don't expect miracles.  Expect to have to work even harder.  

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