round top SU into 280zx maybe. Info help?

[Skatekov]

FIRST OFF... I know a lot of you guys are going to start a war as to "Stick with EFI" "Carbs can be good if tuned right" But I made this thread so I can get some Opinions facts and info for Carb specifically on Dual downdraft webers. 

OK... So I'm not very happy and starting to get bored with the sound of EFI in my 280zx. I am obviously out of budget for Triples,cams or high compression.  But seen people re-convert EFI to SU's in and sound damn awsome without busting a wallet.  So I was thinking Dual SU's until recently, there was a guy selling a dual downdraft weber with cannon intakes out of a parked Z for 250 obo. and its been sitting for 20years so it will deffinetly need rebuild. 

(Pic below is the condition its in.... )

 

However my question was, Cons and Pros of Down draft dual webers onto a stock L28 (1983 stock)? and what the cost of rebuilding a DGV might be. and things I need to replace to go carbs.  ( Fuel pump? filters?  keep the ECU? etc)  

 

Now I am broke, probably won't be able to spend much for everything and is NOT a very smart idea to go carbs in the first place. But I ask you guys understanding that. 

thanks.  

(oh and I have more than enough time on my hands as of now... But lacks power tools....If that helps.) 

 

Edited June 21, 2013 by Skatekov

[T-Bone028]

Well...I cant recall the exact language of the forum rules, but "there is no best" anything...so "facts" could be construed as opinion depending on how you look at it, who does the interpreting, and ultimately what YOU are after.

 

In my OPINION, I would not buy the DGV's for $250.  I would not even pay $50 for DGV's that have been sitting for 20 years in unknown condition that may or may not function as designed by weber even after being rebuilt.  Some might say L-engines are better suited for sidedraft carbs...and I would agree.  If someone were to give me the option between downdraft carbs and sidedraft carbs for a L-engine, I would choose sidedrafts each time.  I would also say you could probably find SU round-top carbs for $250 that are in unknown condition (in fact I have SU carbs in unknown condition with manifold that I would sell to you for $250). If someone were to ask me about my opinion on which performs better on the L-series engine; modern EFI or sidedraft carbs, I would say modern EFI.  Interestingly enough, I contradict myself by having triples because thats what I wanted for my car.

 

If I had a budget of $600, I would get the stock EFI running as well as I can, drill some holes in the stock airbox, and buy a new muffler.  That would satisfy my itch of being bored while increasing the sound (not necessarily the performance), it would also give me the opportunity to really think about what I ultimately wanted for my car, research how I would do it, and then ask some more detailed questions on the things I'm unsure about.  

[Skatekov]

Well...I cant recall the exact language of the forum rules, but "there is no best" anything...so "facts" could be construed as opinion depending on how you look at it, who does the interpreting, and ultimately what YOU are after.

 

In my OPINION, I would not buy the DGV's for $250.  I would not even pay $50 for DGV's that have been sitting for 20 years in unknown condition that may or may not function as designed by weber even after being rebuilt.  Some might say L-engines are better suited for sidedraft carbs...and I would agree.  If someone were to give me the option between downdraft carbs and sidedraft carbs for a L-engine, I would choose sidedrafts each time.  I would also say you could probably find SU round-top carbs for $250 that are in unknown condition (in fact I have SU carbs in unknown condition with manifold that I would sell to you for $250). If someone were to ask me about my opinion on which performs better on the L-series engine; modern EFI or sidedraft carbs, I would say modern EFI.  Interestingly enough, I contradict myself by having triples because thats what I wanted for my car.

 

If I had a budget of $600, I would get the stock EFI running as well as I can, drill some holes in the stock airbox, and buy a new muffler.  That would satisfy my itch of being bored while increasing the sound (not necessarily the performance), it would also give me the opportunity to really think about what I ultimately wanted for my car, research how I would do it, and then ask some more detailed questions on the things I'm unsure about.  

The only EFI That I ever loved the sound of was a 3.1L stroker with 400cc+ injectores, Custom Airbox, ECU and probably well over what I could ever make part-timing. 

 

The thing already has "new" muffler. to be exact something different than stock. But just being loud isn't what I'm looking for...Ultimately I want a smooth raspy Sound, not a muscle-like sound you get by combining stock with headers or glasspack and Honduh loud exaust..   Also to add on, I could care less about performance for now...  

 

And drilling holes would probably be the worst idea as 280zx EFI's are Notorious for running like shit when theres a vacuum leak.  prly will run rich and sound like shit too,

 

But you probably are right about 250 being too much.  Lookse like I got a choice of Re-thinking about it since the Guy Is selling the whole engine this weekend and I don't have the cash ready.  

 

I know the structual difference between SIde and Down draft but Why is it that You'd prefer one over the other? Is it the way that it performs? 

[T-Bone028]

And drilling holes would probably be the worst idea as 280zx EFI's are Notorious for running like shit when theres a vacuum leak.  prly will run rich and sound like shit too,

 

 

I'm suggesting drilling holes in the airbox, before the air filter, not after.  Induction noise should become louder.  Would I do it?  No. But you originally said you wanted louder and you also said you dont care about performance so....

 

 

I know the structual difference between SIde and Down draft but Why is it that You'd prefer one over the other? Is it the way that it performs? 

 

 

Essentially, with the DGV's on a Z inline 6, fuel/air mixture goes down, then goes uphill into the intake manifold.  With sidedraft carbs, fuel/air is more of a straight path to the motor.  So yes, in my opinion it is not an efficient design, and may not yield any better performance over a pair of SU's in good condition.  Here's a picture of DGV's with adapters.

 

[beermanpete]

The DGV set up is not a performance improvement compared to the SU/Hitachi side draft carbs. At best it is a wash. The venturi area of the DGV is the same as the SU. That being said, the DGV is a decent carb and when properly tuned will run fine. The sound will be different than the SU I suppose but who knows which you will like better. For the price of those particular DGVs you could likley get SU set-up in usable condition.

[Skatekov]

The DGV set up is not a performance improvement compared to the SU/Hitachi side draft carbs. At best it is a wash. The venturi area of the DGV is the same as the SU. That being said, the DGV is a decent carb and when properly tuned will run fine. The sound will be different than the SU I suppose but who knows which you will like better. For the price of those particular DGVs you could likley get SU set-up in usable condition.

yeah looks like SU's it is.... Since I'm putting it in a EFI block (83 280zx.. should be P79 F54), How would I set up the fuel pump? Would I remove and bypass the original Electric fuel pump for EFI (waaay too high pressure for carbs) and install Lower pressure ones?  

 

I'm a complete fuel noob, what else in the fuel line would need to be removed or replaced? 

[tecreatta]

Your looking at a carbed intake manifold, a set of decent SUs, a fuel pressure regulator, and time. I'd say your looking around 300 hundred if you get lucky and can find your carbs at one of the many Pick A Parts in the Houston Area and they magically work. I go through them about three times a week, you might get lucky if I don't get there first. I've collected a few sets of SUs and a set of DGVs this way. Since you seem new to carbs, you might try talking to Doug at Awesome Z in Houston. He's a real helpful guy and is fair on part prices.

[beermanpete]

I would replace the fuel pump with a suitable low pressure electric pump. The RX7 pump is popular for use on the Z with SU carbs but I do not know the cost. If you get the correct pump you will not need a regulator. Try to get the OE fuel rail with the carb set. It has the fuel return line with the correct metering orifice.

[Skatekov]

I guess I'd have to download a 240z FSM and compare it with the 280ZX to see what stays in and what gets removed.. 

[Skatekov]

OK, so mine is 83, so turns out I have the E12-92 ign module.    Since I will be keeping the ECU as an ignition will it still retard the timing 8 degrees? or will disconnecting the side connector make it act like E12-80?   I am confused at this matter and would like some info

Edited July 12, 2013 by Skatekov