1.5 JB to 1.8 DX conversion

Hey, at the moment my car is running a 1.5l JB engine with 36 tlp weber carb. I am soon getting a 1.8L DX block but want to keep the weber carb on there and not go down the k jet route. Can anyone make a list of things i need to change and how i can have the carb run on the 1.8l too? I will also have the gearbox from the 1.8l too so i shall be putting both those in together. Cheers

Are you married to the DX engine? It would be much simpler to obtain an EX engine from a later Golf cabby (Clipper, not GTI). Its 1.8 litres and high compression too but not fuel injected. So you won't have the hassle of sorting out a fuel pump, inlet manifold, etc etc

Also another consideration is if your car is over 40 years old, if it has the original engine it can be MoT exempt. An engine swap* takes away the exemption so you'd need to continue having MoTs after 40 years and it would probably devalue the car.

* Look at the regs, it depends on the actual engine used but I don't think a 1.8 would be exempt.

Actually having looked at the regs

1.5 –> 1.8 clipper engine - should be okay
1.5 –> 1.8 GTI engine - probably okay
1.5 –> 1.8 or more 16V engine - probably not okay
1.5 –> something more unusual - definitely not okay

You'd need to look at the rules and decide yourself.

paul_c said

Are you married to the DX engine? It would be much simpler to obtain an EX engine from a later Golf cabby (Clipper, not GTI). Its 1.8 litres and high compression too but not fuel injected. So you won't have the hassle of sorting out a fuel pump, inlet manifold, etc etc

Also another consideration is if your car is over 40 years old, if it has the original engine it can be MoT exempt. An engine swap* takes away the exemption so you'd need to continue having MoTs after 40 years and it would probably devalue the car.

* Look at the regs, it depends on the actual engine used but I don't think a 1.8 would be exempt.

Hey thanks for the quick reply, and i would pick the EX engine if i could but im being given the DX from my uncle as hes doing a swap himself. Ill take the Mot thing into consideration. What would need to be done if i put the DX block in?

I don't know, I'd be guessing on the parts which wouldn't fit and cause issues. Definitely you'd need to sort out another fuel pump though. Maybe exhaust manifold and/or whole system, maybe there's pipework issues when swapping the inlet, maybe flywheel/clutch issues (but you're getting the gearbox too?)

Are both electronic ignition?

Maybe a few other sensors here and there eg oil pressure, coolant ones

Coolant top hose, I think, is different too

Probably want to fit the bigger GTI radiator as well.

paul_c said

I don't know, I'd be guessing on the parts which wouldn't fit and cause issues. Definitely you'd need to sort out another fuel pump though. Maybe exhaust manifold and/or whole system, maybe there's pipework issues when swapping the inlet, maybe flywheel/clutch issues (but you're getting the gearbox too?)

Are both electronic ignition?

Maybe a few other sensors here and there eg oil pressure, coolant ones

Coolant top hose, I think, is different too

Probably want to fit the bigger GTI radiator as well.

Already working on changing the pump to electrical. I already have a 4-2-1 downpipe fitted and i believe the inlet manifold should bolt on with no issues as they look the same. I have a larger rad fitted already too. Yeah ill be getting the gearbox along with the engine and the sensors and coolant hoses along with it so shouldnt be an issue. Cheers for the help

Are you fitting just the engine block or engine block and head?
The DX head has a better cam (more performance) than the EX engine, you can block the fuel injection holes with a 2 pence coin.
The DX complete engine will fit straight in with no mods needed to engine mount.

I would sell the 36tlp Webber carb and get the 32/34 DMTL as the carb is jetted for the 1.8 engine and is twin choke, you will need to re-jet your 36tlp carb to get the best from the engine.

What year is your car and what type of fuse box is fitted, later blade fuses or early bullet fuses?
Best to keep the DX dissy fitted to engine so you may need mod the ignition system to run the DX dissy?

There is 2 sizes of gearbox flanges, 90mm and 100mm so you need to check what size drive shafts are fitted to your car and what’s on the gearbox, it’s possible to swop the flanges over.

info on gearbox flanges and also reversing switch’s as they have also changed over the years.

http://www.brokevw.com/


 Lots of places sell new Webber carb kits so it’s a straight forward swop.

https://fastroadcars.co.uk/store/

https://www.webcon.co.uk/

vw heritage also sell them.



 

mark1gls said

Are you fitting just the engine block or engine block and head?
The DX head has a better cam (more performance) than the EX engine, you can block the fuel injection holes with a 2 pence coin.
The DX complete engine will fit straight in with no mods needed to engine mount.

I would sell the 36tlp Webber carb and get the 32/34 DMTL as the carb is jetted for the 1.8 engine and is twin choke, you will need to re-jet your 36tlp carb to get the best from the engine.

What year is your car and what type of fuse box is fitted, later blade fuses or early bullet fuses?
Best to keep the DX dissy fitted to engine so you may need mod the ignition system to run the DX dissy?

There is 2 sizes of gearbox flanges, 90mm and 100mm so you need to check what size drive shafts are fitted to your car and what’s on the gearbox, it’s possible to swop the flanges over.

info on gearbox flanges and also reversing switch’s as they have also changed over the years.

http://www.brokevw.com/


 Lots of places sell new Webber carb kits so it’s a straight forward swop.

https://fastroadcars.co.uk/store/

https://www.webcon.co.uk/

vw heritage also sell them.



 

Yeah its the engine block and head. Im thinking of rejetting thr 36 tlp as that works on the inlet manifold i already have, however i do not know what jet sizes to go for. Mine is 1983 so it runs on blades. Im not sure what needs changing if i need to use the DX dizzy, would it just be the coil swap? And yeah i will need to check gearbox flanges and change them accordingly or would it be easier to use the drive shafts which are on the DX engine already as my uncle will be removing them as well.

I would just swap to the Weber dmtl carb. Saves a lot of hassle and would be correct. You will need to change the inlet manifold as well.