weber 34 DMTR on a 1300

P

pdxgeo

True Classic
Hi all, I have a chance to buy a new 34DMTR at a reasonable cost for my 1300. In reading through the archives I see that many people have experienced trouble getting their 1300's to run well with this swap. A few of the threads end with no final outcomes so Im wondering if it's a good idea or not...?

The car developed a leak in the exhaust somewhere so im having John Lickley build a 4 into 1 header that i will swap in before doing any exhaust repair. I was hoping to swap the bigger carb in at the same time to increase performance (and hopefully stop there, boy it is so easy to spend $$, like a sickness...).

Thoughts on the carb?

thanks
 
For a stock 1300 the 32 DMTR is hard to beat. With a modified 1300 or 1500 the 34 DMTR is a good bet.

Chris
Oakland, Ca.
 
Paging Court, what do you think?

Court, with the 1300 you built would it be 'modified" enough to justify the 34?

Thanks
 
Which 1300 do you have?

If your car is a Yugo 1300 you have a 1301 engine. If you have a 128 you have a 1290 engine.. Both engines are relatively the same with miner differences. The 1301 is basically a 1500 with a 1290 lower end and lower deck.. The 34DMTR should be a good upgrade for both engines.

Just some FYI for ya!!:)
 
It depends which '34' you've got.

32dmtr has 22/22 venturis.

34's have 22/24 right thru to 25/27, and of course the air flow capabilities of each carb is very different.

SteveC
 
Re: 1301

DTohill said:
If your car is a Yugo 1300 you have a 1301 engine. If you have a 128 you have a 1290 engine.. Both engines are relatively the same with minor differences.
Click to expand...

The main difference is the piston size; 1301 with 86.4mm vs. 1290 with 86.0mm.


DTohill said:
The 1301 is basically a 1500 with a 1290 lower end and lower deck..

Just some FYI for ya!!:)
Click to expand...

:confuse2: :huh: :huh2: :confused:

Just some FYI for ya: The 1301 uses 1500-sized (86.4mm) pistons, but otherwise it has the 1290 style block, crank, rods, flywheel, etc., & a flat-c/c 1290 cylinder head (ie: no recessed ring around combustion chamber) with 1290-sized valves (36mm intake, 31mm exhaust).
 
that's a pretty big jump from 22/22, work out the area of the venturis, and figure out the %age increase from the original ...especially if the motor is otherwise standard, ie CR and Cam...it won't want to rev high enough to utilise the big secondary unless you have a longer duration cam to make sure your efficient at revs... and if you put in a cam like that you need the static CR to justify it.

It will work, just depends how well.

That would work nice on a warmed over 1500.

SteveC
 
Split Pea 1300 engine specs

George,

I would default to SteveC's experience any day so go with whatever he says :). That said, from personal experience, I was always swapping Lancia Beta carbs onto mildly modified 1300s (usually 23/25 venturis) to replace the smog-oriented 32 DATRAs (22/22 venturis) with positive results. I'm currently running a 34 DAT (25/27 venturis) on my Rally and am very happy with it. My Rally is running the same cam as yours (though mine is a made-from-blank SX1 instead of a regrind), a long 4-2-1 header, Marelli Plex ignition (10 deg BTDC static timing), and probably has slightly higher compression.

Been a little swamped with work and still need to try to dig up a few more specs on your engine and will put together some pics and description of the full build. The short version:

This was a very budget-oriented build, intended to make a nice commuter for John. He had specific components he wanted to run so I was more-or-less just doing the assembly (he just wanted someone he could trust to build it). Well, that and doing some serious scrounging in my spare parts cache since it was not a complete engine! Originally he was just going to run the single-barrel carb, then look for a 32 or 34 DMTR.

* 1290cc Fiat block, bored by PBS for 86.4mm pistons. Stock deck height.
* 86.4mm 1500 pistons with big flycuts (stock X1/9).
* 1290cc crank, cleaned out and oil galleys tapped/plugged with set screws.
* 1290cc stock rods.
* 1290cc Fiat head (from my first 128!) with air injection ports plugged; surfaced (have to look up the amount). Combustion chamber volume measured 27-27.2cc. New Fiat valves, back-cut intakes, and 3-angle cut on valve seats. Ports pretty much standard with some minor smoothing.
* PBS SX1 cam (regrind)
 
Hi Courtney,

from your description, it would appear the motor has ended up with pretty much std compression...i.e. 27cc head + 5cc valve flycuts = 32cc which pretty close to a stock euro head...so maybe 9.2:1

sx1 is less duration and less lift than euro 1300 cam.

It comes down to a %age difference in cross section... a 22mm venturi being about 380mm square, and the 27mm venturi is 572mm square... that's a jump of just over 50% increase in cross section of the secondary.

It's easy to over carb a motor, probably the most common mistake made by DIY tuners...

22/22 is conservative, I'll grant that no problem...and the engines can handle more carb in euro trim, no problem

a 34dmtr from something like an A112 abarth is 23/25 from memory... that's 1050cc that makes 70hp from a much smaller capacity, so suits a warmed over 1300 nicely

23/26 feeds a euro 1500 x19 at 85hp, and is again a nice step up...

but a 25/27 feeds a 2 litre engine for a lancia beta (which again is a conservative carb for the engine) but that makes almost 120hp...and works great on a well warmed over 1500 that can make 110 at the crank

23/27 IMO is a bit over carbed for a 1300 that makes maybe 75.
 
Thank you Courtney and Steve, i am going to pass. The seller says ne may use it for his Lancia until he converts it to FI so it will no longer be "new" but Id guess he will sell it then...
 
save the $$ on the custom extractors, and use an OE twin out manifold and front pipe...same result for less $$...and it will last longer.

find a 34 but one with 23/25 chokes ...

if your on a budget that will give you the biggest improvement for your $$

SteveC
 
A few data points

Steve,

I took a look at the various carbs I have. I was wrong about the Lancia carbs - they have 22mm primaries. See below.

Lancia
32 DATRA 12 101 L6
(22-25)
*missing accel pump cam

Lancia
32 DATRA 9 100 B6
(22-25)
"101" accel pump cam

US 128 ('75-up)
32 DATRA 14 100 M5
(22-22)
"128" accel pump cam

US 128 ('75-up)
32 DATRA 4 100 L4
(22-22)
no ID on pump cam

US 128 ('75-up)
32 DATRA 11 100 B6
(22-22)
"101" accel pump cam

Aftermarket sourced, unsure of original application
34 DAT 2 252 5C
(25-27)
"185" accel pump cam

'77 Autobianchi A112 Abarth
32 DMTR 38 230 (or 250? hard to tell) 8L
(22-22)
no ID on pump cam
 
Yeah, my calcs come up with something right around 9.0:1 with 1.5mm thick head gasket and the 86.4mm bore. Stock US 1300s are around 8.5:1 so at least it's a step in the right direction.

I may have to try playing with some of the other carbs again, now that I have the capabilities to properly rebuild them. Some of the bases were in pretty bad shape and may have to go on the mill go get flat enough to seal. Then look at rebushing throttle shafts and maybe deleting some of the emissions provisions to reduce chances for vacuum leaks, etc.

Or just build a motor to suit the carb :)


fiatfactory said:
Hi Courtney,

from your description, it would appear the motor has ended up with pretty much std compression...i.e. 27cc head + 5cc valve flycuts = 32cc which pretty close to a stock euro head...so maybe 9.2:1

sx1 is less duration and less lift than euro 1300 cam.

It comes down to a %age difference in cross section... a 22mm venturi being about 380mm square, and the 27mm venturi is 572mm square... that's a jump of just over 50% increase in cross section of the secondary.

It's easy to over carb a motor, probably the most common mistake made by DIY tuners...

22/22 is conservative, I'll grant that no problem...and the engines can handle more carb in euro trim, no problem

a 34dmtr from something like an A112 abarth is 23/25 from memory... that's 1050cc that makes 70hp from a much smaller capacity, so suits a warmed over 1300 nicely

23/26 feeds a euro 1500 x19 at 85hp, and is again a nice step up...

but a 25/27 feeds a 2 litre engine for a lancia beta (which again is a conservative carb for the engine) but that makes almost 120hp...and works great on a well warmed over 1500 that can make 110 at the crank

23/27 IMO is a bit over carbed for a 1300 that makes maybe 75.
Click to expand...
 
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