Discussion in 'Engine & Transmission' started by rstucke, Jan 13, 2018.
A great man once said "I love the sound of induction in the morning"
Mein homemade twin drain. Been on the van for a while now. Old muffler with a second outlet welded in. Works and sounds OK. Stepson JD was making a custom exhaust for his Harley and the off-cuts did the job nicely. Out of the kombi for an engine clean-up so just had a wire-brush and a coat of rattle can high heat. Ready to go!
OK here we go
Risers for the Weber carbies were less than perfect. Nuts fouled the sides of the tubes, the outlet ends (ports) that fitted to the head were much smaller than the head ports and there were no vacuum outlets for brakes or anything else. So more modifications for ill-fitting parts. Unfortunately I forgot to take pictures of the porting job I did at the outlet end of the risers.
So after modification to the throttle linkage cross bar to be level (had to make some brackets) and allow the carbies to open in unison, and also for a little more throttle control (original kit had fully closed to full throttle at 20mm of movement at the end the cable attaches) the carbies now are fit for purpose (apart from jetting)
The engine has been run on a test bed, syncronised and preliminary jetting sorted. This was a combination of what Rod Penrose supplied and observation. He has a similar spec engine and supplied my carbies with the jets he runs. I ended up running slightly leaner idle jets which gave me more idle mixture control (3/4 turn instead of ¼). Interestingly many say to leave the air bypasses shut but I found (with Rods recommendations) that about 2 ½ turns out was best with the idle jets (I used 50s). There was no hesitation (accelerator pumps disconnected) through the first half of throttle movement even with the 009 distributor I had on the engine at the time, and final sync could be micro adjusted between each throat.
Final jetting will be decided on a dyno.
The engine breather system had to be sorted. The engine I am using came from a t3 donor but was the same as late bays which is what I have (79) The original breather purge valve was cactus and I was told new ones were unobtanium. I found one that was usable (with only slight modifications) for $8.00. It was listed to fit a Pasat, Golf, Audi A4 and Skoda here
When looking at what was left of the original and the new valve to work out what it actually does (there were some bizarre reasons on the samba) I found it was really only a back fire valve (it was connected to the intake system).
I do remember the hose from this valve to the air cleaner on my original worn engine was oily so a catch can was in order. A friend gave me one he had no use for. It was a super cheapy from a store with a similar name. On opening it I found it was empty (almost but not quite useless). For these things to work they need some sort of coalescing filter (basically means pulling the oil out of the engine fumes) and one of the best things to use is stainless steel. So being a tight arse I decided to modify it to have one. The idea is to have the oil laden fumes enter the lower half of the can and then to filter through a stainless steel medium to exit through the top and onto the air cleaners leaving the oil that’s been removed to drip to the bottom. I used a stainless steel scrubber for pots and pans.
The air cleaners pose another problem with down draught Webers. Firstly nowhere to connect. Secondly where to put the fitting in the cover. If you put it over one throat then you run an imbalance risk with one throat of each carby taking on the engine fumes. If you put the fitting in the middle of the air cleaner cover then there is a risk of the air flow through the throats not being able to draw fumes in under certain conditions (because the fitting is toward one side of each throat) and if there is any oil in the fumes then they may end up in the float bowl as the vents for the bowl are directly below the fitting.
My solution is in the following pics.
The next instalment I’ll have pics of the whole lot together.
The engine and transmission is now back in Blitz.
Was going to fit a catch can with the rebuild of Shmett's engine. Heads had a breather fitting so it was block them off or plumb them in. Pipe and tubes and a catch can in hand but no where to fit the catch can with the standard air cleaner etc. Just going to connect the breathers back to the air cleaner for now.
There is nothing to worry about in fitting the breather to a carb top. Only worn and misfiring motors pressurize the crankcase, enough to give oily issues.
Nice work! Happy days ahead!
In an real world I would agree
but the inside the air cleaner the vacuum is well below normal air pressure and can suck especially with smaller air cleaners at high volume flows eg high revs this is why a carby delivers the fuel
Plumbed into air cleaner and will monitor how it looks. Too much oil and I will catch can.
Great thread workmanship by craft, thanks .
There is an oil separator gauze in the earlier breather box, however, separator canister may be necessary on a T25 case... but were not ever fitted even when plumbed from factory into the air duct.
The t25 cases only have labyrinth protrusions going up the vent.
Back in the days of working for a living I was involved in a fair bit of development work on engine dynos for a while.
Not for performance enhancing, more for reliability (piston rings, bearings, metal alloys, emissions, temperatures etc were some of the things being tested.) and sometimes to destruction.
One thing I noticed, oil vapour in the fumes of crankcase ventilation systems when introduced back to the inlet caused detonation in hot combustion chambers (when ignition timing was set for most efficient combustion), most times only perceivable through knock sensors unless excessive, then the engines just pinked their heads off.
So the coalescing filter in a catch can goes on my engine.
The engine is back in the kombi and engine wiring is happening atm. It's a bit different to stock (fuse box, relays, heavier wiring etc.)
Will post photos shortly
I'm starting on a T25 build shortly...most preparatory work done .. cam is quite a bit bigger(more duration and lift) and is still running L-Jet. Cam is big enough to need sleeves on the rocker shafts..911 style adjusters with 10x1mm theads.. going for Hydraulics too.. and new CNC oil pump with tight tolerances I've not had your experience.. in fact, quite the opposite.
The T25 case is no better than the earlier case.... in terms of "labyrinth" .
Irrespective of T2 or T25 case.. you will notice that they don't breath much at all when properly built and tuned.... If you have much windage from a big crank.. then a vent on the left rocker box is needed...If its breathing heavily when it is young... something is wrong...That is all.
Yep.. Tri-metal bearings for forged cranks.. alloy bearings for cast and powdered metal parts.. 600C exhaust temps...at the right time...Metal hardness in cylinder heads like the AMC heads.. and decent quality valves..and springs...been there. AFR's on the road under load are the final test.
Separate names with a comma.