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Sun May 01, 2016 1:58 pm

Hi guys

I am having issues with my Volksrod and the 1600 draw through junkyard turbo engine bolted to it.

Full engine spec:

1600 stroke and bore with forged pistons & con rods
engle ts20 turbo cam
straight cut cam gears
John Maher Racing ported polished heads
stainless valves with double valve springs
bottom end lightened and balanced
8 dowel crank
009 Bosch distributor with max advance limited
dellorto dhla 40 sidedraft
garret t3 turbocharger
215mm flywheel and clutch

Jetting. Mains are 200, 7772.8 emulsion and 190 correction. Idle is a 60. Pump is 33 and choke for what its worth is 80 and 7482.3

A full run down of where I am with it can be found here:

http://www.rodsnsods.co.uk/forum/tech-discussion/drawthrough-turbo-help-436770

But essentially she runs like a bag of nails.

This is static:

Now some spitting through the carb etc would suggest lean? Or poor timing... But in these videos the timing is locked (no advance possible) at about 26*-30* advance (I fiddled a little with it while tinkering and lost track of where it was when the videos were taken).

When I drove the car... First test drive... Fail. No responsiveness at all. As soon as it goes on load it just dies. Takes ages to do anything.

It since developed an ignition fault which I will hopefully fix tomorrow.

You boys in the States seem to get some joy out of these set ups. So any help or advice you could give would be gratefully received!!

Thanks in advance

Sun May 01, 2016 2:12 pm

carburetor is too big.
Put it on a bigger engine.
:P

Use a motorcycle carburetor that is a better fit, they are easier to tune and cheaper too

Sun May 01, 2016 2:32 pm

A Dellorto 40 too big for a 1600 turbo? Really..?

Sun May 01, 2016 2:34 pm

Its worth mentioning that this engine set up has been running before with a previous owner. But for some reason I just cannot get it running right.

Sun May 01, 2016 2:48 pm

In general, yes it's too big.
Using both barrels of the carburetor, it can supply enough air for 200hp,
What size venturis are in it?

Sun May 01, 2016 4:14 pm

Make sure valves are adjusted correctly (not tight) Limit timing to 24* max. Use timing light. Try 50 idle, 155 main gas jets and open pump jets to 50 .. you can do one pump jet, try it then open other if needed to eliminate lean transition. hopefully you have small venturis in carb.

Sun May 01, 2016 9:39 pm

An O2 sensor would save a LOT of heartache.....

Sounds to me it is going dead lean when you open the throttle.

Having a big carb and large venturis will cause a vacuum signal problem on throttle tip in.
You will need a big accel shot of fuel to make up for it since the engine can't draw fuel from the carb when the vacuum disappears as soon as the throttle plates open.
You also have a big, long intake now plus the turbo before the engine will get any fuel.
If you have low airspeed due to big valves, ports or large intake tube it will be even worse.

Get some bigger pump jets or increase the accel pump stroke to give more fuel on throttle tip in.
Some of it may go away then. At least that's a good place to start.

Sun May 01, 2016 11:55 pm

I will check Venturi's today when I buy new plugs (had a spark plug fault).

for what its worth plugs were sooty as hell when I pulled them.

Perhaps a smaller carb then. Although this engine with this setup was working once with the previous owner (I have seen videos).

Mon May 02, 2016 12:14 am

If the PO really did know what he was doing, then maybe the carburetor is setup right. It's possible, but I think the odds are against it.

Mon May 02, 2016 1:25 am

I'm the third owner of this engine (though it has had upgrades through the years). It ran a 14 second quarter mile pass with the first ownder and the second owner ran it in a street car. He dialled the boost up too high, engine pinked and detonated, so was stripped down and new rings and pistons fitted.

Venturis are 30s.

Mon May 02, 2016 1:38 am

I have also dialled up the pump stroke as far as I can get it. Just off to buy new spark plugs, then we shall see!

Mon May 02, 2016 1:54 am

A lean bog on acceleration can be caused by:
-Carburetor too big
-Carburetor passages plugged, carburetor assembled wrong
-Intake manifold too big, allowing fuel to build up on walls instead of sucked into engine. Also, caused by intake manifold too COLD
-jetted too lean

all act NEARLY the same.
The result is engine gets not enough fuel, BUT it does not mean the carburetor plugged, it could be feeding the right amount of fuel BUT the building up in the manifold and not getting to the head, OR the carburetor is fine but the engine is too small to make it work.

It probably IS the carburetor.
If you don't want to become an expert at this carburetor, then get a different one now, before expending too much metal effort doing things the hard way.
It IS somewhat too big, and why two throttles for one hole? Pretty stupid :lol: They used those back in the day because that's what they KNEW, and HAD, and it does work. But it's not very handy for you, now, in the 21st century.
Why a stock engine? Who would use a 300$ carburetor on a stock engine? That's the most expensive thing on the car from the looks of it.

Or make somebody else do it. Whos the guy who set it up to begin with?
is he in jail/deceaced/hates you? :P

So, flip a coin, and decide if you want to be a historian who knows how this thing works, make somebody else do it, or get a carburetor from the 90's and learn to tune that. Those are your options. Chose!!

Also, don't run points and a turbo man, jeez, at least get a compufire. better yet get a more powerful ignition system.
Points alone won't supply enough ignition power to run more than 0.5mm plug gaps under boost.
Get something. MSD, CB magnaspark, or TFI module.

I'l like to see a picture showing the intake manifold. You have one handy?

Mon May 02, 2016 2:14 am

Jetting. Mains are 200, 7772.8 emulsion and 190 correction. Idle is a 60. Pump is 33 and choke for what its worth is 80 and 7482.3

Sounds like stock jetting from a junkyard car with the exception of the mains made larger until it worked at WOT.
33 pump is stupid small. I assume they have been drilled to 60, did you measure them?
the #8 emulsion tube probably means this is what they call the "emissions" models, which......I don't know that anybody used one of these for a turbo setup.......that does not mean it CAN"T work but it means you are more or less off the beaten path.
Anything can be tuned for WOT and idle but the in-between is harder.

Mon May 02, 2016 4:08 am

I take all your points. I just bought this as it was. The project is deliberately a junkyard turbo setup.

Just had some success. It now runs and drives, but only with the choke open. So guessing too rich.

As for carbs.. I got made redundant just before Christmas and don't start my new job until tomorrow. So funds are real tight.

Any suggestions for carbs to swap to?

Mon May 02, 2016 4:10 am

If it ran before it's not to big of carb, :roll:
sounds like too much fuel pressure to me :wink: check floats & do you have a boost referanced fuel pressure regulator?
yes open up the pump jets, my Webers are .70
cam IS a bit large, your set up is more suited for a 1915cc :wink:
Borrow a MSD Boost Timing Master box? if you can
Do u really have a 215mm clutch :lol:

Mon May 02, 2016 4:23 am

So had some success today. It runs and drives, moves fairly well. But it only idles with choke open otherwise dies off. So... Too rich I am guessing? I messed around with the idle screws but no joy yet.

The clutch... It was running a stock clutch when I bought it (someone wanted to keep whatever was on there I guess?). I ended up changing the flywheel, with a larger clutch. If memory serves it was 215mm but I could be wrong.

Cheap fun junkyard giggle is what its meant to be. I do have a Petronix electronic ignition somewhere I will dig it out and see if it works.

The points were just what was on there.

Mon May 02, 2016 4:26 am

Why do I need a boost referenced regulator on a draw through..? Pressure should remain the same surely?

Mon May 02, 2016 5:26 am

A boost referenced regulator has been used on these setups to get more fuel flow. I do not think this engine is large enough to need that, not even close.

Mikuni HSR is a lot simpler to tune.
In olden days smaller engines they often used SU side-draft carb, and the HSR is a improved modern evolution of it. The big ones go for about same price as the dellorto but you can pick up a 38mm one for cheap, and that would suit 120hp at least

Tue May 03, 2016 7:15 am

Ordered larger idles and pump jets. Might get smaller mains too...

Tue May 03, 2016 7:28 pm

Dont need bigger idles.