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New engine will not idle at the correct timing

772 Views 15 Replies 5 Participants Last post by  bug71
Hi all got a small issue.
I have a brand new 1600 running with a engle 110 cam and a pair of del 40's.
Now I done the cam break in run and all was good, been for a drive and all is good but the idle is just not right.
The engine will idle fine at 15⁰ BTDC and any movement on any mixture screw will effect the idle so I know the idle jets are not blocked but at this timing the full advance time is to high.
Now if i set it so the max advance is at 32⁰ BTDC theidle timing is around 7⁰ BTDC but the engine will not idle now below 1200 rpm if I go anywhere near the idle screws to close the throttle valves ( which are open to much) the idle will start to drop but then become unstable at around 1000rpm and any lower the engine will stall unless I give the engine more timing but more timing at idle means the max advance is to high so I'm stuck in a continuous loop.
Any advice would be great
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110 has an uneven rough idle on 1600.,set timing 32 advanced at 3000 revs. The idle timing should be 10 or so. Make sure both sets of carb butterflies are open the same. Balance gauge needed here really. If not back the adjusters off and count the turns to roughly equalise both sets of butterflies, turn dell mixture screws in, then out 3 turns to get it running. You might have to limit the max timing to 28 via the internal advance stops on the dizzy, then advance the dizzy to give the engine more advance at idle. Say 12 to 14 degree
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Thank you for the reply mate, yest the carbs are balanced using a snail gauge BUT normal the reading at idle speed on my stock old engine would be around the 7 mark but on this engine it's at 10/11 reading on both sides of the at 1200 rpm. If I try and lower this reading with the timing at 7⁰ BTDC the engine will just stall. So I will up the idle timing and limit the max on the mechanical stop but I take it I will not damage the engine running more timing at idle?
It won't hurt it to do the advance limit trick
Have you set the mixtures for each barrel so revs are at the peeks for each one? Try and pull one ht lead off at a time to check if you get an even drop in revs for each cylinder. Are you running a fuel pressure regulator, dells don’t like too much pressure.
Hi keekster64
Yes all the mixture screws are set at the highest rpm and they are all around two turns out BUT the rpm was high at 1200rpm when I set them up because I could not get the engine to idle any lower.
Yes I'm running a filter king regulator and is set to 2.5 psi.
Yes I've also done the lead check. Each cylinder dropped the same rpm when I pulled the leads one by one
The only other thought is the size of the Venturi given that it’s only a 1600, and the possibly that the velocity of the air flow is too low at low revs, but that’s out with my expertise.
I had the same idea so fitted 28mm vents to the carbs but it made sod all difference
You need to run it, mine wanted 15 deg for the first part of the break in then would take less and less until it now sits at 11ish, I have a malory distributor which allows you to set the max advance and then adjust the window, currently set at 11 idle and 29 all in.
Right I had another go on the engine today and still no joy. To get it to run at 10⁰ BTDC and get a reading of 7 on the snail gauge the throttle have to be open at lot but the idle screws and the mixture screws have very little to no effect at all. Now if I set 15⁰ BTDC I can close the throttle valves a little more to gain the correct idle and the mixture screws start to work. So I'm guessing the throttle valve's are open so much that the progression ports are being under covered making the mixture screws useless. So have I done something wrong?
Why do I have to have the butterfly's so far open to gain the correct idle?
What I did on my dells is remove the bufferflies from the carbs, drill a 2 mm hole in each one, refit to carbs, this then enables you to back the butterflies right off exposing NO progression holes. The holes allow the engine to gain some air to allow it to idle, the bigger the holes the higher the idle rpm. What distributor is it
It won't hurt it to do the advance limit trick
So you mean get running at idle and then restrict the mechanical advance at say 25 (as it would be if idling 'correctly') so doesn't pass 32 at max advance running? Clever I like that. 👍
Yeah. You limit the max advance by bending the weight stoppers. So with a 10 degree idle timing, you might only have say 28 total. You then advance the dizzy while it's running, using a strobe light to get the engine running at 32, at 3000 revs or so. Then when you reduce the revs down to idle, the idle timing is then around 14, which can help smooth out a lumpy cam on a small CC vw
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Right I e not had time to play on the car today but the next time I get a chance I will be back with an update.
But until then can someone let me know if I'm running the right size jets please.
The jets are
Air correction-200

Cheers all
The numbers look OK. The 200 is usually 180 though
OK for that. I will see if I can find some 180's in the massive box of bits I got with the carbs
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