Ultra-rich Fuel Mixture and Flooding Inlet Manifold Drains

[Walter74]

Jets 0.06 inch below bridge

 

[John Turney]

Sorry for my late response, but the problem is still alive. I have checked carbs, ignition and other usual suspects without result. I am now at the point where I suspect a retarded camshaft to cause all my problems.
After extensive diagnosis I measured inlet valve lift at overlap TDC at 1.30mm against the Denis Welch spec of 2.33mm — confirming the camshaft is retarded.
The camshaft was installed using the standard timing sprocket, aligned on timing marks only — no degree wheel was used during installation.
Current setup:
• Denis Welch DWR8 camshaft with new followers
• 123 GB6 distributor, curve 8
• Twin SU hs6 carburettors
• Compression 150-160 psi all cylinders
• Valve clearance 0.30mm cold (spec 0.38mm — will correct)
Questions:
1. Does this confirm the camshaft needs advancing?
2. Is a vernier sprocket the correct solution?
3. How many degrees correction would be expected given this lift measurement?
Any advice from those with DWR8 experience would be much appreciated.
Thanks

I have a DWR8 camshaft also. I had to use a vernier sprocket to get the timing correct. My compression values are lower than yours because the DWR8 cam has significant overlap, which makes the power come on at about 2700+ RPM; it really sings at 3000+ RPM. I'm using twin HD8 SUs. The valve clearance spec (0.38mm = 0.015") is correct for the DWR8 cam.

 

[Walter74]

Thanks for your comments John. Was your engine also running very rich without vernier sprocket? My timing is also way off and impossible to tune.

 

[John Turney]

Thanks for your comments John. Was your engine also running very rich without vernier sprocket? My timing is also way off and impossible to tune.

I installed the vernier sprocket when I assembled the engine. You will also need to get your timing in the range of 10 deg BTDC.

 

[BobHaskell]

I think your valve clearance is way too high. Mine is set to 12 thousands clearance. Compression looks great.

Walter gave the valve clearance in millimeters. If my math is correct, the current clearance of 0.30mm is 11.8 thousandths (of an inch). The spec of 0.38 mm is 15 thousandths.

 

[John Turney]

Walter gave the valve clearance in millimeters. If my math is correct, the current clearance of 0.30mm is 11.8 thousandths (of an inch). The spec of 0.38 mm is 15 thousandths.

Denis Welch Racing lists the correct clearance for the DWR8 cam as 0.015". This is different than the correct clearance for the stock cam, 0.012".