Tr8 3.9 with CD 175 Carbs

Paul Dryhurst · Post by **Paul Dryhurst** » Fri May 25, 2007 1:39 pm

What would be the best needles for the car. It's a manual 3.9 Engine with valve cut outs in the pistons, SD1 std Heads, Exhausts and Cam and composite gaskets. I've tried std TR8 3.5 Needles B1FL but their isn't enough adjustment to get them rich enough also is it worth putting std gaskets back on to improve the compression what would be the compression as is ? PS Idon't want to move away from the strombergs.

Post by **katanaman** » Fri May 25, 2007 2:17 pm

Cant help with the carbs but your compression will be around 8.7:1 or less. Hoe much less depends on the size of the piston pockets. Definitely yes go back to tin gaskets to get the compression up or skin the heads and manifold if you want to stick with comp gaskets.

ChrisJC · Post by **ChrisJC** » Fri May 25, 2007 2:54 pm

Did you compensate for the fact that a thicker head gasket means that the hydraulic tappets may be running out of spec (effectively the pushrods are now too short), and the valves not lifting as far as you hope?

Chris.

greenmeanie · Post by **greenmeanie** » Fri May 25, 2007 3:28 pm

Unfortunately the options available for ZS needles are extremely limited. I built a modified 3.5L V8 for my LR 101 and ran in to difficulties in this department. I ended up modifying the damper pistons to take SU needles. My ZS175's are the older type with the mixture adjustment on the bottom of the float bowl instead of the fancy tool from the top. An AFM is the next thing to beg, borrow or steal as it will let you monitor your fueling under real world conditions. You should shoot for approx. 13.5AFR idle/cruise and 12.5AFR when the loud pedal is used.

Cheers
Gregor

badger · Post by **badger** » Fri May 25, 2007 4:46 pm

If fitting SU needles, try BAC needles as a starting point.