Tunnel ram or no tunnel ram...
OK I had time to test this and observe how it behaves and I’m not too happy with my findings.
Jets were initially 78 square, IAB 76 and carbs utilize 3 circuit fixed emulsion metering blocks by BLP. I need to ask the builder for idle restriction sizes on top of the blocks.
I already tried 70 jets in fronts with 4.5pv without significant change. I also tried radical iab change in iab from 64 size to 86 size.
I was told that jetting has influence on idle mixture in 4150 carbs that’s why I played with jetting. First problem which I disregarded in the beginning is that I can’t setup good idle mixture both in gear and in park. To be exact when I set it to idle well in gear with around 14.2 afr after putting it in park I get 12.2 afr. With 14.2 afr idle is nice and steady, afr is moving by .2 both ways very slowly. Rpm is 900 which pulls about 4-5inHg. When I put it in park afr goes to as low as 12.2 and never reaches 13, rpm jump to 1100-1200. Behavior is pretty much the same with different iab, just different amount of fuel given via mixture screws.
Seems most stable with 82 iab and 1 1/8 out mixture screws but I can’t really say for sure.
Next problem which I didn’t notice with 1st driving is the fact that I can’t get stable cruising. When I get moving it’s 13.5-14.5 afr after short distance it leans out (I assume no more fuel from squirters) to 16-17 afr and car falls on its face. I need to pump gas pedal to keep it running. When I let off the gas it stabilizes. This is below 3000 rpm. When I push it further into rpm range it seems to be better, it’s on the rich side but drives steady and top and power is very good with lots of torque.
This behavior is consistent with square jetting and pv usage. With 4.5 pv I used 70,71 and 72 size jets.
I guess I need 2 circuit tapped metering blocks and expert configuring then right for my car.
Air bleeds for 3rd circuit have no holes, they are just plugged.
When you drive it hard all the time, you don’t really notice the problem ;-)
OK I had time to test this and observe how it behaves and I’m not too happy with my findings.
Jets were initially 78 square, IAB 76 and carbs utilize 3 circuit fixed emulsion metering blocks by BLP. I need to ask the builder for idle restriction sizes on top of the blocks.
I already tried 70 jets in fronts with 4.5pv without significant change. I also tried radical iab change in iab from 64 size to 86 size.
I was told that jetting has influence on idle mixture in 4150 carbs that’s why I played with jetting. First problem which I disregarded in the beginning is that I can’t setup good idle mixture both in gear and in park. To be exact when I set it to idle well in gear with around 14.2 afr after putting it in park I get 12.2 afr. With 14.2 afr idle is nice and steady, afr is moving by .2 both ways very slowly. Rpm is 900 which pulls about 4-5inHg. When I put it in park afr goes to as low as 12.2 and never reaches 13, rpm jump to 1100-1200. Behavior is pretty much the same with different iab, just different amount of fuel given via mixture screws.
Seems most stable with 82 iab and 1 1/8 out mixture screws but I can’t really say for sure.
Next problem which I didn’t notice with 1st driving is the fact that I can’t get stable cruising. When I get moving it’s 13.5-14.5 afr after short distance it leans out (I assume no more fuel from squirters) to 16-17 afr and car falls on its face. I need to pump gas pedal to keep it running. When I let off the gas it stabilizes. This is below 3000 rpm. When I push it further into rpm range it seems to be better, it’s on the rich side but drives steady and top and power is very good with lots of torque.
This behavior is consistent with square jetting and pv usage. With 4.5 pv I used 70,71 and 72 size jets.
I guess I need 2 circuit tapped metering blocks and expert configuring then right for my car.
Air bleeds for 3rd circuit have no holes, they are just plugged.
When you drive it hard all the time, you don’t really notice the problem ;-)
