Rookie

They also state that they also see the fuel distribution problem with carburetors every once in a while.
https://www.dailymotion.com/video/x3moa13

compedgemarine

based on some issues I had with throttle body injection is the intake design. if you look at that dual plane it is solid between planes. as a result the map sensor on most of these bodies is on one side and so only see's vacuum on one half of the intake which gives it a weird signal. on factory throttle body intakes there is a hole between the two so that it evens out the pulses and signal. from what we found was if you cut a notch into the top of the intake between the two planes it helps with the learning and makes it run more smooth. dont know if that was what caused their problems but it could be possible.

articfriends

If I bolt a 454 or 502 on my dyno with 10 02 sensors with a weiand dual plane or regular performer, its not uncommon to see #2 cylinder in the 10s and # 3 cylinder in the high 14s at wot, to me its almost impossible to tune certain ones on a marine application as theres no way to lean out 2 and richen up 3 since they are fed by same runner and the runner going to 2 is huge and runner to 3 has sharp turn and is 2/3rds as big. Fuel distribution is almost ALWAYS a issue on a bbc with majority of intakes, most people just dont know it. Ive yet to hear or see what afr a cylinder really needs to be to not melt down at continuous wot, I wont send anything out thats leaner than 13.2/13.4 on any one cylinder thats NA but its not always easy to get there, Smitty

JaniH

what is the model of the weiand that you see this problem.

TomZ

I think their Action Plus is the current intake.

**correction, I forgot about the Stealth series. I knew I was missing something.

They’re all based off the factory dual plane so I would think the issue would follow across the board.

compedgemarine

OK, so stupid question. there are plenty of BBC carbs that run different jets left to right to try and compensate for the intake flow. on the Sniper can you change the flow of each of the injectors to do the same or is it just a batch fire type of thing and flow rate is a based on what the four flow.

articfriends

You cant stagger the injection on a sniper, thing is, like in my example of how horrible distribution is on most entry level dual planes, even if you could, the same bbl feeds the lean/rich cyliner so it wouldnt help in that scenario

articfriends

weiand stealth and regular performer intake. % or so years ago a friend brought a 502 to dyno, small cam, vic jr intake. motor was a zz502 he had got cheap and fixed up. motor made a embarrassingly low tq number for a 502. We bolted a ported performer on, picked up tremendous torque AND top end hp (only hgad power to 5400/5500). #3 was burn down lean, #2 was pig rich, talking 4+ afr points apart. we monkeyed with carb spacers, still sucked. He bought a perfomer rpm, picked up even more tq and hp, 2 was like 11.5, 3 was like 13.5 give or take, half as bad.
Fast forward, guys building a similar engine, asked what he should get, I told him a perf rpm, he couldn't get one, so he bought a weiand dual plane. Same deal, 2 in low 10s, 3 in almost the 15s. tried a couple spacers, made no difference. Compared a stock carbed 502 intake I had to his weiand, they were a mirror image of each other BUT the factory intake had little ridges/troughs turning the sharp corner to 3, I assume to help fuel distribution. We looked at a beat up, nasty perf rpm I had, the turn to 3 was much more radiused and port to 2 much smaller than the other 2 , as if they actually put some thought in the design. We found a new perf rpm online, ordered it, swapped it on, picked up tq/hp over the weiand (like around 15/20 at peaks) and again, distribution was half as bad as the weiand. If anyone calls and wants to dyno a marine engine with regular dual plane in future, Im pretty convinced theres no real good way to fix the fuel issues, Smiitty

Rookie

Smitty, do you think I would have any gains going from the low profile single plane Merc 420 intakes to my "Dart" style single plane Professional Products intakes on my Merc 420's upgraded to 500EFI cams in my Panther. My Panther use to run low 70's with my flat tappet 420's and ported Weiand Stealth intakes now with the cam upgrade and different intakes I'm having a hard time breaking the 70mph mark.
Black vs Aluminum

ThisIsLivin

It was season 3 episode 39. I think their analysis was that the jets shoot down under pressure and the fuel can't make the turn. Get a subscription to Motor Trend it's worth the money. Over the seasons they have tested everything I've done and I'm feeling pretty good about my choices. They do a lot of testing on BBC so we can learn a lot.