Is it fat at idle or part throttle? If so that will hurt the 60 ft. times and the rest of the run, which size needles and seats are in the carbs? Which size squirters? To big of squirter shots woll slow it down also on the 60 ft. Put the biggest ones(needles and seats) you can in them and the smallest sqirters that don't stumble

thanks for the ideas.
went out again car ran the same but the driver - damn nut behind the wheel.anyway good to watch some doorslammers,prostock,alky and nitro cars.even had a chat with Cory Mac who is over here to race this weekend
after a lot of thought and talking to others i guess i have a game plan of sorts.
i have a Prostreet meeting in 2 weeks so will swap back to the single carb,picks back up et and some mph.
it may simply be the modman plenum may simply be too large for my ci and rpm range.i have a 440+0.055 ,leave off the footbrake at 2500-2700, shift at 6000,trap 635-6450.this could lead to a poor signal hence having to jet up a lot and leading to a lazy launch.with the manifold off i can set up a cross shaped insert to not only reduce volume but also maybe help direct and speed up the airflow. a mate of mine who races a stroked 409(476ci) chev W motor said Lamar Waldren does a similar intake for these motors and some guys using stock ci or lower RPM motors were finding they needed inserts to get the best results.i may also try something in my M1.
so i can see improvements to come .
BUT it may be this manifold may suit a stroker motor more readily,particularly in a six pack setup.
as to bigger cfm carbs i would think there would be an even more reduced signal,though with an improved signal they might work.
i know on my motor when i tried a ultrahp 950 about a year ago the car lost 3/10 and nearly 3 mph over my BG825.and a hp1000 based carb goes a little better et and mph.
as the saying goes - "your experiance may vary"

Tex

have you tried to advance the cam to help with the lower RPM?

i dont think the plenum volume is the problem, I think the short runners are

What cam are you running? It might want a higher 1-2, 2-3 shift. I also found out last time at the track my car 60 foots better when I go from 1500ish and stand on it then when I pull the rpms up against the convert (26-2800ish) I'm running a Turbo Action 3800. As mentioned take a box of rods with you next time and try a few things. I'd bet you a 6-pack that a pair of holley 650DP's would do wonders. Good luck.

sixpack,
that is also consideration of building an insert to help direct air into the runners.almost like extending them.
MrYuck,
i also think holley type carbs would be better but won't fit this top.Maybe a type like shown by A57RT in the small block manifold thread would
As to tuning at the track i did try a couple of rod and spring changes.Best 60' was with the most fuel and silver spring.But with the silver spring there was some surge,rich,at light idle.Yellow springs are fine.I did find without the silver spring on the dyno and road,but not strip,there was a heasitation as you hit the throttle to the floor from cruise.so it does look like a signal issue leading to fuel issues
oh well 1 step forward - 2 steps backward.
all in the pursuit of speed

Tex

Tex, on my 650 avs carbs i took out the stock pump and put in the one that comes in the 800 carbs. I also drilled my squirters out from .031 to .037

stock on left. you can see the differnce

Sixpack thanks for the pic
took the manifold off yesterday arvo and will play around with insert style over the next week or two.Will also talk to Ben at Promax .
I do see a better result as looking at mph i am not far off the power now
i am stuffed why the pics are so low resolution,will try again

Tex

Look at the picture I posted earlier. Notice the carb spacers. Those are 1" 4-bore. They really make a difference. BUT, the stock hood difinetly will not fit with them.

I would really consider trying a spacer, if it picks up try another, as I did mention in my post on the small block, the BB mod mans we tried with dual 4s just as my sp was very blah and not very responsive and didnt even seem to want to transition to wot well.

As for a few mods in the plenum, a very good Idea the closer 4 ports do try to rob all it can which leave the outter 4 lacking.

I didnt go as extreme as I would if it were a single 4 and would do a dual 4 even different.

Cudadon,
i don't have too much of an issue with clearance as i have a six pack scoop/hood,i can prob go 2" spacer no worries and still run a 3" filter
A57RT,
i will try spacers,but want to get a insert done as well.easier to make up off car.plus like i said have a meeting on the 19th
thanks for the ideas.

Tex

Tex, It's about time I gave you something to think about.
You've been swapping cams, carbs, manifolds, jetting etc to no avail.
You've got a massive fuel system so , delivery, jetting etc is not going to be the problem.
The cam swap was a bit of a stab in the dark because when you put that cam in the other motor it had way too may variables being changed at the same time as well as having different cubes and heads. Although you did see a power increase in that engine,there was no way to say for sure how much extra power was being delivered by just the cam.
Infact your own engine may have not realized the full potential of that cam or the new one you have put in because of one factor.
Your cylinder heads.
You and I have talked about this before.
I'd say they are the choke point of your engine.
Although they are ported, they were done by a guy without the aid of a flow bench and who knows what quantifiable experience he has, as head porter. This could mean your heads flow better, the same, or worse than straight out of the box. You have no data to go by on this subject.
You have always had the attitude that your "RV" cam was what was determining the performance of your engine, when infact it was most likely the biggest cam that your combination would accept.
I think it's time for you to seriously take a look at these heads because your spending $$ hand over fist and going in circles.