i have a 1979 Mustang with a 1969 302 Block and Boss Heads with an Offenhauser Tunnel Ram. we have 2 holly 600 cfm carbs with vacuum secondaries and a friend of mine who builds race cars told us how to get the hesitation out. when we were up to about 3000 rpm's in 3rd gear we floored it and it hesitated then took off. he said to up the squirter size so we put 35's on them and it helped but not enough, we took are old 25 squirters and drilled them out to 40's and it does better now but whenever we are in lower rpms now and just start giving it gas not flooring it it will stumble like it isn't getting enough fuel so wat could be the problem if anyone can help i would appreciate it. o and we don't have a power valve in it there is just block off plugs. any help would be appreciated and if u need more about wat is happening or wat i have done to the carbs just ask. thanks
if the motor is running to rich it will have a stumble when you accelorate because its got to much fuel already. you may be jeted to rich. the idle mixture screws may be to far out. the power valve could be opening to early. aslo the timing could be off.
ok but we don't have power valves we just have block off plugs cause of the way are motor is set up but didn't know if we should be the power valves back in it does run a little rich but we run 110-112 octane (raceing fuel) fuel in it and it runs so much better we have it idling at 1000 rpm's and just need help the number 40 squirters helped the hesitation at around 3000 but now it stumbles at around 2000 when we just get on it also would stiffer springs in the secondaries make it run better and someone said something about the accelerator pump cam we might need a different one.
You STILL trying to make that thing run right ? If I recall you asked questions about this setup on other forums. You'd be far better off replacing the whole setup with an Edelbrock RPM intake and single 700 cfm carb.
Tunnel rams usually have a bit of lag to them, since it is such a distance from the carb to the heads. They are designed more for high RPM use than idle to mid range. With that said, you can run a tunnel ram on the street, but I think mech secondaries would work better in this case than vac secondaries would. It takes longer for the engine to pull enough vaccum to open the secondaries, thus creating a bog. A mech double pumper would give you that extra squirt of gas when you punch it, and help prevent the bog. I would suggest trading the vac sec carbs for two mech sec carbs the same size.
What kind of camshaft are you running? because big cams reduce manifold vacuum.And vacuum sec. carbs rely on low vacuum to open up the secondarys. So example the secondarys come on at say 5 inches of manifold vacuum.Thats where you could change to a stiffer spring or you may want to go to mechanical sec.
When you plugged the power valve did you open up the jets to compensate for the loss in fuel? If not then THAT is your problem. At WOT you are running lean - as lean as you run at cruise.
Nothing's gonna fix a Boss 302 running a tunnel ram on the street as far as the soggy bottom end goes.
To answer some of the questions the camshaft we have is a Solid Lifter COMP Cam but we can't remember the duration or lift and can't find any info on it. also we did not change the jets because 2 600 carbs is to much and we were running rich anyway but it is running better then it has ever before but now we have a stumble at around 2000 rpms but is good up around 3000. what we have done is drilled the squirters to .040 and put power valve plugs in. the pump cam is an orange cam and was wondering if w should get a different cam also wat about the secondary springs should we go to the brown or black springs for a stiffer spring.
If YOU don't know your own combination I'm not sure how anyone else can make a suggestion. Back in the late 60's-early 70's it was not uncommon to run 2 660 center squirters on 289s, they were very streetable. I personally would not take the power valve out of any street driven carb.
