TUNING A SIX PACK

[RJRENTON]

The 2300 Six pak diaphragms are not the same as the 4150/4160. The needle valve deal does work.

I'm aware of the differences, and the reasons for the differences. But the origional question, I believe, was the diaphragm assembly shown in the pix would/could be used for a six barrel application....which is NO.
The use of a needle valve is innovative, but accuracy and consistency of the adjustment may be questionable and will the adjustable factor also slow the closing rate, in addition to the opening rate? And how will the setting be determined.....empirically or ?
BOB RENTON
BOB RENTON

 

[66Satellite47]

I was just making a clarification about the diaphragms. Yes like many tuning adventures, the needle valve adjustment is trial & error, it provides some "fine tuning" without needing to change the springs. And as with many tuning things, they may not remain constant over time. Never considered the effect on closing rate since mine was a drag car application.

 

[Frustration]

Well, our track rental got rained out Memorial Day Weekend. It was rescheduled for yesterday in the 95 degree heat. We had 46 cars show up at Cecil County...mostly mopar, but other brands as well. Everyone was off at least three tenths due to the heat and track condition. My son was driving and made eight passes. We found lots of stuff that we did not see on the dyno. For example, the car developed a serious bog off the line that was not evident on the dyno, and didn't happen before. Guessing it was because of the fatter tune up. Tried different squirters and bringing in the accelerator pump a bit later. That seemed to help. At the end of the day, we ran a best of 11.39 @119. Pretty good, but with the 60' being off more than a tenth, that will be my area of focus moving forward. As a bonus, Tommy made it to the final for the second year in a row. He was unable to defend his title as he lost to a great racer who ran dead on with a zero in the final. I'll try to post the video here shortly.

 

[biomedtechguy]

Thanks for the clarification on the needle valve controlled vacuum pods. I had asked...someone...about the particular one pictured and was told "not compatible" but I thought there may be one.
I've been lucky that is one area I don't have problems with, the rate and conditions that my outboard carbs open. Whether I stomp from a dead stop or roll into the outboard carbs, it works well.
One day I may make the time to tune with my O2 sensor system. It's running fat at "cruise" throttle positions, around 11.8-12.1

 

[Jason Repucci]

View attachment 435752 Any Suggestions for THESE DIRECT CONNECTION SET UPS??

Do you still have this carb set up?

 

[68 HEMI GTS]

After a very long hiatus with running dominators and single planes on my 511 I’m back to the six pack. I’ve spent some more time porting on the intake. The mods seemed to make the big motor much happier. I spent a few days re-tweaking the carbs going after every ounce of drivability with an 02 meter. I can say it’s damn good and the intake mods seemed to improve the top end as well as the low speed distribution and manors. Next on the docket swapping the 727 out for a hemi 4 speed as it is a factory stick car.

 

[beanhead]

After a very long hiatus with running dominators and single planes on my 511 I’m back to the sick pack. I’ve spent some more time porting on the intake. The mods seemed to make the big motor much happier. I spent a few days re-tweaking the carbs going after every ounce of drivability with an 02 meter. I can say it’s damn good and the intake mods seemed to improve the top end as well as the low speed distribution and manors. Next on the docket swapping the 727 out for a hemi 4 speed as it is a factory stick car.

View attachment 1174829 View attachment 1174831 View attachment 1174830

Nice work, as always.

 

[rumblefish360]

View attachment 1174829

Tell me about the grinding you did under the carbs, very interesting work done.

 

[68 HEMI GTS]

Tell me about the grinding you did under the carbs, very interesting work done.

when you come across a full weight 70 superbee at the track running 10.40’s with a 505 six pack you ask questions. Luckily he was nice enough to tell me a few things.

it may not look like it but they are scalloped down a bit to allow cross over.

 

[RJRENTON]

when you come across a full weight 70 superbee at the track running 10.40’s with a 505 six pack you ask questions. Luckily he was nice enough to tell me a few things.

it may not look like it but they are scalloped down a bit to allow cross over.

To me, it looks as if you scalloped enough of the divider wall and approach angle transition to yield an open plenum design. The open plenum usually results in less air flow turbulence an a more even mixture distribution, contributing to additional top end performance........excellent work...your results speak for themselves.
BOB RENTON

 

[68 HEMI GTS]

To me, it looks as if you scalloped enough of the divider wall and approach angle transition to yield an open plenum design. The open plenum usually results in less air flow turbulence an a more even mixture distribution, contributing to additional top end performance........excellent work...your results speak for themselves.
BOB RENTON

They are down about 3/4 of an inch in the very middle. It’s one of those mods your almost afraid to do cause you hate to trash a six pack manifold. Glad I did though! Lol

 

[beanhead]

They are down about 3/4 of an inch in the very middle. It’s one of those mods your almost afraid to do cause you hate to trash a six pack manifold. Glad I did though! Lol

Do you do much to the ports and into the runners? I forget which INDYs you're running on that one.

 

[68 HEMI GTS]

Do you do much to the ports and into the runners? I forget which INDYs you're running on that one.

They’re opened up a bit. The heads are Indy SR’s that are in between standard and MW port. I may open the intake up a bit more, my hesitancy is I could still use it on a standard port head at the moment.

 

[66Satellite47]

Do you think the mods to the dividers would help on a 440/452 inch motor? Are those carbs the Mopar mechanical version end carbs?

 

[68 HEMI GTS]

Do you think the mods to the dividers would help on a 440/452 inch motor? Are those carbs the Mopar mechanical version end carbs?

yes they are the mechanicals. I see no reason why it wouldn’t work. We did it to my buddies pump gas 440 six pack and it seems to like it. Runs mid 11’s @ 119 in a 67 b body street car.

 

[MAPS]

Hi guys
I have a few problems with my six pack set up basically the worst of all is the smell of the gas too too rich but I need to ask.
If I have a cam that's about 540 lift (mechanical) should I drop the 6.5 power valve to a 3.5... I was told because of low vacuum from the cam or is the 6.5 ok?
Thank you

 

[68 HEMI GTS]

Hi guys
I have a few problems with my six pack set up basically the worst of all is the smell of the gas too too rich but I need to ask.
If I have a cam that's about 540 lift (mechanical) should I drop the 6.5 power valve to a 3.5... I was told because of low vacuum from the cam or is the 6.5 ok?
Thank you

PV is part of the main circuit and provides enrichment during acceleration. It will not affect idle unless it’s blown or the gasket is leaking. For reference I run a 10.5 PV in the above pictured six pack with a .630 lift cam that idles at 5.5” of vacuum.

 

[RJRENTON]

PV is part of the main circuit and provides enrichment during acceleration. It will not affect idle unless it’s blown or the gasket is leaking. For reference I run a 10.5 PV in the above pictured six pack with a .630 lift cam that idles at 5.5” of vacuum.

Out of curiosity, because the 10.5" power valve is open with the 5.5" vacuum at idle, why would you not just install the equilivant main jet size and block off the power valve? Have you increased the power valve channel restrictions or just the valve's opening point? As the PVCR are in parallel with the main jet, at the bottom emulsion channel, once the power valve is open, the two orifices just combine their flows, based on differential pressure created at the venturi. Help.....
BOB RENTON

 

[68 HEMI GTS]

Out of curiosity, because the 10.5" power valve is open with the 5.5" vacuum at idle, why would you not just install the equilivant main jet size and block off the power valve? Have you increased the power valve channel restrictions or just the valve's opening point? As the PVCR are in parallel with the main jet, at the bottom emulsion channel, once the power valve is open, the two orifices just combine their flows, based on differential pressure created at the venturi. Help.....
BOB RENTON

the power valve has absolutely no effect on the idle whether it’s closed or open. The reason for the high number is the engine pulls extremely good vacuum once it’s going down the road. I have the jetting as such that it cruises high 13’s to low 14’s depending on the speed. Exactly where I want it. When you throttle it to accelerate with the current jetting it needs the enrichment from the PV to keep the A/F from going lean. I found the 10.5 to be ideal as the vacuum only drops to about 9” when I accelerate (moderately without getting into the secondaries). When I had a lower number PV in it I got absolutely no enrichment from the circuit. So I upped it to take advantage of the circuit. Pvcr is opened up to 0.76. This is a bigger center than stock. It’s a 4412 which is essentially the front half of a 750.

 

[RJRENTON]

the power valve has absolutely no effect on the idle whether it’s closed or open. The reason for the high number is the engine pulls extremely good vacuum once it’s going down the road. I have the jetting as such that it cruises high 13’s to low 14’s depending on the speed. Exactly where I want it. When you throttle it to accelerate with the current jetting it needs the enrichment from the PV to keep the A/F from going lean. I found the 10.5 to be ideal as the vacuum only drops to about 9” when I accelerate (moderately without getting into the secondaries). When I had a lower number PV in it I got absolutely no enrichment from the circuit. So I upped it to take advantage of the circuit. Pvcr is opened up to 0.76. This is a bigger center than stock. It’s a 4412 which is essentially the front half of a 750.

THANK YOU FOR YOUR EXPLANATION.....I understand your premise....
BOB RENTON