[Goldenblack440]

HI- have spent a while searching for this topic to no avail, so have posted it here. See the attcahed pic. That divider cut out-- in theory, does anyone have any opinion or experience as to what this will do? I have a standard Performer almost ready to go onto a warm 360 (still doing the port matching at the moment) and am considering doing this mod. I need all the torque i can get as its a heavy car and the cam is rather racy, (2700-6000), so was wondering if doing this divider mod will improve or hinder bottom end torque? All i can think of is that it will give a more balanced signal to the carby- also perhaps give a slight Single Plane effect while keeping most of the attributes of low down torque.

However i'm only guessing.

[Eddie]

I would be careful about this approach. Have you thought about increasing plenum volume with a spacer instead. The low end torque may be compromised by removing that divider plate. It would seem to me that it would do the exact opposite of what you wanted,(increasing the signal to the carb), the cam already produces a lot of overlap, this would weaken the signal by decreasing the pressure

[Goldenblack440]

Thanks AFE, can always rely on you to be reading and replying quickly. I understand what you're saying, however here is a quote from a young guru on our Aussie Mopar site: the mod above lets the 2 sections "share" both sides of the carby, so at high revs it will hold on longer before running out of breath. Without this, each section only gets half of the carby's cfm rating to feed it. you can get by with a smaller carby using this trick.

on a holden [GM product- ugggghh] v8 - this is reputedly a 30hp modification, with little if any effect on low end torque.

and here is another quote from a fellow on the other side of Australia who is rebuilding a Thermoquad for me and has induction experience: the picture you show is what was commonly done with dual plane manifolds in the US and was recommended by Mopar Performance. I think it was more a consequence of some of the class racing rules in the US. What you are doing is trading off a little low down torque for a little more top end power. In your case you have selected a sensible sized cam (not too big like most people go for) and I would recommend you use a stock style US Mopar carb to manifold gasket on your performer. These are about 1/4 inch thick and have an open style plenum. If after a while you want more power then try doing the mod but you will end up with a lumpier idle.

It certainly wouldn't reduce the torque too much as the percentage removed compared to the whole divider would be about 15%. As i am running a Thermoquad, most initial startoff's will be on the small primaries- so it will be helpful ( i think) for the engine to "see" both primary barrels. Hopefully the site master will give his verdict.

[Jon]

The edelbrock LD340 also received this mod. A mopar oriented shop I used frequently cut the divider completely out on mine. Sorry I don't know exactly why but that was the modification recommended back then.

[dave-r]

It will give you a little more top end HP.

But that has to come from somewhere you know? No gain without pain you understand.
So guess what? It is the lower rpm torque and throttle response that suffers.

High end HP is gained by moving the torque curve higher up the rpm scale.
Also, because each cylinder can now "see" both sides of the carb, the air flow though the carb and manifold is slower. Which makes throttle response less good and low rpm power will suffer too because of poor mixture quality.

The effect is not as great as with a true single plane manifold. But that depends on how much you cut out. If you keep the material removed to around a 1/4 inch at most the negative effects can be minimised.

On the whole though, I wouldn't do it if you want torque more than high rpm HP because you are working in the wrong direction. Unless you have a stroker motor with a rod ratio on the short side. then it would be a good thing.

[Eddie]

GoldenBack, too bad you cant or wont use an Eds AirGap. It will give you everything you are seeking and with that cam it's perfect for it.(I love mine)!!

[ianandjess]

gday steve you will need a spacer to fit a thermoquad to a performer manifold so just get 1 thats open & you will have the same result but it will be undoable if it doesnt work
cheers ian

[Goldenblack440]

Thanks for great feedback fellows- Air Fuel- i would love that manifold you speak of, but this is a budget freshen up- just using up what i have in my parts room or what i can get cheap (eg that manifold was only $130), but it was a priority as i needed the torque

Dave- thanks for theory on that- you're right, i'm sort of going backwards from what i was originally wishing for, however, Ian, that is great advice- didn't realise that, and i think the TQ guy in Sydney i quoted actually said to use an open spacer for a similar effect- so that's what i'll do. Glad i havn't touched it with a die grinder yet! I'll get a 1/2" or 1" spacer with no middle bit- if i remember, there's still one attached to the base of a TQ i got from the States off ebay.

Looks like more good advice coming from your way. After you pointed out about the rear dump on the SB stock driver side exh manifold, i lashed out and ordered some TTi headers from Dave Dart in QLD. Ceramic coated lovely things, not cheap, but will not be overcapitalising on that car when it comes time to sell it.

Good luck with your 6pack, Hope you're keeping an eye on ebay for the stuff you need.

[Eddie]

Good Luck with it GoldenBack and keep us posted of your results with it.

[Goldenblack440]

Will do A.F.E., ps was very impressed with the dyno results of 405 from that small block in your RT- is it a 340, 360, or a stroked something or other? (i'm hoping 340- as that's my favourite engine)