Intake recommendations

So on the advice of Jim Wise in another thread, I have a new Holly 950 carb on the way! Rather than throw it on the Poston Divider, I think the smart move is to buy a better intake. I’m ok with not being able to use the stock air cleaner. Car is mostly used for bracket racing. SP1? eldebrock?

 

Sorry! 30 over, iron stage 1 heads, mild Poston cam 116, that makes power to 5800, hooker comp headers,, built turbo 400 with 3,000-3200 stall, into a 9” with 3:70’s. 275-60-15 drag radials.

 

I personally do not think you will find any gains with an Edelbrock. I would go to an SP1 if you really want to change. The gains with it will likely only be from 5000 up though. I would play with different spacers first with the new carb. I have tried all kinds of spacers with my Poston and surprisingly did the best with a 3/4" 4 hole with a 1/4" open gasket for the quadrajet. I have a milder cam though. Factory Stage 1 cam in mine. I left the plenum divider as delivered but it is the later S divider with the milled plenum divider. I just rounded it over and smoothed things out. Since you are swapping to a Holley I would grab a variety of 3/4" or 1" spacers and try them all at the track with the new carb.
Greg

 

I wouldn’t bother switching the intake I do agree buy some spacers and experiment

 

SP1

 

Sp1

 

While I would not encourage anyone to go out and find a Poston intake to run, if you have one on your engine or just have one in your parts already, I would give it a try. It seems there are folks out there that have had them work fairly well. Most would state it needs the plenum cut 3/4" which was done during manufacturing on most of them short of the first run. I had always heard the open spacer helps the most but had the best luck with a 4 hole. I was just routing around for some more comments on the manifold and came across this quote.

"Can the Poston S-Divider perform with the B4B?

Well, in the following note I received from Jim Burek of PAE Enterprises, he outlines the results of a dyno test he did of the S-Divider. Jim is a pretty sharp guy. The Turbo 400 trans I use was built by his shop and it works beautifully:
"Hey Jeff, how's it going? I thought I 'd drop you a line on some recent manifold tests we did. I had an engine on the dyno making approx 470 horsepower, we had run it with the TA and The cool runner, both manifolds ran pretty much the same, the cool runner made a little more horsepower. Then we set it up with the S-Divider. The power was down about 20 horses or so in this application. Then I did something I had never tried before, I installed a 1 inch tall 4 hole spacer under the carb, the manifold had the center divider cut down about 1 inch. When I did my next pull, wow, power came up like crazy, torque picked up about 30 to 40 pounds and the horsepower came up to around 478. I had never tried a 4 hole spacer on the manifold before, I will be doing much more testing to see what happens."
Jim Burek "
I found it interesting to see this info as I had not heard any comments on 4 hole spacers. That kind of confirms what I found. Without dyno sheets or time slips there is no data to confirm this. If you do go this route let us know what you end up running at the strip with the new carb and maybe some spacers. I also found this little info piece from the GSXtra back in the day.

If you are intent on swapping the intake I would take the opportunity to also swap out the cam and go with an SP1 and a cam that will work well with your combo to take advantage of the SP1 added upper RPM performance.
Greg

 

To be honest. I’m not looking to experiment, or chase numbers. I’ve read the Poston isn’t a good design, and since I’m doing a nice carb upgrade, I figure might as well get a better intake. Currently have the stock hood, and with GS air cleaner the foam is crushed. I appreciate you posting the Poston info. Maybe a drop air cleaner would allow me to try a spacer. Good food for thought.

 

I wouldn’t worry too much about what people say about the intake it works well for most combos.

 

Most anyone that has bad things to say about the Poston manifold only comment with hearsay. I have yet to see anyone say they installed one and their car ran like crap or was way slower. Part of my comments comes from personal experience. My suggestions come from someone that has limited cash to spend on car goodies as well so my suggestion would be give it a try with a new carb and a 3/4" or 1" four hole spacer and maybe compare to an open spacer with your new 950 Holley. I would suggest a GM L88 Corvette style drop base air cleaner base for more hood clearance. This is what I personally run as hood clearance is tight on a 66'. https://www.ecklerscorvette.com/196...tml?crosssell=Product_Viewed&sscid=91k6_ykw04 These are a deep drop yet flow well. I really don't think you will see much if any gains over that combo without a cam change as well. I would plan the next step of a cam swap and SP1 later, especially if you don't find the performance you are looking for out of this. Do follow up on what you end up doing for us though.
Greg

 

Thanks for the link! I’ll miss the GS air cleaner but gotta do what I gotta do with my current hood. I’m around 400hp at the wheels now, so hoping I get a small gain getting rid of my eldebrock. Just don’t want to leave anything on the table keeping my current cam with my limited budget.

 

If you indeed have a Poston GS112 cam then yes, it is pretty mild. It will be all over by the time the SP1 starts to come alive. The Edelbrock is not a terrible carb in the right application. On a quadrajet intake I would prefer a quadrajet. On an aftermarket intake with dual bolt patterns like you have the Holley should work well once tuned.

 

Looking at the chart you posted, it’s the 116.

 

You have a fairly mild combination. I would run everything that you have,including the intake. Leave the center divider. A dual-plane intake will take more cfm carb,compared to a single-plane,but that 950 might be a little much. Work with it. A little less converter would work better with what you have.

 

I agree most say the 950 is too big.....when I was running 12.20s I played on day and pulled my 850 off and put a 1050 on.....no change.

You motor will only pull the needed air through the carb........if properly jetted it won't hurt top end to bad going to big.....but it can hurt the bottom from lazy air speed through the carb. Too small can be crazy responsive and die on top.

But I also ran upper 10s on a 950 and low 10s on a 1050

 

I installed a Poston intake on a friend's 455 years ago and it needed a whole lot of grinding to get the ports matched. (way smaller) Almost like it was unfinished. Picked up .10 over stock after it was done. Did notice plug readings were all over the place on Poston....

I always found the B4B or Performer picked up .10-.15 AFTER jetting the carb .003 to .005 richer on the primaries of qjet. Many people bolted them on and went slower or no quicker. If it flows more air you need to feed it more fuel.

Also: block the heat riser when you put an aluminum intake on. Aluminum transfers heat faster and more efficiently and will cook your carb.

 

I think the Poston S-divider was "debunked" decades ago by folks that knew what they were doing, and the only way they could make it "work" was to ironically remove the feature that was to suppose to make it work, aka the S-divider. Also be careful using spacers when hood clearance is an issue. What good is a spacer if you have to use a drop-base L88 filter base and short filter that leaves very little room between the lid and the top of the carb?

The OP's mild combo would likely work best with a Qjet and B4B or Performer, budgetary concerns aside.

On my convertible street car, I ran a SP1 and Qjet for over a decade, no spacer and no L88 drop base. The highlights are in my signature. It used to run 10.90's until I recently switched to the Q950. The performance increase from the Qjet to the 950 measured by the butt-dyno is probably the best bolt-on item that I've done to that car in over 40 years of owning it. It's that significant. It's all about the combo though, and obviously this combo was "under-carbed" bigtime. I use a 9375 on my 9.50 X, also in my signature and avatar. Sitting in a box is a Dale Cubic 2.350 carb, and one of these years it will find its way to the top and it will be interesting to see how that works out.

 

The 116 cam is a little bigger. The description is below.



And the drop base air cleaner works fine. If it performs on a L88 it will perform for you. I have a 3" filter and with the dome of the lid there is plenty of flow.