I had a previous thread going on this subject. Several suggestions for my TH350 shortshifting issue from ajrothm, larrywalk etc. included readjusting the downshift detent cable. Open the throttlle wide and pop the lock on the cable at the bracket near the carb and the cable adjusts itself. That worked good and got my shift points back where they were before I changed manifolds, Performer to RPM airgap. After running the car yesterday in good air (3rd time to the track this year), I'm convinced this manifold makes no more power than the Performer did, on my motor. I only had 3 runs yesterday due to a first round exit (-.002 RT), which also served to aggravate me, so I didn't get alot of data. Best was 12.68 @ 105.4. I'm sure it would have run that with the old manifold. Oh well, live and learn.

 

Thats pretty interesting about the manifold, as everyone on here pretty much $hits on the performer manifold. Please update this thread when you get some more data.....as I have a performer on mine as well and have been thinking of changing it out....Thanks

 

That is very suprising.... So does this 12.68@105 match your previous bests? I can't believe that manifold didnt pick up 1 tenth/1 mph atleast.... Only think I can think of is either

A) There is an airflow restriction of some sort above the intake...(carb/air cleaner)

B) Your mild cam is just not letting it breath enough to pull any more air in.....

That does suck for your efforts that it didnt pick up......sometimes thats how it goes though..... Lord knows I've done it a million times...


Can you repost the incrementals from your PB with the Performer and PB with the RPM? Also DA numbers would help for each race day.

 

Did you have the Performer Air Gap or the RPM Air Gap Edlebrock makes them both ??

I did back to back test with the RPM Air Gap and Victor Jr and both were about the same until about 5500 RPM where the Vic Jr. picked up a couple extra HP.

The RPM Air Gap is probably the best dual plane manifold on the market today. If you had the Perfromer Air gap and switched to the regular performer there wouldn't be much difference in power or 1/4 miles times


Even if it was the RPM Air Gap you are only looking at 1-2 tenths in the 1/4 mile but that is enough to make a win out of a loss in
a heads up race

*I put this on all my posts: Please post back to those who helped you, the final outcome of your initial post

 

The manifold says RPM Air Gap right in front of the carb.
Keep in mind that I only rev it to 5,500. I'm using the same air cleaner, carb secondaries open 100% at WOT.
I am planning to change the cam after this season, but now I'm thinking of putting the Performer back on at that point.
Here are incrementals of best with Performer and best with Air Gap.

................. Perf............Air Gap
60..............1.75.............1.74
330............5.083...........5.143
1/8.............7.934......... 8.036
mph.............85.66.........none
1000...........10.421........10.549
1/4.............12.535........12.683

The DA on the Perf run was better than yesterday. But yesterday wasn't bad so I don't think that could have made 1.5 tenths difference. Thats why I said I would have run the same yesterday with the old manifold. I have over 100 runs on the car and with yesterday's conditions my car was normally in the 12.7 range and thats where my two later runs were, 12.74 & 12.76. One last thing to consider - I only broke into the 12.5 range on one day last season 11/6/10. My previous best, with Performer, was 12.66. So if that day was exceptional air, I'm about equal with both manifolds.

 

So maybe the Performer intake is all your motor needs but I would keep the AirGap on the motor it is flat out is a better intake than the Performer, if you are into the 12's then the AirGap would be the better choice IMHO

 

I am thinking your intake is the restriction.... You REALLY need to try running it with the air cleaner base only on the carb....

Is it the stock dual snorkel air cleaner? On my stock 350, the stock dual snorkel air cleaner with a new filter killed 8 rwhp.....that was only on a 194 rwhp engine....(270 crank HP or so...)

Something to try for sure. You need to run atleast the base though....normally carbs don't like to be completely open on the sides....especially if running a mech fan.

I agree with Wayne, keep the air gap for sure. If you do a cam upgrade, thats when you'll see a good difference I believe.....(although I still think it should be improving 20hp over your Perf intake).

A difference in DA could still be messing with the results. You need to get the dates/times off of your two PB slips, go to www.dragtimes.com and go to the DA calculator and plug in the dates/times....Get the DA from the two nights and compare them. if there is 1000' delta between the two nights, that is easily 1 tenth/1 mph.

I am disappointed your car didn't show improvement with the air gap though...

 

The air cleaner is an open element, 3 inch X 14 dia, drop base unit.
Thanks for that link for the DA info. I will report back on that.

 

Hi Bkbroiler, suprised with your results when I had the performer on the dyno my first pull was 247rwhp with hood closed 14x3 open filter + filter lid (best mph 104.1), opened the hood with no filter 259rwhp, then the air gap made 282rwhp with hood open no filter (best mph 106.7 no filter). just some food for thought.

 

phil - I remember seeing your data. Did you make any tuning changes when you switched manifolds? (other than air cleaner difference)

AJ - Get this - DA on 11/6/10 was -691, DA on 4/9/11 was -771. So I actually lost power going to the Airgap.

 

yes possibly....It could have also needed more jet if it was borderline on AFR before the intake swap, especially that bad *** air but.... It still shouldn't have slowed down. The only way to 100% know is to throw the Performer back on, then re-test the car in similar air but....You're talking such a small amount of difference between the runs, its hardly worth it...

I guess I would just concentrate on a good hyd roller cam swap, possibly port those vortec heads if the budget allows and stick the air gap back on. That 383 will really wake up with some air flow.....Those 170cc Vortecs are really just WAY too small for a hard running 383.....

headwork + cam = 11s.

 

Headwork & cam seems like the way to go. In the meantime, I might borrow a Holley. Its at least a 780, double pumper. It came off a stick shift car so I might have more trouble with my detent cable. Using that carb I won't need the adapter thats under my Qjet now. I'll report back if I try that setup.

 

Just for a pseudo comparison....

Many years ago I had a 78 Trans Am with a pontiac 400. It was bored .030b(406"), 69' GTO d port heads with some light port work, (your Vortecs stock likely flow more then these did ported). It had 10-1 compression with flat top, 4 valve relief TRW pistons. An Ultradyne hyd flat tappet, 231/239*, .485/.507" lift on a 110 lsa and a Torker II w 1" 4 hole spacer and a 4779 Holley 750 DP. 1 5/8" x 3" headers and 3" exhaust. A cheap a$$, highly ineffficient Boss Hog 10" 3200 converter and 3.42 gears. The car weighed 3650lbs with me in it and it ran 12.00s@108 with 1.60-1.62 60's. It had no MPH because the converter was so sloppy up top and frankly, the engine didn't make much power(maybe 425 crank HP....maybe)......Best ever was an 11.98@109 in -500' DA. Only did that once. Car was consistant 12.0-12.10s.

I think your car could EASILY outperform this with some compression increase, head porting and most importantly a real cam....that little 262 cam you have is probably killing 50-60hp atleast over a properly sized cam.... even a mild 224* hyd roller will make 480-500hp in a 383 with the right heads. (ie. not Vortecs though unless they are MAJOR worked.)

Your engine and car combo is solid....just needs a little tweaking.... I think 11.50s would be no problem with some Dart 210s or AFR 210s and a nice 224-230* hyd roller and drive as perfect as can be....