What size headers
 

New to the group & first post. I’m running a DCI 5 combo, the guy that build my Taj Mahal intake also spec’d my headers. The trq numbers were a good bit lower than my previous build & thinking it’s a combination of huge plenum & too big of header tubes 2 1/4 to 2 3/8 5” collector. Anyone else running tubes this big on 1050-1100 hp range. My dad’s combo has 2 1/8 to 2 1/4 w/4” collector, smaller intake plenum as well & made roughly 80 ft lbs more trq.

On the headers it is a combination of tube diameter and tube length.

You say your Fathers combination has less plenum volume than yours, what about total intake track length for each combination?

Stan

We’ve had both intakes scanned I’ll have to find that information. Wilson intake built my dads & made two hats for it, a single & a dual. Self Racing built mine. I’ve had a local guy take some plenum area out of my intake last year & it helped some but still not right. Yet to make a clean pass with it, it coughs, spits , sputters & tries to die on the launch. The general consensus is the intake is so big it’s losing carb signal on the launch.

What size carb do you run?
Have you ran the dual 4bbl top?


:confused:

I run a 1250 Get’m carb that is a twin to dads. My intake is strictly for one carb. I have a 1050 on now that I will try next week. Was hoping to run this weekend but our little girl has been pretty sick the past week & we’re all struggling right now lol.

That is definitely a large header. Not sure if you're trying to get the 80tq that your dad is up or what you're looking to gain. But my honest opinion is it'll take a combination of intake and header work. If the plenum is so large you're having issues on the leave that's definitely not right and you will see gains once that is fixed (I'd bet your shift recovery is bad also due to it).
One thing you could do with the headers is move to a 4 or 4.5 inch collect and lengthen it. See how that works. I'm guessing yours are removable so that would be a very easy thing to test.
Fwiw, I ran 2 1/8 to 2 1/4 4" collector on my 1050hp 511ci.

I just want all I can get & not pull the motor out every 4 or so passes. Apples to apples dads dyno #s were with his two 1050s so I was happy to get as close as I did. His motor made peak trq @ 5800 & mine @ 6700. Peak hp for him was around 7600 & for me over 8000 each piull. As far as shift points once it clears up it’s pulls strong through both shifts. 2.24 lenco 4.56 rear it leaves hard.

Interesting, how different are the cams? By the numbers you posted it would seem your cam is quite a bit bigger?

Launch RPM?


:confused:

Dads is 280/294 .855 .837 115 lobe sep
Mine 284/306 .954 .936 121 lobe sep

Sorry it didn’t post the 1st time for some reason but 5800.

My heads were also hogged out. Once dad’s new set of 5s & his new intake are ready I’ll decide whether I take his old heads or back up & punt. These 5s made good #s on the dyno but we haven’t seen the gains on the track to match the #s. I gained 100hp & lost 60ft lbs of trq compared to my 535 with 11 degree eldebrocks. Dad gained 140hp & about 80 fr lbs trq over his 535 11degree combo. We throttle stop race & the cars are running the same mph with this combo than the old. Both 535s had cams in .763 .780 range & both cars went 5.20s on a single carb i@ Huntsville Dragway.

Just curious who picked/made you cam?
I would try another cam.

Engine builder & LSM.. I had a twin to dads cam in it at first but it was worse.

There is going to be a huge difference between those two cams. That second one is going to move the power band much higher in the RPM range.

A overly large primary tube on a given race motor can sometimes be partially compensated for by a longer then needed collector extension.

Yea, dad’s motor only dropped 11hp from 7000-7800 but by 7800 it was dropping. My motor just starts making good #s @
around 7800 & I pulled it to 8400. Only 7 passes on this setup & no clean runs yet but I was only crossing @ 7550-7600 @ Gainesville for the gator nationals this year.

Talked yesterday to guy that’s helped some with my intake & is working the 3rd set of DCI 5s. He mentioned as someone here did as well swapping the collector. He said go with a longer 4” collector. I can’t go much longer & still make it fit but it’s an option. Mine & my dad’s cars were supposed to be identical builds but my his headers hit my steering so I can’t try his.

Can you post dyno sheets for both engines?

What does each engine have for stall speed?

Stan

Both have 6400.