What Will It Run?

[PRHeads]

Thanks!!

Looks like it’s getting the job done.

 

[dvw]

Theses combos sound similar to my old 498. Unported -1. 63 crossram. .650 roller from Indy. Flat tops with heads milled .100";4.10; 5600 converter, 3450lbs. Best of 10.1x@131. Usually 10.3-10.4@127-129.
Doug

 

[ksurfer2]

Great weekend at the NMCA race in Rockingham, and very frustrating at the same time. Those that have been following this thread have seen me struggling to get my car into the 10's. I am finally there. This weekend, I was struggling to get back into the 11's to run my number. I am not set up yet to add weights to the car so I was making changes by putting the air cleaners back on, and "blipping" the throttle at about 1000 feet and dragging the brake at the stripe. The closest I got to my 11.0 was a 10.985. My first test hit of the weekend, I did set a new personal best:

60' 1.474
330 4.335
1/8 6.780
mph 100.17
1000 none
1/4 10.741
mph 123.04

DA at the time of this run was 500ft, so the air was really good. I had not made any other changes to the car from the previous best run. I may have been able to change my Index to 10.75, but I don't think I could have run that number during the afternoon sessions when the air wasn't as good.

 

[PRHeads]

Numbers are still lining up nicely

Yup...... slowing down to a consistent, predictable number without a positive means of doing so(like adding weight)
is a challenge.

 

[dvw]

Congrats on the new best. When I ran my old 63 Dodge with a stock cross ram in N/SS it had a 90 degree tab bolted under the carb linkage bell crank. A 3/8x24 nut was welded to the tab. A bolt thru the nut would contact the bell crank preventing the carbs from opening fully. It worked very well. Once the adjustment range was figured out you could move the ET .01. Won a lot of races with that set-up. This method didn't work as well on the current car. I have used it along with weight when the air gets really good.
Doug

 

[ksurfer2]

I was on the phone yesterday with Comp Cams to spec a new cam for my combo. After nearly an hour on the phone discussing specs of my motor, trans, rear end, tires, weight, etc., they came up with is a solid roller Duration at 260* intake, 272* exhaust, lift at 660 intake and 681 exhaust. He did state in order for this cam to work, it would require a 4/7 firing order swap. Why would a cam profile require a firing order swap? Does this sound like a good cam for my set up? The tech stated the benefits to the firing order swap were primarily in harmonics. True?

 

[biomedtechguy]

4/7 firing order swap

I've read about this "mystical" swap, but I sure would like a detailed explanation of the benefit(s) and the process (is it just swapping plug wires on the cap?)
Also, would this swap be something that a cam designer should or must be made aware of?

 

[ksurfer2]

I've read about this "mystical" swap, but I sure would like a detailed explanation of the benefit(s) and the process (is it just swapping plug wires on the cap?)
Also, would this swap be something that a cam designer should or must be made aware of?

I had the same question for the tech, the swap is as simple as moving the plug wires on the distributor cap.

 

[dvw]

I had the same question for the tech, the swap is as simple as moving the plug wires on the distributor cap.

Mine is a 4/7 swap. Just have to remember the new firing order.
Doug

 

[biomedtechguy]

None of the brilliant guys here have explained the firing order swap yet.
C'mon guys, I really want to know!

 

[biomedtechguy]

This may help. I'm reading it.
https://www.enginelabs.com/engine-tech/engine/firing-order-swaps-whats-best-for-your-engine/
Of particular NOTEWORTHYNESS is header design. If you do the swap, some say the headers have to be made for it. (For best scavenging I assume)

 

[440rb]

Here's another, Mr. F>

 

[69sunfireGTX]

I did it on my SB 400 Chevy some of years back. It has a different sound now. More like an LS then a small block. Why did I do it? Because I felt like it, no other reason. Just to be different.

 

[ksurfer2]

It has been quite some time since I have updated this thread. I have made some significant changes to the car over the summer and this weekend will be my first real shot at unleashing the car to its full potential. Early in the summer, I finished a cam swap, new cam specs are a couple of posts up in #126. I also swapped to Mickey Thompson 30X9 drag radials. I did run this combo at the NMCA event in Inday and it was running low 10.80's (a little off from my current best with the old cam and street tires), but I was trying to slow the car down to run an 11.00 index and never let it really eat.

Last weekend, I completed the swap of the factory style cross ram to an Indy 440-25 (keeping the same dual eddy 750's on top). I know....I said the crossram would be pulled from my cold, dead hands, but I really want to be running faster, so the switch was made. I did keep all the cross ram pieces and parts so its an easy swap back in case there is a show or something I want to go to and would prefer the cross ram look.

I am looking forward to a test n tune event this Sunday to see what is in it now. My reference is a 10.741 with the old cam and street tires. I would love to be below 10.50 with this new combo.

 

[biomedtechguy]

I completed the swap of the factory style cross ram to an Indy 440-25 (keeping the same dual eddy 750's on top)

I can't WAIT to see how that works out!
If I were to ever give up on 3x2 of something, both the ported X-Ram and the 440-25 are on my watch list.

 

[PRHeads]

Looking forward to the results.

Did you ever happen to do a cranking compression test with the new cam?

 

[NSS Guy]

The story goes: Indy 440-25 is 90 - 100 HP increase over factory crossram. We'll see........

 

[dvw]

The story goes: Indy 440-25 is 90 - 100 HP increase over factory crossram. We'll see........

View attachment 1365134

My old 498 with box stock -1's, 270/.650 cam, made 650@5750 with a stage 1 63 crossram. It made 710@6750 the same day, same carbs with a 440-25. Never even made a jet change. So there was probably more in it. Started the pull at 4000. It was better from 4000-6750 everywhere, lost nothing at any rpm level.
Doug

 

[NSS Guy]

I haven’t raced any dyno’s, so curious what ET difference will be.

 

[33 IMP]

I haven’t raced any dyno’s, so curious what ET difference will be.

I would think that would depend a lot on car weight. 50 hp won't help a 4400 lb car as much as it would a 2400 lb car. I'm sure your car can put every one of them to good use.