How much quicker and faster?

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408 Nova
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How much quicker and faster?

Post by 408 Nova » Tue Apr 11, 2017 12:00 am

I have a bracket race 408 SBC in a 3000 lb '68 Nova. Current bests are a 1.28 60', 6.05 eighth mile, at nearly 111 mph, footbraked, not fully tuned. Most of the time it's right on a 6.10 in 2000' air.

It has Mahle flattops in it, 11.5:1 compression, Scat crank and rods, Moroso 20191 pan, stock competition ported AFR 220cc heads, 1.6/1.5 rockers, AFR Titan plastic intake, 950 4150 carb, 1 7/8" headers, HEI with an MSD programmable ignition, 1.76 'Glide with a 5900 converter, 4.88's, Hoosier 28x9's, and on gasoline.

The existing cam is a Competition Cams solid roller, 289-261 .430" intake lobe, 297-264 .432" exhaust lobe, 104 LSA, in on a 100 ICL. 1" base circle. It was a cam for another project that I just stuck in this motor.

Going to another Competition Cams solid roller, 291-263 .430" intake lobe, and the same 297-264 .432" exhaust lobe. The LSA is 107.5, ground 2.5 degrees advanced, and I'm gonna put it in at a 105 ICL. 1.65/1.6 rockers. It's on a 1" base circle also. It's a Vizard COS-Cam specified cam. I already have the cam.

Also, it's getting a SRH ported 2892 Super Victor 2, 4150. Chad has it now working on it.

I'm also getting a GZ Motorsports Sportsman vacuum pump. Gonna order it Friday.

It's going on a Stuska dyno before going back in the car.

Everything else will be the same. How much is it gonna pick up?

bigjoe1
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Re: How much quicker and faster?

Post by bigjoe1 » Tue Apr 11, 2017 12:08 am

Very little




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Re: How much quicker and faster?

Post by 408 Nova » Tue Apr 11, 2017 12:56 am

Lol. That figures!

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Re: How much quicker and faster?

Post by groberts101 » Tue Apr 11, 2017 9:21 am

I guess around 20-25 @ peak with slightly fatter torque hitting the converter. Also think you may need a little shorter tire height or more rear gear to take better advantage of it.

Depending on the previous springs stat's(sufficient enough or overkilled) you may want to add 5-10% more seat pressure to go along with the higher rocker ratio/faster valve accel/decel. What rpm did you cross the stripe at with the old cam in comparison to peak power?

To answer the question though.. if the converter likes that cam/rocker as I think it will.. you'll have a solid tenth and loose change ET reduction even in hot sticky air. Maybe 2 tenths in good air if the converter REALLY likes it and edge's closer towards 6,000 stall.

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Re: How much quicker and faster?

Post by Fastvette94 » Tue Apr 11, 2017 10:24 am

Baseline for your old setup I calculate around 670hp w/ lots of assumptions (peak RPM, rotating inertia, drivetrain losses, stator multiplier, etc.). I arrived at the number by backing out horsepower based on your time slip.

My 1D engine simulator is still in the works so I cannot do HP predictions based on parts changeout yet. It is close but without a completed header/collector module I wouldn't take a guess.

I will edit this post at lunch and add video of the 1/8 pass simulation for baseline.

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Re: How much quicker and faster?

Post by CGT » Tue Apr 11, 2017 10:28 am

If there any gains, they will be coming from the vacuum pump in my opinion. The cam is not very much different at all, and I don't see the manifold doing much of anything.

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Re: How much quicker and faster?

Post by bigjoe1 » Tue Apr 11, 2017 11:16 am

I have been going to 1/8 mile drags now for about seven years. It is much harder to see an improvement than when we were running the full 1/4 mile. MUCH HARDER !





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Re: How much quicker and faster?

Post by mag2555 » Tue Apr 11, 2017 12:12 pm

Any reason why you can't go a full point more in compression by milling the Heads, as that would be the ticket!

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Re: How much quicker and faster?

Post by RevTheory » Tue Apr 11, 2017 12:15 pm

It would be nice to make some pulls without the vacuum pump so you can isolate its effect on output.

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Re: How much quicker and faster?

Post by Fastvette94 » Tue Apr 11, 2017 1:17 pm

As I discussed earlier, the engine prediction code isn't completed but here is a single cylinder animation for your original engine showing pressure pulses (top) and pressure (lower white), velocity (green), and temperature gradients:

Link: https://youtu.be/xEdyahRf0QQ

Also, here is the simulation of your current configuration (ignoring standin image for the nova)
Link: https://youtu.be/P7s8lC39FYs

(I didn't have time to tune the suspension so it wheelied pretty hard which dipped the RPMs on the output page)

As stated in first post, baseline is estimated at 670ish with assumptions

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Re: How much quicker and faster?

Post by fdicrasto » Tue Apr 11, 2017 2:38 pm

As Joe said, 1/8th mile gains are not going to be dramatic so don't look for big gains. I would concentrate on 60 fts, trap rpm's, tire heights to gear ratio and optimize those stats as was mentioned by groberts. Why not try the rocker ratio change on the present cam first and see if there are any gains. I like the one step at a time approach so you don't get tangled up figuring what worked and what didn't. Actually shedding some weight might be the best thing with that 1.76 glide.

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Re: How much quicker and faster?

Post by F-BIRD'88 » Tue Apr 11, 2017 3:50 pm

bigjoe1 wrote:I have been going to 1/8 mile drags now for about seven years. It is much harder to see an improvement than when we were running the full 1/4 mile. MUCH HARDER !





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That's because you get there too quick, to pick up any speed. :-)

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Re: How much quicker and faster?

Post by 408 Nova » Tue Apr 11, 2017 9:00 pm

My dyno time should go something like this: existing combo, then swap the cam, then rockers, then swap the intake, then put the belt on the vacuum pump. That's all the dyno time I can afford!

Putting lightweight brakes and a lightweight rack and pinion on are on the list too. Heads have been flat milled .030" already to bump compression to 11.5:1.


I'm shifting at 7200 rpm, crossing the stripe at 7000-7100. The converter was way to loose initially, flashing at 6300, and it just seemed like it was blowing through it on the top end. PTC tightened up for me, and that helped it a bunch.

Fastvette94, you're a little above my head here. It's gonna take me a little while digest your info. Thank you! I was just guessing it might have 580 hp, if I was lucky.
Big Joe, I know you're not to fond of vacuum pumps. But I'm gonna check it out on the dyno, and the drag strip.

I'd be really happy with a 25 hp increase, and a solid 5.90 in 2000" air.

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Re: How much quicker and faster?

Post by bigjoe1 » Tue Apr 11, 2017 9:16 pm

I have seen the vacuum pumps make a 55 HP increase IF the engine was made for it. If you just bolt one on, it might make 5 or 10 more hp. I put vacuum pumps on all the serious race car builds






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Re: How much quicker and faster?

Post by greywolf » Tue Apr 11, 2017 11:40 pm

With the motor changes only, you may break into the high 5.90's.
IMO.
When I turned 47 years old, I entered into my 5th decade of drag racing.

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