Leaning on 11.90 motor

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Leaning on 11.90 motor

Postby Kern Family Racing » Tue May 01, 2018 12:28 am

From my previous posts, you can look back and see that my son bought a basket case of a car and we finally got it going at the end of last year. We are truly on a 13 year old’s budget with some help from us for entry fees and fuel. Anyway, my soon to be 14 year old is in the major class and he is the slowest car at almost every race. He is finding it difficult to run the stripe with the other cars flying up on his tail. Because we are on a budget, we are very conservative with the tune. It has a sleeved 33mm Mikuni and stock head on a Raptor motor. It does have billet rod and a DynoCams 108 cam. I have it set at a 6.83 gear ratio (12/82) which spikes to 7800 3.5 seconds into the run and hits the trap at 6400 running a Gaged Clutch setup. We have been running 11.50 at 58 mph with a molly chassis in a 235 pound car and 365 with him in it. For those of you out there that have played with Raptors, what can I really expect out of it and still make it live? Will a billet head push the car into the 10’s? He doesn’t really care that he is the slowest, but I would like to help him run the stripe a little easier.
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Re: Leaning on 11.90 motor

Postby Kern Family Racing » Wed May 02, 2018 4:33 pm

Any advice is much appreciated.
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Re: Leaning on 11.90 motor

Postby WILD BILL » Wed May 02, 2018 6:37 pm

I can't see a head change giving you a half sec. I was once told that it could slow down a Raptor due to the quench difference. Not sure of the truth of that though.

What I do know is, If you try to push one to get ever last once out of it, it will come apart on you one day.

I have even seen them come apart running 11.90

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Re: Leaning on 11.90 motor

Postby Kern Family Racing » Tue May 08, 2018 8:16 pm

I have confirmed that a change to a billet head does slow the car down, but it increases the consistency. With the information I have at the beginning of this post, I would like to still try to at least get him back in the 11’s. We run a 12/82 gearing for a 6.83 ratio and I am not sure which direction to go. The car spikes at 7700rpm and goes through the traps at 6200. It is pretty much a pooch off the line so my “big car” gut tells me to put it in the 7ish gear range. Then again, he might stand to have more mph if I put him closer to a 6.0. What is your opinion?
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Re: Leaning on 11.90 motor

Postby tmartel » Tue May 08, 2018 9:13 pm

We have not been in your position with age , but have ran 11.90 quite a bit , lower your gear , Deep stage , and hope the mile n hour helps. You have a tough way to go but It does not mean you cant get there. Try to lower your RPM and maybe you can gain some Longevity. Great to see you enjoying the family time !! IMHO
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Re: Leaning on 11.90 motor

Postby sprintb2 » Sat May 12, 2018 1:22 pm

Instead of cramming more gear on it, I would start looking at the clutch. With the rpms your showing I would look at taking some load off the motor. What is your current clutch set up? I would also try taking the sleeve out of the carb. I’ve got guys running low 10’s with fairly stock raptors and weight packages only about 30 less.
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Re: Leaning on 11.90 motor

Postby jtracr » Sat May 12, 2018 2:53 pm

Times two on clutch! Going from 7800 to 6200 tells me too much load on motor. Lighter arms or a differen ramp might help. IMO 7800 a little high on a raptor but 6200 too low. Get a clutch to give you 7500-7600 for the entire pass you will be faster. More than likely your engine makes a lot more HP at 7600 than 6200.
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Re: Leaning on 11.90 motor

Postby Kern Family Racing » Sat May 12, 2018 11:53 pm

It is a Gaged Clutch with purple primary and red secondary one notch left of center. I am running 10 grams of weight on each arm. The ramps are not marked so I am not sure what they are. I am showing my ignorance because I thought it was supposed to spike and then ramp down as the clutch engages. I never thought about taking the sleeve out because I thought it would be too much for it without the sleeve. I guess I will try it and see what happens. I also messed up on the gearing. I had 14/82 which was a 5.85 and I changed it over to 13/82 for a 6.30. I will report my findings.
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Re: Leaning on 11.90 motor

Postby jtracr » Sun May 13, 2018 11:01 am

You are correct that usually you will spike at the hit then the clutch pulls rpms down BUT 1500 rpms down is too much. Our little motor goes about 7400 at the hit, pulls down 6700 rpms and then gains rpms through out the rest of the run crossing the finish around 7200. To get ideal performance of any engine you should know where in the rpm range your engine makes max HP. Let's just say that number is 7400, then your goal should be to keep rpms as close to 7400 thruout the hole run. Going a lower gear should help. With that much drop sounds like either a ramp off or a belt too loose. Might try tightening the rear spring a hole too. If the rear clutch shifts too early that will pull rpms too much down. Good luck and let us know how things go.
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Re: Leaning on 11.90 motor

Postby Kern Family Racing » Sun May 13, 2018 11:01 pm

Here is the report. Removing the sleeve did not do a thing and we slowed down about a tenth. Plug looks good and no popping or complaining from the engine. So, I moved on to the clutch and took a look at what I had. I have a Gaged Clutch with purple spring in the primary and yellow (not red) in the secondary. I borrowed some ramps that were GE-15 ramps. The car launched better than it ever had and a tenth better 60 foot. The funny thing was you can hear a very pronounced “shift” in the clutch now. Mph actually stayed the same, but the E.T. Improved. We went from a 12.08 to 11.86 after ramp change still at 6300rpm at the trap. Now I am convinced I need to work with the clutch to try and get the rpm more stable. Regardless of all going on, the kid pulled out a win with no buybacks. I would appreciate ramp suggestions and clutch tuning advice.
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Re: Leaning on 11.90 motor

Postby sprintb2 » Mon May 14, 2018 1:00 pm

Congratulations on the win!!! I don’t know Gaged ramps but in a polar ramp I would try a 18-28-22. Less ramp may even work since you still aren’t turning any rpm at the finish line. Just to be clear, when you say 10 grams per arm you do mean two five gram weights? The only other thing is you may be out of valve spring and that’s all it will turn under load. Are you running an overdrive clutch? If you are I wouldn’t be afraid to go to 6.50-6.80 gear. I still think there is more in the clutch though. I know you guys are on tight budget but a cam change would probably pick you up a bunch, a Dyno 98 EXP works really well with stock sized valves and is fairly easy on parts. It would also require a valve spring change. Do you you know what valve springs the engine has?
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Re: Leaning on 11.90 motor

Postby Kern Family Racing » Mon May 14, 2018 11:21 pm

I looked on the information pages on here and I can’t seem to see the Gaged ramp chart. I am also not sure of the angle on the secondary helix so I need to check that. I know what I want it to do, but not certain how to get it there. I am not certain of the valve springs or valves for that matter. I do know it has an older 108 Dyno cam. Right now I just want to get the clutch sorted out just for consistency and give up on making it any faster. Safe and consistent is really what we should shoot for on our budget anyway. We can’t run a bigger engine without extreme chassis modifications so we will just have to make do with what we have.
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Re: Leaning on 11.90 motor

Postby Kern Family Racing » Tue May 15, 2018 9:52 pm

Anyone know where I can find the Gaged ramp profile chart? We went from a 2.79 60 foot to a 2.56 60 foot so I think I went in the right direction. I just don’t know what the profile is so that I can figure out where to go with the ramps. I would think that I can tweak the secondary as well. The shift is pretty pronounced and spikes very quickly to 7750 rpm and 6300 at the traps. Now I just don’t know how to flatten it out.
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Re: Leaning on 11.90 motor

Postby Kern Family Racing » Wed May 16, 2018 2:18 pm

Crap. I pulled the primary apart to check it and it has an orange primary spring. So orange primary, yellow secondary in 5th hole, GE-15 ramps, 10g on arms, and it looks like it says a Gaged 33 secondary roller helix. I assume it is the number stamped on the front. It sounds like I need to just start from scratch. I am going to use the purple primary spring since we are starting over. I am also starting over with new ramps with "normal" numbers and checking all the clearances so I am positive I know what I have and can adjust from there.
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