I need a drag motor
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| Building a race motor http://www.dlkweb.org/phpBB3/viewtopic.php?f=10&t=7041 |
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| Author: | ConcreteAce [ Fri Nov 27, 2020 2:16 pm ] |
| Post subject: | Building a race motor |
This thread will be an information dump as I find bits of information online. As some of you may know I have built my first race motor and It was a great learning experience. Right now I am researching valve pockets, I didnt get mine notched correctly , mainly because I did not know I needed to have the valve center punched on each piston. Here is information on how to do that correctly. To mark the piston tops: Important to do with YOUR heads and pistons, the deck set, the copper gasket in place, the cam dialed in where you intend to run it. No valves in the head, but piston in place (no rings), and a degree pulley or degree wheel and 1" dial indicator. Most normally aspirated race cams (the FK8X series falls into that category) are such that the greatest valve-to-piston interference happens at 10degrees before or (after TDC). That's where you want to set the piston during the piston marking with a punch process. Mock up the crank in the case, dial in the cam, have at least one rod, piston, and barrel in place, torque plate snugged in place. First confirm TDC of your degree wheel or degree pulley. Put on the copper gasket, torque the head to at least 50% of spec (no valves). Run the piston down the bore 10 degrees. This is where the piston-to-valve will interfere the most, and where you should mark the valve centerline on the piston top, so the machinist knows where to put the notch. Slide a tool called a transfer punch down the valve guide, and punch it with a hammer with a medium hit. What's the heck is a medium hit you ask? Hard enough to put a .010-.020 deep dimple into the piston top, but not so hard as to knock the piston down the hole and turn the crank. Double check the degree wheel. Punch the other valve centerline. Do the other 3 pistons in their respective holes. Since you have already set the deck height on your race engine, you should have already numbered your pistons and cylinders. If not, do it before you take it apart. |
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| Author: | ConcreteAce [ Fri Nov 27, 2020 2:21 pm ] |
| Post subject: | Re: Building a race motor |
some other failures that are noteworthy. When building a drag motor that is going to see RPM's in the range of 7K-9K rpm's you are going to want to have the flywheel and crank wedgemated and larger dowels installed. I did not do this and when the clutch is dumped at 7500 rpm it bent the dowel pins. Had I not torqued the flywheel down to 450 ftlbs I would have probably sheared the dowels completely off. Also noteworthy on a drag motor: it is good to fix a spring to hold your dip stick in place. I blew mine out on the first pass. |
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| Author: | jasonE [ Fri Nov 27, 2020 6:51 pm ] |
| Post subject: | Re: Building a race motor |
I need a drag motor
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| Author: | Chisel_86 [ Sat Nov 28, 2020 9:11 pm ] |
| Post subject: | Re: Building a race motor |
Dump at 7500?? Geez |
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| Author: | mk-Zero [ Sat Nov 28, 2020 9:53 pm ] |
| Post subject: | Re: Building a race motor |
Great info Ethan! Even with .650" lift at the valve i didn't have to clear mine, but my compression is only 10.2:1 and cam duration only 310-deg. Easy to see how with smaller chambers and/or more cam timing it would be needed. 
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| Author: | ConcreteAce [ Sun Nov 29, 2020 1:10 am ] |
| Post subject: | Re: Building a race motor |
mk-Zero wrote: Great info Ethan! Even with .650" lift at the valve i didn't have to clear mine, but my compression is only 10.2:1 and cam duration only 310-deg. Easy to see how with smaller chambers and/or more cam timing it would be needed. yeah right now running 14.4:1 CR , I had to have the pockets cut to run the 1.4 rockers. I was slightly off centered (basically the machine shop had a set of pistons they had cut for another customer and he used those measurement to find center. well they were weisco pistons so it was off) I ran playdoh and figured I could use the 1.1 installed them and the motor did not lock up. But I did notice when i took the motor apart that both intake and exhaust slightly kissed the top of the piston with the 1.1. |
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| Author: | ConcreteAce [ Sun Nov 29, 2020 1:18 am ] |
| Post subject: | Re: Building a race motor |
engine specs 94 mahle P&C CB wedge port 44x37.5 34cc 84 DPR crank balanced and wedge mated H beam rods (clevite CB-610P-1 bearings) FK89 cam 53g race lifters Scat 1.4 rockers .048 DH 48 IDA w/cb manifolds MSD ignition with digital 6AL and 2 step |
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| Author: | mk-Zero [ Sun Nov 29, 2020 8:45 pm ] |
| Post subject: | Re: Building a race motor |
That's a nice setup for sure. Wedgeports are probably the weak link power-wise. Should make north of 250-260 easily though! Do you guys plan to dyno it? |
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| Author: | ConcreteAce [ Sun Nov 29, 2020 11:45 pm ] |
| Post subject: | Re: Building a race motor |
mk-Zero wrote: That's a nice setup for sure. Wedgeports are probably the weak link power-wise. Should make north of 250-260 easily though! Do you guys plan to dyno it? yeah the wedgeports are definitely the weak link in the entire setup. There might be some dyno time in the future. |
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| Author: | tommiebsmith [ Fri Dec 04, 2020 4:54 pm ] |
| Post subject: | Re: Building a race motor |
Cool thread
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