Broken 4.1 NA Block

Thanks. I love the way it runs. I posted a video my wife took with a I-Phone a while back with the same engine with 9.75 compression and 269 cubic inches. They put me up against a big block Camaro that was doing a practice run for a 6 second index race ( 1/8 mile ). I did a little street tire weenie burn out and had to wait for this guy to do his 2 burnouts and a tire chirp. They used a pro tree, which I had no idea was going to happen. As you can tell by who shut off first, he beat me by well over a second. I think I had a 150 shot of NOS on that run. Here is the link.

http://www.youtube.com/watch?v=3KOk_CPXn_M
 
ek02 said:
Thanks. I love the way it runs. I posted a video my wife took with a I-Phone a while back with the same engine with 9.75 compression and 269 cubic inches. They put me up against a big block Camaro that was doing a practice run for a 6 second index race ( 1/8 mile ). I did a little street tire weenie burn out and had to wait for this guy to do his 2 burnouts and a tire chirp. They used a pro tree, which I had no idea was going to happen. As you can tell by who shut off first, he beat me by well over a second. I think I had a 150 shot of NOS on that run. Here is the link.

http://www.youtube.com/watch?v=3KOk_CPXn_M
Click to expand...
I wish we were closer, seeing your video really gets my blood pumping! total mini-truck action. one day, some day.... id like to square up aganst you for a grudge run.

but again, it looks so cool man.... impressive and keep up the good work!
 
I finally got around to working on my NOS return fuel system. I used a Jeg's return fuel pressure regulator and plumbed in a pressure guage and fuel pressure shut off sender. The fuel comes from a seperate pump drawing from my auxliary tank with race fuel, activated when the progressive nitrous controller is switched on. The main pump also draws from the auxiliary tank when switched from the stock tank. I still have to run the return line to the tank. Summit sent be the wrong braided hose size. The return line comes out of the back of the regulator and will run next to the trans bellhousing and back to the auxilary tank. The system worked fine with one pump when I tee'd into the main fuel line, but with the dedicated fuel system, the fuel would drain back into the tank and the fuel solenoid would not spray the first time I hit the NOS. With this system, there will be no air in the line. Probably overkill, but I do not want to hurt this engine.

P9280041.JPG
 
I ran the return line from the regulator to the tank this week. I plumbed it into the filler neck with a steel pipe fitting, brazed it in with a piece of 5/16" tubing bent on a 90 degree angle down the filler neck into the tank. I used a pipe to 4 an fitting and ran braided hose to the regulator. With the pump on, I adjusted the fuel pressure down to 4.5 psi and with a test light on the safety switch, I adjusted it to turn off. I adjusted the pressure back up to 6 psi and tested the system free revved at 2500 rpm with the NOS bottle off. It works perfect. I turned the bottle on and drove it and hit the throttle in second gear. It all works perfectly. I need some more break in miles before I test it at the strip.
 
I did a compression test today to compare the difference between my old 9.5-1 engine and this new 10.5-1 engine. I have only put 300 miles on it since it was built. Compression was the same as the old engine. 220 PSI with the throttle blocked open and engine cold on 4 cylinders. # 6 had 200 PSI and # 5 had only 180 PSI. I squirted some oil in #5 and it came up to 210 PSI. I did a leakage test, and no air is getting by the valves or head gasket. It is evident that the rings on #5 are not sealing very well. The percentage of leakage was 15% higher than the other cylinders. The engine runs perfect, has a ton of power, and has not used a drop of oil. I believe I seated the rings properly when I drove it the first time. The cylinders were honed with a deck plate installed and finished to JE's recommendations. Maybe I need to put more miles on it and recheck it. The cranking compression should be higher with a point more compression than the old engine. It runs so strong, so I was disappointed to not see even compression on all cylinders, and a little higher than the old engine. Has anyone had the same results on a new engine? Maybe no one but me would check a new engine that runs perfect. I may have too much time on my hands. I am thinking that the rings are sealing ok under combustion pressure when running, and just need more run time to get the cranking pressure where it should be.
 
Warm the engine up to operating temp and do it again. I bet you just had a cold slug or two......maybe a cold bore, If it runs that well, your test parameters are off.
 
I plan to do that tomorrow. I drove it today and jumped on it a few times. I had a couple thousand miles on my old engine before I checked the compression. I don't drive it that much anymore, so it will take some time to get there. I also thought maybe the ring gaps had lined up since they do rotate. They were staggered properly when I built it. I double checked to be sure the rings were on right also before putting the pistons in, and put them in gently so no rings were broken or chipped. I really could not hear much air going into the crankcase on the leak check.
 
I drove about 45 miles today and then let it cool enough to pull the plugs. #5 and #6 had 210 psi, #4 had 220, and the rest 235-245. 235-245 is what I was expecting cold. The plugs are clean. When I get to 1000 miles I'll check it again, but I think it will be ok considering how well it runs.
 
IMO with only 300 easy miles on it I don't think the numbers are very meaningful. If you had 3000 miles on it then I would be a bit more worried but not much. Are you using the same cam as the 9.5 cr engine? Cam profile makes a huge difference in cranking compression. I have seen a 14:1 engine with only 160 psi cranking compression. That cam was a wee bit radical :D
 
Everything is the same including the roller cam. Just .030 over and higher compression than the old engine. The 108 LSA builds a lot of cylinder pressure. The mid range comes on strong, lots of torque. JE only had file fit rings for a 4.005 bore. My bore is 3.995. My old rings were file fit for a 3.967 bore. JE said the 4.005 rings would work fine. I just wonder if compressing a larger diameter ring made any difference, but then why would only some cylinders be lower? Who knows. I will keep on driving it and check it on down the road.
 
I now have 750 miles on this engine. I checked the compression again today and the 2 lowest cylinders have come up 20 psi, still 20 psi lower than the rest of them which are at 220 psi cold. Whats odd is that the lowest cylinder leak checks at 2%, but is 20 psi down on cranking compression from the rest. I rechecked the valve adjustment and it is ok. I think it will keep getting better as I put more miles on it. I have a set of custom Caltrac cantilever traction bars on order to replace my slapper bars, and I'll run it after I get them installed. They are supposed to be the hot setup for leaf spring cars and trucks. Video attached of how this thing sounds.

http://youtu.be/frzSOPErxco
 
That sounds amazing!! It sure is nice to hear a high compression V6, very snappy. I need to get in the garage and get mine done already.
 
I looked at my Comp Cam card yesterday to check the lobe profiles. According to their master lobe catalog, the lobes on my roller cam are a High Energy 4X4 profile. No wonder it has so much torque. It's great on the street. The lobes are 3307S int. and 3308S exh. These lobes may be the only ones they had that would give me the duration, lift, and LSA I wanted on a cast cam. They supposedly gave me the maximum duration and lift they could get on that blank. I also had it ground 4 degrees advanced. I may try retarding the cam 4 degrees to kill some bottom end. I sent Comp a request for a cam recommendation for my combo to see if they can come up with anything better than the specs I gave them.
 
Duration on the roller is 228 int 232 exh @ .050 with a 108 degree LSA and .526 lift with 1.65 rockers. I had the cam ground 4 degrees advanced just like the old KB MK II R. It's degreed on a 104 intake centerline. It's about as much cam as I want for the street with A/C. It idles about 850-900 RPM in gear and has a kicker solenoid that activates when the A/C clutch clicks on. Vacuum is good with the 274 displacement, but on the 3.8 with the same grind on a flat tappet cam, I had to add a vacuum tank for the brakes.
 
Correction. The duration is 224 int and 230 exh. That was all they could give me on a cast roller cam blank. 228 and 232 is on my flat tappet cam. A billet roller would be needed to go bigger. With the 3.625 crank, rod to cam clearance is an issue with H beam rods, but a billet cam could be ground with a smaller base circle for increased clearance and still be strong enough. I had .060 clearance on the lobes that interfeared, and advancing or retarding the cam 4 degrees made that number about .040.
 
I installed the Caltrac traction bars, but have not tried it at the strip yet. The right side tire still pulls harder, but I can still adjust the preload on the left bar a little more. I checked my JE piston build sheet and invoice and found out the ring set they gave me has a hardend ductile iron top ring that is compatible with Nitrous. My old ring set had a moly top ring and broke in fast with even compression almost right away. I wonder if hardend ductile iron rings take longer to fully seat? I have a little blow by at the breathers by after a long run on the highway, but it still has not used a drop of oil.
 
The caltrops help with traction but you need to scale it to see where the weight's sitting. That will help with the launch and get you better times.;)
 
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