Dry sump or being brave with a wet sump at 7500?

 

Dry sump is the plan. Right now I dont know what will be in the car when the engine is complete. I have a 3qt accusump in the current stock LS6 setup, which has a 7400rpm limiter and sees above 7000 regularly. With aero and almost 2.0G's in corners it has kept the engine alive the past 2 season with no bearing material in the oil. It might be the accumulator initially but working on piecing together dry sump components.

 

I see an RPM Transmissions sticker on the front bumper. Are you running an automatic?

 

it’s got a 6 speed manual shift pattern right next to that same sticker

 

While RPM builds both, mine started life as a C5 Z06 which only came in manual. I do have a built T-56 from RPM and I just got a Stage 2 diff with the billet pinion support from them to handle the new power.

 

I agree with all these guys, the 255 heads and probably a different intake that will not neuter the midrange so much. A ported MSD or Fast 102 might be the ticket and should still reach 550. I'm sure Brain can test some things out with you I know they have some dynos to try things.

 

Brian is a sharp guy with a lot of experience. I feel like his recommendations must be grounded in data and experience. It is feeling extremely "bottom of the page" build on both cam size and cylinder head size which has me curious, but I don't think Brian would miss the mark. He might just be picking the rowdiest stuff off the shelf that Summit has however.

I have also seen Brian on Facebook shilling the new 280cc head. Maybe being a new head there are other improvements, but 280cc is a touch large even on a 427 unless you're really spinning it - hence Mamo's success with his 265cc ls7 stuff.

I personally kind of don't see the need to neuter the low end on a c5 - especially with a short stroke engine. You have aero and large rear tires and can run the stickiest of icky super 200 tires. Super 200's are faster than slicks from not that long ago.

With the combination you've got piecing together, it'll be a lightswitch powerband when it "comes on cam" around 4500 rpm. Might be easy to floor it at the apex, but want to swap ends by the corner exit. When I had my rx7 tuned, they showed me some of the > 600whp packages with huge cams and they jumped like 100+ ft lb of torque in 500 rpm or less. That is not conducive to good drivability on track unless you can keep the engine speed well above that transition point.

I would also seriously want 4.10 gears with this engine, and honestly 12.5:1 compression for 93 octane with such a large camshaft. 38 degrees of overlap is more than most run even on a "stage 4" 427 camshaft haha. With 3.42's and an engine that wants to turn over 8000 rpm you're going to be geared way too long.

I mean...I'm all for it. It is going to be badass and sound rowdy as hell and scream on track lol. The cool factor is going to be quite high. I'd be disappointed if you don't exceed 550whp with these parts. I want one, but also would recommend not building it this way if that makes any sense? Lol. I would like to see a lot of videos

 

Brian and I use the same dyno at Back Street Performance here in Ohio. We will have to see what we can test when the time comes for sure.

I had similar thoughts as all of you going over the parts list with Brian, but I do trust his judgement and part selection. I do think the 255 heads and possibly a slightly smaller cam (like the SUM-8743R1) would be a little more punchy. These big Summit cams are bigger on paper than in actuality. The 0.005" duration is not as big meaning the ramp rates are less aggressive to help with valvetrain stability and can use a lower pressure spring like they advertise. We have time before anything needs to be decided on heads and intake, but will definitely be having these conversation when the time comes. I am trying to get the rotating assembly to the machine shop that has the block right now.

There are several guys in the road race world with short runner intakes and its not as light switchy as it sounds. Both Ryan Mathews at After Dark and Justin Peachey have BTR trinity intakes. They key is just keeping it in the optimal powerband, which is just shifted up. Ill be in the 4500-8000 range vs 3500-7000 for example. My driving style would for sure have to adapt to the new powerband, but that shouldnt take too much time. I might just have to drop a gear in some spots to keep RPM up vs letting it pull down low. When I put the LS9 cam in the stock LS6 it hurt the bottom end too, so I kind of already got used to it. It was +21hp, but -16ftlbs. Vmax on straights was the same but it felt more sluggish on corner exit and pulled harder at the end.

I had RPM put 3.42s back in the rebuilt diff. With most of the tracks I go to I want to avoid using 5th in the MN6 trans I have. If I had the stock M12 gearing still 3.90 or 4.10 would be good and use 3-4-5 gear more, but with the MN6 2-3-4 and higher rev limit the 3.42 is still the sweet spot.

 

I spent some time with Brian and Summit the other day gathering parts for the build. There have been some wrenches thrown in the mix which has delayed things a bit, but I think we're back on track.

This is mostly just the internal stuff for now (rotating assembly, bearings, cam, timing set, etc.) and some of the bigger stuff we will get later. The pistons and rings were not in stock locally unfortunately, so waiting on those to come from the Texas location. Should be here next week and then I can take it all to the machine shop where the block is now.



We talked about the 280 vs 255 head. Brian assured me there would be no loss on the bottom end. He said the 280 is bigger on paper than it really is. It is just a little bigger than a stock 265ish 821/823 head. It has similar low rpm port velocity as the 255 just with more breathing room at high rpm. Since this engine will live in the 4-7.5k rpm space it should work out well. It will certainly be interesting to see on the dyno when its done!

Also, if anyone has a stock LS3 intake they would let me borrow we are interested in doing back to back pulls with the Summit Max EFI intake once this project is completed. Let me know if you have one for testing purposes when the time comes.

 

Very cool! And which bump stick did you wind up with? I zoomed in on the picture like CSI but I couldn't see the specs

I can believe that a modern port design on the 280 could just be better all around. I don't think the Trickflow 255's were ever a record setting pair of heads.

 

Cam is the SUM-8743R1. 242/262, 110LSA +5 adv, 0.625 lift

 

This thing is going to be badass. Can't wait to see it!

 

HI, WE NEED a F-1 Fourm "sub" in THIS AREA ?

 

Not a big update, but rotating assembly is at the machine shop this week. We are using Summit pistons, rods, rings, and bearings. The crank will be an OE LS3 long nose crank and I am using a C7 dry sump tank with a C6Z oil pump and pan. I installed a billet 24x wheel on the crank to keep using the factory PCM in the C5. I was originally working with a company to develop a new dry sump system for the C5, but that got delayed. I had some of these parts already as a back up to the 3qt accumulator I was running so the factory style dry sump became the new plan for now. I also picked up an ARE LS7 pan for cheap which looks to have better oil control and scavenge. Still debating on using it or not at this point, as I would lose a drain plug, and I would need to plumb in a remote oil filter.

Summit mini dome pistons should be around 11.7:1 compression, assuming the deck is flat and using a thinner Cometic head gasket.

 

Another small update. I picked up the heads for the build yesterday (hot topic in here I know, lol). After some discussion, and due to availability I went with the 255 head. Primarily due to availability at this point. The 280 castings were still a few weeks out yet, and that would put me too far into the start of the season. Brian believes their new 280 casting would still show benefits up top vs the 255, but the 255 is still a great head! It would have been interesting to see on the dyno, and might still be a test we do later on down the road.

We went with the HD version though which has the heavy duty valves and smaller 67cc chamber to keep compression close to 12:1. Final number will be decided when the block is back and I pick a head gasket thickness.

I also went with some flow matched 42lb LS3 injectors by Trick Flow.

 

Got the old engine out over the weekend. While waiting on the block to come back I am going to work on mounting the C7 oil tank, relocating the PCM, and cleaning the engine bay. I got a bunch of stuff from DEI to help control heat and protect wires and fluid lines. It will be easy to do while I have so much room now.

 

Another small update. Got the C7 dry sump tank mounted on the passenger frame rail. I previously had my accusump mounted here so the frame has some extra "lightening" holes now. This tank is a tight fit!












I also made brackets for a larger oil cooler. It fits inside the bumper behind the brake duct opening.


I had to move the PCM out of the way for the oil tank. It's mounted to the frame from the factory. There was enough room for the accusump and PCM under the cowl area, but the C7 is so much bigger I had to bring the PCM into th passenger foot well.


My brother was able to 3D print a new bracket to hold the PCM for me.

 

Last night I changed fuel pumps and ran the Racetronix "Hot-wire" harness up through the driver rocker. Since I have a a stupid '03.5 it has the newer C6 style fuel system and not a ton of aftermarket support without spending big bucks. I used a C6Z pump (which seems to just be the common consolidated replacement for all models now I guess) since it will provide more volume than the C5 pump. Not as big as a Walbro 450 but more than the stock C5. Lots of C6s running 600+ wheel HP on a stock pump without having to do a return style system. The pre '08 uses the same sending unit for the gauge also.

The hot wire kit is something I fell upon looking for pump stuff. It replaces the small gauge factory wiring, and uses a direct wire off the alternator for power. Keeps a constant 14v to the pump so it's more consistently making good pressure. The factory trigger for the pump now just runs a relay for the alternator power. Supposedly as the pump and car get hot the amp draw is more and actual voltage drops through the small gauge factory wiring. Meaning the pump starts losing pressure. The wire kits were like $120 shipped, so cheap insurance I can get max voltage all the time. Didnt want to risk the new engine going lean.






You can see the wire gauge compared to the factory connector here.

 

Just watch the fuse for the 10g off the alternator. Mine started getting hot and melting the plug, so I upgraded the hot path to the pump between two of the bulkhead pins, made sure the hat/pump was adequately grounded and eventually tossed the hotwire in the trash and I have a leash dual relay board on the frame rail with a 4awg (wayyy overkill) powering it from the alternator, then 10g off that to the pump.

 

What LSA advance if any 🤷?