403 LS2 FD - LS7 Build for 2020!

[Exidous]

It's dependant on the cam. I run 93 here. Running a bigger cam drops dynamic compression and allows you to raise static.

My cam has a mild intake lobe duration and I'm the at the safe limit for DCR. About 8.7:1. If I ran a big cam I could easily go to 12.5 on 93.

With 91 you'd want more like 8.5:1 DCR.

[MPbdy]

Yeah it is a big ol solid roller.  My original plan for the engine was to clip the heads to 13.5:1 compression but I ran out of piston to valve clearance at 12:1.  This seems like a chance to go back to the original plan. 

91 would always have a heavy dose of boostane and would only be for when E85 is not available. Half a bottle on a full tank would be ~98 octane.  At that compression the idea would be to run straight E as much as possible.

289/303 on 113+3, advertised duration for the solid lobes rated .020" lift.

If I put in numbers to make the static compression at 14:1, dynamic is ~10.2.  That is with a 75 degree IVC.

Bore - 4.185
Stroke - 4
Gasket bore - 4.200
Head CC - 68
Dome - 8cc
Quench - .040"

STATIC Compression Ratio:
14.05:1
DYNAMIC Compression Ratio:
10.21:1

At some point you need to factor in things like VE, horsepower per cube and RPM for octane requirements too.  A 1 degree change in cam timing makes way too big a swing in DCR for me to feel confident following it as a rule.  Also, a hydraulic roller of this size would show a much lower DCR because it is rated at .005 instead of .020" - but I doubt it would result in a significant reduction in cylinder pressure.

I've seen people successfully run up to 16:1 on E85 with a very well optimized NA combo.  Trying to determine at 14:1 if 98 octane would be enough to drive around on, and what the minimum octane requirement for WOT would be.

[largeorangefont]

This was going to be a short post to talk about something else but I kept rambling about the car so I'll just make two posts.

I wouldn't be a car guy if I didn't make a boring cold start idle video so here you go -



I drove the car 2 hours yesterday and spent 15-20 minutes in miserable LA traffic.  The 15N to Vegas is down to 1 lane and everyone was trying to get there for the superbowl.  I moved my IAT sensor and epoxied it into the intake manifold and it works phenomenally.  The IATs sitting idle climbed from 75-80 up to 150+ and the ECU kept everything perfect.  I could feel the self learn continue to do its thing and get better the longer I was idling around.  Cooling performance was great with the electric water pump keeping coolant temp below 200 with a 185 thermostat.  The cooling fans also didn't impact the engine tune like it did before with the MAF sensor.



The tune continues to improve everywhere and honestly drives quite well right now.  It'll buck like mad if you don't give it throttle on take-off so I need to see what is causing that, but if you give it some load the car drives very smooth.  It also tries to stall if you clutch in from too high of an RPM so I need to either slow down the drop, or make the catch more aggressive.  It is a bit of a mind-f to tune on the tables in this car because of the giant 105mm throttle body. It idles with this cam around 65 kPA and when you first give it load it drops to 30-40 range, but from 40% throttle position you're back up to ~90kPa.  I have this giant fuel and spark table but it feels like it spends most of the time in just a few rows.  Because of this I've found some areas where I had spark jumping 5-8 degrees as it goes in unexpected directions in the table causing bucking so I just need to continue to manually review these trouble spots and improve them.   

There are some light chuggles when going on/off load in low rpm regions, but I also have extremely low driveline intertia with the RPS clutch and it honestly always did this with the smaller cam and the e40 ecu as well to some extent.  I need to experiment with more/less timing in those areas and see what it likes.

I got my fuel pressure, flex fuel and speed input all working in the Holley. Still struggling with the tach - worst case I can buy a dakota digital converter but I really feel like I should be able to get this work via the Holley.  I can't believe they output an 8cyl tach output that isn't programmable when so many of these go onto LS engines.  I've burned enough fuel now that I can throw in some E85 and start playing with that.  It won't be night and day power gains, but at 11:1 compression making ~600hp I think e85 will help it out some especially in the midrange and part throttle high load regions.  It also keeps the engine cooler while hammering on it.

Power is insane and the powerband has never been as broad or as smooth.  This is definitely feeling like a very optimized engine package now with the "proper" duration camshaft for the engine combo.  It is a pretty big dickhead machine, but as the tune improves it is mellowing out some.  The easier it is to drive the less I feel like it draws attention at low speeds.

My dad took it for a spin while I rode passenger and watched the logs.  It pulls very hard to 7200 and even if you short shift it at 6700 it doesn't feel like it loses any momentum.  Estimation is it is solidly a 135+ mph trapping car right now making it faster than our 9.9x drag car with a 416.  Power is still very manageable on these Maxxis slicks, and the car gets your heart racing.  The way the power is delivered from the FD right now is very impressive.  All the work I've done to the driveline to improve efficiency and smoothness is finally paying off.  For an engine with dead stock ls3 heads I couldn't be more impressed with the performance.

I noticed my 275 wide 18's are rubbing on the inner fenders up front.  I also haven't been thrilled with the steering feel on the street for the giant tire.  I think in the future I'll throw a 255 up front on the 9.5 wheel it'll fit better and the slight stretch should improve steering response.  I loved the steering feel of the 255/40/17's.

I also want to schedule a corner balance and alignment appointment.  I'll probably reach out to CHE Works for anyone in Socal that knows who I'm talking about.  I corner balanced the car myself when I first got the car together but have made tons of changes since then.  The car has always been a little ass-down in the rear which improved the cross weight and f/r balance - but I don't think is the correct way to setup the car and it always looks a little off.  I could also use a little more ride-height with the 18's and I want more camber so I can put my spacers on in the rear and take more advantage of these tires all around.

Here's the dirty girl still with the road grime and snow residue from when I blew the coolant surge tank in January 2020 up on Angeles Crest lol.

You probably don't want to buy new wheels, but 1 inch wider wheels would tighten the steering response. If you want to do a run one morning soon, lets roll!

[MPbdy]

Yeah definitely sticking with these wheels. I'll go the other route and shrink the front tire eventually. If the rubbing gets bad I can pop these off and save them for the rears.  I have no doubt it'd be faster with the 275 up front but until I'm actually putting this thing against a stopwatch (probably never) I'll just go with whatever drives the best. 

I want to corner balance and align it before I go too wild with it, but I'd love a redemption run up Angeles Crest someday soon especially before it gets too hot. I'm also out here just off Santiago Canyon but aside from some nice scenic views that's more or less a straight line with some bends in it.  We can make something happen soon I'm really happy with how the car is running right now and the tune is good enough at this point I can drive it anywhere.

[MPbdy]

Filled up with e85.  Ran perfect at E65 mixture trouble free.  Everything worked as expected with the flexfuel sesnor, fuel map multiplier, and a timing modifier table I built up.  I have it at 27* WOT for 91 octane and fed it 31* and it seemed to love it.

I need to soften my rear shocks the tires won't stay on the ground lol.  My acceleration logs are all jagged.  Not sure if you can expand the image but the red line going up is RPM and it is jumping here up to 7300 rpm and 109 mph lol.  2nd gear was spinning over every bump.



The Holley datalogs are pretty useful, and what is nice is you can open a datalog and it shows an overlay in your tune of which cells the ECU is referencing. Really helps find in the fueling and timing tables where an issue is coming from.  The white lines are showing you what cell in the fuel map it is on in the datalog.

[MPbdy]

After calling around and emailing with ~5 shops that install sleeves - 2 local and 3 I'd have to ship the block to - most are recommending starting with a fresh block.  MAST won't sleeve LS7 blocks as they've only done one and it didn't go well.  TSP also recommends starting with a 5.3 truck block.

Steve @ RED would do it, but can't guarantee when I'd be able to even get on his list.  I guess really backed up right now.  Waiting 2 months with no guarantee of getting my block done doesn't fit my goals right now.

I'm going to just close my eyes and assemble the engine.  Many have said it'll run fine and ls7 blocks move around a ton. Hopefully it seals up and doesn't have a ton of blow-by.  It costs nothing but time at this point to put together and I have zero interest in starting with a fresh block right now.  I want this to be the end all be all engine, but at this point I just need to move past it and see what it does.

[driftnfb]

Long time but was able to get threw all 64 pages. Nice work.

[MPbdy]

Long time but was able to get threw all 64 pages. Nice work.

Thanks man. I read through it all from the start recently and it was a good time. Glad I've kept records of the car.  I'm excited to have the chance to have the engine out soon and maybe try to get it as clean as it was at the beginning.

[MPbdy]

I cannot believe how much of a struggle it has been for the stupidest shit with this car.  I can't keep water in this thing.  I guess I should have replaced the radiator hoses when it overheated from the cracked surge tank.

I was 20 minutes deep into the canyons when the lower rad hose split and dumped all the water out.  I only noticed because I pulled over to adjust the tune.  Yolo'd it back to a gas station and my girlfriend rescued me with duct tape and water so we could get it home.  I have a habit of ruining holidays with this car. I also smashed the oil pan on a dark offramp on Christmas Eve one year driving to her Uncle's lol.

If I broke something at least I have another engine ready to assemble.  If it stays in one piece I think I have e85 to thank for keeping the chambers cooler than gasoline.  I tried to coast as much as possible but there's only so much you can do.

[MPbdy]

My ignition cut no lift shift tune worked great off my clutch pressure switch.  If the engine still runs after all this I'll grab a video.  Shit was cool.  I was going to do one on the way home but that didn't happen. 

[1993_FD3S]

Any updates?

[MPbdy]

Life has been wild since Covid.  I still laugh at the title "LS7 build for 2020."  Too much to list that put cars on a much lower priority both time and motivation wise, but I should be getting back to it here soon! 

I tried my best to revive the engine after it lost the radiator hose, but something is unhappy.  It needs to be disassembled to see what happened.  It still runs and drives. I did a quick 5 mile cruise recently to drain the e85 and refill with 91 to prevent corrosion.  It is a shame because I did get on it a couple times and the fuel/airflow numbers show it makes every bit of horsepower it did before, but it does get hot under load.

Interesting you bump this up though I have a new bullet coming for it, should be here in a couple weeks.  The radical solid roller ls7 is still there and ready to assemble, and I will still get it together someday, but I want to enjoy the car again and a 650+whp solid roller race engine is not what I dream about when I think about sitting in local OC traffic.  The LS7 build I can't even remember how updated I kept this thread, but it went wrong every step of the way. Machining that block was a disaster, and the bores are still not round as we want them. Enough people said just slap it together so that's what we're doing eventually.

A week or so ago I found a takeout LS7 w/ 55k miles and fresh heads at 45k.  It did see a hard life owned by an HPDE instructor, but he has oil analysis records for every oil change and is very professional with his cars.  It is well broken in, and won't see an easier life here.

I've ordered everything to swap everything to wet sump and get it in the car ASAP.  I also am grinding a cam for it, 234/247 on 116+2 with .658/.651 lift.

No clue what it'll make for power, but I imagine it should be just as fast as the 242/250 cam in the 402.  Honestly not concerned at all with how fast it'll be. 

LS7 SBE 427, 11:1 comp
Stock ls7 heads
Stock intake (or Holley low pro sniper, undecided)
234/247, .658/.651" lift, 116+2 w/ PAC 1207x 700 lift springs
EWP, 10% UD ATI, 1 7/8" headers, RPS 28 pound carbon clutch and flywheel

A ported MSD would make this a 550+whp combo all day, but not worth the $2k and fitment challenges right now.  I'm just grinding the cam to shift the powerband up to 4k-7k because I know a small/stock cam 4" stroke LS in an rx7 is not the jam.

[kinger]

Sounds like a lot more then what your saying, nice summary though! 

I do have some GPI ported oem ls7 heads if you wanted to go ported just hit me up. 

Can't wait to see it driving again!

[MPbdy]

Sounds like a lot more then what your saying, nice summary though! 

I do have some GPI ported oem ls7 heads if you wanted to go ported just hit me up. 

Can't wait to see it driving again!

Haha, nah I’m good on the heads. I won’t be taking the heads off or checking the bearings or anything. Close my eyes, slap a cam in it and run it. It’s a good running engine with proof I don’t need to mess up the plan. Knowing my dad and I the thing would be torn apart to “fix” something and 2 years later it still wouldn’t be running lmao.

I saw you post you’re having an engine built? Who’re you going with?

I could babble about a bunch of the other stuff that’s been going on but the top highlight is my wife and I got hitched last year! We’re both in relatively new exciting jobs and we house hunted really aggressively Dec-Feb. Got our teeth kicked in even with solid offers, but it is what it is. Luckily we own our condo that we’re in, and cars can always go on the back burner. Been dealt a few pretty rough hands recently with the good but we’re coming out the other side.

[1993_FD3S]

Life has been wild since Covid.  I still laugh at the title "LS7 build for 2020."  Too much to list that put cars on a much lower priority both time and motivation wise, but I should be getting back to it here soon! 

I tried my best to revive the engine after it lost the radiator hose, but something is unhappy.  It needs to be disassembled to see what happened.  It still runs and drives. I did a quick 5 mile cruise recently to drain the e85 and refill with 91 to prevent corrosion.  It is a shame because I did get on it a couple times and the fuel/airflow numbers show it makes every bit of horsepower it did before, but it does get hot under load.

Interesting you bump this up though I have a new bullet coming for it, should be here in a couple weeks.  The radical solid roller ls7 is still there and ready to assemble, and I will still get it together someday, but I want to enjoy the car again and a 650+whp solid roller race engine is not what I dream about when I think about sitting in local OC traffic.  The LS7 build I can't even remember how updated I kept this thread, but it went wrong every step of the way. Machining that block was a disaster, and the bores are still not round as we want them. Enough people said just slap it together so that's what we're doing eventually.

A week or so ago I found a takeout LS7 w/ 55k miles and fresh heads at 45k.  It did see a hard life owned by an HPDE instructor, but he has oil analysis records for every oil change and is very professional with his cars.  It is well broken in, and won't see an easier life here.

I've ordered everything to swap everything to wet sump and get it in the car ASAP.  I also am grinding a cam for it, 234/247 on 116+2 with .658/.651 lift.

No clue what it'll make for power, but I imagine it should be just as fast as the 242/250 cam in the 402.  Honestly not concerned at all with how fast it'll be. 

LS7 SBE 427, 11:1 comp
Stock ls7 heads
Stock intake (or Holley low pro sniper, undecided)
234/247, .658/.651" lift, 116+2 w/ PAC 1207x 700 lift springs
EWP, 10% UD ATI, 1 7/8" headers, RPS 28 pound carbon clutch and flywheel

A ported MSD would make this a 550+whp combo all day, but not worth the $2k and fitment challenges right now.  I'm just grinding the cam to shift the powerband up to 4k-7k because I know a small/stock cam 4" stroke LS in an rx7 is not the jam.

So glad to hear this build will be getting some more love!