Educated Con-s of my build?
Thread Starter
Teching In
Joined: Aug 2013
Posts: 23
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Educated Con-s of my build? Long story short, I built a forged 5.3 shortblock 3 years ago with factory top end and have been beating it with PT4788 and later twin 72-s for too long(7.7 best at quarter). The 317-s just won't seal any more and the LS9 cam, although good, is now deemed too small. Also, the spoolup with the 8.x CR is way lazy for my liking.
So, I have ordered some new pieces, to up the bar and would like to know have I missed anything.
Current bottom half:
5.3 iron block, forged crank, forged rods, forged pistons. 3.78 bore, 3.622 stroke. Custom rev-kit (21lb seat, 53lb open)
New top half:
Dart Pro1 205 heads, undersize 2.00/1.59 valves to help reduce shrouding, 918 springs shimmed 0.06, Trickflow 228/230 .585/.585 cam.
It is on E100, no IC with two extra nozzles spraying upstream for air cooling.
How much timing should I initially take out? Since the CR goes up from 8.5 to 9.9 and combustion chamber is better suited for small-bore block, I'm guessing around 8 degrees? With 317 I ran 18* at 30psi. Shift-point is at 7200. Glide, 1600lb rail.
So, I have ordered some new pieces, to up the bar and would like to know have I missed anything.
Current bottom half:
5.3 iron block, forged crank, forged rods, forged pistons. 3.78 bore, 3.622 stroke. Custom rev-kit (21lb seat, 53lb open)
New top half:
Dart Pro1 205 heads, undersize 2.00/1.59 valves to help reduce shrouding, 918 springs shimmed 0.06, Trickflow 228/230 .585/.585 cam.
It is on E100, no IC with two extra nozzles spraying upstream for air cooling.
How much timing should I initially take out? Since the CR goes up from 8.5 to 9.9 and combustion chamber is better suited for small-bore block, I'm guessing around 8 degrees? With 317 I ran 18* at 30psi. Shift-point is at 7200. Glide, 1600lb rail.
I think on your fuel choice you made the right decision in increasing CR. I doubt you will have to drop your timing that low. Those heads should be a huge increase in power. How's lag on that set up? That seems like a ton of turbo for a 5.3. Twin 66's is good for over 1500 to the wheels. It's clear you are flying though nice work.
Thread Starter
Teching In
Joined: Aug 2013
Posts: 23
Likes: 1
Lag is tolerable thanks to .64 turbine housings but I want more.
Currently, I 3-step at 3500 on brakes to build 3psi, then to 2-step at 5250.
1psi under a second, 3 to 19psi in 2 sec after that, but that's a little slow to go to stage with 3-step. I currently need to bump in while already in 2-step. Not so consistent and not so good on trans temp.
Currently, I 3-step at 3500 on brakes to build 3psi, then to 2-step at 5250.
1psi under a second, 3 to 19psi in 2 sec after that, but that's a little slow to go to stage with 3-step. I currently need to bump in while already in 2-step. Not so consistent and not so good on trans temp.
your compression increase will help spool alot.
what ecu are you running? you could configure a timing table to assist in building boost while on the brake?
what crank and rods are you running? just curious
, and I'd love to see a pic of the custom rev kit, I would like to make 1 myself
what ecu are you running? you could configure a timing table to assist in building boost while on the brake?
what crank and rods are you running? just curious
, and I'd love to see a pic of the custom rev kit, I would like to make 1 myself
your compression increase will help spool alot.
what ecu are you running? you could configure a timing table to assist in building boost while on the brake?
what crank and rods are you running? just curious
, and I'd love to see a pic of the custom rev kit, I would like to make 1 myself
what ecu are you running? you could configure a timing table to assist in building boost while on the brake?
what crank and rods are you running? just curious
, and I'd love to see a pic of the custom rev kit, I would like to make 1 myself
Thread Starter
Teching In
Joined: Aug 2013
Posts: 23
Likes: 1
your compression increase will help spool alot.
what ecu are you running? you could configure a timing table to assist in building boost while on the brake?
what crank and rods are you running? just curious
, and I'd love to see a pic of the custom rev kit, I would like to make 1 myself
what ecu are you running? you could configure a timing table to assist in building boost while on the brake?
what crank and rods are you running? just curious
, and I'd love to see a pic of the custom rev kit, I would like to make 1 myself
3-step is done with timing retard (Goes to 1deg advance whine rpm goes over, so no fuel is taken out).
Eagle crank, Lunati rods, Wiseco pistons.
Rev kit pics attached.
Last edited by FogOfWar; Aug 14, 2017 at 09:53 AM.
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918 springs are really mild... Esp for a 7 second engine. I wouldn't bother with those. Run a good dual spring on there so you can run decent RPM. Single springs aren't really meant for performance IMO.
No right answer for timing. Start at an overly low safe number and work your way up slow watching plugs. No one is racing anything as light as you I'm aware of. So what the engine wants and what you can get away with will differ a lot from most of the builds on here.
No right answer for timing. Start at an overly low safe number and work your way up slow watching plugs. No one is racing anything as light as you I'm aware of. So what the engine wants and what you can get away with will differ a lot from most of the builds on here.
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Verdad Gallardo 918 springs are really mild... Esp for a 7 second engine. I wouldn't bother with those. Run a good dual spring on there so you can run decent RPM. Single springs aren't really meant for performance IMO.
No right answer for timing. Start at an overly low safe number and work your way up slow watching plugs. No one is racing anything as light as you I'm aware of. So what the engine wants and what you can get away with will differ a lot from most of the builds on here.
No right answer for timing. Start at an overly low safe number and work your way up slow watching plugs. No one is racing anything as light as you I'm aware of. So what the engine wants and what you can get away with will differ a lot from most of the builds on here.
Thread Starter
Teching In
Joined: Aug 2013
Posts: 23
Likes: 1
That's what I thought, to take around 8 degrees out(to 10*) and work it up from there until no power gain is seen. The weight that the engine sees is actually far greater thanks to 1.8:1 first gear and 3.5:1 rear coupled with 34" tire (for 200+mph trap goal)
The 918-s have been good to me. I have bounced on the 7200 limiter for 5+seconds many times (broken PG planetaries and other pieces). LS9 cam came out with no hint of lifter bounce and I'm still running stock pushrods/lifters/rockers.
With the new cam, I need to check the agressivness of the TrickFlow lobes. I'm not afraid about the .023 additional lift, but do am about the lobe profile witch is unknown to me right now.
The 918-s have been good to me. I have bounced on the 7200 limiter for 5+seconds many times (broken PG planetaries and other pieces). LS9 cam came out with no hint of lifter bounce and I'm still running stock pushrods/lifters/rockers.
With the new cam, I need to check the agressivness of the TrickFlow lobes. I'm not afraid about the .023 additional lift, but do am about the lobe profile witch is unknown to me right now.
Also a good idea to run a dual on any performance engine. If those beehives fail (which 918’s are known for). And you drop a valve it will do some damage. With a dual spring there is a much better chance the remaining spring will keep the valve from dropping. Don’t get me wrong I use good beehives all the time on JY stuff (not the 918’s though) But I wouldn’t use them on an engine I had a decent amount of money in like described above. It’s not worth the risk IMO.
AS mentioned, A factory cam VS aftermarket will usually have a much more radical ramp rate as well. Another good reason to have more valve control/pressure.
Thread Starter
Teching In
Joined: Aug 2013
Posts: 23
Likes: 1
Rev kit, if done right will take lifter mass out of valve spring equation, and the hydraulic roller lifters do weigh a ton(122g to be precise).
That means -71.5g out of valve side of rocker since the lifter moves 1.7x less than valve.
I have done these calculations when I first speced the kit out to be made and if I remember correctly, the weight of the valvetrain was down 20% even with added parts so from the formula of acceleration, that means about 11% of additional engine speed pushing valve control issues for example from 6.6K to 7.2K. That all can be accomplished without extra strain on pushrods/rockers.
I do like the beehives, and would swap them out to dual conicals/beehives is these would be available. Conical/Beehive spring has superior natural frequency dampening and also, since weaker(larger diameter) coils bottom out first and are taken out of weight equation mid-lift, again less pressure needs to be set out compared to duals. (This last statement is true only, if these are shimmed correctly, not just thrown in)
If outer spring of duals fail on drag engine mid-run, carnage is the same as single beehive failing.
Only downside of rev-kit for LS is cam change needs heads-off. Thats one reason why I have not done cam change earlier. Since I now melted the 317 badly while leaning on them, now is the time.
That means -71.5g out of valve side of rocker since the lifter moves 1.7x less than valve.
I have done these calculations when I first speced the kit out to be made and if I remember correctly, the weight of the valvetrain was down 20% even with added parts so from the formula of acceleration, that means about 11% of additional engine speed pushing valve control issues for example from 6.6K to 7.2K. That all can be accomplished without extra strain on pushrods/rockers.
I do like the beehives, and would swap them out to dual conicals/beehives is these would be available. Conical/Beehive spring has superior natural frequency dampening and also, since weaker(larger diameter) coils bottom out first and are taken out of weight equation mid-lift, again less pressure needs to be set out compared to duals. (This last statement is true only, if these are shimmed correctly, not just thrown in)
If outer spring of duals fail on drag engine mid-run, carnage is the same as single beehive failing.
Only downside of rev-kit for LS is cam change needs heads-off. Thats one reason why I have not done cam change earlier. Since I now melted the 317 badly while leaning on them, now is the time.
That Rev kit sounds great. What’s the approx. price on it? Seems like a mild cam to need something like that though. Is the cost VS performance really there?
Maybe comp has fixed the issues the 918’s were having. I know if you do a quick search on 918 failures you get a ton of hits and the general consensus was to stay away from them. Maybe that’s not the case anymore. The PAC 1218 was similar to the 918 and I’ve never heard of one failing. They are the most common performers in the single spring mild cam LS world to my knowledge.
As far as the inner VS outer spring failures go, I don’t agree. I’ve had both types of failure happen in the BBC world. Neither dropped a valve
Maybe comp has fixed the issues the 918’s were having. I know if you do a quick search on 918 failures you get a ton of hits and the general consensus was to stay away from them. Maybe that’s not the case anymore. The PAC 1218 was similar to the 918 and I’ve never heard of one failing. They are the most common performers in the single spring mild cam LS world to my knowledge.
As far as the inner VS outer spring failures go, I don’t agree. I’ve had both types of failure happen in the BBC world. Neither dropped a valve
