Strongest bottom end without upgrading?
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Both LT1 and LT4 cranks are forged. Both have wet and dry sump crank options. Dry sump cranks have a shorter snout.
LT4 crank info from GM:
◾A 1528MV forged steel crankshaft with tungsten balancing inserts, ground pin collars and intermediate pin drills for rods 1-6
LT4 crank info from GM:
◾A 1528MV forged steel crankshaft with tungsten balancing inserts, ground pin collars and intermediate pin drills for rods 1-6
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From: Ohio
I think the rod and main journals might have the same diameter, but I don't think that the dimensions are the same at the back of the block, where the oil pump goes or the snout where the balancer goes.
The newer 5.3 "notched" pistons work with the wider LSA rods. It's been verified on the Sloppy facebook page that the LT4 rods are actually 6.098 and not 6.125 like gm says they are. The crank is the same as a LSA crank, 8 bolt flange and keyed balancer. I have yet to use a LT1 crank but will be doing a dry mockup of everything once I have the rods in my hands. TCI makes a sfi flexplate with the 8 bolt pattern. The bottom of this link shows the part numbers for everything. The crank I have is GenV LT1 wetsump 12623492
https://docs.google.com/document/d/1...fA/mobilebasic
https://docs.google.com/document/d/1...fA/mobilebasic
I think the gen 1 (small block chevy) rods are the same as LS, you have to watch the small end as I think one side could interfere with the pin boss in the piston. Years ago I bought some advertised as LS rods off Ebay, my bud at the machine shop said they were SB's, worked on the small end-they have been in for 4 years. I think they were part of the confusion with the rod lengths of LS rods.
Surprised there wasn't some opinions on the gen 3/4 blocks as far as head bolt length vs strength.
Surprised there wasn't some opinions on the gen 3/4 blocks as far as head bolt length vs strength.
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The newer 5.3 "notched" pistons work with the wider LSA rods. It's been verified on the Sloppy facebook page that the LT4 rods are actually 6.098 and not 6.125 like gm says they are. The crank is the same as a LSA crank, 8 bolt flange and keyed balancer. I have yet to use a LT1 crank but will be doing a dry mockup of everything once I have the rods in my hands. TCI makes a sfi flexplate with the 8 bolt pattern. The bottom of this link shows the part numbers for everything. The crank I have is GenV LT1 wetsump 12623492
https://docs.google.com/document/d/1...fA/mobilebasic
https://docs.google.com/document/d/1...fA/mobilebasic
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Hard to say . Timing was verified/synced. But each engine was a little different. I lost gen4 5.3 with too much lead I believe at 25lbs and 17*. It seemed ok at 14* but kept gaining MPH with No signs of detonation on plugs. Since I’ve not run more than 13* above 20lbs and have still had detonation problems. Crunched ring lands, bent rods, lifted heads, etc.
I think small cams, tall gearing, tight converter, and high back pressure put weird loads on things at low RPM. I do think they all ran into detonation in some way though. All failures were on E70 or higher, A2A IC, and 7GPH or so water/meth nozzle.
I think small cams, tall gearing, tight converter, and high back pressure put weird loads on things at low RPM. I do think they all ran into detonation in some way though. All failures were on E70 or higher, A2A IC, and 7GPH or so water/meth nozzle.
Using detonation to identify timing limit and then back off x degrees will typically still be > 5* higher than MBT and that much closer to killing a motor.
OP, don't mean to highjack thread but curious since the strongest bottom end won't survive be rattled at serious hp levels.
Most with a big power turbo SBE aren't interested in running MBT timing. The cyl pressures and temps will be highest here and compounded with boost. Generally all the "baby soft" low timing tunes steer well clear of MBT and shoot for big power with boost after PK TQ.
Having drastically lower compression makes much less heat in the chamber at like power levels and allows for timing to be closer to MBT without runaway cyl pressures/temps.
Having drastically lower compression makes much less heat in the chamber at like power levels and allows for timing to be closer to MBT without runaway cyl pressures/temps.
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Gotcha. Cylinder pressure induced failures not detonation. Not aware of any cyl pressure transducers that are reasonable $$. Think you'll get to MBT or knock limit with e85 at low SCR?
Some interesting insight on E85 timing
I thought e85 burned slower than 93. Data says otherwise (in this application/data point).
Some interesting insight on E85 timing
I thought e85 burned slower than 93. Data says otherwise (in this application/data point).
But knock is most likely to happen at the highest peak cyl pressure point and I believe it is still happening on my stuff. Most likely because I’m applying a ton of power at or below PK TQ with the tall gearing and a peaky “high compression” cyl pressure curve. If I were to run a short gear and larger cam that bled off cyl pressure a ton… then revved the engine out pouring on power well past PK TQ I doubt I’d have the problems I’m having. In my case this means switching to an OD trans to keep it what I consider street friendly. Or figure out a way to have much less peak cyl pressures while maintaining my average power level. That’s why I’m considering such low compression as a solution.
I think it means what its always meant. E85 will need roughly 3-5* less timing than race fuel to hit MBT. If you’ve tuned C16/Q16 or other higher octane fuels this is pretty clear they *usually* don’t do diddly with “baby soft” timing.
I think the reason most say to run “higher” timing on E85 is because they run into knock well before the MBT points on standard “pump fuel”. So you might only get away with 11* timing on 15lbs with 91 octane. On E85 you can run say 20* and Q16 would be 25*+…
Last edited by Forcefed86; Jan 2, 2018 at 09:15 AM.
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Tjabo, not sure what you mean, "suppose it means what it appears to mean".
Video shows, before boost (60kpa) 3* less timing needed for MBT on e85 compared to gas (octane not known). At 120kpa (2.5psi and 12.5:1 SCR) knock occurred at 19.4* on gas (fuel limited). With e85, MBT achieved at 24.9* with no knock. With -2* margin from timing limit on gas, +7.5* of timing on e85 at 120kpa.
I was surprised to learn that, you don't automatically need more timing with higher octane to achieve MBT (at least not with e85) before boost.
86, Not sure how good the knock sense and control is in MS3 (or gold box, can't remember what you're using). The Plex Knock Monitor setup seems most comprehensive. With baseline reference (at safe timing) thru rpm range, can very easily see knock events. Would surely help identify and eliminate knock events, especially at low rpm and peak tq area, if you think some of your failures are knock induced. just a thought.
Video shows, before boost (60kpa) 3* less timing needed for MBT on e85 compared to gas (octane not known). At 120kpa (2.5psi and 12.5:1 SCR) knock occurred at 19.4* on gas (fuel limited). With e85, MBT achieved at 24.9* with no knock. With -2* margin from timing limit on gas, +7.5* of timing on e85 at 120kpa.
I was surprised to learn that, you don't automatically need more timing with higher octane to achieve MBT (at least not with e85) before boost.
86, Not sure how good the knock sense and control is in MS3 (or gold box, can't remember what you're using). The Plex Knock Monitor setup seems most comprehensive. With baseline reference (at safe timing) thru rpm range, can very easily see knock events. Would surely help identify and eliminate knock events, especially at low rpm and peak tq area, if you think some of your failures are knock induced. just a thought.
Last edited by tblentrprz; Jan 3, 2018 at 11:01 AM.
I use the MS3. I have solid mounts all around so my knock sensors won’t work. Way too much noise. I think race transmissions in general are noisy as well. A buddy has poly eng/trans mounts in his mustang. Runs a glide as well with straight cut gears, same issue. I think a lot of drag racing applications just make too much noise to use a knock sensor effectively.
Interesting thread. The L33 is the fan fav but the physics as mentioned do favor the 4.8 simply because rod failures seem to be the most common and 4.8's have the shortest stroke so the side load on the rod will be the lowest vs the larger displacements. SBE 4.8L spinning upwards of 9K RPM with a 98mm single or something like that will end up king SBE if we keep pushing these contests to the max, and I sure hope we do. Its a great show although im officially bench racing these days I have a couple L33's waiting to go.
you guys see the article and dyno video that was made for how much can a stock 6l bottom end take. easy to find on google. gen 3 rods made 1482 hp on 28.5 psi boost to kick a rod out of it. i'll look for a link it is a good read and vid.
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