Turbos and effects of overlap.
Thread Starter
Launching!
Joined: Mar 2022
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Get back here ! Lmao.
Im not going for much power, if anything I can have the crank nitrated. 500 hp is a nice spot I’ve found where it stays “cheep” and not complicated.
Thread Starter
Launching!
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Similar specs to the cam my friend had in his car when we took off his PD blower and slapped a turbo on. He was concerned about swapping the "blower" cam to a "turbo" cam, I told him it wouldn't make a bit of difference he would notice. We threw it on the dyno for me to tune and sure enough it made almost 200whp more than the blower on about the same boost, he didn't care about the cam anymore, he went to buy new tires. 
Not sure what power level you are at but this was at 900whp thru an auto, we only stopped there because he was concerned about his drivetrain. In other cars I've used existing "NA" cams to well over 1000whp in turbo setups. If you like the way it currently drives, spools, powerband range, etc, you aren't going to get much of a gain swapping cams.
Not sure what power level you are at but this was at 900whp thru an auto, we only stopped there because he was concerned about his drivetrain. In other cars I've used existing "NA" cams to well over 1000whp in turbo setups. If you like the way it currently drives, spools, powerband range, etc, you aren't going to get much of a gain swapping cams. I'd lower your max rpm to 7000 and see what it does to your times. Thanks. Bob
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Certainly has to take some power to turn it, I've heard from 50 up to 100hp just to turn the blower. LSA was kinda tapped out at 17-18 psi so IAT's were higher and wasn't making very large gains per lb of boost added, etc. Turbo was very efficient and was running about 19 psi. Blower also had a full exhaust, turbo setup had a bumper exit so perhaps some gain there as well.
If you aren't an LT1 purist then I'd start rat holing parts away for an LS swap, you already have an iron block so if you aren't looking to save weight any iron 5.3 would be a very cheap bolt in and then your cheap and not complicated goal moves up by about 200hp easily.
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Turbo vs Supercharged or nitrous engines. Iron cranks and P.M rod (due to lower rpm with combustion pressure buffers and lower torque spikes) allows them to make higher general hp before breaking. Turbo cylinder pressure cycles are relatively easy on parts. Easier than N/A too due to less tension loads on rods and wristpins at the elevated rpm they would require to run strong. Gen 2 has injection and ignition issues, but those being solved…with the additional cylinder head holding capability of 5-bolts per cylinder…could be a contender with modern coil near plug tuning
Last edited by Summitracing; Sep 13, 2022 at 09:30 PM.
Thread Starter
Launching!
Joined: Mar 2022
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Factory LT1 cranks look to be nodular cast iron so 500hp will probably be at the very limit of what it can handle, don't spin it very high and should probably be pretty careful with the tune.
If you aren't an LT1 purist then I'd start rat holing parts away for an LS swap, you already have an iron block so if you aren't looking to save weight any iron 5.3 would be a very cheap bolt in and then your cheap and not complicated goal moves up by about 200hp easily.
If you aren't an LT1 purist then I'd start rat holing parts away for an LS swap, you already have an iron block so if you aren't looking to save weight any iron 5.3 would be a very cheap bolt in and then your cheap and not complicated goal moves up by about 200hp easily.
Though a thought I had about boost and compression. When others say one would want to lower compression to 9.5 or possibly lower, is this referring to static compression or dynamic ?
Thread Starter
Launching!
Joined: Mar 2022
Posts: 247
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Could you elaborate what kind of ignition and injection issues the gen 2 had ? Id assume the ignition issues are related to the Opti spark. Are you saying that the 5 bolt per cylinder makes up for these negatives when compared to other things ?
Bringing up cylinder head bolts, that reminds me of a buick gnx that had what looked like giant clamps which held down the cylinder heads to the block. Im curious if other track cars used something like this before.
Bringing up cylinder head bolts, that reminds me of a buick gnx that had what looked like giant clamps which held down the cylinder heads to the block. Im curious if other track cars used something like this before.
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Verdad Gallardo Not wanting to get too off topic, I do not see anything wrong with the lt1 that would warrant getting a different engine. I will just enjoy building what I have. I saw a debate about if it was nodular or not, or if only the corvette cranks came that way since it was a four bolt. Id assume 500 hp is roughly the limit of the single timing chain any way.
Though a thought I had about boost and compression. When others say one would want to lower compression to 9.5 or possibly lower, is this referring to static compression or dynamic ?
Though a thought I had about boost and compression. When others say one would want to lower compression to 9.5 or possibly lower, is this referring to static compression or dynamic ?
Regarding compression I think most are referring to static compression ratio as dynamic compression ratio will be lower than that and is usually significantly affected by camshaft profile.
I'd probably keep it around 9.0-9.5:1, not 100% on the LT1 heads but I know the older SBC heads did not have very efficient combustion chambers in that they burned very slowly so the compression needed to be lower on pump gas to give the burn more time, get too low and the car will be a pig out of boost.
The new LS stuff has far more efficient chambers hence they can get away with more base or static compression with boost.
I had thought there was an LT1 specific forum on here, or maybe jump on another with some folks who have spent a lot of time around these engines for some good real world experience info.
Thread Starter
Launching!
Joined: Mar 2022
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Plenty of people making power with the Gen II LT1, check out the Grubb Worm iirc, stupid fast six speed turbo car with an LT1.
Regarding compression I think most are referring to static compression ratio as dynamic compression ratio will be lower than that and is usually significantly affected by camshaft profile.
I'd probably keep it around 9.0-9.5:1, not 100% on the LT1 heads but I know the older SBC heads did not have very efficient combustion chambers in that they burned very slowly so the compression needed to be lower on pump gas to give the burn more time, get too low and the car will be a pig out of boost.
The new LS stuff has far more efficient chambers hence they can get away with more base or static compression with boost.
I had thought there was an LT1 specific forum on here, or maybe jump on another with some folks who have spent a lot of time around these engines for some good real world experience info.
Regarding compression I think most are referring to static compression ratio as dynamic compression ratio will be lower than that and is usually significantly affected by camshaft profile.
I'd probably keep it around 9.0-9.5:1, not 100% on the LT1 heads but I know the older SBC heads did not have very efficient combustion chambers in that they burned very slowly so the compression needed to be lower on pump gas to give the burn more time, get too low and the car will be a pig out of boost.
The new LS stuff has far more efficient chambers hence they can get away with more base or static compression with boost.
I had thought there was an LT1 specific forum on here, or maybe jump on another with some folks who have spent a lot of time around these engines for some good real world experience info.
I think I will actually ask about that on an lt1. For curiosity’s sake.
Now could that just be a rule of thumb and people would usually be running a turbo cam with a wider lsa so their dynamic wouldn’t go too far off from their static compression ? I used a dynamic compression calculator and weigh the cam I am using my Static will be 10.6 and the dynamic will be 9.22.
I think I will actually ask about that on an lt1. For curiosity’s sake.
Now could that just be a rule of thumb and people would usually be running a turbo cam with a wider lsa so their dynamic wouldn’t go too far off from their static compression ? I used a dynamic compression calculator and weigh the cam I am using my Static will be 10.6 and the dynamic will be 9.22.
Now could that just be a rule of thumb and people would usually be running a turbo cam with a wider lsa so their dynamic wouldn’t go too far off from their static compression ? I used a dynamic compression calculator and weigh the cam I am using my Static will be 10.6 and the dynamic will be 9.22.
You'd be fine on E85, pump would have to be very careful.
Thread Starter
Launching!
Joined: Mar 2022
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e85 isnt available in my area so ive been running 93 octane. I should have my methanol fogger done way before the turbo is even on the car so I am not concerned. This should be a fun experiment.