lt1 engine balance question
Thread Starter
Instructor
Joined: Jan 2003
Posts: 165
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From: Marianna FL
lt1 engine balance question
my lt1 bottom end is stock and i'm ready to start buying parts to do a mild build. because of short funds i will be keeping the stock crankshaft and i want to buy pistons and rods. i already have a lightweight flywheel and i want to know if i buy some trw forged pistons and some good h beam rods will it all balance out, or do i have to buy a certain weight piston and rod for it to balance? i'm looking at trw forged 13cc dish and eagle h beam rods. also how much rpm is the stock crank good for all balanced out?
Instructor
Joined: Jul 2009
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The original owner of my LT1 car cracked his pistons and ended up doing the short block with new pistons and rods.
The shop used Eagle SIR rods, which are probably close to stock weight and they used Sealed Power blower/turbo pistons with -21cc dishes. Let me know if you want the part numbers.
With the LT1 head chamber this bring compression to around 9 or 9.25 to 1.
The shop told me they did a static weight balance.
Keep in mind the H beam rods are most likely heavier and may not balance right without mallory metal, which Iunderstand is expensive.
I have been told that the cast crank should be good up to 600FWHP as long as you do not detonate. Golen engine works told me that crank failures are not typically castostrophic and usually IF one fails it cracks rather than turns into shrapnel. He thought I would be OK at this power level, but gave the caveat "don't quote me on that". I think the prerequisite here is as long as you do not detonate.....
The C5 guys run some sick power on their stock cranks, some guys are doing over 600 RWHP on stock cranks with no problems and I have seen a few claiming 800 horses at the crank (not the wheels).
I am around 400RWHP and no problems on my stock crank. There was another LT1 guy on the forum doing 500RWHP with no problems.
The shop used Eagle SIR rods, which are probably close to stock weight and they used Sealed Power blower/turbo pistons with -21cc dishes. Let me know if you want the part numbers.
With the LT1 head chamber this bring compression to around 9 or 9.25 to 1.
The shop told me they did a static weight balance.
Keep in mind the H beam rods are most likely heavier and may not balance right without mallory metal, which Iunderstand is expensive.
I have been told that the cast crank should be good up to 600FWHP as long as you do not detonate. Golen engine works told me that crank failures are not typically castostrophic and usually IF one fails it cracks rather than turns into shrapnel. He thought I would be OK at this power level, but gave the caveat "don't quote me on that". I think the prerequisite here is as long as you do not detonate.....
The C5 guys run some sick power on their stock cranks, some guys are doing over 600 RWHP on stock cranks with no problems and I have seen a few claiming 800 horses at the crank (not the wheels).
I am around 400RWHP and no problems on my stock crank. There was another LT1 guy on the forum doing 500RWHP with no problems.
Instructor
Joined: Jul 2009
Posts: 121
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I am running 7 - 8 pounds and should be in the neighborhood of 400RWHP and close to 500 at the crank.
I have over 25K miles on this with no problems so far. I drive it daily.
I was doing the research on the crank so I knew when to "stop" as I am going to turn up boost, do some cam work and get a bigger intercooler.
From everything I researched 500RWHP or 600 at the crank should be safe.
There was another LT1 forum memebr doing 499HP at the wheels with no problems.
I have over 25K miles on this with no problems so far. I drive it daily.
I was doing the research on the crank so I knew when to "stop" as I am going to turn up boost, do some cam work and get a bigger intercooler.
From everything I researched 500RWHP or 600 at the crank should be safe.
There was another LT1 forum memebr doing 499HP at the wheels with no problems.
Thread Starter
Instructor
Joined: Jan 2003
Posts: 165
Likes: 0
From: Marianna FL
well i sold my yamaha virago 1100, so my rebuild buget just went up. bought trw forged 13cc dished pistons, a 230/236 cam, will be ordering trick flow 195cc heads with 62cc chambers, and a scatt stroker crank and forged rods, and all the other little things needed to build 1 sweet 383. i cant wait to get started on this..
Race Director
Joined: Sep 2001
Posts: 14,685
Likes: 753
From: NEwhere Ohio
Im curious:
If funds are short, why build up your engine first, in anticipation of boost? do you have super high rwhp goals?
I run 8 psi boost (procharger p600b), and intercooler on a stock bottom end on my 93.
I will also be running meth/water injection once I get the meth kit installed
Will it eventually destroy itself? maybe. According to everyone on here, probably.
Thats fine, enjoy it until that point, then rebuild.
Who knows, maybe it will last. In that case, I saved a lot of money.
Also, why go dished pistons? Get AFR heads with a bigger combustion chamber. This way you can run flat pistons.
Im not saying anyone's advice is bad. Just adding my thoughts.
If funds are short, why build up your engine first, in anticipation of boost? do you have super high rwhp goals?
I run 8 psi boost (procharger p600b), and intercooler on a stock bottom end on my 93.
I will also be running meth/water injection once I get the meth kit installed
Will it eventually destroy itself? maybe. According to everyone on here, probably.
Thats fine, enjoy it until that point, then rebuild.
Who knows, maybe it will last. In that case, I saved a lot of money.
Also, why go dished pistons? Get AFR heads with a bigger combustion chamber. This way you can run flat pistons.
Im not saying anyone's advice is bad. Just adding my thoughts.
Instructor
Joined: Jul 2009
Posts: 121
Likes: 0
well i sold my yamaha virago 1100, so my rebuild buget just went up. bought trw forged 13cc dished pistons, a 230/236 cam, will be ordering trick flow 195cc heads with 62cc chambers, and a scatt stroker crank and forged rods, and all the other little things needed to build 1 sweet 383. i cant wait to get started on this..
Take a look at your compression ratio. with a 383 and that 62cc head chamber you are going to be a tad over 10:1, which is higher than ideal for supercharged application.
On stock 54cc LT1 heads, my piston dish is -21cc to get around 9:1 with a 355. Typical 383 application with stock 54cc head chamber use a -31cc dish.
Also, there was a recent shootout on LT1 cyclinder heads and the AFR 195 eliminators won hands down. You may want to look at this as you will get a better head and you can get even larger chamber volumes to lower compression and not have to go with a dished piston.
Thread Starter
Instructor
Joined: Jan 2003
Posts: 165
Likes: 0
From: Marianna FL
your right i was misinformed bad online calc. but if i skip the crank i can aford the afr's with the 65cc chambers and with a .039 head gasket it should put me at 9.4 with the 13cc dished pistons i got or so i think (you let me know what you think) kinda a trade off do to budget. thanks guys i was off on my comp and i didn't know that afr had the 65cc head. and im doing this because it has 125k miles and it feels tired.
Last edited by Guitarguy; Mar 25, 2010 at 02:17 PM. Reason: info
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Racer
Joined: Aug 2009
Posts: 337
Likes: 6
From: Kanata ON
An LT1 tired at 125k miles?!? Are you sure? My L98 has about 180k miles and it still pulls better than when it rolled off the showroom floor!
Most stock LT1s do a high 13s quarter. Is yours significantly slower than that?
Most stock LT1s do a high 13s quarter. Is yours significantly slower than that?
Thread Starter
Instructor
Joined: Jan 2003
Posts: 165
Likes: 0
From: Marianna FL
my lt1 does not pull as hard as when i first put my vortech on. some l98 came factory with forged pistons, lt1's did not. that is good that yours is still going strong. how much boost are you putting to it?
Racer
Joined: Aug 2009
Posts: 337
Likes: 6
From: Kanata ON
Anyway, my miles are all stock but nitrous is going in now. It's my understanding that all '85 L98s came with forged pistons and rods so I am going to be counting on those once the juice hits
Thread Starter
Instructor
Joined: Jan 2003
Posts: 165
Likes: 0
From: Marianna FL
one hot day last summer the car bagan pinging under boost i pulled my plugs to find some were missing the platt. and they didnt have that much miles on them. i replaced all of them, the car stoped the pinging but just never felt as strong as it did. from what i read on this forum the rings and pistons are the weak points. plus i get the puff of blue smoke on cold starts. valve seals i'm sure. we're just ready.
Racer
Joined: Aug 2009
Posts: 337
Likes: 6
From: Kanata ON
one hot day last summer the car bagan pinging under boost i pulled my plugs to find some were missing the platt. and they didnt have that much miles on them. i replaced all of them, the car stoped the pinging but just never felt as strong as it did. from what i read on this forum the rings and pistons are the weak points. plus i get the puff of blue smoke on cold starts. valve seals i'm sure. we're just ready.
Regardless, sounds like you have a good plan to build your engine. Good luck!
