1970 LS5 rebuild
08-23-2014, 01:00 PM
#1
Intermediate
Thread Starter
1970 LS5 rebuild
Hi guys, I think it's time to pull the engine and do a rebuild, so I wanted to ask for some advice, please. It's a 1970 LS5, 60k miles, never been apart as far as I know.
It runs perfectly until around 3500 rpm, then above that it runs rough and backfires through the carb. I replaced ignition, carb, fuel pump, (etc), to no avail. I also checked the usual things like ignition timing and checked for vacuum leaks.
I just did a compression test and a leakdown test, and here are the results. All tests were performed cold, and dry (no oil added through the plug holes):
Compression, psi, 1 through 8: 215, 215, 200, 190, 205, 205, 205, 200
Leakdown %, 1 through 8: 12%, 28%, 66%, 44%, 16%, 32%, 24%, 10%
While the cylinders were pressurized, air could be heard escaping from the valve covers (only). I'm thinking it has worn and/or broken rings.
So, before I pull the engine, just wanted to make sure I'm not missing anything. If it requires a rebuild, I'd be interested in suggestions such as keeping it 100% stock, vs. minor mods such as hardened valve seats, better cam, etc.
Also, should I rebuild the heads if the problem turns out to be just the rings, or should I just leave the heads alone?
The car is a survivor, 99% stock.
Thanks guys - I very much appreciate your thoughts here!
John
It runs perfectly until around 3500 rpm, then above that it runs rough and backfires through the carb. I replaced ignition, carb, fuel pump, (etc), to no avail. I also checked the usual things like ignition timing and checked for vacuum leaks.
I just did a compression test and a leakdown test, and here are the results. All tests were performed cold, and dry (no oil added through the plug holes):
Compression, psi, 1 through 8: 215, 215, 200, 190, 205, 205, 205, 200
Leakdown %, 1 through 8: 12%, 28%, 66%, 44%, 16%, 32%, 24%, 10%
While the cylinders were pressurized, air could be heard escaping from the valve covers (only). I'm thinking it has worn and/or broken rings.
So, before I pull the engine, just wanted to make sure I'm not missing anything. If it requires a rebuild, I'd be interested in suggestions such as keeping it 100% stock, vs. minor mods such as hardened valve seats, better cam, etc.
Also, should I rebuild the heads if the problem turns out to be just the rings, or should I just leave the heads alone?
The car is a survivor, 99% stock.
Thanks guys - I very much appreciate your thoughts here!
John
08-23-2014, 06:53 PM
#2
Le Mans Master
Member Since: Oct 2002
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Why do u want to rebuild a motor that only needs a vlv job and tuning?
Have u ever rebuilt a motor before let alone a collectable classic LS5 BB?
Seems to me if u knew what u were doing u would have fixed your leakdown and tuning problems and not even posted here.
Take it to the dealer or a real experienced mech for diagnose and repair. Take a ASE class on tuning and rebuilding engines at the local tech school before u create a problem u dont have and ruin a collectable BB C3.
Have u ever rebuilt a motor before let alone a collectable classic LS5 BB?
Seems to me if u knew what u were doing u would have fixed your leakdown and tuning problems and not even posted here.
Take it to the dealer or a real experienced mech for diagnose and repair. Take a ASE class on tuning and rebuilding engines at the local tech school before u create a problem u dont have and ruin a collectable BB C3.
08-23-2014, 07:20 PM
#4
Race Director
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St. Jude Donor '12-'13, '15- '16-'17-'18-'19, '21
Hi guys, I think it's time to pull the engine and do a rebuild, so I wanted to ask for some advice, please. It's a 1970 LS5, 60k miles, never been apart as far as I know.
It runs perfectly until around 3500 rpm, then above that it runs rough and backfires through the carb. I replaced ignition, carb, fuel pump, (etc), to no avail. I also checked the usual things like ignition timing and checked for vacuum leaks.
I just did a compression test and a leakdown test, and here are the results. All tests were performed cold, and dry (no oil added through the plug holes):
Compression, psi, 1 through 8: 215, 215, 200, 190, 205, 205, 205, 200
Leakdown %, 1 through 8: 12%, 28%, 66%, 44%, 16%, 32%, 24%, 10%
While the cylinders were pressurized, air could be heard escaping from the valve covers (only). I'm thinking it has worn and/or broken rings.
So, before I pull the engine, just wanted to make sure I'm not missing anything. If it requires a rebuild, I'd be interested in suggestions such as keeping it 100% stock, vs. minor mods such as hardened valve seats, better cam, etc.
Also, should I rebuild the heads if the problem turns out to be just the rings, or should I just leave the heads alone?
The car is a survivor, 99% stock.
Thanks guys - I very much appreciate your thoughts here!
John
It runs perfectly until around 3500 rpm, then above that it runs rough and backfires through the carb. I replaced ignition, carb, fuel pump, (etc), to no avail. I also checked the usual things like ignition timing and checked for vacuum leaks.
I just did a compression test and a leakdown test, and here are the results. All tests were performed cold, and dry (no oil added through the plug holes):
Compression, psi, 1 through 8: 215, 215, 200, 190, 205, 205, 205, 200
Leakdown %, 1 through 8: 12%, 28%, 66%, 44%, 16%, 32%, 24%, 10%
While the cylinders were pressurized, air could be heard escaping from the valve covers (only). I'm thinking it has worn and/or broken rings.
So, before I pull the engine, just wanted to make sure I'm not missing anything. If it requires a rebuild, I'd be interested in suggestions such as keeping it 100% stock, vs. minor mods such as hardened valve seats, better cam, etc.
Also, should I rebuild the heads if the problem turns out to be just the rings, or should I just leave the heads alone?
The car is a survivor, 99% stock.
Thanks guys - I very much appreciate your thoughts here!
John
You need to pull the heads and have them rebuilt. Check the valve guides while they are off.
Other than that you should be ok but you will not know until you pull the heads.
You seem to have some mechanical experience.
Take your time and you could do the top end by yourself.
Good luck.
Bman
Once the heads are off post pics here with any questions.
08-23-2014, 07:49 PM
#5
Le Mans Master
Member Since: Oct 2002
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So, does everyone need to be ASE certified before they ask for advice here? Dang, check into Ritalin.
No but ASE training will help someone from getting too far ahead of themselves. Rebuilding at 60k mi on an engine with good compression and runs well at low rpm would be absolutely the wrong advice. Having rebuilt a few motors myself i cant encourage someone with a good block and little or no experience to try a rebuild.
I guess i could say politely he should take it all apart and spend thousands on machine work and parts. Tell him how easy it is to measure bearing clearance, crank thrust, set ring gap and adjust the lifters the first w/o wiping a flat tappet cam. No! No! No Zoomin, i cant do that. In fact my experience tells me to discourage it. The truth can hurt but it fixes the real problem also.
BTW what is Ritalin?
No but ASE training will help someone from getting too far ahead of themselves. Rebuilding at 60k mi on an engine with good compression and runs well at low rpm would be absolutely the wrong advice. Having rebuilt a few motors myself i cant encourage someone with a good block and little or no experience to try a rebuild.
I guess i could say politely he should take it all apart and spend thousands on machine work and parts. Tell him how easy it is to measure bearing clearance, crank thrust, set ring gap and adjust the lifters the first w/o wiping a flat tappet cam. No! No! No Zoomin, i cant do that. In fact my experience tells me to discourage it. The truth can hurt but it fixes the real problem also.
BTW what is Ritalin?
08-23-2014, 08:03 PM
#6
Melting Slicks
Your compression readings are similar to what I get, also an LS5 which was rebuilt many years ago, maybe several thousand miles at most since the rebuild.
Have you checked the pickup strainer in the tank? Sounds like it may be running out of fuel at higher RPMs.
Mechanical and vacuum advance all working correctly?
Possibly a valve train issue? Someone with more experience with cams and valve trains may have some thoughts on this?
Have you checked the pickup strainer in the tank? Sounds like it may be running out of fuel at higher RPMs.
Mechanical and vacuum advance all working correctly?
Possibly a valve train issue? Someone with more experience with cams and valve trains may have some thoughts on this?
08-23-2014, 09:51 PM
#7
Race Director
Why do u want to rebuild a motor that only needs a vlv job and tuning?
Have u ever rebuilt a motor before let alone a collectable classic LS5 BB?
Seems to me if u knew what u were doing u would have fixed your leakdown and tuning problems and not even posted here.
Take it to the dealer or a real experienced mech for diagnose and repair. Take a ASE class on tuning and rebuilding engines at the local tech school before u create a problem u dont have and ruin a collectable BB C3.
Have u ever rebuilt a motor before let alone a collectable classic LS5 BB?
Seems to me if u knew what u were doing u would have fixed your leakdown and tuning problems and not even posted here.
Take it to the dealer or a real experienced mech for diagnose and repair. Take a ASE class on tuning and rebuilding engines at the local tech school before u create a problem u dont have and ruin a collectable BB C3.
Why would you demean and criticize the poster for simply asking for advise? Seems you are the one who need to take a class. No way do bad valves leak at the valve covers. The leakdown test will show a "leak path". If the intake valve is not sealing it will leak out of the carb. If the exhaust valve is not sealing it will leak out of the exhaust. It can have horrible guides but still seal at the valve seat. If there is a ring seal issue it will leak out of the valve cover since everything else is sealed. Anything over 20% is a sign of wear but if it is uniform it is not as big of issue, even approaching 30% and uniform lets you know it is getting close to time. The 66% and 44% are big red flags, especially with decent compression. I would guess he has a couple broken rings and or pitting in one or more cylinders from corrosion seizing those rings to the cylinder wall on the cylinders with open valves while sitting for extended periods of time considering the year and mileage. Time for a rebuild. Good news is it is probably an easy rebuild with little wear. .030 Bore, torque plate hone, pistons, rings, polish crank, Resize rods, new bearings, valve job is likely all your looking at.
08-23-2014, 10:21 PM
#8
Race Director
Hi guys, I think it's time to pull the engine and do a rebuild, so I wanted to ask for some advice, please. It's a 1970 LS5, 60k miles, never been apart as far as I know.
It runs perfectly until around 3500 rpm, then above that it runs rough and backfires through the carb. I replaced ignition, carb, fuel pump, (etc), to no avail. I also checked the usual things like ignition timing and checked for vacuum leaks.
I just did a compression test and a leakdown test, and here are the results. All tests were performed cold, and dry (no oil added through the plug holes):
Compression, psi, 1 through 8: 215, 215, 200, 190, 205, 205, 205, 200
Leakdown %, 1 through 8: 12%, 28%, 66%, 44%, 16%, 32%, 24%, 10%
While the cylinders were pressurized, air could be heard escaping from the valve covers (only). I'm thinking it has worn and/or broken rings.
So, before I pull the engine, just wanted to make sure I'm not missing anything. If it requires a rebuild, I'd be interested in suggestions such as keeping it 100% stock, vs. minor mods such as hardened valve seats, better cam, etc.
Also, should I rebuild the heads if the problem turns out to be just the rings, or should I just leave the heads alone?
The car is a survivor, 99% stock.
Thanks guys - I very much appreciate your thoughts here!
John
It runs perfectly until around 3500 rpm, then above that it runs rough and backfires through the carb. I replaced ignition, carb, fuel pump, (etc), to no avail. I also checked the usual things like ignition timing and checked for vacuum leaks.
I just did a compression test and a leakdown test, and here are the results. All tests were performed cold, and dry (no oil added through the plug holes):
Compression, psi, 1 through 8: 215, 215, 200, 190, 205, 205, 205, 200
Leakdown %, 1 through 8: 12%, 28%, 66%, 44%, 16%, 32%, 24%, 10%
While the cylinders were pressurized, air could be heard escaping from the valve covers (only). I'm thinking it has worn and/or broken rings.
So, before I pull the engine, just wanted to make sure I'm not missing anything. If it requires a rebuild, I'd be interested in suggestions such as keeping it 100% stock, vs. minor mods such as hardened valve seats, better cam, etc.
Also, should I rebuild the heads if the problem turns out to be just the rings, or should I just leave the heads alone?
The car is a survivor, 99% stock.
Thanks guys - I very much appreciate your thoughts here!
John
It will probably get you 40-50 HP across the operating range with good vacuum and never have to worry about wiping a lobe. Or this if your looking for a milder, stockish idle. http://www.summitracing.com/parts/hr...make/chevrolet
Both have about the same DCR and will need 93 octane.
Don't worry about the valve seats unless they are recessed now. Cam will require new springs and possibly Beehive springs, +.100 valves or cut spring seats, maybe not. Have to check.
08-24-2014, 03:23 AM
#9
Le Mans Master
Member Since: Oct 2002
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Same as air gets by worn rings, if the vlvs dont seal and the guides are bad enough air will leak out. That's a fact Jack!
Broken rings and pitted cyl's would burn plenty of oil - didnt read that - lowers compression too. Read it "runs perfectly below 3500rpm".
New "roller" cam, beehive springs with cut spring seats. Ya, that should fix anything leaking in the cyl'rs.
Broken rings and pitted cyl's would burn plenty of oil - didnt read that - lowers compression too. Read it "runs perfectly below 3500rpm".
New "roller" cam, beehive springs with cut spring seats. Ya, that should fix anything leaking in the cyl'rs.
08-24-2014, 04:38 AM
#10
Melting Slicks
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Sounds to me like you have a broken valve spring. Could be one of the inner springs. Those can be replaced easily without pulling the head with compressed air. Broken valve springs are a common problem on BB.
Bullshark
Bullshark
08-24-2014, 10:04 AM
#11
Intermediate
Thread Starter
I will double check the leakdown and pull the valve covers and check the springs. The ignition advance was checked some time ago but I'll do that again as well.
The fuel strainer/sock was replaced when I replaced the fuel pump. The engine does not burn oil, which I thought didn't square with air leaking past the rings during the leakdown test. But there was no sound of air from the carb or the exhaust during the leakdown test - just from the valve covers.
Thanks for all the advice … I won't be working on it for a couple of weeks, but will check back in when I have some more info!
John
The fuel strainer/sock was replaced when I replaced the fuel pump. The engine does not burn oil, which I thought didn't square with air leaking past the rings during the leakdown test. But there was no sound of air from the carb or the exhaust during the leakdown test - just from the valve covers.
Thanks for all the advice … I won't be working on it for a couple of weeks, but will check back in when I have some more info!
John
08-24-2014, 10:12 AM
#12
Race Director
Same as air gets by worn rings, if the vlvs dont seal and the guides are bad enough air will leak out. That's a fact Jack! You think with his compression numbers that enough air is getting past the valve seat to pressurize the intake runner enough to force air past the valveguides into the crankcase instead of following the least resistance path of the runner to the carb??? That would be pretty special. My name is not Jack.
Broken rings and pitted cyl's would burn plenty of oil - didnt read that - lowers compression too. Read it "runs perfectly below 3500rpm". Oil control ring is likely intact. Middle compression rings are likely good. Upper compression ring is what rusts to the cylinder wall when engines sit for prolonged periods. This is why you pull the plugs and lubricate the cylinder before starting an engine that has been sitting for a long time. Likely has a couple broken upper compression rings. Compression readings are lower on the bad leakdown cylinders.
New "roller" cam, beehive springs with cut spring seats. Ya, that should fix anything leaking in the cyl'rs. The OP asked for opinions on if he should do a cam upgrade while he was there. My point is if he is rebuilding the engine I would go back stock with the exception of a higher lift roller cam and new springs to increase power and eliminate the chances of a wiped lobe on startup or in the future. It might need beehives or cut seats or +.100 valves to do this. Might get a spring that will work without any modification at .600 lift all but probably not, have to measure. When it is torn down is the time to do this sort of improvement not after you wipe a lobe on your low mile fresh rebuild. Rebuild will require new cam, lifters and springs anyway. It is a 1970 LS5. Spend a few hundred extra and do it justice.
Broken rings and pitted cyl's would burn plenty of oil - didnt read that - lowers compression too. Read it "runs perfectly below 3500rpm". Oil control ring is likely intact. Middle compression rings are likely good. Upper compression ring is what rusts to the cylinder wall when engines sit for prolonged periods. This is why you pull the plugs and lubricate the cylinder before starting an engine that has been sitting for a long time. Likely has a couple broken upper compression rings. Compression readings are lower on the bad leakdown cylinders.
New "roller" cam, beehive springs with cut spring seats. Ya, that should fix anything leaking in the cyl'rs. The OP asked for opinions on if he should do a cam upgrade while he was there. My point is if he is rebuilding the engine I would go back stock with the exception of a higher lift roller cam and new springs to increase power and eliminate the chances of a wiped lobe on startup or in the future. It might need beehives or cut seats or +.100 valves to do this. Might get a spring that will work without any modification at .600 lift all but probably not, have to measure. When it is torn down is the time to do this sort of improvement not after you wipe a lobe on your low mile fresh rebuild. Rebuild will require new cam, lifters and springs anyway. It is a 1970 LS5. Spend a few hundred extra and do it justice.
1. If air is leaking out of the carb it is an intake valve not sealing.
2. If air leaks out of exhaust an exhaust valve is not sealing.
3. If air leaks out of the valve cover ONLY it is rings.
If you have 44% leakdown in one cylinder and 66% leakdown in another and the only place that air is leaking is the valve covers it is rings period.
A broken spring could explain the miss above 3500 but not the leakdown results.
Last edited by 63mako; 08-24-2014 at 11:37 AM.
08-24-2014, 10:41 AM
#13
Burning Brakes
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could the OP get by with a mild hone job and new rings ? I would get all new bearings .I would check every thing for wear and proper clearances .I would do a valve job while the engine is apart .a roller cam would really wake the engine up .
08-24-2014, 11:22 AM
#14
Melting Slicks
My guess would be possibly valve train issues causing the higher RPM break up, assuming fuel and ignition are fine. Quite possible there are issues with rings in a few cylinders, a secondary issue, not likely to cause the misfires but something which may need to be addressed if the OP is getting deep into the engine.
Tightening up the top end on an older engine often reveals weakness in the bottom end afterward. May as well do it right.
Tightening up the top end on an older engine often reveals weakness in the bottom end afterward. May as well do it right.
08-24-2014, 06:35 PM
#15
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St. Jude Donor '12-'13, '15- '16-'17-'18-'19, '21
If at all possible post pics of the spark plugs.
They would give a good indication of any issues.
I just don't see how consistent compression readings indicate a ring problem.
More likely upper valve train. Especially with only 60k on the motor. Valve springs go weak and seals hardened and dry out. Rings just sit there.
One more thought.....compression getting into valve covers could be small crack in head or faulty pcv system.
IMO
Bman
Keep us posted. Interested to see the final issue.
They would give a good indication of any issues.
I just don't see how consistent compression readings indicate a ring problem.
More likely upper valve train. Especially with only 60k on the motor. Valve springs go weak and seals hardened and dry out. Rings just sit there.
One more thought.....compression getting into valve covers could be small crack in head or faulty pcv system.
IMO
Bman
Keep us posted. Interested to see the final issue.
08-25-2014, 08:42 AM
#16
Le Mans Master
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I will double check the leakdown and pull the valve covers and check the springs. The ignition advance was checked some time ago but I'll do that again as well.
The fuel strainer/sock was replaced when I replaced the fuel pump. The engine does not burn oil, which I thought didn't square with air leaking past the rings during the leakdown test. But there was no sound of air from the carb or the exhaust during the leakdown test - just from the valve covers.
Thanks for all the advice … I won't be working on it for a couple of weeks, but will check back in when I have some more info!
John
The fuel strainer/sock was replaced when I replaced the fuel pump. The engine does not burn oil, which I thought didn't square with air leaking past the rings during the leakdown test. But there was no sound of air from the carb or the exhaust during the leakdown test - just from the valve covers.
Thanks for all the advice … I won't be working on it for a couple of weeks, but will check back in when I have some more info!
John
A leak down test measures the air leak down. If vlvs are sealed then the leak down can only go out through the rings gaps into the crankcase. Then the air goes out wherever it can - vlv cover grommet, bad gaskets/seals unless the dip stick is out and then blows out there. Even Jack would know this.
Or that someone could be ready to sell u something like a cam or full rebuild - who knows, but please let us know if u get a PM with any propositions.
Bad vlv springs can make it rough and rougher at hi rpm. But the backfiring through carb is a fairly significant change and sounds more like a timing issue (not even a mixture issue). Kinda like the timing springs or weights fell off the dist. Ive had my dist weights freeze up before so that can happen also and it ran terrible though i dont recall backfire through carb.
FYI John, a head R&R is much simpler that an entire rebuild - much cheaper too, more like 500 bucks and only one weekend if u do it your self and worth the try before rebuilding. But i would spend the time and go through the dist first as all that really costs is patience.
If u want to learn how to rebuild u should get a boneyard engine core to learn on rather than a lo mi numbers match LS5. Something i have to warn is that a lot of experienced mech's here can mislead a new enthusiast into thinking it will be easy to rebuild. While we can read here a story every week of cars taken apart that never run again. Something as simple as adj the vlvs/lifters wrong can make a brand new motor/rebuild eat itself putting metal all through the block and bearings. What im saying is that overconfidence is nearly a disease here.
I wish u good luck and im sure your low mi BB is a nice car and makes me somewhat envious. Hope u can get to drive it more than work on it.
Last edited by vettebuyer6369; 08-25-2014 at 11:39 PM. Reason: removed reference to Jack
08-25-2014, 08:45 AM
#17
Intermediate
Thread Starter
bman - this photo isn't great but hopefully good enough. The plugs are oriented as if looking at the engine from the front (#1 cylinder is lower right). These plugs only have a couple hours of running time on them.
I can get a better photo later if necessary - thanks!
I can get a better photo later if necessary - thanks!
08-25-2014, 08:52 AM
#18
Intermediate
Thread Starter
A leak down test measures the air leak down. If vlvs are sealed then the leak down can only go out through the rings gaps into the crankcase. Then the air goes out wherever it can - vlv cover grommet, bad gaskets/seals unless the dip stick is out and then blows out there. Even Jack would know this. Someone that doesnt know Jack will imagine stuff up like broken rings that dont burn any oil, recommend hyd roller cams with a full rebuild before u even know what the problem is. Or that someone could be ready to sell u something like a cam or full rebuild - who knows, but please let us know if u get a PM with any propositions.
Bad vlv springs can make it rough and rougher at hi rpm. But the backfiring through carb is a fairly significant change and sounds more like a timing issue (not even a mixture issue). Kinda like the timing springs or weights fell off the dist. Ive had my dist weights freeze up before so that can happen also and it ran terrible though i dont recall backfire through carb.
FYI John, a head R&R is much simpler that an entire rebuild - much cheaper too, more like 500 bucks and only one weekend if u do it your self and worth the try before rebuilding. But i would spend the time and go through the dist first as all that really costs is patience.
If u want to learn how to rebuild u should get a boneyard engine core to learn on rather than a lo mi numbers match LS5. Something i have to warn is that a lot of experienced mech's here can mislead a new enthusiast into thinking it will be easy to rebuild. While we can read here a story every week of cars taken apart that never run again. Something as simple as adj the vlvs/lifters wrong can make a brand new motor/rebuild eat itself putting metal all through the block and bearings. What im saying is that overconfidence is nearly a disease here.
I wish u good luck and im sure your low mi BB is a nice car and makes me somewhat envious. Hope u can get to drive it more than work on it.
Bad vlv springs can make it rough and rougher at hi rpm. But the backfiring through carb is a fairly significant change and sounds more like a timing issue (not even a mixture issue). Kinda like the timing springs or weights fell off the dist. Ive had my dist weights freeze up before so that can happen also and it ran terrible though i dont recall backfire through carb.
FYI John, a head R&R is much simpler that an entire rebuild - much cheaper too, more like 500 bucks and only one weekend if u do it your self and worth the try before rebuilding. But i would spend the time and go through the dist first as all that really costs is patience.
If u want to learn how to rebuild u should get a boneyard engine core to learn on rather than a lo mi numbers match LS5. Something i have to warn is that a lot of experienced mech's here can mislead a new enthusiast into thinking it will be easy to rebuild. While we can read here a story every week of cars taken apart that never run again. Something as simple as adj the vlvs/lifters wrong can make a brand new motor/rebuild eat itself putting metal all through the block and bearings. What im saying is that overconfidence is nearly a disease here.
I wish u good luck and im sure your low mi BB is a nice car and makes me somewhat envious. Hope u can get to drive it more than work on it.
John
08-25-2014, 08:52 PM
#19
Race Director
A leak down test measures the air leak down. If vlvs are sealed then the leak down can only go out through the rings gaps into the crankcase. Then the air goes out wherever it can - vlv cover grommet, bad gaskets/seals unless the dip stick is out and then blows out there. Even Jack would know this.
Last edited by 63mako; 08-25-2014 at 09:05 PM.
08-25-2014, 09:27 PM
#20
Race Director
Are you doing your leakdown test with all the plugs in except the cylinder your testing and absolutely sure your exactly TDC on the compression stroke? If not your test is not accurate. I would really hate to see you rebuild it if you don't have to but if your test is accurate it is time. I would definitely get a very good builder to rebuild it. Don't do it yourself. With that engine I would also have that real good builder run it in and dial everything in on the dyno. You could pull it and drop it in yourself.
Last edited by 63mako; 08-25-2014 at 09:30 PM.