LS3 – 525HP / Legend LGT-700 Conversion in a 66 Pontiac GTO Convertible
08-25-2014, 08:21 AM
#1
LS3 – 525HP / Legend LGT-700 Conversion in a 66 Pontiac GTO Convertible I have owned my GTO for 17 years and the car has undergone several revisions over the years. The car is a real 66 GTO convertible born with a 389 tri-power, M-21 and a 3:90 posi. I bought it back in 1997 when my wife and I had started dating and we drive this thing. The only time it has been on a trailer is when the body work was getting done and we have enjoyed thousands of miles in this car.
In 2005, the 389 started chugging oil out the breather and instead of rebuilding the anemic 389 I had a 455 built by a guy in Virginia. The 455 was a turd from the get go and the build quality was less than stellar and after dealing with the short comings of this thing for 5 years, I decided to cut my losses and I sold the engine for a huge loss. I replaced the 455 with a 461 that was built by a reputable builder in Ohio. The engine made a butt load of HP and TQ, but after living with 550 HP and 14 MPG for 4 years I concluded that I needed to re-think my strategy for a car that is easier to drive and is a bit easier on fuel. My wife hated the 461 for various reasons and I would rather have something that is more civilized so she can drive it on occasion.
For several months prior to the decision to sell the 461, I struggled with the “it’s not a Pontiac in a Pontiac” crap. I decided that life it too short to worry about what others think and I decided that a LS3 525 HP conversion would be a wonderful succession. The engine has attitude and those who have this engine love it. Let’s face it, you can’t beat a LS based engine and the newer technology and factory available parts make this a great platform. After selling the 461 back in July, I have been doing my homework trying to figure out the best use of my money and time. I had initially thought about an LSA, but the extra $4K (adder of the LSA plus the heat exchanger and misc. things that are required) pretty much squashed that idea. I would have loved to do an LSA, but I am spending way too much already and the extra $4K seemed like a hard sell to the finance department. So, it is LS3 NA for me. I am going to re-use things like my Legend LGT-700 5-speed, hydraboost, EFI tank, and electric fan setup…Anything I can re-use should help with the sticker shock of an LS build.
Follow me as I navigate through the build and search out the best prices and the best vendors. I am anticipating a April 2015 completion date. I am posting identical posts in Pro-touring and Performance Years so please excuse the duplication. I know there are people that don’t frequent LS1tech so it seemed like a good thing to do.
I few pictures to start. I will post more as I go and I will post the final parts list and the prices for the parts.
Frame off restoration in 2012. Who would have thought I would be ripping things apart so soon?
Thanks for following along. Bob
In 2005, the 389 started chugging oil out the breather and instead of rebuilding the anemic 389 I had a 455 built by a guy in Virginia. The 455 was a turd from the get go and the build quality was less than stellar and after dealing with the short comings of this thing for 5 years, I decided to cut my losses and I sold the engine for a huge loss. I replaced the 455 with a 461 that was built by a reputable builder in Ohio. The engine made a butt load of HP and TQ, but after living with 550 HP and 14 MPG for 4 years I concluded that I needed to re-think my strategy for a car that is easier to drive and is a bit easier on fuel. My wife hated the 461 for various reasons and I would rather have something that is more civilized so she can drive it on occasion.
For several months prior to the decision to sell the 461, I struggled with the “it’s not a Pontiac in a Pontiac” crap. I decided that life it too short to worry about what others think and I decided that a LS3 525 HP conversion would be a wonderful succession. The engine has attitude and those who have this engine love it. Let’s face it, you can’t beat a LS based engine and the newer technology and factory available parts make this a great platform. After selling the 461 back in July, I have been doing my homework trying to figure out the best use of my money and time. I had initially thought about an LSA, but the extra $4K (adder of the LSA plus the heat exchanger and misc. things that are required) pretty much squashed that idea. I would have loved to do an LSA, but I am spending way too much already and the extra $4K seemed like a hard sell to the finance department. So, it is LS3 NA for me. I am going to re-use things like my Legend LGT-700 5-speed, hydraboost, EFI tank, and electric fan setup…Anything I can re-use should help with the sticker shock of an LS build.
Follow me as I navigate through the build and search out the best prices and the best vendors. I am anticipating a April 2015 completion date. I am posting identical posts in Pro-touring and Performance Years so please excuse the duplication. I know there are people that don’t frequent LS1tech so it seemed like a good thing to do.
I few pictures to start. I will post more as I go and I will post the final parts list and the prices for the parts.
Frame off restoration in 2012. Who would have thought I would be ripping things apart so soon?
Thanks for following along. Bob
08-27-2014, 08:17 AM
#3
I am currently working with Mark Bowler on a hydraulic clutch setup. My hydrobooster makes it a bit of a challenge so Mark set me a bracket to prototype for him and will be making some changes to the bracket based on my trial. He sent me a tilton master and a 4th gen master to try. His bracket will allow the use of both master setups.
Nice bracket. Once this is in full production it will be a winner. I like the fact that the bracket is adjustable.
Clears my hydrobooster bracket
4th gen master. I am working with Mark to figure out if we need to cut down the internal stop in the cylinder.
The master comes with an eyelet on the end of the rod. Not long enough so I decided to take the rod off and try my hand at threading the rod for a long nut coupler.
The threads went on crooked, so I am trying to decide what to do here
Nice bracket. Once this is in full production it will be a winner. I like the fact that the bracket is adjustable.
Clears my hydrobooster bracket
4th gen master. I am working with Mark to figure out if we need to cut down the internal stop in the cylinder.
The master comes with an eyelet on the end of the rod. Not long enough so I decided to take the rod off and try my hand at threading the rod for a long nut coupler.
The threads went on crooked, so I am trying to decide what to do here
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08-27-2014, 04:37 PM
#9
TECH Senior Member
iTrader: (7)
Bob,
Tell Mark that they should make a bracket to accept the Girling style master cylinders. They are readily available, reliable, and have a 1.4" stroke. They are also much easier to adapt because they already have a threaded rod to which an extension can be attached to. There is no reason to use a factory MC, considering their questionable performance and future availability. The last 4th gen f-body rolled off the factory floor 12 years ago!
Andrew
Tell Mark that they should make a bracket to accept the Girling style master cylinders. They are readily available, reliable, and have a 1.4" stroke. They are also much easier to adapt because they already have a threaded rod to which an extension can be attached to. There is no reason to use a factory MC, considering their questionable performance and future availability. The last 4th gen f-body rolled off the factory floor 12 years ago!
Andrew
09-08-2014, 06:27 PM
#10
Had a long talk with Mark Bowler and they are re - designing the adapter plate to accept a wilwood master that can be clocked 0, 90, 180 and 270 degrees. Once complete, the bracket will be able to use either a 4th gen or a girling style master. They are sending me a prototype soon to try out. Thanks for the feedback.
09-20-2014, 08:13 AM
#11
Firewall is done. I have a friend that is is body guy and he came over and did a clean up of the firewall. We filled some dimples and gave it a coat of satin. I left the throttle cable hole, heater wire hole and the firewall pad holes open for possible future use. Turned out nice.
11-09-2014, 08:31 PM
#13
Its been awhile so it is time for an update.
I bought the LS3 525 HP engine from Gandrud in Green Bay, WI at the beginning of October. Nice guys and they price matched Pace Performance and delivered right to my door. I bought the engine, drive accessories, flywheel, clutch and fasteners.
Not a very pretty engine, but this thing ought to make this bucket of bolts haul. Brand new, full warranty and a butt load of potential.
Engine stuffed in the car. Not bad. Notice that I am prototyping a set of Ultimate Headers shorties. More on that to come.
I played around with the Holley 302-2 pan for a bit and I had excellent clearance in the front of the pan. I didn't like the lack of clearance between the back side of the frame and when I spun the motor over without a gasket, I noticed a little incidental contact between the pan and one of the rods. I would assume that the 1/8" thick oil pan gasket would take care of this, but I opted for the 302-1 pan instead
I can keep the full length windage tray with the 302-1 and it is a better casting overall. The 302-2 casting was not nearly as nice as the 302-1. I have about 1/4" clearance before the gasket and should have better than 1/8" with the gasket.
Tie rod clearance that is acceptable for my application. The Ridetech arms limit a tight radius. Even if I had more tire turning radius, I think I would be OK to a point.
Note the Lakewood scattershield that I am using with my LGT-700. Sourced from Bowler Performance. More on that later.
Holley engine adapters 12611, Car Shop BOP to Chevy frame mounts and energy suspension 3.1114G mounts (short and wide required.
Bosch SR8581N starter from Rock Auto. $107. No core and brand new.
Trail and error with Doug's D3336-R headers. The headers fit fine at the frame and clear the steering column OK. I tried the Dougs SK100 mounts which are IDENTICAL to the Hooker mounts except that the engine can move forward by 3/4" from stock location. If I put the engine 3/4" forward, the headers barely clear the lower a-arm suspension pockets.
While the D3336-R headers fit OK at the engine and between the frame rails, they are really tight to the floor. I have about 1/2" at best between the header flanges and the floor. I am exploring other headers with Ultimate Headers to see what they can do. My other option is to cut off the flanges, weld in some 3" elbows to move it away from the floor and clear the crossmember. I ordered a new Summit Racing cross member and should have a good idea where things are going after that arrives.
I bought the LS3 525 HP engine from Gandrud in Green Bay, WI at the beginning of October. Nice guys and they price matched Pace Performance and delivered right to my door. I bought the engine, drive accessories, flywheel, clutch and fasteners.
Not a very pretty engine, but this thing ought to make this bucket of bolts haul. Brand new, full warranty and a butt load of potential.
Engine stuffed in the car. Not bad. Notice that I am prototyping a set of Ultimate Headers shorties. More on that to come.
I played around with the Holley 302-2 pan for a bit and I had excellent clearance in the front of the pan. I didn't like the lack of clearance between the back side of the frame and when I spun the motor over without a gasket, I noticed a little incidental contact between the pan and one of the rods. I would assume that the 1/8" thick oil pan gasket would take care of this, but I opted for the 302-1 pan instead
I can keep the full length windage tray with the 302-1 and it is a better casting overall. The 302-2 casting was not nearly as nice as the 302-1. I have about 1/4" clearance before the gasket and should have better than 1/8" with the gasket.
Tie rod clearance that is acceptable for my application. The Ridetech arms limit a tight radius. Even if I had more tire turning radius, I think I would be OK to a point.
Note the Lakewood scattershield that I am using with my LGT-700. Sourced from Bowler Performance. More on that later.
Holley engine adapters 12611, Car Shop BOP to Chevy frame mounts and energy suspension 3.1114G mounts (short and wide required.
Bosch SR8581N starter from Rock Auto. $107. No core and brand new.
Trail and error with Doug's D3336-R headers. The headers fit fine at the frame and clear the steering column OK. I tried the Dougs SK100 mounts which are IDENTICAL to the Hooker mounts except that the engine can move forward by 3/4" from stock location. If I put the engine 3/4" forward, the headers barely clear the lower a-arm suspension pockets.
While the D3336-R headers fit OK at the engine and between the frame rails, they are really tight to the floor. I have about 1/2" at best between the header flanges and the floor. I am exploring other headers with Ultimate Headers to see what they can do. My other option is to cut off the flanges, weld in some 3" elbows to move it away from the floor and clear the crossmember. I ordered a new Summit Racing cross member and should have a good idea where things are going after that arrives.
11-10-2014, 02:49 AM
#14
Dougs' swap plates are junk IMO.
Sweep build. I disagree though. Thats a nice looking engine. LOL
Sweep build. I disagree though. Thats a nice looking engine. LOL
11-16-2014, 10:03 AM
#18
TECH Fanatic
I used the Dougs headers and swap plates. Everything worked out quite well. I wanted the exhaust really tight to the floor pan, which the Dougs accomplished. I got tired of dragging exhaust over every speed bump in previous projects, has never happened here.
You will really appreciate the improved driveability with the LS over the Tin-Indian. I have owned and built "MANY" Pontiacs in the past, none have been as versatile as the LS. I have seen 23 MPG with a previous tune up and can spin the tires at cruise speed pretty much any time I want. How much more can you ask for.
You will really appreciate the improved driveability with the LS over the Tin-Indian. I have owned and built "MANY" Pontiacs in the past, none have been as versatile as the LS. I have seen 23 MPG with a previous tune up and can spin the tires at cruise speed pretty much any time I want. How much more can you ask for.
11-16-2014, 11:45 PM
#19
VERY nice car. I'm impressed.
One thing to think about: Instead of sticking with the 4th gen clutch master, you might consider switching to a Wilwood or something similar. I made the switch because I really didn't like the angle at which the 4th gen clutch master rod connected to the clutch pedal in my 2nd gen (nearly 45 degrees, when I'd preferred 90 degrees)
One thing to think about: Instead of sticking with the 4th gen clutch master, you might consider switching to a Wilwood or something similar. I made the switch because I really didn't like the angle at which the 4th gen clutch master rod connected to the clutch pedal in my 2nd gen (nearly 45 degrees, when I'd preferred 90 degrees)
Last edited by 1981TA; 11-16-2014 at 11:51 PM.
11-17-2014, 03:27 AM
#20
Dougs's swap plates didn't allow my DOUGSs headers to fit in either location. I had to trim my pass rear LCA mount. But they keep the collector real close to the floor as 1981TA said. Still worth the hassle and waste of money spent on the DOugs plates that I couldn't use.
OLD66Tiger,
What control arms are you running? Keep the pics coming.
OLD66Tiger,
What control arms are you running? Keep the pics coming.