90GT Greg Brown Engine Build
01-28-2016, 12:27 PM
#1
Rennlist Member
Thread Starter
90GT Greg Brown Engine Build
Greg Brown completed an engine build last week for Sue's car, a 1990 GT. What started out as a simple refresh evolved into something more, as those projects often do. We're insanely pleased with how it all came out, and want to share the story.
This is the car that we bought from Louie Ott in October 2008, with 151K miles on the clock (thread here). It was Jim Hurt's car for a few years (the one he didn't crash or burn) and before that was in the San Fran area. Jim and Louie had fitted Devek L2 headers, and Louie built a 2.5" dual exhaust and spent a lot of time Sharktuning.
Since then we've done lot of driving including a few trips cross-country to various events, and a lot of maintaining and refreshing. Mileage was getting close to 250K and although it was still running strong, we didn't want to break it. The regular oil analyses continued to be good, but copper was sneaking up so something was going on with bearing somewhere. We thought about diving into it ourselves, but we didn't need another unfinished project-- and we wanted it done right. So off to GB's it went.
What Greg found on disassembly was interesting: The rod bearings were worn, but showed no particular signs of distress and could have gone many more miles. There was quite a bit of carbon built up but the bores looked good. The head-gaskets were seriously trashed and there was some corrosion on the heads from coolant. The piston skirts were worn but looked OK. The main bearings were not as happy, #1 main bearing had an odd wear pattern that Greg had not seen before, and the thrust bearing was starting to show some copper from clutch pressure. (That was likely the copper that we were seeing in the oil analysis).
At this point it looked like a good candidate for new bearings and rings, refresh the heads and button it up. We also wanted to go with Greg's cosmic new crank and rods (better oiling and more robust bearings). But after Greg did some careful measuring the cylinders had more wear than was evident. If we wanted it to be "as new" then that meant boring/polishing and new pistons. Suddenly there were more choices to make, and with boring and pistons added to the shopping list we could do anything. Talk about slippery slopes...
The basic choices for cylinder boring are to stick with Alusil and use ferrous-coated (i.e. factory) pistons, or go the Nikasil route (nickel plating) which allows a wider selection of pistons (including shorter pistons and longer strokes). We chose to stick with the original Alusil technology and 968 pistons, and the GTS-stroke (85.9mm) version of GB's cosmic crank with matching Carillo rods. The character of a GT that we like very much is the balance and the eagerness to rev, which suggested not going crazy with stroke. (On the other hand, Greg correctly points out that there is no such thing as too much torque). Bore went up by 4.5mm, stroke got longer by 7mm and displacement came out to 5.9L.
The heads got welded and skimmed and had new guides fitted. Greg spent quite a bit of time with porting, and also gave the intake some attention. We stuck with stock valves, and Greg took advantage of the larger bore to unshroud the intakes a bit more. We had upgraded the cams a few years ago and were happy with those (224/217 duration @ 1mm, 10.8/10.4 mm lift, 110 LSA-- stock GT is 219/205, 10/9 and 110) and GB had set us up with new springs and DLC lifters which were perfect.
Greg fired the engine up on the stand just before the holidays (thread here), then rebuilt the tranny (new synchros and bearings) and dropped everything back in. Sue and I spent a day tuning (including lunch in Palm Springs) and hit Superior dyno before the final blessings and heading home.
The results are terrific. This car was strong before, but this takes it to a whole new level. And working with Greg and Mary was great, what a treat!
How was the dyno, you ask? And more details of course! All to follow....
But first a picture, or it didn't happen:
This is the car that we bought from Louie Ott in October 2008, with 151K miles on the clock (thread here). It was Jim Hurt's car for a few years (the one he didn't crash or burn) and before that was in the San Fran area. Jim and Louie had fitted Devek L2 headers, and Louie built a 2.5" dual exhaust and spent a lot of time Sharktuning.
Since then we've done lot of driving including a few trips cross-country to various events, and a lot of maintaining and refreshing. Mileage was getting close to 250K and although it was still running strong, we didn't want to break it. The regular oil analyses continued to be good, but copper was sneaking up so something was going on with bearing somewhere. We thought about diving into it ourselves, but we didn't need another unfinished project-- and we wanted it done right. So off to GB's it went.
What Greg found on disassembly was interesting: The rod bearings were worn, but showed no particular signs of distress and could have gone many more miles. There was quite a bit of carbon built up but the bores looked good. The head-gaskets were seriously trashed and there was some corrosion on the heads from coolant. The piston skirts were worn but looked OK. The main bearings were not as happy, #1 main bearing had an odd wear pattern that Greg had not seen before, and the thrust bearing was starting to show some copper from clutch pressure. (That was likely the copper that we were seeing in the oil analysis).
At this point it looked like a good candidate for new bearings and rings, refresh the heads and button it up. We also wanted to go with Greg's cosmic new crank and rods (better oiling and more robust bearings). But after Greg did some careful measuring the cylinders had more wear than was evident. If we wanted it to be "as new" then that meant boring/polishing and new pistons. Suddenly there were more choices to make, and with boring and pistons added to the shopping list we could do anything. Talk about slippery slopes...
The basic choices for cylinder boring are to stick with Alusil and use ferrous-coated (i.e. factory) pistons, or go the Nikasil route (nickel plating) which allows a wider selection of pistons (including shorter pistons and longer strokes). We chose to stick with the original Alusil technology and 968 pistons, and the GTS-stroke (85.9mm) version of GB's cosmic crank with matching Carillo rods. The character of a GT that we like very much is the balance and the eagerness to rev, which suggested not going crazy with stroke. (On the other hand, Greg correctly points out that there is no such thing as too much torque). Bore went up by 4.5mm, stroke got longer by 7mm and displacement came out to 5.9L.
The heads got welded and skimmed and had new guides fitted. Greg spent quite a bit of time with porting, and also gave the intake some attention. We stuck with stock valves, and Greg took advantage of the larger bore to unshroud the intakes a bit more. We had upgraded the cams a few years ago and were happy with those (224/217 duration @ 1mm, 10.8/10.4 mm lift, 110 LSA-- stock GT is 219/205, 10/9 and 110) and GB had set us up with new springs and DLC lifters which were perfect.
Greg fired the engine up on the stand just before the holidays (thread here), then rebuilt the tranny (new synchros and bearings) and dropped everything back in. Sue and I spent a day tuning (including lunch in Palm Springs) and hit Superior dyno before the final blessings and heading home.
The results are terrific. This car was strong before, but this takes it to a whole new level. And working with Greg and Mary was great, what a treat!
How was the dyno, you ask? And more details of course! All to follow....
But first a picture, or it didn't happen:
01-28-2016, 01:17 PM
#4
Rennlist Member
Thread Starter
OK, here's the dyno results. A couple of things to keep in mind: First, the engine only had a few hours on it, and only a few hours of tuning, and was running on what passes for gasoline in California. There is more to be found. Second, this was a Dynojet at Superior Automotive in Anaheim, very experienced folks and very consistent results, but stingy compared to others. Great for comparisons run on the same dyno.
The "before" number was the baseline from the tests with Greg's plenum project a couple of years ago, same dyno and same engine configuration except had no cats then. Max power was 321 (rw, SAE) but was cut off a bit early. The identical Dynojet that we usually use up here in Marysville put peak power (340) right at 6000 so I don't think there was much if anyhting missing there.
Max torque is up 87 ft-lbs, +29% -- versus a displacement increase of 18%. That is astounding. Max power is up 73hp, +23%. And that's with cats (there were none in the baseline run), not exactly the CARB sorts of cats but cats nonetheless. Truly a testament to Greg's skills at engine building.
Here's the video:
The "before" number was the baseline from the tests with Greg's plenum project a couple of years ago, same dyno and same engine configuration except had no cats then. Max power was 321 (rw, SAE) but was cut off a bit early. The identical Dynojet that we usually use up here in Marysville put peak power (340) right at 6000 so I don't think there was much if anyhting missing there.
Max torque is up 87 ft-lbs, +29% -- versus a displacement increase of 18%. That is astounding. Max power is up 73hp, +23%. And that's with cats (there were none in the baseline run), not exactly the CARB sorts of cats but cats nonetheless. Truly a testament to Greg's skills at engine building.
Here's the video:
01-28-2016, 01:41 PM
#6
Three Wheelin'
Jim,
Thanks for sharing. I have a complete engine and tranny in the garage that I will love to send to GB. Just waiting for some $$$ to be available for that project.
Thanks for sharing. I have a complete engine and tranny in the garage that I will love to send to GB. Just waiting for some $$$ to be available for that project.
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01-28-2016, 01:56 PM
#9
Rennlist Member
thats awesome.... so comparing what i have, which is a 6.4 liter vs your 6.0 liter, it has 20 more HP with less displacement.
reasons: cams are 1mm more lift on intake and 1.9mm (a big increase) on exhaust or 10.8 and 10.9mm? (10mm /9mm is stock gT) and some nice head porting work. however, your cams were used before in the 5 liter engine when it made 320rwhp ( same as mine with all stock stuff).
so, it looks like, at first glance that most all of the gains were done in the displacement, and the head work accounted for another 15hp. (or maybe even allowed for the extra displacement to add proportional gains, along with the higher lift cams)
the engine looks brand new.... i think i might need to take my heads off and do some nice work on them as well, maybe taking the bace circle down on my 85 cams and get 1mm more lift too!
congrats.
reasons: cams are 1mm more lift on intake and 1.9mm (a big increase) on exhaust or 10.8 and 10.9mm? (10mm /9mm is stock gT) and some nice head porting work. however, your cams were used before in the 5 liter engine when it made 320rwhp ( same as mine with all stock stuff).
so, it looks like, at first glance that most all of the gains were done in the displacement, and the head work accounted for another 15hp. (or maybe even allowed for the extra displacement to add proportional gains, along with the higher lift cams)
the engine looks brand new.... i think i might need to take my heads off and do some nice work on them as well, maybe taking the bace circle down on my 85 cams and get 1mm more lift too!
congrats.
01-28-2016, 01:59 PM
#10
Rennlist Member
Great job all around. That's the way to go all in and leave doubt aside. Also, pretty jealous of that area you live in. Did some kayaking there once and will never forget it.
01-28-2016, 02:28 PM
#12
Rennlist Member
Congrats Jim and Sue! Fantastic work and results - would love to do similar work to my 90GT someday. Like Fred, I'm a bit "green" at the moment. Enjoy!
Enjoy!
01-28-2016, 02:59 PM
#13
:)
Magnificent!
Knowing firsthand how Rob's stroker 6.5 spins effortlessly, I can only imagine what Sue's engine is like. Once again, another potent motor by Brown!
I saw this beauty on the engine stand, I am sorry I missed the start up.
Best thing is I know you fine folks will drive it with passion!
Knowing firsthand how Rob's stroker 6.5 spins effortlessly, I can only imagine what Sue's engine is like. Once again, another potent motor by Brown!
I saw this beauty on the engine stand, I am sorry I missed the start up.
Best thing is I know you fine folks will drive it with passion!
01-28-2016, 03:20 PM
#15
Rennlist Member
Excellent upgrades Sue and Jim.....essentially a 400hp car with a 6L engine.
The video audio is so good I watched 3 times with increasing levels of volume........my laptop may need new speakers!
How is the before and after gearbox operation?......my GTS tranny needs a little TLC on 3rd
I should also ask how much did the Sharktuning change?
The video audio is so good I watched 3 times with increasing levels of volume........my laptop may need new speakers!
How is the before and after gearbox operation?......my GTS tranny needs a little TLC on 3rd
I should also ask how much did the Sharktuning change?
Last edited by the flyin' scotsman; 01-28-2016 at 04:22 PM.