Need to Rebuild a Trash Rebuild: 87 GN Help Needed...

[Joe Rainville]

Hi Guys,

I accidentally bought a project car that was supposed to be a nice condition original, 68,000 mile car. It had no codes or issues via the scanmaster gauge except a lousy idle and hunting IAC. While chasing a rough idle, turns out the timing chain had jumped because someone replaced the cam and lifters, but when they did the chain, they only replaced the top gear. So, the chain stretched and jumped. While looking to repair that, I pulled the rear main bearing to replace the seal (since I pulled the pan) and found the bearing was down to the copper.

What I though was an original engine had a "260" grind cam and 0.030" over Summit Racing pistons on the worst quality rebuild I have every, every seen. Even the hone job was trash. So here we are. My crank is scored, bores are questionable. I already had the intake corrosion repaired around the coolant ports, new Delphi fuel injectors, (new 20% over stock fuel pump), new stock replacement ignition system, (except the cam sensor), most all new sensors on the intake such as temp, TPS, IAC etc. I have a Cordone rebuild MAF and a new factory turbo. Stock intercooler stays but the terrible hack 3" exhaust will be updated. Aside from the overbore and cam, the motor looked 'stock'. Here is what I have in mind for my rebuild:

Regrind or new crank. Looking at stroker vs. std stroke kits. Have the block evaluated to see if the 0.030" overbore is useable or if I need to go 0.040" to clean up the mess. Pistons are a question as T/A sells 8:1 cast, while GN1 sells more expensive forged. I am planning a mild roller cam and roller lifters. Thinking of TA Steet Intimidator aluminum heads and increasing the head bolt count from 8 to 14. Probably going to add billet main caps for the center two, plus line bore, decking and whatever else my block needs. I want to keep the stock intake and valve covers for factory appearance. A full SS exhaust with street headers and a 3" downpipe with the built in wastegate will replace the factory cast elbow.

End goal is a smooth idle, good drivability and of course more power over the stock 247/355. HP goal is around 350-400 ish hp on pump gas. And ya, going to get the 200R rebuilt while I am at it...

Questions: Does this round reasonable? What about the factory computer? Are folks still burning chips?

Thanks,
-Joe
87 GN, chasing demons out of it since 2016.

 

[Pronto]

My stock 30k engine went 11.3 with only changed valve springs and external mods/fuel/alky control/exhaust/chip/drag radials/trans and converter. So a goal of 400hp is very easy on a fresh rotating assembly, roller cam and turbo with good exhaust, fuel mods, alky or E85, good tune with TT chip. Now to build creep, you can do ported iron head which is frankly silly not to while you're at this point. Billet caps adds more to the build creep but again if you're there and adding new rotating assembly then it does make sense. Do not skimp on fuel and injectors. Go for a good downpipe and full 3" exhaust. Make sure your stock headers are in good shape, repair or go new but that's a big expense. Now do not forget to get an O2 wideband and a Powerlogger for the stock ecm. No sense at all spending thousands on an engine and not knowing wtf is going on with the tune at WOT. That's my take. Sure others will add or subtract. PS, use machine shop familiar with Turbo Buicks and local if you can.

 

[Chuck Leeper]

Thinking of TA Steet Intimidator aluminum heads and increasing the head bolt count from 8 to 14.

??

 

[THensley]

chuck he is new to the TR and dose not know that's not possible. Really why is the heads made with 14 bolt we know why but it just seems reasonable to tap the block and finish what the factory didn't do.
Pronto is correct find a TR builder, Where are you located? you seem to be looking at TA performance parts, so if your in the AZ area code you will find a few builders up to the task.
I fill the two best 200r trans people are east of the Mississippi.

 

[Reggie West]

Hi Guys,

I accidentally bought a project car that was supposed to be a nice condition original, 68,000 mile car. It had no codes or issues via the scanmaster gauge except a lousy idle and hunting IAC. While chasing a rough idle, turns out the timing chain had jumped because someone replaced the cam and lifters, but when they did the chain, they only replaced the top gear. So, the chain stretched and jumped. While looking to repair that, I pulled the rear main bearing to replace the seal (since I pulled the pan) and found the bearing was down to the copper.

What I though was an original engine had a "260" grind cam and 0.030" over Summit Racing pistons on the worst quality rebuild I have every, every seen. Even the hone job was trash. So here we are. My crank is scored, bores are questionable. I already had the intake corrosion repaired around the coolant ports, new Delphi fuel injectors, (new 20% over stock fuel pump), new stock replacement ignition system, (except the cam sensor), most all new sensors on the intake such as temp, TPS, IAC etc. I have a Cordone rebuild MAF and a new factory turbo. Stock intercooler stays but the terrible hack 3" exhaust will be updated. Aside from the overbore and cam, the motor looked 'stock'. Here is what I have in mind for my rebuild:

Regrind or new crank. Looking at stroker vs. std stroke kits. Have the block evaluated to see if the 0.030" overbore is useable or if I need to go 0.040" to clean up the mess. Pistons are a question as T/A sells 8:1 cast, while GN1 sells more expensive forged. I am planning a mild roller cam and roller lifters. Thinking of TA Steet Intimidator aluminum heads and increasing the head bolt count from 8 to 14. Probably going to add billet main caps for the center two, plus line bore, decking and whatever else my block needs. I want to keep the stock intake and valve covers for factory appearance. A full SS exhaust with street headers and a 3" downpipe with the built in wastegate will replace the factory cast elbow.

End goal is a smooth idle, good drivability and of course more power over the stock 247/355. HP goal is around 350-400 ish hp on pump gas. And ya, going to get the 200R rebuilt while I am at it...

Questions: Does this round reasonable? What about the factory computer? Are folks still burning chips?

Thanks,
-Joe
87 GN, chasing demons out of it since 2016.

If you are going for 400 hp you do not need to go with aluminum heads to get there. On a stock block, you cannot use 14 bolt head studs its an 8 bolt deal and that is all you got. Only on Stage1 or Stage2 blocks can you go that route. A TA block will of course do it as well but that is $8000 just for the block.

You CAN make 400 hp on stock crank, rods using a set of forged pistons to fit the bore.

For the cost involved and what you are going for I would suggest the following.

If you can get away with using a .030 over bore piston, use the block you have.
If not then find a good 109 block and build on it.

109 block
Forged rods
Forged pistons go to a 9 to 1 CR.
Port and polished iron heads will work just fine on your combo ($2300 vs $4000)
Hyd roller cam
Roller rockers and that will require a set of aftermarket valve covers to clear.
Rebuild timing cover with a high volume pump
Deep sump oil pan
Clean and flow test injectors
Alkycontrol kit
You can get a chip from Turbotweak for the new combo using the stock ECM and be good.

Turbo. You can get away with a stock turbo to make 400 hp or there are other options that will work just fine. A 58/58 is more than enough.
I would recommend getting a converter specd out to match your combo. It will help with spool up and handle the power. Your stock trans may not hold up to the additional torque but we will leave that for another discussion.

Ask away if you have more questions.

 

[greeneyegi]

Where are you located?