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?

 

[Joe Rainville]

Gentleman,

This is my first GN, but I have always been a gearhead. But I do not know all subtleties of the GN, but being a former fuel injection engineer for Delphi early in my career has been helpful with straightening out the fuel and ignition system issues I had when I first bought this thing. Like I said, it wasn't "supposed" to be a project car and the motor was claimed to be a stock original, not a 0.030" over POS rebuild. I am quite sure it was put back together with junk, scored crank, as some of scored journals have unscored bearings. Finding the original lower timing gear on the crank was pathetic. The cross hatch from honing is more like 5 degrees, not 45 deg. Whoever "rebuilt" this engine with Summit parts should have his tools confiscated.

I am located in Fort Worth, TX.

I not sure my block is useable, as the lower end of one of the bores looks thin. I am also not sure the scored crank is savable without breaking out the micrometers. But, I am budgeting for a new forged crank in case mine is hosed. I have been looking at GN1's rotating assemblies, but they seem aimed at race cars.

I was assuming there was enough meat on the top deck of the block for extra head bolts, but apparently this is incorrect by what you guys are saying. The TA SI aluminum heads are pretty reasonable, starting at $1,370 for a bare set. Valve size increased to 1.94/1.6 from 1.71/1.5 and the flow is improved, especially on the intake.

If my block is hosed, how hard is it to find 109 blocks? The TA aluminum block is sweet, but serious overkill for a street cruiser at moderate power levels.

As for pistons, I was going to stay with 8:1 compression, but the engine builder I am talking with (race motor builder in NY) thought that was low, and I should consider going to 8.5 or 9:1. Forged vs. Cast? Always thought forged are stronger and light, but cast are usually more durable. GN1 offers forged, and TA offers cast, or custom order pistons it seems.

I am keeping the stock turbo because I just bought the darn thing and car hasn't left the garage with it on yet.
I already installed new AC Delco Injectors that I now have to dig up the spec on, but they were rated to flow more than stock, just not sure how much more.
Fuel pump was rated for 20% over stock flow also, but when the original died, I wasn't planning to modify the car
I want to do a hydraulic roller, haven't spec'd the profile yet. I want a smooth idle though, as running the AC in TX summers is a requirement.
I have a new timing cover, oil pump head, and gears.

Reggie,
I will check out "Turbotweek" for a chip, as the $2,500 standalone computer seems a bit much for street cruiser.
How bad are the stock rods as far as how much HP can they handle? I should probably build a bottom end that can handle a larger turbo in the future in case I get frisky later on.
I hope I can keep the stock valve covers, but roller rockers are obviously desirable. If not, I guess I will try to find stock looking ones.

And once I get the engine rebuild under way, the Turbo 200 will get sent out for the strength updates.

Thanks for all the feedback guys, and sorry for some of the "nube" questions. Despite being 55, this is my first time rebuilding a GN.

-Joe Rainville,
Fort Worth, TX

 

[THensley]

Your in Texes Zimmerman and TA are in Phoenix both build good Buick stuff GN1 has good stuff I will always be a repeat customer to Full Throttle.
I think that have the largest selection of roller cams. about to have a good pissing match to what cam you should use. I do like there rotating ass as will but GN1 .RJC has a spacer for the OE valve cover to run roller rockers. Ta will send you all the things you need for there heads. Aluminum heads you should be 9.5 - 10:1 9;1 Min.
Stock rods have not been found as a week point, But if you need crank and pistons might put new rods between them