Yeret

Hey, all! First time here, so I'll poke around and dig up what I need to know but I figured to get some pointers on general info of the LB9 engine. So, long story short, I scored a '92 Pontiac Trans AM GTA for damn near nothing a few weeks back. Either the engine's seized or the starter's messed up because it won't crank. Starter seems to draw power but no crank. The oil was over a quart low and black as motor oil can get (yeesh). I'm hoping that a new starter will get her whirling and then it's all hoping that it doesn't knock. I've got preps in place to rebuild the engine if need be but in any case, I'm curious to know the general ins and outs of the Tuned Port engines. Weaknesses, ease of modifying, popular mods. I'm especially curious of more "involved" stuff to do if I do need to yank the engine. Thanks in advance!

Vader

Weaknesses are that same for any other SBC. Mechanically, the design is pretty sound. Wear and neglect are its main weaknesses.

It's a 305 so there are a few differences between that and a 4" bore SBC. Head chambers would necessarily be smaller, and thus the valves are limited in practical size. It will produce reasonably good torque numbers, especially with the TPI system, which will favorably compare to a 350.

If it were my project, I would attempt to get it running, assess the overall condition, then determine the best course of action. If minor repairs were necessary, a little research into potential upgrades associated with the repairs would be prudent. If major rework is indicated, I would be tempted to prepare a fresh 350 or other 4" bore engine in the stand then prepare for an exchange.

Before getting too much capital invested, it may be worthwhile to remove the spark plugs, attempt to move the engine by hand, and determine if it is actually locked or simply stubborn. If a starter is necessary, a later version reduction gear starter may be a good choice for a multitude of reasons.

Yeret

Thanks for the input. As a Mopar guy, I'm a bit aghast at how little respect the 318 gets despite plenty of people building some pretty badass ones and the Chevy 305 seems much the same. Is it reasonable to push these engines to 300 horsepower with the TPI without having to run ridiculously high RPMs or just generally getting into high dollar stuff? I'm well aware that a 305 is going to cost the same, if not more, to build up than a 350 and the 350, with it's larger bore, is simply going to make more power per dollar. But, hey, I've already got the engine and I'm always for working with what you got, even if it's not the best route. I guess I'm just weird like that, LOL.

Also, I know different manufacturers measure their figures differently. From what I've read, the 305 Tuned Port in my car should be around 205 horsepower. Is this crank or wheel horsepower?

chazman

iTrader: (4)

At the flywheel.

The big bottle neck in your particular car is the exhaust. It uses the smaller 2" exhaust manifolds and 2.25" intermediate pipe from the L03 engine. On the plus side, '90-'92 LB9s all come with the preferred L98 cam. Even the factory N10, dual cat exhaust adds 25 horsepower to your engine.

Yeret

Ah, so it's got the same cam as the 350? That's neat, so what would be a baseline cam for the larger engine functions as an "upgrade" on the smaller engine. Just like how the old 383 used the same camshaft as the 440.

Does anyone have the mechanical dimensions/specs of the engine? Stuff like combustion chamber volume, piston volume, cam specs. I already know the bore, stroke and rod length but seem to be having difficulty finding the numbers on the internal stuff of a factory Tuned Port.

ray jr

iTrader: (2)

the cc on your heads should be 58cc and if you got the l98 cam it should be
.413-.428 lift 202-207 duration

Yeret

Thanks for the info. One more thing. I started looking at mini starters as they seem to be a sweet upgrade from OEM (smaller size AND more power!). However, I noticed that there are two bolt patterns for these: inline and staggered. Which pattern do you think I'm most likely to have?

Tuned Performance

iTrader: (92)

Straight across, a lt1 starter is a good choice for stock replacement. Look on amazon or RockAuto.com . You will need shorter bolts though.

Yeret

Well that's mighty handy. Looks like I can mail order one for $80-90. Smaller size, higher power and considering the local O'Reilly's is getting about a hundred for a remanned old-style unit, I'd say it's a no-brainer!

You say I'll need shorter bolts. Would I need to nab a pair meant for an LT1?

Tuned Performance

iTrader: (92)

Correct, or I saw a starter on amazon for $58-59 bucks that came with the bolts.

BOTTLEDZ28

iTrader: (9)

shorter bolts? I am running a starter from a 1996 Corvette (LT1) and I reused my OEM bolts and everything bolted up just fine. How much shorter are the " correct" bolts?

Tuned Performance

iTrader: (92)

https://www.thirdgen.org/forums/tech...l31-block.html

BOTTLEDZ28

iTrader: (9)

That must be a 153 tooth L31 engine considering he has the straight bolt pattern on it. My 98 Tahoe has a staggered bolt pattern and I am also running a mini starter in that and reused my OEM bolts.

My 91 Z has the LT1 starter from a 1996 Corvette with the straight bolt pattern and I was able to resuse the OEM bolts with no issues.

Apparently, the shorter bolts needed for certain applications is part # 12338064


This is the LT1 starter in my car

Tuned Performance

iTrader: (92)

Must be for certain blocks that might not be tapped as deep.
That’s the vette lt1 starter the shorter bolts are for the f body lt1 starter

Yeret

What do you guys recommend for spark plugs? No idea when these were last done so I'm going to plan on these. Awful damned tight under the hood and the job appears to be a PITA, so I wanna choose right the first time!

ray jr

iTrader: (2)

ac delco plugs from your local parts store will do just fine

Yeret

Yeah, I kinda figured AC Delco would be the way to go but I probably should have been more specific. Should I go with a single platinum or double platinum or just run plain ole coppers? I'm certain OEM doesn't call for iridium. The problem with the local O'Reilly's is they have all styles of their offered brands, including AC Delco, and they always try to pitch iridium, probably because they're expensive and it means a higher commission for the clerk if they sell 'em.

I'm a little picky with plugs because I have read way too many stories of people having misfiring problems in their Magnum (Dodge) engines after screwing in a set of precious metal plugs. The OEM coils on those engines are relatively "cool" and really don't work well with the higher resistance of platty-tipped plugs. I've only ever run copper-tip plugs in mine and have never had a problem. Basically, since the intention is to keep the engine stock with maybe a few bolt-ons, I just want to avoid creating misfire problems by using the wrong plugs.

vinny R

i used AC/Delco Rapidfire single platinum plugs I believe it was #2. No misfire and the engine runs really smooth.

Yeret

Okay, so I replaced the starter, which was actually rather easy once pops and I got the front up propped up just several inches. Nothing but a loud "chunk." Charged the battery, which turned out to be weak. Electronics seemed a lot happier but turning the key still produced nothing but a "chunk." Took the battery in, had it load tested, tested good. Bought new terminal screws since the hot was kinda rusty. Brought everything back home, stuck it on the charger a while longer, threw it back in, scuffed up the cable connectors since the hot was a little gunky. Still nothing but a "chunk." Checked all connections, they look fine to me.

Kinda getting the jist that the engine's just plain stuck. Thinking about yanking the plugs tomorrow and blasting the cylinders with penetrating oil. Hell, if I can just get the engine to loosen up and fire, I can at least move the car down to the barn and prepare for removing it.