94 4.3 CPI to 92 4.3 TBI

[vallesfj]

Recently threw a rod out the oil pan on my 92 4.3 TBI. I’m on a tight budget and have the opportunity to buy a low mileage 94-95 4.3 CPI. Wondering if I can swap intakes and install engine ? Are the bolts holes the same for alternator and ac brackets. I’ve seen some engines have the alternator on the driver or passenger side

 

[Schurkey]

Use your accessory drive system, TBI intake and sensors, etc with the "new-to-you" long-block.

I don't know if the CFI 4.3L in those years used a crank sensor. If so, just leave it disconnected. The CFI 4.3L was "almost" a '96-up Vortec-style "spider" injection system, but batch-fire instead of individual, sequential-fire injection.

GM made a million changes to the 4.3L including adding a balance shaft at some point. I don't know all the details.

 

[vallesfj]

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[vallesfj]

That’s the engine I’m looking at

 

[98 Nitro]

Heads are better on the 94 engine if original.

 

[SAATR]

Two knock sensors? Interesting.

I'd be tempted to keep the CPI system and run that. Always thought those intakes were really cool looking, though I'm not sure if there is any performance benefit.

Edit: Evidently those L35's were rated at 200hp versus the 155 or 160 that the original 4.3 was rated for. If it's more complete than the pictures suggest, it might be worth the effort. The compression ratio IS higher than your original engine, and it supposedly has a more aggressive cam, so bear that in mind.

 

[Schurkey]

Good luck finding a "spider" injection unit for that. The sequential "Vortec" units are available, but my friend with the older, batch-fire job couldn't get a suitable replacement.

 

[L31MaxExpress]

That setup might require a later model 4.3 TBI intake manifold. Been a number of years, but I tried to fit an earlier Q-Jet manifold to a 4.3L and the balance shaft ran into the manifold casting. IIRC the engine was a 95 CPI, it had the plastic valve covers stamped Vortec. I ended up having to buy a used marine Q-Jet manifold for a boat application that had a balance shaft equipped engine. So watch for balance shaft to manifold clearence. I would also assume that it needs larger injectors, just some rough napkin type calculation says 61 lb/hr 350 units. The stock everyday 4.3L TBI injectors are 46 lb/hr and the B vin HO 4.3 in the 91-92 Astro that had the CPI cam and larger exhaust system but kept the swirl port LB4 heads used the 55 lb/hr 305 injectors. Going from 150 hp to 200 hp is roughly 28% increase. That is roughly the same increase that the stock 200-210 HP TBI 350 has. 46 lb/hr to 61 lb/hr is also 28%. Kind of like GM engineers scaled the fuel system up proportionally from the 1985 4.3L TBI to use on the 350 TBI when it came out in 1987. The CPI 4.3L also had the timing advance bumped up a bit compared to the swirl port head 4.3L. I would start with 350 injectors and the base/initial timing set about 6°. I imagine it will run well, better than the stock TBI 4.3L ever did anyway.

 

[L31MaxExpress]

Two knock sensors? Interesting.

I'd be tempted to keep the CPI system and run that. Always thought those intakes were really cool looking, though I'm not sure if there is any performance benefit.

Edit: Evidently those L35's were rated at 200hp versus the 155 or 160 that the original 4.3 was rated for. If it's more complete than the pictures suggest, it might be worth the effort. The compression ratio IS higher than your original engine, and it supposedly has a more aggressive cam, so bear that in mind.

Some 4.3Ls, some LT1s and some 454s all had dual knock sensors well before the LS came out. The older ones are a bit weird. The knock sensors in those applications have 2x the normal resistance values of other GM knock sensors. They are then wired in parallel on the same knock circuit into the PCM. You can keep a single sensor in the stock location by changing the knock sensor in the block to a sensor compatible with the single sensor setup or leave both sensors from the dual sensor setup and wire them in parallel into the old knock sensor wire. Either setup has the same resistance value and the ESC system will function normally. The dual sensors are better IMO, but more of a pain because you have more wiring and 2 sensors. If only 1 sensor fails, it throws codes and retards the timing in failsafe mode.

 

[L31MaxExpress]

Use your accessory drive system, TBI intake and sensors, etc with the "new-to-you" long-block.

I don't know if the CFI 4.3L in those years used a crank sensor. If so, just leave it disconnected. The CFI 4.3L was "almost" a '96-up Vortec-style "spider" injection system, but batch-fire instead of individual, sequential-fire injection.

GM made a million changes to the 4.3L including adding a balance shaft at some point. I don't know all the details.

GM actually started using the platic timing cover, crank reluctor wheel, crank sensor and crab style Vortec distributor as well as the black box style underhood PCM in late 94ish on some of the 4.3L CPIs and TBIs. I have worked on a Bravada that had the CPI and a S10 that had the TBI engine that were both built in late 94 with that setup. Those had the goofy OBD2 port that a regular OBD2 scanner will not hook up to. My grandmother had a 1995 Achieva with the 3100 that had that same dumb OBD2 port setup. Such a weird transitional era. Then get into 1996-1998 and some vehicles were still OBD1. I ran across numerous 1996-1998 vehicles that were not OBD2 complient when the state of Texas smog machine thought they should have been. Good old 1996 G30 350 TBI, 1997 P30 454 TBI, 96 F350 460, 1998 Kodiak 427 TBI, none of those were OBD2.