I purchased a 1988 caprice 305 5.0l vin code H from my grandfather 6 years ago. The vehicle has been stored until now and I am trying to get it running for a daily driver. I am in the process of replacing exhaust and have been debating whether to remove air and cat or replace it to stock. All this talk about different engines lo3 tbi or tpi has me so confused. Could anybody help me identify the engine I have and maybe suggest what mods will give me the best mileage?? Thank you very much, I hope this is posted in the correct place. I should mention I live in MN and no smog testing and can't remember in my 25 years of driving ever having a visual inspection. Thanks again!

 

I'm not sure where it would be at on an '88 Caprice, but you could start with the SPID (Service Parts ID) label. They are often in a glove box, on a spare tire cover, etc. It will be a note card sized decal with a lot of 3 digit RPO (Regular Production Option) codes on it.

An '88 may still have a carburetor. Assuming it's a sedan, it's likely a 305. If it's a wagon, it's likely and Olds 307. I don't know what engine RPOs were used in the B-bodies (Caprice/Parisienne), but in the F-bodies (Camaro/Firebird) they were LG4 (std. 305) and L69 (High Output 305).

If it has TBI (Throttle Body Injection), which looks sort of like a carb but uses two centrally located fuel injectors to spray the fuel into the intake manifold, those engines are RPO L03 (305) and LO5 (350). There was also a dual throttle body motor used in 1983 (?) that was RPO LU5 (305).

TPI (Tuned Port Injection), which uses 8 injectors, one at each intake port, was not used on the Caprice. In an F-body they are RPOs LB9 (305) and L98 (350).

If you can post a picture of the SPID label, or the engine itself, we'd know more.

 

Wow! Thank you Dave for all the good info, I am 95% sure it is the 4 barrel carburetor, I will pass by this evening and get a pic of the service card. If it is carb will the RPO be listed on this card for the engine? The reason I ask is I'm thinking of eliminating the air system and putting in a smog delete pulley but need to know which one to get. Would doing this affect mpg at all? As a daily drive and 78 miles round trip to work mileage is what I'm looking for, my grandfather always claimed 22-24 mpg with this car. Thanks again for your help!!

 

A properly working CCC Q-Jet is very hard to beat for MPG with a conservative driver.

I had a 1988 Cadillac Fleetwood Brogham. Basically a heavier stretched version of your car. Had 2.53 gears with a 200-4R and the high output 180 HP Vin "9" 307. It would pull down 25-27 mpg on long trips. 70 mph was practically off idle when in OD with the converter locked. I think it turned 1,400 rpm @ 70 mph and the 307 was happy doing it. However I can only imagine how gutless the 170 HP LG4 and 140 HP vin "Y" 307s must have been. The roller cam in the 307 actually had pretty decent specs and the swirl port heads gave it alot of low-end torque.

If you can get away with it for emissions reasons, it would be good to eliminate the air pump and injection manifolds. They really get in the way doing basic things like tune-ups and valve cover gaskets. Those manifolds are highly restrictive as is the factory Y-pipe and catalytic converter. I picked up a set of headers and fabricated a pair of 2.25" pipes to connect the header reducers to a dual in/single out catalytic converter and ran a 3" high flow RV muffler that had a 48" case. The car had plenty of room for the large round muffler. Was very quiet on the highway with that setup and gained a ton of power. I eventually swapped that car to a 403 from a GMC Motorhome. Had ALOT more power and still got mid 20s for MPG.

 

Thanks for all the info once again. What I was thinking was eliminating the a.i.r. Plugging the pipes on manifold and leaving egr there, then would put a pipe in where cat convertor is supposed to be. Would this be an ok option? I'm not by the car but I actually think the air pump had a seperate belt, if that's the case I could skip the smog delete pulley and just cut the belt. Any other thoughts?

 

How is this A Good Idea???

LEAVE IT ALONE. It doesn't hurt a thing. MIGHT MAYBE be costing you ½ HP; probably not even that.

If the car works, RESIST THE TEMPTATION to just arbitrarily hack on it.

Replace the cat. It's only like $100, it will cost you the same OR MORE to hack it off. Like the AIR, it costs you NOTHING in terms of performance or gas mileage, and might save your butt someday. (like it did mine when I got a new job and they transferred me to California...)

Your Caprice has the LG4 engine. Very common, there were literally MILLIONS of em made and put in EVERY chassis type; Camaro/Firebird, Monte Carlo and all its siblcngs, Caprice, etc. etc. etc. It's not TBI, not TPI, not L03 or L98 or LB9, not HO. Just the plain low-perf LG4. Which while not "high-perf", is still AHELLUVALOT better in its unmolested state, than about 95% of the HACK JOBS you see driving around with the same motor in them.

Don't hack it up. Make it right, and enjoy the benefits it will give you; which include, the lowest possible cost of operation.

Instead of HACKING on it, MAINTAIN it. Put a new fuel filter in it, new spark plugs, new dist cap & rotor, new brakes, new shocks, new fluids in the brakes engine trans & diff, get it aligned, put a set of quality tires on it, etc. etc. etc. etc. ALL far more likely to make the car BETTER than just HACKING on it.

 

Once again very great info an do thank you for that. I want to be very respectful when I say this but I do not believe this is a hack job. I have been a crane operator/truck driver for over 25 years and have noticed in this time manufacturers of equipment/vehicles either can make mistakes or in this case I believe the air system was the first attempt with emissions and a catylytic convertor. This does not by any means mean it is a hack job without it on the engine. The engine runs great without it. Personally I will eliminate the cat all together because I see no need for it but you are also suggesting by removing air and adding a high flow cat would also be a hack job. I once again thank you for the info and had a chance to take picture of service card and it is exactly what you said an lg4. But I still do not see why removing the air system would be a bad thing, one less thing to have to replace. By no means take this as wanting to argue you have shared your opinion and now I have shared mine. Thanks again.

 

Sometimes it doesn't matter what we "believe".

REALITY trumps "belief" in ALL circumstances. Most especially when dealing with the physical sensible visible world. Which of course, CARS are without question, members of.

Put aside a bunch of "believe" crap and put your considerable intellectual horsepower to work on "is".

Don't HACK on your car. There is NO benefit. Which is not "opinion"; it's FACT.

I guess you can tell I'm not very religious. I guess you can also tell, when I get into arguments with those who are, THEY LOSE. Every time. It's too easy. Like shooting fish in a barrel.

 

Sorry, no religion here either, not much of a believer in that. But reality is there was never an argument to win or lose you stated your "reality" and I have my opinion. Done.