I have a 1992 Firebird convertible with 175,000 miles and i was wondering if it would be feasible to rebuild the engine to stock specs and get a new transmission? How much would I have invested in this? I will do the work myself, my uncle will rebuild the engine at no cost. But will it be worth it?

 

If your uncle is in the auto repair scene, he should know of a good tranny guy that would do a good rebuild of your 700R4 'on the side' - I had mine rebuilt really strong several years ago for an unbelievable $500 (most rebuilds are closer to $1200).

Opinions vary on top end rebuilds, and I guess you'd have to kinda inspect the bottom end to make a final decision - but alot of times you can do a top-end rebuild and really wake a motor up without going into the block. If there's no knocking, you have a decent history of the maintenance of the car (oil changes especially), your bottom end might be fine ( can't believe I actually said that to another guy!). You could inexpensively redo the top end (heads) and do it without having the car out of commission by getting a used set of heads and having them worked over, and then just swapping.

The TBI cars have really crappy heads that are really restrictive. But the carbed cars had much better heads (casting #416). If you were NOT planning to do any other engine mods, you could probably get away with a #416 head swap without any chip reprogramming. You could hunt down a pair and take them to machine shop for a 3 angle valve job and valve stem seal replacement, and have the shop look over the springs valves and such to see if anything needs replaced. That should be under $400 at a machine shop (again the uncle might have a bud in the biz to lower cost). Then you could just swap heads in a day.

And if you were feeling adventurous, you could do a little porting, polishing, and gasket matching to them - all it takes is an electric die grinder and some carbide cutters (about $60) - there's several threads here about porting/polishing these heads. I did a set a few years back, it wasn't hard and I'd neve done anything like that before - but I followed the threads here about it and they turned out nice. But again, you don't want to go too far or your TBI chip will choke on all the new airflow and the car won't run very well. I'd think that would wake up that sleepy 305 and all for under $600!

Anyway - something to think about. Not sure I'd personally rebuild a 305 bottom end when the rebuild cost is the same for a 350 and they are easily obtained and cheap. I believe you can transplant a 350 into your car using 350 injectors, a 350 chip (from a 350TBI Caprice), and a 350 knock sensor - if I had to do a bottom end rebuild I think I'd grab a 350, rebuild it's bottom end, and swap that in.

My car was a 305 TBI and I swapped to an old 'nothing special' 350 I picked up for $600 carb to pan - but here I can get away with a carb swap. It's amazing how much difference there is with that old 350 in there - my car is fun to drive now! And I didn't even rebuild it - just swapped it in.

Good luck with whatever you choose, and keep us updated!

 

Im not against the head work your talking about but I wanna stay with the fuel economy im getting now 23-25 mpg. What would be a good set of heads for my car?

 

Your 700R4 with the overdrive, along with your stock 2.73 rear gears are going to keep your mileage good anyway (I mean to a degree). Those #416 heads were on the carbed 305's, I wouldn't think you'd lose but maybe just a few MPG but I think you'd definitely notice a little pep in your step. My 305 TBI was getting a few more MPG's than yours, and even after I did LT1 cam, carb intake, larger valves, headers, gutted cat, and that headwork on those #416's, I was still getting just slightly lower than you are now (about 22mpg). My current carbed 350 still gets 17mpg, and I always have my foot in her!

Again - I'm certainly no expert - just telling you my idea and what I have done in the past. Your comfort level, available downtime, and wallet will dictate your best course of action. I guess my main points were 1) (to me) it's kind of cash wasted rebuilding a 305 bottom, and 2) you could rebuild heads off the car cheaply, swap them out in a day, and freshen up your bottom without alot of downtime.

I'll be interested in what you decide and how it goes!