86 305TPI IROC engine questions


Old 01-11-02, 11:37 AM
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86 305TPI IROC engine questions

Im restoring an 86 IROC 305 and wanted some advice. I found a good source for used engines and thought about replacing the 305 with a 350. To my suprise the stock 350 engine for this model only provides a marginal increase in HP. With that in mind i will locate a good used one or rebuild my 305. The engine has 115,000 miles and smokes a little. What type rebuild should i do here? all stock parts or after market upgrade? i would like a better cam with a little more "pep", but not anything radical. What else could i do to boost up performance a little? my budget is limited so anything extreme not practical. thanks. jwd
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Old 01-11-02, 02:51 PM
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You will have to pull the engine and disassemble it to tell what kind of rebuild it will need. Sometimes a re-ring job will freshen it up, along with bearings, but its not too often you find an engine that will not need at least a little machining. 115k is not too bad on the ol 305's, but in a car like that it may have seen a rough life. I like the 305, but it's hard to beat a 350 for performance. I get plenty of power from my 305 and better gas mileage than most any 350 would. You could boost power a little with a mild cam, depending on what you have to work with, and what you want from it. Edelbrock has performance packages that have dyno-matched cam, intake, heads, etc... Go to edelbrock.com and see what there is. You will need to account for your rear-end ratio, your fuel system capabilities, your heads..if you plan to reuse them, and your wallet. You can squeeze a lot of power from a 305, but it's not the ideal engine to start with if you have performance in mind.
Old 01-13-02, 05:32 AM
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There was no 350 in 1986 in an F body like this. The L98 350 used in this generation starts in 1987. About 225 hp stock. It's a decent engine to work with.

Go for a GM ZZ4 crate motor from www.gmpartsdirect.com. They are likely to be the best as a "Drop in" replacement.

At the same time, you should upgrade the cooling system, brakes and suspension accordingly if going to a 350. If you browse the Camaro and Firebird newsgroup, (I do, as I own 2 Trans Ams), there's a wealth of knowledge in there and many guys have done it. Check it out.

Souping up a 305, (I'm assuming you have the tuned port 305 and not the carbed one) is a collosal waste of time. Can things be done to it? Sure, but again, a 350 is a better performance base to start with. Time after time, a 350 will smoke you at the stoplight and he's probably put less money overall in his package than you do for the 305 .

Me personally? I would find a 1987 and up 350 that is stock and in need of work. This way whatever you do is original looking and reliable, because it is designed for that engine. I'm a stickler for "looks original but performs better"

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