Happy Thanksgiving all!

After buying my 1987 Iroc Convertible 12 years ago I am finally able to start property restoring it. I want to keep it as close to Matching numbers while updating as much as I can to maximize MPG while adding some power.

After a LOT of thought, I have decided to keep the Factory 305 TPI. I love the look of it and would rather not have to worry about storing the 305 somewhere in case down the road someone wants to put the original motor back in it.

So, I WILL NOT BE SWAPPING OUT THE 305! Just to keep everyone from suggesting a 350.

This will mostly be my daily driver minus bad weather. I don't care about racing it, but would like to surprise anyone who might want to show off their tiny import.

My plan is to lighten it as much as possible and try to sqeeze as much power out of my little 305 as I can.

My thoughts for losing weight:
K member
A arms
Coil overs? Worth the money to do the swap?
Aluminum heads
Thinking EGR system delete? No emissions where I am
All new sway bars, control arms, bushings, most everything to do with the front and rear suspension needs replacing/updating.
Is an aftermarket Torque arm worth the investment?
And last thing I can think of the Aluminum driveshaft

I will be putting LS1 big brake upgrade kit on the front and better rotors and pads on the rear disks with upgraded brake lines. If I'm not mistaken the 87 rear disks can be upgraded/improved with a later model 3rd gen disk?

Now my biggest question is the engine. I am aiming for the best MPG possible while slightly increasing power/performance.


My car came with the more aggressive factory cam so keeping it for the moment (depending on condition). Any suggestions if it's gone bad sitting in the engine for 12 years?

If the cam is still good, would different lifters help? Or just better stock ratio lifters?

I have a line on a set of Corvette Aluminum heads. They have been cleaned, milled .020, valve guides milled, new valve stem seals installed, LT4 Hotcam valvesprings and LT4 lightweight retainers. Should give me a 55-56cc combustion champer. Is $600 a good price for these heads?

I am not sure of the condition of the internals of the engine as it has not run it at least 12 years. I know it's practically pointless but thinking I may go ahead and have the block bored out a bit so I have a fresh, brand new engine.

It's been a long time....What type of pistons should I be looking for? Or would be best for the set up I'm looking to do.

Of course I"m looking to upgrade the ignition system. What would be the best?

Same for the injectors, I am going to need new ones I'm sure or have the ones I have rebuilt. I believe the factory ones are 19lbs?

Some other improvesments on the engine side:
Large tube TPI runners
Bored out TB 58mm (if I remember correctly)
I believe I have a ported stock intake manifold and plenum
Planning to have everything port matched
Ram air system built behind fog lights with K&N filters
Underdrive pulleys

Heads will be ported and polished and what ever yall think will help it run the most efficiently.

I will be keeping the A/C and power steering.

This car has been a dream of mine for over a decade and I want to do it right the first time. Any help and suggestions will be appriciated and once I get my phone fixed I'll start posting some pics of the car as is and as it progresses.

Thanks!

 

Well, I won't be able to help w/everything, but I'll answer what I can, to the best of my ability!

If you already have a ported intake manifold and plenum, that's a good start. Upgrading the runners is a must. I would upgrade the entire exhaust system, from the headers to the tips before messing with the heads/cam. Ditching the restrictive factory exhaust and TPI parts, and getting the engine to breathe freely is the best place to start. If you still want more power after that, then consider porting the heads/a head swap, and a cam upgrade. Upgraded fuel injectors and a tune would be a good idea as well.

The factory T5 is an area that may need attention too, depending on your driving style (especially w/a modded engine). There are aftermarket parts available to upgrade the world-class version of the T5 (In '88-'92 year F-bodies), but I'm not sure about earlier versions. Some people swap over to a T56 or TKO 500/600, but either option is an expensive endeavor. T5's aren't known for being the strongest transmissions, but the main problem is the factory case that houses all of the internals - It's weak, and can flex under heavy loads, causing gears to misalign, and fail. On the flip side, T5s can be found for pretty cheap in boneyards/on craigslist.

Suspension-wise, the first thing I would spring for are some subframe connectors, especially if you're gonna be modding the engine for more power. Well, that, and replacing any worn out suspension parts. I wouldn't go too crazy w/stuff like tubular k-members or coilovers for a non-track car, but that's just me.

LS1 brakes are a good upgrade, and actually a cheaper route to go than the good stuff that came on the later third gens (The 1LE system), as the calipers can get spendy. It's up to you if you want to keep more third-gen era stuff on your car, or save a few bucks, and get even better braking performance (Although either option will be plenty adequate).

Good luck, and have fun!

 

Cat back exhaust...........check
sub frame connectors.....check
Hi flow cat...................check
headers and y pipe........check

Forgot to mention those but good suggestions.

Yeah, the T5 has me worried. Was going to ask if they had stronger upgrade kits for the factory unit. May have to look into getting a World Class.

Thanks for the suggestions

 

Np.

And about the T-5 - If there isn't anything available part-wise for the older versions, a world-class one can be found fairly cheap (I see used, working units for $200-300). There are a number of upgrade parts available for the WC versions, but do bear in mind, it's not worth it to go too crazy w/upgrades, because for the cost of a fully upgraded T5 (gears, case, mainshaft, etc. - The upgraded gears themselves being the most expensive part), you can switch to a TKO 500 or 600, with proven toughness. And upgraded gears in a stock main case is pointless, as they will still eventually fail due to case flex under load.

I'm planning to go w/a cluster support plate, an upgraded case (G-Force sells the only one I know of), and a better clutch w/my T5 (But keeping stock gears). Get an aftermarket shifter too, they're much better than the sloppy factory units. Pro 5.0 is a popular choice, although I enjoyed my Hurst Billet Plus while I had my 'bird on the road.

 

87irocvert and I seem like a kindred spirit. I want to attack IROC-Z performance the same way that 87irocvert does. I have a complete stock 89 IROC-Z with about 15K original miles. I would like to increase performance without a drastic change in overall stock appearance. I plan to work on the exhaust next year and work my way from there. Any comments on manufacturers, etc. would be appreciated. I'm not a mechanic (I'll be the first to state that) so your advice is greatly appreciated. Thanks!

 

The single biggest seat of the pants and bang for the buck performance boost that you will get out of these cars is a rear gear swap. Start there first and then see if you want to keep increasing performance. As someone who has done all the 305 TPI performance mods (heads, cam, bigger TPI, ETC) the gears were the most impressive boost. And if you dont have the ability to tune the ECU, or at least have someone who can tune it for you, Dont even think of doing any major engine mods you will be wasting your money.

 

Keep the EGR if you are concerned about mileage. You'll lose about 10% without it.