I have an 85 coupe with loads of problems so rather than try to address problems one at a time I plan on doing the whole car at once, almost a frame off job. It is a long term project that is currently in the planning budgeting phase. The first thing on the list is the drivetrain. I would like to get 400+ hp, ft/lb out of the engine. Since it needs to be rebuilt anyway the sky is the limit(or wallet). Should I just send the block out to a shop to be rebuilt(phoenixengine.com has some very reasonably priced services for their hp claims), or buy a crate motor?
Second, and yes, this is a serious question, how bad of an idea is it to trash the computer totally and build it like an old school pre-ecu muscle car? I understand the gauges et. al. would have to be replaced with custom parts and I am willing to do the work there, but lets face it you wouldn't use a 25 year old computer at home so why use one in your car? Technology has advanced so far since then that newer designed engine components unhindered by having to fit into a basically obsolete system might have the edge. Then a gain I have been wrong before...

 

Pick your poison
http://forums.corvetteforum.com/c4-t...m-control.html
http://forums.corvetteforum.com/c4-t...ical-swap.html
http://forums.corvetteforum.com/c4-t...lp-please.html
http://forums.corvetteforum.com/c4-t...i-to-carb.html

http://forums.corvetteforum.com/c4-t...gine-over.html
http://forums.corvetteforum.com/c4-t...-c4-vette.html
http://forums.corvetteforum.com/c4-t...ld-vs-zz4.html
http://forums.corvetteforum.com/c4-t...-on-c-4-a.html

 

Biggest problem with the 85 is getting a chip burn for your mods,nobody wants to do them,Switching to a carb is not that bad of an idea,you will have to change intake anyway, TPI will be hard to get 400+ hp.Mini Ram or Lt1 intake conversion will work if you want to stay efi.Look at a 383 to make that kind of power.

 

I would be really tempted to go with a carbed crate engine if they will take your engine in exchange. Keep all the TPI stuff, wiring harness, and ECM just in case you don't like the carb. Buy the strongest engine your budget allows.

 

I would go with a crate stroker engine, some kind of aftermarket intake and have Jesse Azzato, http://www.azzatochips.com/AzzatoChips/Testimonials.htm
do your chip for you. I have one of his chips in my '85 and although it isn't making the kind of power you are looking at it runs real strong. If you are going to drive the car then I would stay with the EFI simply for the mileage it can give. If it's going to be a race car only then I guess I would carb it, and then you wouldn't need the chip.
The way I see it, getting the chip done would be much easier than converting the gauges, fuel, and ignition system. JMO

 

Lots of people have went to a carb engine. I've seen lots of them on ebay. I've seen 3 at car cruises over the years. 95% of what I seen was done to 84s. And I think it's a good idea getting rid of the computer (but not for me and my 85). Anyway, what I don't like is the replacement gauges I've seen in these cars. I never seen any that looked nice.

 

Midnight is on the right track. Have the engine built as a 383, Swap out the ECM for an 86-89 and either a miniram or an LTx intake with AFR heads. Be aware you are getting into some serious coin here. Transmission will require some serious rebuild,plan on a Dana 44 rear end and seriously upgraded brakes. Add new wider wheels and tires to that list. Total bill will very likely be more than the cost of a reasonably good C5. With all that said, you can do some upgrades to the 85 and have a car that is a blast to drive but not cost an arm and a leg.

 

All of this will need to be done anyway, especially looking for 400hp. Regardless the tranny will need a rebuild but since I'm doing it I might as well do it right and convert to a tremec or other quality 5 or 6 speed. wheels need replacing anyway, someone down the line before I bought the car decided to take the vette rims off and put on epsilon two piece gold chrome combo rims. But speaking of serious coin buying a whole new ECM doesn't exactly sound cheap. This would require an entire rewire at least for the engine compartment, a lot of headache could be avoided by pulling the old system and going to the carb.

 

Best cost alternative, make your 350 a 383, but aluminum heads, and have Jims Performance re-pin your harness for a 86-89 ecm or a speed density if you like.
($150)

www.jimsperformance.com

 

You can remove the harness in 30 minutes and it will come back form Jim after a full re-pin and inspection, major peace of mind.

 

I will be driving the car, but not on a regular basis. I am considering a lot of custom mods to the interior/exterior that would make driving it very often impossible any way. I am shooting for a show/track thats street legal car if that even makes sense. Either way good mileage is not my goal, pure fun is. As far as more work is concerned, yes but it also gives more freedom. I wanted to get rid of the atari gauges anyway but I haven't found any replacement digital gauges. Look I love my car and have since I was 21, but lets face the interior on the 85's is hideous! It might however be less work than replacing the computer with another system since many of those things are in need/wat of replacing anyway.

 

Thanks LD85 I will look into that

 

I took my 85 harness and unwrapped it, pulled it thru the firewall, sent it to Jim,

he found an intermittent ground problem that I would NEVER have found,,, he re taped it the harenss and it looks like new,

replaced broken connectors, took wires out that were not needed, upgraded the wiring to eliminate the 85 MAF burnoff which is discontinued and made the harness to be used with common 86-89 relays.

 

Thanks to all who posted I appreciate it. Lots to think about still but I think I will go carbed and cut out switching out efi systems and old ecms I do appreciate the advice from everyone its good to know there are lots of people who have done what I would like to- This sight is the s!#$!

 

If you've got the coin, 2 words: LS1 Swap

 

The ECM swap can be done for less than $100.00. Takes about an hour to do. From 85 to 86-89 is a snap.

 

We got 400hp out of a tpi intake before heres what I can remember...
original tpi engine, +.30
erson roller cam {I can probably find out the part # if you like, I remember we ended up useing 1.5 and 1.7 ratio roller rockers}
scat stroker crank {3.75},
6.0" rods,
speed pro pistons {120 dome specifically made for 6" rod and 383 stroker},
AFR aluminum heads
for an intake we used the stock tpi plenom {w/bbk throttle body} with slp runners and an edelbrock base, after about 30 hours of opening everything up and matching it all together we had it chrome plated and they lost one of our SLP runners {so we had to do it all over again, but they chromed it for free and bought the new runner}..
We used accel injectors, a granatelli adjustable MAF {this wasnt a SD motor}, and had a guy from ebay do the ecm for us, the car made a ton of low end torque and a little over 400hp....
I remember the total cost was around $4500 after materials and machine work, and after it was all in we tryed to use the stock ignition system but in the end wound up useing a complete MSD setup with a 6am pro distributor ect......
IMO the low end torque from the long tubes is what makes the TPI better than any other sBC injection setup, while they dont flow as well as an LT1 or a miniram Im sure you can get around 500hp out of one and for the street you dont need much more than that...

 

When it comes to the engine i would just get it rebuilt. Since you only live in austin i would go down to san antonio and have it built by Mission Performance. They build high quality high performance engines.

 

ok that isn't bad at all. Waht about speed density conversion is it as simple? I'm reconsidering...

 

Was this on the stock 85 TPI or what work was done to it? I gotta be honest I didn't think that kind of hp was possible with the stock tpi. I didn't think the airflow was sufficient.