I bought an 89 IROC a few months ago, and have slowly been getting things to stop leaking (valve covers, intake manifold, rear main seal... the list goes on). The previous owner removed the TPI from the engine, and claims to have replaced the stock 305 (it's manual) with a 350 out of something. The engine is now carburetted. I got the car dyno'd the other day, and quite frankly I almost cried. At 2750 rpm, I'm making 280 torque and at around 4000 rpm i'm making (tear) 180 hp. Here's my set up, and I'm hoping someone can shed some light on something.

Supposedly a 350 with the stock exhaust manifold, torker 2 intake w/edelbrock performer 600 electric choke. I have the stock distributor with points... and frankly it's all a big mess.

Here are my questions-
Where is the block ID and is it possible to see without taking the engine out (I'm curious if it really is a 350 or the same 305 without the TPI)? I want to see if I got screwed.

I'm looking for a new top end, what's a good combo to make around 350whp? Can I do it for less than or around 2K? I can do the work myself.

I realize that the stock exhaust manifold is terrible, but is it as bad as my dyno run says?

My tachometer is apparently off by a lot. During the dyno run I ran my engine to 6500 rpm, but the dyno only read it as 4200 rpm. Any idea what that is all about? I got my distributor replaced at a local garage (couldn't wait) and just don't know what is wrong.

Lastly, is it possible to put a harmonic balancer on wrong? I can't set my timing with a light because I can't see the mark on the balancer AT ALL. Just curious if it's possible that it was put on like... 180 degrees off.

Thanks for reading, I'm hoping to get this all figured out...

One last thing, I get around 14mpg mixed and 17mpg highway. Does that seem really low to anyone else? I just replaced my cat with a highflow magnaflow cat...

Just trying to figure everything out

 

Don't worry too much about the tach, ALL these cars have crappy tachs. Just use it as a reference point (ie, you now know that 4200 = 6500 so at any given RPM it's off by about that percentage). If RPM is that important to you buy a small aftermarket tach and put it on your steering column (doesn't have to be a r!c3r style "Back To The Future" clock tower sized tach)

If it has points it's not the stock distributer.

Casting numbers for the block are on the back of the block stamped on the top of the bellhousing flange. You can see it if you climb up and shine a light down behind the motor on the driver side. It's also important to get the head casting numbers, this will tell us even more about your motor than the block number will. It's under either valve cover, give us the last 3 numbers and double check it because they can be deceiving.

Did the previous owner hack off the wiring harness? Are you looking to switch back to TPI?

The 180hp doesn't surprise me one bit, is that to the wheels or flywheel? Sounds like your typical haphazardly thrown together backyard carbed 350 swap. Probably came from a truck or something, assuming it's not still the original 305 in there. PS those numbers sound suspiciously close to what a stock 305 would pump out.

Got any pictures of it to show us?

As for your power goals, it sounds like you have a LOT you need to deal with before you can even think about putting down those kind of numbers. You need to get the car ready for a motor like that, this means making sure you have the fuel delivery to support it, suspension, gearing, and most importantly EXHAUST. I assume you don't have emissions testing? Those stock manifolds are killing you. Get a set of headers and a full 3" exhaust, make sure your engine is all tuned up, make sure your suspension isn't ragged out (if it's original, it is) then see where that gets ya. Even then I wouldn't want to just swap some top end parts and try to put those numbers down....those goals call for a built transmission, maybe a built up rear end, built up suspension, get some Sub Frame Connectors, and maybe a whole new engine from the bottom up. 2K may get you JUST the top end parts for 350WHP, but it wont get you what you need to properly support such a power level.

Mileage sounds about right, although I would think the highway would be slightly higher. My TBI 350 gets 27mpg on the highway, and there are plenty of people on here getting better than that. What transmission do you have? The highway MPG sounds like you don't have overdrive, so maybe he swapped in a TH350 transmission with the engine?

 

That's for sure. Would not surprise me one bit if it was a 305 as the two motors have the same block and are almost identical.

 

Thanks for the info, this is one of those things I'm trying to figure out as I go I guess...

A couple things. I have the spohn subframe connectors, although they are not yet in my car. That is going to be done mid summer. The transmission in the car right now is the Borg Warner 5 speed. I'm not sure if this is stock, but I have a 3.20-3.08 rear end (checked by spinning the tires, watching the drive shaft). I do not have to deal with emissions anymore because it is getting historic tags on it in the next... 6 months, and I don't have to have emissions done again after that. My shocks are definitely toast. I was looking to pick up a set up koni's, but quite frankly, that's a lot of money for shocks that I doubt I will ever use to their potential. I was considering Tokico Illumina shocks. They carry the same lifetime warranty as long as they are professionally installed. I'm planning on putting the moog stock replacement springs on too. I've already done the trans mount, and I plan on doing the motor mounts, sway bar bushings, torque arm bushings, and the whole deal with energy poly bushings. I have the time and money to make this car take the power, I just can't make it... and that is what is bothering me. I don't know how to make the power without spending a ton of money. That was the draw of a top end kit, I was just curious if that was a realisitic thing to do. And as for gas milage... I just don't know why it is so bad. Just lucky I guess. I'm pretty sure I have an overdrive because the 4th to fifth drop (based on the linearly incorrect tach) is about a 1:1 to .67:1 shift. Just thinking, that's all.

As for the wiring harness, it is all still in the engine compartment, although a few of the connectors were cut off by him for whatever reason. I wouldn't mind switching back to TPI except that I don't have the intake, or the ECU, or really anything. It would be cool if someone was trying to sell their entire TPI setup, because I could definitely be all over that. We'll see I guess.
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I can definitely take some pictures of the engine, although I'm not sure how much they will help. And in advance, yes the wiring everywhere is ridiculous. Whoever had their hands in the car last time was... awesome.

 

They don't have the "same" block, although they are externally identical.

350 RWHP is more than you think. You have to make around 425-450 flywheel to get there. Although that is possible, you aren't going to do it with stock exhaust manifolds and an Edelbrock carb and still be able to drive it on the street.

350 flywheel HP is a different matter, and headers, Vortec heads (upgraded) and intake, and something like a Comp XE274 cam, and a real carb will get you there - IF it is a 350.

If this is a T5 manual transmission, its lifespan will be very short behind an engine like that.

 

I guess the question I'm really trying to get is this...

I obviously don't know what displacement engine I have. So after I figure that out....

Is it a better idea to build it myself or pick a crate engine up and build off of that so I know it isn't beat to death? Will heads, a cam, intake and headers really get me to my 350 crank (good point above) hp or is it fighting a losing battle??

 

If you have a 350 (not hard to figure out by shining a light back behind the motor driver said as I said earlier) then heads/cam/intake package can easily get you a 350HP motor.

If you end up having a 305 then you should have a motor like what five7kid said above built, solid short block with vortec heads, cam, and a good carb etc etc. If driveability and fuel mileage is a concern then switching back to TPI is a viable option, but you should expect to spend an extra $300 - $500 to make that work, and stock TPI base wont work with Vortec heads so you'd need to use different heads or get a Vortec TPI base which is probably a couple hundred more, I don't know. You would also need to learn to do custom chip tuning so it's up to you if that is all worth it. Sticking with carb would allow you to put a bunch more money into the heads and cam and elsewhere.

 

i looked on the top of the block on the driver side

here are the numbers i've found

CPT40 or CFT40
and
57LG SGT

i assume the 57 means 5.7L? or i'm hoping anyway. as for the other numbers, the C?T40 came was closer to the top of the block (in the center) and the 57LG SGT was what i assume the block ID is... maybe? any insight would be great, thanks a lot!

 

here is a good thread on the thirdgen tach issue.

https://www.thirdgen.org/forums/elec...meter-fix.html