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TPi to Carb Conversion - views?
http://classiccamaroclub.mfatw.com/viewtopic.php?f=5&t=4578		 Page 1 of 3
Author:  jon_buss [Sun Jul 12, 2015 12:15 pm ]
Post subject:  TPi to Carb Conversion - views?
I'm thinking about ripping the TPi off my car and replacing it with Edelbrock Performer intake with Holley carb and vacuum advance MSD distributor.

The main reason is I'm getting fed up with slightly odd issues on my car. Like slightly erratic throttle pickup when pulling away (like a small stutter / non smooth power delivery) plus when it's properly hot (after about 20 miles of driving) it won't rev past 4,500 rpm, it's like there is a rev limiter but only after driving a reasonable distance.

In the last year (to sort other problems) I've changed all eight injectors, fuel pump, fuel filter, air filter, TPS sensor, PCV valve, temperature sensor (both of them), dizzy cap, rotor, plugs, HT leads, ignition module. Air is removed as is the charcoal canister. I have a new O2 sensor to fit, which 'may' help and I'll try shortly. The only other thing I can think of is a bad chip / program or throttle body. But to buy these from the states will cost as much as all the parts needed to go over to a carb, so I'm starting to think I may as well ditch all the sensors / injection and make the leap, at least that's easier to fix and gives more power per dollar.

Any view / thoughts / experience on changing over to carb or what my problem may be with the current injection setup? Or can anyone provide a decent ECU with reprogram to take into account the exhaust / filter / air removal? Some time later in the future I will also change heads / cam as well.

The car is currently standard other than full twin exhaust, K&N filters and some kind of ECU flash by a previous bodger (sorry owner!). It's a 1991 5.7tpi.
Author:  ukzz4iroc [Mon Jul 13, 2015 11:23 am ]
Post subject:  Re: TPi to Carb Conversion - views?
Hi Jon,

It's all down to what you want the car for. If you are thinking of it as an investment (very unlikely for all of us :)) then I would say stay Tpi. If you want power and to use it, then carb wins. I've had both, from a ZZ4 with Holley 750 dp to my current LB9 with tpi. The Tpi's have really nobody knowledgable in them anymore and those smallish problems start getting bigger and harder to sort. Parts are getting pricey for them too. Bang for buck, carb wins easily.

The other option would be to go for modern EFI- like the EZ systems but again costly. So I say carb. Nothing bigger than a 650 needed.
Author:  jon_buss [Tue Jul 14, 2015 7:01 am ]
Post subject:  Re: TPi to Carb Conversion - views?
One day I'd like to sell it, but only to fund a 1971 2nd gen :D But I'm not so worried about it as an investment as to be worth decent money it would probably need to be 100% original and it's already too modified to really get back there (paint, wheels, SFC, exhaust, cat+air+a/c removal, brakes, suspension etc. etc.) However I wouldn't want to do something which may really devalue it.......

To be honest I just don't really want to throw much more money at the TPi, as you say there are very few that know much about it and to get any decent extra power it will cost me much more via injection than it would via carb.

You reckon a 650 carb? I wasn't sure if that was too big for a fairly standard 5.7, though eventually it will end up with heads / cam or I may even one day buy a stroker long block crate engine if budget allows so I'd like the carb to manage any / all of that to avoid wasting money.

Cheers for your advice, any other views (or pointers on specific parts / makes) would also be appreciated from anyone!
Author:  chevy-stu [Tue Jul 14, 2015 11:58 am ]
Post subject:  Re: TPi to Carb Conversion - views?
It's a shame the there's a fault somewhere, as the TPI should be a brilliant system that gives nice smooth running with semi decent economy. I replaced the TPS sensor on mine a few times, and the engine ECU once on my old IROC but I did over 70k+ of daily driving in it. I thought it was relatively simple system ? Maybe some Corvette folks have some knowledge as it's same motor.
If you fit the carb, you'll be able to possibly get more power but it would seem like a slight backwards step to me unless you're drag racing it.
Author:  Twistedsanity [Tue Jul 14, 2015 12:53 pm ]
Post subject:  Re: TPi to Carb Conversion - views?
I'm afraid I ripped the entire tpi set up off of my IROC as soon as I got it and put a 650 Vac sec on, I like to have control over what is happening which the TPI didn't give me
Author:  jon_buss [Fri Jul 17, 2015 1:28 pm ]
Post subject:  Re: TPi to Carb Conversion - views?
Quote:
I'm afraid I ripped the entire tpi set up off of my IROC as soon as I got it and put a 650 Vac sec on, I like to have control over what is happening which the TPI didn't give me
Any hints and tips on what to do? I know there are LOTs of articles out there about it, but first hand advice is better than anything. Any info you can give me would be greatly appreciated before I start collecting parts......

Cheers
Author:  Twistedsanity [Fri Jul 17, 2015 2:10 pm ]
Post subject:  Re: TPi to Carb Conversion - views?
I not sure what to suggest really as I just steamed in and got on with it also depending on whereabouts in the states it was made for has a lot of bearing on what is under the bonnet in regards to smog/emissions control. For a carb setup you are only going to need one small vacuum pipe from the carb to the advance on the distributor and also to feed the breather from the top of one rocker cover into the base of the air filter.
I am going on memory from about 12 years ago here! If you have a viscous fan you don't need any electrics for it, I recall having electric fans on my IROC and vying a thermostat kit from real steel to run them which fitted into the rad. You may have water pipes feeding the manifold as a preheat which you can junk. Probably have a return pipe to the fuel tank from the TPI which from memory I just blanked off (I would check that one with somebody else first)
I'm not sure of your level of experience/competence as you are going to have to re do the timing after you remove the distributor to change the inlet manifold. I had a few Chevy friends local with good brains I could pick when I did mine. Clearly you don't need all the temperature sensors/airflow/lambda or their wiring , cruise control etc. if your not too far from Watford I'm happy to pop round and give you hand ?
In short you need to retain the engine and cabin heater cooling pipes, one vac hose for the dizzy, fuel supply, ignition feed , engine block temp sensor, unsure about your current ignition set up but you'll need an ign feed for the coil, I replaced my tacho with an aftermarket unit so can't remember if you need the ecu wiring to operate your current one or not.of it has an ecu bodge flash have you considered popping a s/h ecu in ? That might be an easy and cheaper way to solve your problems and rocky in Watford seems to be constantly breaking 3rd gens so must have a mountain of them in his workshop by now
Author:  3rdGenmalc [Sat Jul 18, 2015 9:52 am ]
Post subject:  Re: TPi to Carb Conversion - views?
I've got a 750 Speed Demon on mine.....love it !!!

Image
Author:  NeilTheCop [Sun Jul 19, 2015 12:00 am ]
Post subject:  Re: TPi to Carb Conversion - views?
Quote:
I not sure what to suggest really as I just steamed in and got on with it also depending on whereabouts in the states it was made for has a lot of bearing on what is under the bonnet in regards to smog/emissions control. For a carb setup you are only going to need one small vacuum pipe from the carb to the advance on the distributor and also to feed the breather from the top of one rocker cover into the base of the air filter.
I think you will find that the distributor is computer controlled. Vacuum advance went the same way as the dodo and the carburetor a long time ago.
Author:  NeilTheCop [Sun Jul 19, 2015 12:10 am ]
Post subject:  Re: TPi to Carb Conversion - views?
IMHO get it fixed. The last car made in the US that was fitted with a carburetor rolled off the assembly line 25 years ago, why turn back the clock.
Sort of like saying I can't find out why my hydraulic disc brakes keep juddering so I'm going to convert them to this:
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