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PostPosted:Sun Jul 19, 2015 9:42 am 
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Big Block
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Joined:Sun Jan 13, 2013 7:00 am
Posts:1158
Car Details:1986 Camaro, bought into Spain by me in 1993.
305 replaced by a 355, 750 Demon carb, RPM AirGap intake, Brodix heads, Hedman Hedders, 3" Flowmaster exhaust.
Wheels are Summit aluminium 5 spokes, tyres are 245 rear 225 front BF Goodrich.
B/M transmission, battery relocated to the rear, GoodMark 4" cowl steel hood.
Location:Spain East Coast
Quote:
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.

A non computer controlled distributor is needed.

And you can tear out all the computer related wiring.

Image

I did´nt have TPI, which I would have preferred, I had the computer QJet......dreadful.


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Re: TPi to Carb Conversion - views?

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PostPosted:Mon Jul 20, 2015 11:05 pm 
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Big Block

Joined:Mon Aug 25, 2014 12:06 pm
Posts:131
Car Details:1971 2nd Gen Camaro
RS, 350ci auto
Location:Devon
Many thanks for all the advice.

If I could fix it I would, for the time being. However I want to ultimately tune the car and to upgrade the injection will be $2,000 plus. To convert to carb will be more like $700 from what I can tell. And then I can get it setup for £100 on a local rolling road. To setup the injection I need to learn myself and buy yet more kit, despite being an IT person it's still a lot to learn.

Considering all bar the Ecu is new, I may try and see if Rocky has one for now as I can't see what else it can be. Did the O2 at the weekend as well which made no difference. But ultimately I'll go carb as it's easier to adjust / fix / setup and the car isn't a daily driver anyway, seen dunno printouts and peak power is way improved, only loss seems to be low down torque.

If anyone can help me source an Ecu for now, and / or build a carb parts shopping list I'd appreciate it!

Cheers

Jon


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PostPosted:Tue Jul 21, 2015 7:53 am 
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Big Block
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Joined:Sat Jun 28, 2014 6:55 pm
Posts:808
Location:Croxley Green, Hertfordshire
Quote:
Quote:
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.

A non computer controlled distributor is needed.

And you can tear out all the computer related wiring.

Image

I did´nt have TPI, which I would have preferred, I had the computer QJet......dreadful.
Yep, get a proper dizzy and you can scrap ALL the ecu and associated sensors/wiring. If you keep the existing dizzy it's a guessing game as to what wiring and sensors you will need to retain to feed the ecu Information regarding ignition advance, there must be a surplus of second hand vaacum advance dizzys for small blocks floating about

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1997 30th Anniversary SS SLP
1993 GMC Typhoon


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PostPosted:Wed Jul 22, 2015 1:30 pm 
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Big Block

Joined:Thu Nov 12, 2009 10:24 am
Posts:219
Car Details:88 IROC Convertible
305 Tpi
Tpi was developed specifically for the 305. On the 350's it can't feed enough air/fuel above 4.4k rpm. Changing to carb on a 350, will I guarantee, you gain you power all over apart from initial low down torque.

jon I would say faulty ecu would probably show more symptoms that it is but worth a shot. Is the MAF/MAP ok? Test a MAF by running the car and tapping it- if it stumbles it could be the fault.

Have you replaced the coil pickup, coil and ICM?

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PostPosted:Wed Jul 22, 2015 3:35 pm 
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Big Block

Joined:Sun Jul 25, 2010 3:40 pm
Posts:206
Location:Roswell New Mexico
Just give it the ultimate fuel system upgrade :lol:



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PostPosted:Thu Jul 23, 2015 9:39 pm 
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Big Block

Joined:Mon Aug 25, 2014 12:06 pm
Posts:131
Car Details:1971 2nd Gen Camaro
RS, 350ci auto
Location:Devon
Quote:
jon I would say faulty ecu would probably show more symptoms that it is but worth a shot. Is the MAF/MAP ok? Test a MAF by running the car and tapping it- if it stumbles it could be the fault.

Have you replaced the coil pickup, coil and ICM?
MAP is brand new, as are most direct parts / sensors. Only bits of note that I haven't done are ICM, throttle body itself (have done the TPS) or the fuel regulator. It smells very rich generally and pops etc. on over run when driving. Plus the stutter on pickup when pulling away and the fact it hits a 'wall' at around 4k rpm when warm, when cold it's fine (i.e. for the first 10 miles of driving)

I asked Rocky if he had an ECU, but no go. However I have ordered a custom chip from the states so hopefully that will sort it when it arrives.

If not I'll wish I'd put the $149 spent on the chip towards a carb / dizzy / intake instead.....


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PostPosted:Thu Jul 23, 2015 10:47 pm 
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Big Block

Joined:Thu Nov 12, 2009 10:24 am
Posts:219
Car Details:88 IROC Convertible
305 Tpi
I would definitely do the ICM, they can be a but tempremental. What about injectors? Ohmed them hot and cold? Fuel pressure? What is PSI.

Custom chip won't help. Been there.

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PostPosted:Fri Jul 24, 2015 12:08 pm 
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Big Block
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Joined:Fri Mar 19, 2010 1:35 am
Posts:2566
Car Details:79' camaro road & track day toy. 383 stroker, 5 speed TKO trans, lots of suspension stuff, 13" Vette brakes, 18" wheels.
Location:Luton
My IROC ICM went, and it was tested by fitting a spare one from another car... which obviously pinpointed the fault....

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“You only live once, but if you do it right, once is enough.”


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PostPosted:Fri Jul 24, 2015 3:27 pm 
Offline
Big Block

Joined:Sun Jul 25, 2010 3:40 pm
Posts:206
Location:Roswell New Mexico
Quote:
Quote:
jon I would say faulty ecu would probably show more symptoms that it is but worth a shot. Is the MAF/MAP ok? Test a MAF by running the car and tapping it- if it stumbles it could be the fault.

Have you replaced the coil pickup, coil and ICM?
MAP is brand new, as are most direct parts / sensors. Only bits of note that I haven't done are ICM, throttle body itself (have done the TPS) or the fuel regulator. It smells very rich generally and pops etc. on over run when driving. Plus the stutter on pickup when pulling away and the fact it hits a 'wall' at around 4k rpm when warm, when cold it's fine (i.e. for the first 10 miles of driving)

I asked Rocky if he had an ECU, but no go. However I have ordered a custom chip from the states so hopefully that will sort it when it arrives.

If not I'll wish I'd put the $149 spent on the chip towards a carb / dizzy / intake instead.....
Pull the vacuum pipe off the fuel pressure regulator and give it a sniff. If you smell petrol the regulator is leaking internally and pulling raw fuel directly into the intake manifold, very common problem and it could explain some of the symptoms you describe.


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PostPosted:Sat Jul 25, 2015 8:32 am 
Offline
Big Block

Joined:Mon Aug 25, 2014 12:06 pm
Posts:131
Car Details:1971 2nd Gen Camaro
RS, 350ci auto
Location:Devon
Quote:
What about injectors? Ohmed them hot and cold? Fuel pressure? What is PSI.
All eight injectors brand new, fuel pump / filter brand new. All fitted by me last year. Haven't got kit to test fuel pressure unfortunately. Also changed TPS, O2 sensor, plugs, cap, rotor, leads, coil, temp sensors, ignition module, air filters, map, oil and set timing!
Quote:
My IROC ICM went, and it was tested by fitting a spare one from another car... which obviously pinpointed the fault....
I will look at / order an ICM as no-one else near me with similar car. In my naive mind I just assume this would only effect the idle, which is perfect. Could this effect throttle pickup / high revs when warm / general rich running then? Sorry, just thought it only controlled the idle itself.
Quote:
Pull the vacuum pipe off the fuel pressure regulator and give it a sniff. If you smell petrol the regulator is leaking internally and pulling raw fuel directly into the intake manifold, very common problem and it could explain some of the symptoms you describe.
I'll try this, think I should be able to reach the vacuum with the plenum still on. Presumably to change it I'll have to remove all the intake again! Is there a decent aftermarket alternative?


My only thought with the custom chip was that the car has had a lot of changes (removal of Air, CATs, A/C, charcoal canister etc.) which all need re-programming to compensate for. I've ordered a custom chip to compensate for these so thought that can only help, in theory! Also, the amount of strange things / bodges I've found on the car (including a second O2 sensor half way down the exhaust, without cats...) makes me think someone may have a bad prom in there. Just a theory though as it's hard to prove without an alternative to try.


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