Holley replacement for Q-jet.

[trevbeadle]

Hi,

I need to replace an ECM Q-jet currently fitted on a non-ECM engine. The engine is a Goodwrench 350 crate motor, Mexican origin, Block number 10066036 and engine number 1M0615 9VP. I have been told that Holley #0-80555C model 4175 is a direst replacement (as is the 0-9895 although emissions don't need to be a consideration) although Holley only quote Chevrolet applications with a 'spread bore' up to 1969 and mine is a much later engine. How do I tell if the engine is a 'square flange' or a 'spread bore'? Has anyone any experience of a Q-jet/Holley swap and any complications? It looks like its cheaper to buy over here (UK) than pay $+shipping+taxes.


Thanks

 

[Roscobbc]

Hi,

I need to replace an ECM Q-jet currently fitted on a non-ECM engine. The engine is a Goodwrench 350 crate motor, Mexican origin, Block number 10066036 and engine number 1M0615 9VP. I have been told that Holley #0-80555C model 4175 is a direst replacement (as is the 0-9895 although emissions don't need to be a consideration) although Holley only quote Chevrolet applications with a 'spread bore' up to 1969 and mine is a much later engine. How do I tell if the engine is a 'square flange' or a 'spread bore'? Has anyone any experience of a Q-jet/Holley swap and any complications? It looks like its cheaper to buy over here (UK) than pay $+shipping+taxes.


Thanks

OEM Rochester Quadrajet is a 'spreadbore' configuration - i.e primary venturi's are relatively small compared with secondaries - said to improve economy and driveability. 'Squarebore' (i.e Holley and Carter/Edelbrock configuration is where all venturi's are of the same size. Whilst fixing bolts may have the same or similar hole centre's the square and spreadbore types are not really interhangeable except with an adaptor. This may then give underhood clearance issues which means considering a new inlet manifold....

 

[Oneball]

Qjet spread bore at bottom, Holley square bore at top. As Rossco says the holes in the manifold will be different. It’s pretty easy to tell which manifold you have with the carb off



The non-ECM Qjet in the photo is surplus if you want to go down that route.

 

[Roscobbc]

Nothing wrong with QJet's fella's - in some respects far easier to tune than Holley's (if you know what you are doing - and know somewhere you can get the jets and needles)

 

[trevbeadle]

Problem is Rosco, that the Q-jet I have is off a mid 80's truck with ECM! It runs but there is absolutely no manual adjustment even slow idle! If I could find a working Q-jet in UK I would gladly lookat that option.

Qjet spread bore at bottom, Holley square bore at top. As Rossco says the holes in the manifold will be different. It’s pretty easy to tell which manifold you have with the carb off

View attachment 4197

The non-ECM Qjet in the photo is surplus if you want to go down that route.

Oneball?....whats the condition of the Q-jet and i.d number?..What are you asking pricewise?

 

[trevbeadle]

Ros

Nothing wrong with QJet's fella's - in some respects far easier to tune than Holley's (if you know what you are doing - and know somewhere you can get the jets and needles)

Sure, but I need to replace the ECM controlled junk I have at the moment. If I can't find a correct year Q-jet I'm looking at options. Thanks.

 

[antijam]

Ros

Sure, but I need to replace the ECM controlled junk I have at the moment. If I can't find a correct year Q-jet I'm looking at options. Thanks.

What year are you after? I have a Q-jet #7043212 from a '73 350 Auto, surplus to requirements. It has been stripped, cleaned and re-assembled with original jets and rods, but it may need some adjustment.

 

[Roscobbc]

More Information for AUTOLINE C9435
Link is to Rock Auto for a 1975 spec re-manufactured Quadrajet @ £260 or so (not perhaps correct for your car but gives an idea) you'll need to add duties and vat to get a true price (which you can do on-line before buying)

 

[trevbeadle]

Best guess for my engine so I'm told with a Block number 10066036 and engine number 1M0615 9VP is it's a 1989 unless anyone knows different!

 

[Oneball]

The date isn’t really going to tie in to a spec as it’s a Goodwrench engine. The big things to match on the carb will be manifold type, and choke type (electric, manual or bimetallic).

 

[trevbeadle]

I presume its the standard manifold as it has a Q-jet fitted. The choke is not manual and think it is bi-metallic as no wires to it.

 

[Oneball]

The black thing on the side nearest the camera is an electric choke. There should be a wire connected to the brass nipple.

The ones with the bimetallic strip in the manifold have a rod coming down from the choke to the manifold and connect to an inch by half inch box on the manifold with a bimetallic strip inside.

The electric ones work in a similar way. There’s also a bimetallic coil inside the black housing that is heated by an electric current when you turn the ignition on.

You can convert non electric choke to electric choke using a kit.

Where are you based? You can borrow my Qjet if you want to see how it runs.

 

[trevbeadle]

Hmmmn!....I shall search for a wire!.....maybe that's why there is such a high tick-over when shes warmed up !! (1400 rpm) and there's no 'idle' adjustment on the carb! I'm near Colchester, Essex.

 

[kentvette]

I'm no real expert on carbs, but I have got my Q-Jet running very nicely now (with a little help from a friend in California who definately is an expert!). But, out of interest, can you not get any idle adjustment from this screw?


It is how I set the idle on mine, but maybe its different on an ECM/ECU controlled carb?

 

[Oneball]

I’m in Worcester so a fair way away.

The carb is electronic controlled by an ECU, if you’ve not got one you probably won’t get that carb to work properly even with the choke connected. Although someone has been playing with yours the air bleed by the choke flap should be covered with a cap

I’m not 100% sure but I don’t think Vettes ever came with ECM carbs.

 

[trevbeadle]

I'm no real expert on carbs, but I have got my Q-Jet running very nicely now (with a little help from a friend in California who definately is an expert!). But, out of interest, can you not get any idle adjustment from this screw?
View attachment 4206

It is how I set the idle on mine, but maybe its different on an ECM/ECU controlled carb?

Thats a picture of the carb with the screw backed all the way out. I don't think the choke is fully open and off the fast idle cam.

 

[trevbeadle]

I’m in Worcester so a fair way away.

The carb is electronic controlled by an ECU, if you’ve not got one you probably won’t get that carb to work properly even with the choke connected. Although someone has been playing with yours the air bleed by the choke flap should be covered with a cap

I’m not 100% sure but I don’t think Vettes ever came with ECM carbs.

Oneball, can you point me to the air bleed to which you refer? Someone has identified this carb as being off a mid 80' truck.! The car has a US title as 'Salvaged' from 1986, built on a new chassis with blank VIN where one would expect one on the windscreen frame,and subsequently given a VIN by the Californian Department for motor vehicles. The car has spent all ts life in California until it was imported here in the summer. Probably never needed choke in the warmth of California! I'll hook up the choke and see if it works and whether that makes it better warm. Otherwise I think I may go down the line of a Holley #0-80555C easily obtainable over here

 

[Oneball]

Green arrow is the idle air bleed. Without the electronic control systems it’s never really going to run properly. The system is much like modern fuel injection with an ecu and exhaust gas sensors. Red circle as said by Kentvette is base idle speed

 

[Oneball]

This is a really good article on the ECM carb

https://www.hemmings.com/blog/article/carburetion-for-the-new-age/

 

[Martinshort]

Problem is Rosco, that the Q-jet I have is off a mid 80's truck with ECM! It runs but there is absolutely no manual adjustment even slow idle! If I could find a working Q-jet in UK I would gladly lookat that option.

Oneball?....whats the condition of the Q-jet and i.d number?..What are you asking pricewise?

Gavin at emc has a fully rebuilt Rochester, built with an electric choke