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Old GM guys....1986 K5 square body question

Old GM guys....1986 K5 square body question

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by: TXtransplant Active Indicator LED Icon 13 OP 
~ 7 years ago   Aug 26, '16 2:33am  
K5 series Blazer; 86; 5.7 automatic w NP208 4x4. Vintage square body at it's finest. However:
 
Anyone know the original carb cfm spec? Currently running a Holley 650 w vac secondary but it seems a bit above for the factory engine. Seems like the accelerator pump is way too strong (low rpm stall).
 
Aside, great vac pressure; perfect compression and new Edelbrock mechanical fuel pump pressurizing well within spec.
 
Engine not an issue. Fresh rebuild less than a year.
 
Chokes from 800-1300 rpm if you hit her hard and upper range everything is fine following.
 
Not looking for an aftermarket fix....just am trying to find the original 5.7/350 ci spec and can't seem to locate to benchmark the jets.
 
All help appreciated.
 
I've played with the accelerator quite a bit and it still bogs. Considering a retro back to a vintage Rochester. 4951
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TXtransplant Active Indicator LED Icon 13 OP 
~ 7 years ago   Aug 26, '16 2:46am  
Btw...any woman who can chime in correctly on this one gets not only 10,000 points but also a marriage proposal.
 
4951
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buffaloglenn Active Indicator LED Icon 11
~ 7 years ago   Aug 26, '16 7:14am  
Don't know other than it probably had a Rochester to begin with, rather than holley.  Wait a minute - I think by '86 they were all running throttle body injection.  IIRC, the last carbureted models were in 85.  Now I'll have to look it up!In any case, that should be a fun ride for you.  4951
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buffaloglenn Active Indicator LED Icon 11
~ 7 years ago   Aug 26, '16 7:27am  
Don't know other than it probably had a Rochester to begin with, rather than holley.  Wait a minute - I think by '86 they were all running throttle body injection.  IIRC, the last carbureted models were in 85.  Now I'll have to look it up!In any case, that should be a fun ride for you. 
 
@buffaloglenn: 87 was the first year for TBI.  It looks like most of the Rochester quads I see for sale, which may be aftermarket, are 650's.
4951
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Katzen Active Indicator LED Icon 9
~ 7 years ago   Aug 26, '16 7:32am  
A good 350, probably around 700. More scientific approach, cid*MaxRPM/3456.Figuring 85% efficiency puts you at 715.Brings back memories of working on my brother's K10, nothing beats the hum of a well tuned 350.  4951
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lola Active Indicator LED Icon 17
~ 7 years ago   Aug 26, '16 7:33am  
Btw...any woman who can chime in correctly on this one gets not only 10,000 points but also a marriage proposal.
 
 
@TXtransplant:
 
Really? That's too hard.
 
That's like me wanting a man who can make me some tortillas.
 
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4951
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Fallon Active Indicator LED Icon 18
~ 7 years ago   Aug 26, '16 7:38am  
Removed By Request 4951
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yankeejessica Active Indicator LED Icon 12
~ 7 years ago   Aug 26, '16 7:47am  
I'm impressed that you have a 86 blazer that runs!! We saw an old cutlass last night. You don't see many older cars anymore! 4951
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sweetie Active Indicator LED Icon 11 Forum Moderator
~ 7 years ago   Aug 26, '16 7:48am  

- - - - - - - -
>> Btw...any woman who can chime in correctly on this one gets not only 10,000 points but also a marriage proposal.
 

@TXtransplant:
 
Really? That's too hard.
 
That's like me wanting a man who can make me some tortillas.
 
Emoticon
 
@lola:
 
Lol!! 4951
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Ebola Active Indicator LED Icon 9
~ 7 years ago   Aug 26, '16 8:11am  
There's many reasons why you get bog when the secondary open. Could be a ignition coil or a vacuum leak. If it's a mixture problem you have a better chance fixing it with a Holley. Rochester is a pita to work on. Male a list Check your ignition coil check for vacuum leaks check your fuel pressure. if someone has opened the carburetor the float level may be off. Change the fuel filter while your at it. 4951
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Burnsway Active Indicator LED Icon 13
~ 7 years ago   Aug 26, '16 9:19am  
Your accelerator pump isnt working. Second, never use a carb with vacuum secondary. Always get the mechanical secondary. 3rd, buy an edelbrock carb, its a carter carb which is better than the holley and rochester for small perf and everyday driving. Recommend the 600 or 650. Youll be much happier.
 
I like my diamonds big and weddings small......
 
Emoticon 4951
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gigem09 Active Indicator LED Icon 7
~ 7 years ago   Aug 26, '16 9:25am  
I thought the original was a 750 cfm... not 100% sure though so marriage proposal not necessary. 4951
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buffaloglenn Active Indicator LED Icon 11
~ 7 years ago   Aug 26, '16 9:26am  
Your accelerator pump isnt working. Second, never use a carb with vacuum secondary. Always get the mechanical secondary. 3rd, buy an edelbrock carb, its a carter carb which is better than the holley and rochester for small perf and everyday driving. Recommend the 600 or 650. Youll be much happier.
 
I like my diamonds big and weddings small......
 
Emoticon
 
@Burnsway: Good answers!  I think he may trying to keep it somewhat stock and work with what it already has, but mechanical secondaries are definitely better.  I absolutely hated all the vacuum operated crap on those 80's cars, and also love fuel injection.  I don't care how much more it costs; it's so much better.  We are quite spoiled today with our technology. 
4951
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WskyTngoFxtrt Active Indicator LED Icon 10
~ 7 years ago   Aug 26, '16 9:31am  
Check the flux capacitor. Either that or the blinker fluid is low. Could also be bad muffler bearings. 4951
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TexasTideFan Active Indicator LED Icon 4
~ 7 years ago   Aug 26, '16 9:53am  
nothing beats the hum of a well tuned 350. 
@Katzen: Especially if it is sitting in a CJ7.  4951
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Fallon Active Indicator LED Icon 18
~ 7 years ago   Aug 26, '16 9:58am  
Removed By Request 4951
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