Pale340 Posted July 11, 2017 Share Posted July 11, 2017 Hey all, I rebuilt my Q-Jet and thought I sealed the ports on the bottom of the bowl. Well, I obviously did not do a very good job as the bowl empties out in about a 24 hour period and takes forever to refill to get the car started. I have a 6210 Holley that I have had a few people tell me was a great replacement for the Q-Jet. Just want to get some opinions on it. The engine, as I recently found out, is the original 2bbl engine that was converted to a factory 4bbl set up. So, it has an original late 69 4bbl Q-Jet that has been rebuilt, on a 70 part number intake manifold, but the heads are 70 2bbl heads. Would the Holley be a better choice? It is 650 cfm compared to the 750 cfm of the Q-Jet. My concern is the Holley 6210 is a double pumper. It is a spread bore and it looks like the factory choke rod of the Q-jet will fit without any issues. Let me know your thoughts. This engine only has 61k miles on it. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted July 11, 2017 Share Posted July 11, 2017 trying to tune a double pumper for a stock engine will be the tricky part Quote Link to comment Share on other sites More sharing options...
Paul Bell Posted July 13, 2017 Share Posted July 13, 2017 Back in the day, a Holley spread bore was the best thing I ever did to my daily driver '73 Impala. Go for it. Quote Link to comment Share on other sites More sharing options...
MCfan Posted July 13, 2017 Share Posted July 13, 2017 Charles, I also had good luck swapping a Holley Spread-bore for a leaking Q-jet on my '70 Monte 402 back in '73. I was going to replace the Q-jet after accidentally cross-threading the fuel inlet fitting into the carb body, but the local speed shop highly recommended the Holley instead (possibly more margin for them) so I went that way. I have no idea which model it was but it ran great right out of the box. Your particular model may not be so street-friendly (as Sam suggests) but unless it won't bolt right up, it shouldn't take much time or effort to give it a try. Good luck. Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted July 13, 2017 Share Posted July 13, 2017 My concern would be the sb heads for a 2bbl vs 4bbl, smaller intake valves and lower compression motor. Although, maybe you may be able to lean it far enough to meter properly, my dislike would be...jetting, power valves, or accelerator pump settings. I dislike Holleys for that reason, some would argue, yet that's me. Keep us informed on the outcome, and good luck. 1 Quote Link to comment Share on other sites More sharing options...
Paul Bell Posted July 14, 2017 Share Posted July 14, 2017 The 250HP 2 barrel heads were 3932441 and the 300HP 4 barrel heads were 3947041. Both had 1.94"/1.5" valves. The difference is the 300HP heads has smaller combustion chambers. Source: http://chevellestuff.net/qd/head_casting_by_year.htm Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted July 15, 2017 Share Posted July 15, 2017 You learn something new everyday, I had my info all wrong. Thanks for clearing it up for us, I thought the lower compression motor would hence have smaller valves. I stand corrected. That's why having this forum is so great, the wealth of knowledge here Is bar none. Quote Link to comment Share on other sites More sharing options...
Pale340 Posted July 31, 2017 Author Share Posted July 31, 2017 All, I have an update and need some help. First off, I have not replaced the Q-Jet with the Holley just yet. I did remove it and did some tests and proved it is not leaking fuel from the jet ports on the underside. Due to my findings, I replaced the fuel pump as the original was still on the on the engine. After replacing it I am still having initial start up issues after the car has sat overnight. There is no fuel in the bowl or the fuel line from the pump to the carb. I have a check ball fuel filter in the carb and have read where the heat of the engine can evaporate the fuel in the bowl. That being said, how am I losing fuel from the pump to the carb? Could there be an issue between the pump and the tank? Once the car gets fuel to the bowl it will start the first turn of the key for the rest of the day. Any ideas or opinions are greatly appreciated. I don't want to drive it because it takes so long to get it started in the mornings. It cannot be good for the engine to turn over for so long before it starts. Thanks for your help in advance. Quote Link to comment Share on other sites More sharing options...
Leghome Posted July 31, 2017 Share Posted July 31, 2017 Pale340 I have the same problem with my 72 with a 350 and Elderbrock 1406 carb. Mine is caused by the fuel pump not holding the pressure and the fuel bleeding back. I rep[laced the fuel pump a couple of years ago and it helped as it is not nearly as bad as it had been. Now mine only does it if it sets for longer than a week. Quote Link to comment Share on other sites More sharing options...
Pale340 Posted July 31, 2017 Author Share Posted July 31, 2017 Leghome, I replaced the pump with a new AC and it is still just as bad. It is not holding the fuel from the pump to the carb. I am lost on what to do other than pull the tank and replace all the rubber hoses. Quote Link to comment Share on other sites More sharing options...
Pale340 Posted December 28, 2017 Author Share Posted December 28, 2017 So I am finally pulling the trigger and am going to replace the Q-Jet with the Holley 6210 that I have. I will rebuild it, but I am concerned about the factory specs. The primary jets are 62s with a 25 squirter and the secondaries are 83 with a 37 squirter. Do you think the secondaries are to big for an original 2bbl 350 that was changed to a 4bbl? I would think smaller jets and a smaller squirter for the secondaries.Your thoughts? Quote Link to comment Share on other sites More sharing options...
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