mercarb and engine swap

[MBAKER]

I am going to be repowering from a 2000 year 5.0 to newer 5.7 longblock. I currently have a Mercarb and am trying to figure out if it will run out ok on the new engine. I have no doubts it will run but question the off idle and transition and am curious as to the differences in the 2 carbs listed for the 5.0 and 5.7.. The old setup always seemed to suffer under acceleration from idle and in transition off idle, a little hesitant etc. even with fresh carb and tune. Any thoughts?

Will I notice a difference at all?

Do I need to look for a carb that matches the one listed for the 5.7?

Can I just swap venturi clusters and fix it?


Other thoughts... possibly change intake and use a edelbrock 1409 carb. I know its not going to net a bunch of HP, but part of me wonders if it would help off idle.

Are there any other 2 barrels, Rochester or Holley that would bolt on in place of the Mercarb without an adapter plate. I know fuel lines etc would be different but I can work with that if it bolted straight to the intake.



thanks.

 

[Don S]

Re: mercarb and engine swap

The 5.7 carb used a different Venture cluster from the 5.0. Larger accelerator pump holes. You would have to drill them out (If possible) or replace the cluster. The Venturi Cluster itself lists for about $235.
Probably would be better off to go with the 1409. You would feel the difference then.

 

[MBAKER]

Re: mercarb and engine swap

Thanks.



Do all the mercarbs suffer somewhat off idle. I looked into it a few years ago, and seems like that was a common complaint. Eventually went through the carb and it was better but still there. Maybe its a product of heavy boat but I had an older boat with Rochester 2G on a 3.0 and dont remember having any issues with it. In fact from a dead stop I think it pulled harder on takeoff. If the edelbrock will help that would be another plus. But if changing the cluster in the Mercarb works then thats 250$ vs the new carb/intake combo looks to be around 600+$ with the correct bracketry, fuel lines etc..



I have seen ads for a Rochester 2G to replace a Mercarb, is that possible? For some reason I thought the bolt pattern was just slightly different.