I am currently swaping on some Mustang EFI onto a 78 400 ford. Engine is putting out arounf 350-400 hp. Before I buy parts I am going to get a dyno run under the belt of it. But What I am having problems finding is info on what size mass air and throttle body to run. I know the stock mustang ones are too small. I am going to run a elbow on to my machined intake manifold which will alow me to go up to a single 90mm throttle body.

Any pointers?

 

I have tried a 58(way too small) a 65 (worked ok) and now 80mm. To me the 80mm works the best but I have no stock engine. I would think that for something with a 5000 or close rpm limit then a 70mm would be the best.

 

I spin it to 5400 where the rev limiter is at.

 

Really the way to tell throttle body size is just try one and look for vaccume. Your motor should loose all vaccume at wot and not start making any. With a 58mm my truck wouldn't loose all vaccume. My truck ran decient with a 65 so that or a 70 should work fine. I am turbocharging my truck so throttle body side makes no difference.