Box Body 351 Questions

[TomO]

I don't know anything about the 351, but I noticed from reading through some figures in an automotive book that the 351 was apparently offered in civilian panthers from '79-'81 only, with the power rating varying from about 140 hp to 150 hp depending on the year and whether the car was a Ford or Mercury.

I also noticed that the police 351 rating jumped from 165 hp in the 1983 model year to 180 hp in the 1984 model year.

1st question: what accounted for power rating differential between the civilian and the police 351? Was it simply the addition of dual exhaust to the police motor or were there other differences?

2nd question: what accounted for the power increase in the police motor between the '83 and '84 model years? I'm assuming it was something to do with the induction system because I vaguely remember reading that the police 351 had either the variable venturi carb or a 4bbl depending on the year model.

[1990LTD]

they typically rated dual exhaust +10hp

[johnunit]

Not sure what exhaust the early civi 351s had but canadian spec cars could get 351w up until 91 and my drivetrain is 100% the same as police models. There was never a 351 in a production panther with a 4barrel, police or otherwise.

The cam did get more aggressive at some point, which isthe likely difference, but I doubt 40hp. Search cs674 and cs764 for the early and late model 351 cam specs on here.

[Mercracer]

I'm assuming it was something to do with the induction system because I vaguely remember reading that the police 351 had either the variable venturi carb or a 4bbl depending on the year model.

Only the trucks got a Holley 4V with the 351HO. The last passenger car to get a 4V 351W was the 1970 GT350. Every other Mustang and Ford/Mercury got a Clevelend in 1970 under a 4V carb.

[gadget73]

I think they also changed the heads in 1985 to something that sucked a little bit less. The 79-84 engines had the D8 head casting, 85 onward was E5. Slightly smaller chambers on the E5, maybe marginally better flow as well but I think mostly it was a compression bump. Its still not very high, like 8.5:1 or so.

[johnunit]

Factory claimed 8.3 for all years of 351.

[Brown_Muscle]

What Gadget said... The variable venturi really didn't change much...there were two different ones if i remember correctly and i think the main difference was the way the computer "controlled" it, there may have been addition sensors. Not 100% sure on that, maybe someone can chime in. However i don't think it made a difference in power

[johnunit]

The venturi and throttle bore size did not change between the 7200VV and the 2700VV. I'm not sure if the Panther chassis 351w ever had a 2700. A larger throttle bore and venturi would be the primary way you'd gain top-end power without a total redesign of the carb.

I really think it was mostly the cam and perhaps the way they measured the power.

[Brown_Muscle]

I know in my 82 they measured it behind the tranny...(all 140hp of it) which is known to suck up at least 25 hp...would make sense if they decided to measure it at the flywheel later giving it the 165HP... then the cam or head change resulting in the 180 hp perhaps..

[johnunit]

if they did measure it from behind the trans for a while that would make sense, yeah.

[GM_Guy]

an automotive book that the 351 was apparently offered in civilian panthers from '79-'81 only,

Except in Canada, where it was a civilian option throughout the life of the box bodies.

Alex.