Are all DOHCs interchangeable?
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Are all DOHCs interchangeable?
I've been doing some reading about the Modular 4.6 engines and I've seen information about them being manufactured in both the Windsor and Romeo plants. From what I've read there are interchange issues between engines built at the two plants.
Were all of the DOHC engines (Cobra, Mark VIII, etc.) built in the same plant, or was the production of the DOHCs also split between the plants? I'd like to put together a DOHC that looks like a Cobra, but it seems like it might be easier to find the engine out of a Mark VIII and add the Cobra intake and trim accessories if they will interchange.
I understand that there are internal differences (at least the crankshaft material and cam duration/lift), but do the parts interchange between all of the DOHC engines?
Mike Bayler.
Were all of the DOHC engines (Cobra, Mark VIII, etc.) built in the same plant, or was the production of the DOHCs also split between the plants? I'd like to put together a DOHC that looks like a Cobra, but it seems like it might be easier to find the engine out of a Mark VIII and add the Cobra intake and trim accessories if they will interchange.
I understand that there are internal differences (at least the crankshaft material and cam duration/lift), but do the parts interchange between all of the DOHC engines?
Mike Bayler.
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From: South Kitsap County, WA
Perhaps you mean to say the current tune the DOHC's use don't produce torque in the range a truck would be more suited to use.
Remember the DOHC 5.4s were available in Navi's, a 5800lb (empty) vehicle. They produced slightly more torque and hp than the SOHC 5.4 version available in 2003, it's just that the peak numbers were a bit higher in the rpm band. The curves were actually relatively flat, so I'd say the DOHC engine is just as useable as a SOHC.
The same argument was made about pushrod vs SOHC when Ford introduced the 4.6 in cars. It really doesn't matter how the engine is configured, you have to tune it and dress it out for the particular application and you'll get suitable results if you do it right.
2003 5.4s
Navigator DOHC 5.4 - 300hp@5000rpm, 355ft-lbs@2750rpm
F150/Expy SOHC 5.4 - 260hp@4500rpm, 350ft-lbs@2500rpm
For ease of maitenance and reliability would be a better argument to justify not using a DOHC in trucks. However, that's soon going to become a point not worth arguing over, as well.
-Kerry
Remember the DOHC 5.4s were available in Navi's, a 5800lb (empty) vehicle. They produced slightly more torque and hp than the SOHC 5.4 version available in 2003, it's just that the peak numbers were a bit higher in the rpm band. The curves were actually relatively flat, so I'd say the DOHC engine is just as useable as a SOHC.
The same argument was made about pushrod vs SOHC when Ford introduced the 4.6 in cars. It really doesn't matter how the engine is configured, you have to tune it and dress it out for the particular application and you'll get suitable results if you do it right.
2003 5.4s
Navigator DOHC 5.4 - 300hp@5000rpm, 355ft-lbs@2750rpm
F150/Expy SOHC 5.4 - 260hp@4500rpm, 350ft-lbs@2500rpm
For ease of maitenance and reliability would be a better argument to justify not using a DOHC in trucks. However, that's soon going to become a point not worth arguing over, as well.
-Kerry
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Correct, thanks for going into more detail. But most people aren't going to retune their engine.
btw, are you sure about those spec's? I'm not up to date, but I thought the SOHC 4.6/5.4 made peak torque a little sooner than 2500. And I thought they peaked their HP a little sooner too.
btw, are you sure about those spec's? I'm not up to date, but I thought the SOHC 4.6/5.4 made peak torque a little sooner than 2500. And I thought they peaked their HP a little sooner too.
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Joined: Jul 2001
Posts: 4,038
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From: South Kitsap County, WA
Straight from fte's specs page - note that I used the 99-03 2V, not the 2004 3V specs.
I have the trucks' 2002 dyno sheet in my gallery... kinda hard to see, but those have been the 5.4 SOHC PI numbers since they were introduced in '99.
The torque curve is fairly flat... that's what makes the SOHC in the truck a good pulling engine. If Ford chose to use a DOHC, I'm very certain they could produce the same results. I think they went the 3V route to eventually go to a reduced displacement configuration. The variable valve timing lends itself to that application.
-Kerry
I have the trucks' 2002 dyno sheet in my gallery... kinda hard to see, but those have been the 5.4 SOHC PI numbers since they were introduced in '99.
The torque curve is fairly flat... that's what makes the SOHC in the truck a good pulling engine. If Ford chose to use a DOHC, I'm very certain they could produce the same results. I think they went the 3V route to eventually go to a reduced displacement configuration. The variable valve timing lends itself to that application.
-Kerry
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From: Las Vegas
Originally Posted by kspilkinton
Perhaps you mean to say the current tune the DOHC's use don't produce torque in the range a truck would be more suited to use.
Remember the DOHC 5.4s were available in Navi's, a 5800lb (empty) vehicle. They produced slightly more torque and hp than the SOHC 5.4 version available in 2003, it's just that the peak numbers were a bit higher in the rpm band. The curves were actually relatively flat, so I'd say the DOHC engine is just as useable as a SOHC.
The same argument was made about pushrod vs SOHC when Ford introduced the 4.6 in cars. It really doesn't matter how the engine is configured, you have to tune it and dress it out for the particular application and you'll get suitable results if you do it right.
2003 5.4s
Navigator DOHC 5.4 - 300hp@5000rpm, 355ft-lbs@2750rpm
F150/Expy SOHC 5.4 - 260hp@4500rpm, 350ft-lbs@2500rpm
For ease of maitenance and reliability would be a better argument to justify not using a DOHC in trucks. However, that's soon going to become a point not worth arguing over, as well.
-Kerry
Remember the DOHC 5.4s were available in Navi's, a 5800lb (empty) vehicle. They produced slightly more torque and hp than the SOHC 5.4 version available in 2003, it's just that the peak numbers were a bit higher in the rpm band. The curves were actually relatively flat, so I'd say the DOHC engine is just as useable as a SOHC.
The same argument was made about pushrod vs SOHC when Ford introduced the 4.6 in cars. It really doesn't matter how the engine is configured, you have to tune it and dress it out for the particular application and you'll get suitable results if you do it right.
2003 5.4s
Navigator DOHC 5.4 - 300hp@5000rpm, 355ft-lbs@2750rpm
F150/Expy SOHC 5.4 - 260hp@4500rpm, 350ft-lbs@2500rpm
For ease of maitenance and reliability would be a better argument to justify not using a DOHC in trucks. However, that's soon going to become a point not worth arguing over, as well.
-Kerry
If I may ad, Toy and Nissan use the DOHC 4V config. quite nicely in their rigs.
It's been beat to death here but I suppose if the product run lasts long enough, (sometimes doubtful with Ford) the 3V SOHC's one less cam and valve will prevail $$$$$ wise(even though the VVT adds cost and complexity to equal the 4V's #'s)........
I've just always felt the DOHC 4V was bought and paid for (been in production since the early '90's) and would have benefiitted more with devolopment (including VVT) than re-tooling for a TOTALLY new head.
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From: Louisville,Ky.
I agree, the 4.6 DOHC in my sister-inlaws Mark VIII has 198,000 miles on it and still runs like a scaulded dog!! Plenty of torque since it has the dual intake runners with the flaps that shuts off 1 to each cylinder until about 3000rpm to keep intake volocity up.
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