8" to 9" swap cost question

[bryonbush 85]

right now im sticking with the C4. Later down the road ill go four speed but running out of money. Most 90% of my driving is long country roads or highways so thats why i want to stick close to the 2.79. Im thinkking about buying some axles and a some form of locking diff and sticking with an 8". if need be ill buy a new gear set. ive got some quotes from some local shops and im looking closer to the $2K mark for a well built 9". from what i see, i can get hardened axles and with a locking diff id still be under $1K for it. thoughts on that?

[1969_Mach1 333]

Have you thought of building the rear end yourself? If you have fairly good mechanical aptitude you should be able to do it. You can be more selective with the components, some used some new, and more than likely save some money. The biggest hurdle is setting up the ring and pinion mesh. Manufacturers like Motive Gear ( I've had good luck with theirs) come with good instructions for doing it yourself.

[1969_Mach1 333]

Have you thought of building the rear end yourself? If you have fairly good mechanical aptitude you should be able to do it. You can be more selective with the components, some used some new, and more than likely save some money. The biggest hurdle is setting up the ring and pinion mesh. Manufacturers like Motive Gear ( I've had good luck with theirs) come with good instructions for doing it yourself.

[bryonbush 85]

yeah i have actually. thats why im kinda thinking about just going with a modified 8. just this forum discussion alone you can see how many mixed opinions there are about it and im getting more from everyone ive talked to. i would like to believe that with a new set of axles, updated third member, for what im doing with the car there shouldnt be a problem with the 8 but who knows. i would really like to get with someone around here who knows what they are doing and has the proper tools and knock it out one day.

[bryonbush 85]

yeah i have actually. thats why im kinda thinking about just going with a modified 8. just this forum discussion alone you can see how many mixed opinions there are about it and im getting more from everyone ive talked to. i would like to believe that with a new set of axles, updated third member, for what im doing with the car there shouldnt be a problem with the 8 but who knows. i would really like to get with someone around here who knows what they are doing and has the proper tools and knock it out one day.

[SA69mach 39]

Rebuilding your 8 inch and installing a posi (of your choice) and forged 28 spline axles will give you a strong rear that can eat up 450 flywheel hp.

 

Check this video put - and the 3 other parts- to see what effort is needed to build your own 8 inch. Make your own mind up as to whether you are willing to have a go at it yourself. They are fairly detailed, and as good as a tutorial.

 

[SA69mach 39]

Rebuilding your 8 inch and installing a posi (of your choice) and forged 28 spline axles will give you a strong rear that can eat up 450 flywheel hp.

 

Check this video put - and the 3 other parts- to see what effort is needed to build your own 8 inch. Make your own mind up as to whether you are willing to have a go at it yourself. They are fairly detailed, and as good as a tutorial.

 

[bryonbush 85]

thanks for those videos man! im getting a list of things to rebuild the 8". anyone got suggestions on brands?

[1969_Mach1 333]

Before you start spending money on parts, you might want to consider the cost to build your 8" vs. a 9" rear end. The cost difference may come down to the housing and center section (third member). Used 9 inch center sections are plentiful and usually cheap. I would think the biggest hurdle and cost difference is the housing. That shouldn't be too hard to find. You may not need the strength of a 9" rear end, but if it were my car, I'd have a hard time spending my money to build up an 8" rear end.

[barnett468 418]

barnett: i forgot to mention that the whole reason for this is because the new motor im putting in should be around 450hp. I wont be running drag tires or even taking it to the drag races but will probably be letting it rip every now and then. Why wouldnt i be able to run a 3.0 for gears? curious as when the builder was getting the specs on my gears, i told him i had 2.79 so he went with a cam combo that works well with that end.

 

well you "can" use 3.00 gears but those are for your grandma . . if you want decent acceleration, you need to go with at least 3.23 . . if you run 3.0 you need around a 500 ci engine to get decent acceleration off the line

[1969_Mach1 333]

The 3.70:1 ratio is the most popular in my area. Overall, ratios of 3.50:1 to 3.89:1 seem to be good for street driven performance. Unless, you plan on cruising down the freeway for a significant distance and don't have an overdrive transmission. The 3.00 and numerically lower ratios are mainly for daily drivers without overdrive transmissions that also see a lot of freeway time.

 

I'm curious to what type of cam combo works with a 2.79:1 ratio and will make 450 hp?

Edited December 18, 2014 by 1969_Mach1

[bryonbush 85]

After pricing out the cost to get some nice parts for the 8, I'm back to the cost of the nine I was quoted. As for the engine its a bored 351w with performer heads, intake and comp cams 270 with 500 duration. I don't have the engine yet or even a full build sheet so we will see what it actually comes out to.

[1969_Mach1 333]

Sounds pretty good. If your budget can build a 9" rear end, I'd go that route.

 

If it were my motor, I'd do some homework and at least call Comp Cams and ask their recommendation on a cam. That is, unless your engine builder has built a lot of 351W motors. From my experience most shops lump the 351W together with a 302 as far as parts selection is concerned. The larger cubic inch 351W can tolerate more cam than a 302 and still have good street manners and driveability. The camshaft characteristic descriptions in the Crane Cams catalog is another indicator of that. For example, I've run both a Comp Cams 284 Magnum Hydraulic Roller cam and Ford Racings X303 Hydraulic Roller cam in 351W motors. Both had good drieability, street manners, and a mild rough idle. The X303 having a slightly smoother idle.

 

Anyway, do some homework is my 2 cents.

Edited December 18, 2014 by 1969_Mach1

[bryonbush 85]

I'm not sure of all the engine specifics because I'm not building it. Guy in California made a good deal to me that I couldn't refuse. Been making race engines for over 20 years so I don't question it. From the quality of gun parts he made me, I'm not worried one bit. This weekend I'm going to go meet this guy with the 9 and see what it's all about and go from there