Building for street

[68CoupeWimWhite]

I have a 1968 Mustang 289 w/original C4 3 speed and stock rear with power steering. The 289 is stock with weiand Stealth intake and a Holley 670 CFM 4bbl. I want to put Heddman Shorty headers on it but have no idea how they will fit. Does anyone know if they will be clearance issues or if they flow well with this combo? I also want to know what is the top gears i can install with a 3 speed w/out over drive to still be manageable on the highway?

For Grins Does anyone have any cam suggestions for this combo?

 

[latamud]

I have a 1968 Mustang 289 w/original C4 3 speed and stock rear with power steering. The 289 is stock with weiand Stealth intake and a Holley 670 CFM 4bbl. I want to put Heddman Shorty headers on it but have no idea how they will fit. Does anyone know if they will be clearance issues or if they flow well with this combo? I also want to know what is the top gears i can install with a 3 speed w/out over drive to still be manageable on the highway?

For Grins Does anyone have any cam suggestions for this combo?

The shortys will flow better than cast manifolds, you shouldn't have any clearance issues in a 68. Keep the stock 2.79 rear end gears to maintain highway management with a 3 speed.

An Edelbrock Performer RPM cam is a nice upgrade compared to stock and will be fun on the street. Don't limit yourself to this one though, for street you will probably be happy with any cam that is mildly better than stock.

 

[D.Hearne]

Gears? Nothing bigger than 3.50's. Cam? You're going to want something like an "RV" style grind (204-214 duration @.050 with no more than .500 lift)with stock heads, anything bigger tends to pull the stock pressed in studs out of the heads. You might also consider 289 Hi-po manifolds too, they're going to be more expensive, but they'll breathe like shortys and last a lifetime

 

[tx65coupe]

The HiPo manifolds would be a good choice.

I agree about the rear gears. Since you don't have OD, I would go with 3.00 or 3.20 ish. I have 3.50 with a T5 so I have OD and its great. If I didn't have OD the RPM would be a bit high on the highway.

I think the 670 carb is a bit large for a stock or near stock engine. I think something closer to 500 is more suitable, maybe a 570.

I agree, you'll probably want an RV cam.

 

[68conv4sp]

I had 3.25s when I had the 4 speed - no OD in those days. It was a good compromise. Currently in the 302 for the cam, I am very happy with a conservative Crane that has .469 lift. It is matched with a 500 cfm Edel. and currently a TKO 5 speed and 3.55 rear end. Nice and torquey (is that a word? Anyone remember Fawlty Towers?).

 

[rbohm]

for gears the 3.25's are a nice compromise for the street. good for daily driving in the city, and still not bad for freeway driving.

for a cam i suggest the comp cams he268h. it gives good all around performance and has a slight lope to it.

as for the exhaust, jmy choice would be tri-y headers as i prefer the better torque curve, but since you seem to be set on the shorty headers, i would also recommend the hipo exhaust manifolds instead. they fit well, and look stock, and will out last the steel tube headers.

 

[65FBE2]

I currently have a 306 with hp manifolds and a 500 carb and 3.25 gears. I would say the gears would be fine with a man trans but to low for the automatic unless you are happy with 14 mpg and 2800-3200 cruse rpm. I would go with 3.0-3.10 with an auto. My setup also runs a RV type cam and I hate it. Makes great torque upto 3,500 rpm but is dead at 4,000 rpm. When you go to pass a car on the hwy and you stand on it, you want it to go and this thing is a slug! I can fry the tires off a light but I'm getting to old for that(its my driving record thats getting to long). I would look for a cam with about .475 lift and 218-225 @.05 for your combo. The 268H looks like a good fit for you. My engine has heavly ported heads and can use a little more cam so I have decided on the XE268H .510 lift and 224 @.05 to replace the slug I currently have

 

[68CoupeWimWhite]

Thanks for all the great info! So, a cam with about .470 is about where i need to be. I should also run the stock rear for the first season to see how it does driving. I should try and tone down the holley as the CFM might be a bit too much. I think i will try the shorty headers and see how that does. This has to be the best forum. I have some pics on my profile of the ride.

 

[D.Hearne]

The 670, while a tad big, will work fine. You can fine tune the cfm's by using a stiffer secondary spring. A 570 will have better throttle response, but only slightly.

 

[rbohm]

one nice thing about using vacuum secondary carbs is that you can over carb a bit without many of the usual problems. however you do want to get the carb sizing as close as possible for best results.