in 7.5 rear end anything bigger than 4.10 you need a speical cross pin. up grade to a 8.8. had a 7.5 in one of my races and it had a c-4 in it and it was fine untile I put a t-5 in it. It lasted 3 passes. on the third it broke a carrier cap and all the teeth on the pinion and all but one on the ring gear.

 

We built a motor for an 85 mustang. We found a 79 302 block and put in new rings and bearings all stock with a ford motorsport e303 camshaft and factory roller lifters and double roller timing chain(I drilled the block for the lifter girdle). We used 70 cast iron 351w heads with a fresh valve job an offy intake w 750 holley carb the rockers are stock but are fully adjustable with poly locks. We used a cheap proform distributor that's like a GM setup. We expected the car to run 8.50s or so but even with a 4.10 gear setup in the 1/8th mile its only running 9.90s at 70mph. If you use a drag race calculator that's only making about 160hp. I was hoping that someone had used this easy basic setup and had better success. A stock 302 that year was rated at about 225hp I think, so we have been really disappointed so far. The car seems to run strong and sounds good ,it just doesn't perform well. Maybe we need to turn more rpm to be in the power band but I have been afraid to go too high. If you could let me know what you think hp and max rpm would be on this setup we would appreciate it greatly. Thanks for your help.

 

In 79 the 302 only put down 140hp but that was also with a 2 barrel carb. In 83 when it was stepped up to the 4 barrel it was 175hp. Tuning, suspension, and tires have alot to do with that time. The 1/8th mile is all about that launch.

 

I have slicks on the car so there is no tire slipping. The best 60ft time is a 2.23 with the 4.10 gear. The 69 mph ET is what I don't understand. It just seems to have no real power.

 

Yea that 60ft is hurting you. Its not bad but could be alot better.

Clear this up for me though, stock rockers that are fully adjustable with poly locks? The carb is too big for that setup and if not tuned right it can and will kill your times. Do you have any suspesion work?

 

The Windsor cyl heads use floating rocker arms, not positive stop like most newer 5.0 use therefore, they were adjustable on early model 351w. I had trouble with the rocker nuts pulling off so I put on 5/16 poly locks in order to correct it. No, I don't have any suspension work but, with the slicks on my 60ft time went from 3.33 originally down to 2.23. I was wondering how high this motor could turn so I could get a rev. limiter in order to launch harder to try to reduce my 60ft some more. Even if I run 1.80 60ft then the car still only runs 9.60s and I thought it would be a lot faster.

 

Well first off that cam isn't going to run you much over 5500 and did you upgrade the valve springs?????

 

The valve springs are the stock 351w 69 model. Checked the spring rate with some cam shaft web sights and the springs are supposed to work fine with the lift and duration of a E303 cam.

 

IDK about those but I know the stock E7 springs are not the best for it. Are they at least new??

 

Yes they are.