Yeah, my rear differential is an 8.25

[efriedrich]

I didn't know much about M bodies before I bought my 86 fifth ave the other day. I started doing a little research and evidently it could have either a 7.25 or an 8.25 so I just looked and its a 8.25. Thats great because I'm itching to start adding a little HP with a edelbrock 4 barrel performer intake and a 600 edelbrock carb that's for sale locally. Stock HP for the 318 is suppose to be 140 so I'm hoping to add dual exhaust and maybe headers with the new Carb and intake and be around 200 HP. I would think the 8.25 should be able to handle that and then sum. Also I want to take off the lean burn system and do some ignition up grades, any sugestions are appreciated. I dont plan on cracking into the motor any time soon so I just want to find some easy HP.

 

[bremereric]

I didn't know much about M bodies before I bought my 86 fifth ave the other day. I started doing a little research and evidently it could have either a 7.25 or an 8.25 so I just looked and its a 8.25. Thats great because I'm itching to start adding a little HP with a edelbrock 4 barrel performer intake and a 600 edelbrock carb that's for sale locally. Stock HP for the 318 is suppose to be 140 so I'm hoping to add dual exhaust and maybe headers with the new Carb and intake and be around 200 HP. I would think the 8.25 should be able to handle that and then sum. Also I want to take off the lean burn system and do some ignition up grades, any sugestions are appreciated. I dont plan on cracking into the motor any time soon so I just want to find some easy HP.

I don't mean to burst your bubble but I don't think you will get close to 200 with the current changes you plan to make...play around with Comp Cams cam selector software that you can download from there site....stay honest with the 8.5:1 CR ratio and add the headers and better intake manifold...it will suggest 5 or more cams that will get you there...my mild 440/440 lift cam will get me about 247 hp at 5000 rpm...others will tell you the same as me...the cam is the heart of the engine...download yours now at

http://www.camquest.com/

 

[efriedrich]

So if I go with a cam whats heads should I use. What HP neighborhood do you think I will be in with cam and head change with the other modifications. My goal is to have some fun and maybe surprise a few ricers at the stoplight and a couple 1/4 mile runs.

 

[crayzcuda]

Best performance gain you should do to start is rear gear change, as most 5th Ave's came with 2.2 / 2.45 gear. If it has these gears, it will need a rear end change to one with 2.76 or better. These rear ends will accept gear changes to something like 3.21's. I would run at least a 3.21 to get all that weight moving. Comp cams 262 cam would be a good choice with your above combo to keep the torque up. For a little more get up and go, I would run a 2400 stall converter. What you need more than horsepower is torque. Hope this helps.

 

[bremereric]

So if I go with a cam whats heads should I use. What HP neighborhood do you think I will be in with cam and head change with the other modifications. My goal is to have some fun and maybe surprise a few ricers at the stoplight and a couple 1/4 mile runs.

Stay with all of the same right now and play around with the Camquest software...lifters are no more than 80 bucks and a flat tappet cam is 200 bucks...cheap for the horsepower...most of them have notes...such as smooth idle....good for power brakes...stock torque convertor and such....after you pick a couple call them and they will point you in the right direction....lots of money is one and little money is the other..as before mentioned torque convertor and such....

 

[volarerob]

More horse power is always a good thing lol so don't get me wrong here but my stock 130 hp 318 felt like it had more power than my 300 hp tons of $$$ 318 because my stock rear had 3.23's but it gave out and I swapped it with a good junkyard 8-1/4 only to find out it had 2.71 gears. It's a dog off the line but tons and tons of top end. Torque is a funny thing and is often overlooked in the never ending pursuit of more power. I’m not saying don’t do some engine improvements but speaking from experience, I was really disappointed with the new 318 build until I realized the real problem. Way to tall of gears in the rear, only good for top speed. Make sure to budget in some money for a gear change or even a new rear end.

 

[A38Valiant]

There's probably a 3.55 geared 8.25 sure-grip under a rusty Dakota in a junkyard near you......

 

[efriedrich]

Its funny you say that because I was in a bone yard the other day looking at a few. Would I need to move the springs.

 

[A38Valiant]

Was thinking just to grab the guts, i.e. the ring and pinion, along with the carrier / sure grip unit. If you are thinking about the whole rear, make sure you are looking at 1990 and earlier, as 91 to 03 Dakotas use six lug wheels. Also, 2 wheel drive Daks mount the rear on top of the springs like a car, while 4 wheel drive Daks have the axle under the springs like a fullsize pickup.

 

[Shorty Thompson]

What year's your car/motor ? Could be as low as 8:0-0 compression range . cams with this combination are really tricky to play with . Crack the valve cover off and see what your casting numbers are . Need combustion chamber sizes and valve sizes . 302 / 308 heads make a huge differance over open chambered heads . Jmo .