get a lil faster speed with stock 4 banger

get a lil faster speed with stock 4 banger

skituc

Jeeper
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Location
Tucson, AZ
Vehicle(s)
1985 CJ7,2.5L 4cyl,4 speed trans
I have a stock 85 CJ with a 4 cylinder engine, stock steel rims with 31x10.5x15 BFGoodrich tires. it scrambles good in the desert climbs like a champ. But lately I have been using it as my daily driver (it gets better gas mileage than my 4x4 F150). How can I get it to go a little faster than 55 mph? Will Aluminum wheels and maybe a 30x9.5 mud tire be better? any suggestions?
 
Droping down to a 30 will help a little, I wouldn't expect alot though.
A cj has a lot of wind resistance.
 
Pull it behind the F-AMC 150 ??

get a tune up.. with the four speed it should do a little better then 55.. the only other thing you could do would be drop to a smaller set of gears 3.55, 3.30 but then you will loose what ever off road manners it has. Also keep in mind that if your running tires larger then the stock tires your speedo will be off. I think for every percent up you go in tire size the speedo goes 1 percent slower.

If it came stock with 28" tire and you went to a 31 thats a little over 10% so at 55 on the speedo your doing 60ish.
 
Pull it behind my F150, lmao...
the little 4 cylinder runs good pulls the jeep up to speed fast but after 3rd gear fourth just kind of holds it. She moves about 65 mph with no wind going downhill, uphill is a different story. I just bought it and seems to be par from what the forums say. I looked up stock tires and found it came with 205x75r15, Tire guy laughed and said they were trailer tires. I dont want a wimpy mail postoffice looking jeep, lol.
It has weather cracked 31x10.5r15 BFG's on stock steel rims. It has manual steering and braking. Since I have to put new tires on it I was wondering by going down one size and thinner if it would make steering and top end a little easier. I really like the look of the 31" BFG's. But was thinking the 30x9.5 BFG MUD tires would still keep the aggresive look and saw where someone said they turn alot easier too. Just picking some brains before I make a purchase.
 
yeah the 205s end up being about 27" tall.. that thing wasnt meant for speed.. honestly I dont think 1 inch will make that big of a difference.
 
it might.. alittle. power steering would make it alot easier and alow you to run the more stable 10" tires.. I had a 61 buick with manual steering and it turned like :dung:. I think its just the manual part that sucks. Have you tried to put the front end on stands and compare it turning to make sure you have no binding in the box..
 
Hmmm, i had another guy tell me to add power steering. is that a hard conversion? My wife would like that but then she would be driving it all the time... I'll have to try that tip you suggested, I don't think the steering is binding just under inflated BFG's.
 
Hmmm, i had another guy tell me to add power steering. is that a hard conversion? My wife would like that but then she would be driving it all the time... I'll have to try that tip you suggested, I don't think the steering is binding just under inflated BFG's.

Number one would be to make sure the tires are atthe recomended presure

As far as the conversion goes you should be able to find all the parts relatively easy. you have tilt wheel?

If not a wagoneer set up should bolt into your CJ- colum, gear box, pressure and return line and the shaft goes between them. you may want to keep your pitman arm since the waggies are longer. I would think the pump is the same to but you would need different mounting brackets for the 4 cy. you should double check with some one who has a 4cyl to see what the bracket that mounts it to the block looks like. ..
You will also need the bracket that bolts it to the frame. If this is something you decide to do let me know i might have an extra bracket, if not they make HD versions that you can buy for about $65.

That would be alot better then down sizing to 30 tires especially if you have to buy a set new. Im pretty sure you could get all the parts together for less then the cost of a new set of tires.
 
I have a stock 85 CJ with a 4 cylinder engine, stock steel rims with 31x10.5x15 BFGoodrich tires. it scrambles good in the desert climbs like a champ. But lately I have been using it as my daily driver (it gets better gas mileage than my 4x4 F150). How can I get it to go a little faster than 55 mph? Will Aluminum wheels and maybe a 30x9.5 mud tire be better? any suggestions?

Try going down hill or down wind.:rolleyes:

Like Old Dog say's a lot of wind resistance.
Also very little horse power.
A exhaust header may help some.
View attachment 5948
 
Try going down hill or down wind.:rolleyes:

Like Old Dog say's a lot of wind resistance.
Also very little horse power.
A exhaust header may help some.
View attachment 5948

yea, I've been seeing just by adding a custom intake with filter and putting headers on adds a good percent of horsepower! was gonna wait for stock engine to wear out but I hear those 4 bangers last forever!
 
yea, I've been seeing just by adding a custom intake with filter and putting headers on adds a good percent of horsepower! was gonna wait for stock engine to wear out but I hear those 4 bangers last forever!

If a bigger motor is in store for it down the road I would just save my cash for that. If you put on a header and intake that may help you get to top speed faster but gearing and tires is what determine your overall speed. If the motor is almost tacked out to run 55 nothing added to the motor will help it.. But if your topped out at say 2000 rpm and the motor won't go highe then that you may have other issues that need to be addressed.
 
If a bigger motor is in store for it down the road I would just save my cash for that. If you put on a header and intake that may help you get to top speed faster but gearing and tires is what determine your overall speed. If the motor is almost tacked out to run 55 nothing added to the motor will help it.. But if your topped out at say 2000 rpm and the motor won't go highe then that you may have other issues that need to be addressed.

You are correct to a point, the problem with you hypothesis is wind resistance.
Even with a 2.73 gear in the diff, if you don't have enough horse power to over come the wind resistance your top end will be drag Limited .

Example: most 4cyl. cars will pull a higher top speed in 4th gear than 5th, because with the 25% reduction in gear ratio they can no longer pull to redline.
 
I'm sure that even with the added 20-25hp he may get with the header and what ever add ons he throws into it, it still won't be enough to help him get past the 55 mark that he wants.. I understand the jeep is shaped like a toasted and sucks areodynamicly but how many guy out there run their 4cyl CJ on 33's and still make it to decent cruising speed.
 
thanks guys for all your feedback! Bought this jeep from a guy that just had it sitting outside for over two years... After changing out the vital fluids, rodding out the radiator and running it constantly for the past few weeks its getting around better, must have blown out some of the cobwebs, lol. I like the fact of the smaller engine getting good MPG's, just wont go on any freeway road trips, I have a new F150 4x4 for that. like my friends tell me you get jeep fever and want to start changing this and adding that! I guess I have the fever...
 
yeah its deffinately an epidemic. My buddy started with redoing the brakes, then that turned into getiing new axles then we had to out board it to fit the full width axles and went to 35's for the bigger axles. Now Im in the hunt for some bigger gears for it. never stops.
 
I put new tires on it yesterday 31x10.5xr15 Falkin Rocky Mtn's...
My good buddy is a manager at Discount Tire he says all the Military people are putting these on their 4x's. they are a hybrid between highway tread and offroad. My Jeep seems to run easier wirh less road hum and they climbed the dirt area where I park it easier than the BFG's that were on it.
 

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