302 and more power questions

[matts460]

At 70mph would be 3279rpms with 35's and 4.88's not bad good power to the ground! Ratio x speed x 336 divided by tire size. Pick a speed you like to cruise at and stay around 3000rpms

 

[4x4livn]

At 70mph would be 3279rpms with 35's and 4.88's not bad good power to the ground! Ratio x speed x 336 divided by tire size. Pick a speed you like to cruise at and stay around 3000rpms

Wont all of that change when I add an overdrive transmission to this thing? What is a good cruising rpm with an overdrive at say 65? Sorry but its been so long since I have owned a gas vehicle that i really dont remember.

 

[matts460]

Oh with over drive youd be just fine for cruisen then!, that would drop the rpms down a good bit disregard what i said! LOL i didnt realize you mentioned overdrive that math was all for 1:1 ratio. Also i found engine build article again it was a 302 from 91 mustang all stock and they didnt test differnt carbs like i had first thought. But it made right at about 400hp at 6000rpms and well over 300 ftbs at 4000rpms stock cam! Just Heads,headers, intake,and roller rockers all added one at a time making differnt HP/tQ numbers. Pretty cool read.

 

[4x4livn]

Oh with over drive youd be just fine for cruisen then!, that would drop the rpms down a good bit disregard what i said! LOL i didnt realize you mentioned overdrive that math was all for 1:1 ratio. Also i found engine build article again it was a 302 from 91 mustang all stock and they didnt test differnt carbs like i had first thought. But it made right at about 400hp at 6000rpms and well over 300 ftbs at 4000rpms stock cam! Just Heads,headers, intake,and roller rockers all added one at a time making differnt HP/tQ numbers. Pretty cool read.

While that kind of power would be awesome, I cannot think of a time that i would ever want to be spinning them motor that fast! In my case would swapping the heads really make that big of a difference? I'm not looking to spin a ton of rpms, so I wouldnt think i would run out of air flow volume in the heads. With that in mind, would my money be better spent on a cam?

Speaking of cams, I was looking at Comp cams the other day, it appears they have a cam that makes power from ~800rpm to ~5000rpm. Having power off idle like that is something I could really use.

 

[matts460]

Ya thats were things get tricky remmember thats peak HP at peak rpms but you can bet that the HP and torque is much more than what it was stock at the lower end too. Then Add the RV cam you mentioned and bingo youll be set. You can basically get good ideas from that build up even minus the heads add everthing else plus your as mentioned cam and youll be fine. A 302 small block will have to spin a little more RPMs to see most power gains A healthy 302 thats all done at 6000rpms is really not crazy at all! its about right. But thats were the gearing helps take avantage of the HP too, but mostly in the mud were keeping the tires cleaned out is important. I guess im trying to say is you could have a motor that takes full advantage of its power in all aspects of its rpm range. From low to high.

 

[4x4livn]

Ya thats were things get tricky remmember thats peak HP at peak rpms but you can bet that the HP and torque is much more than what it was stock at the lower end too. Then Add the RV cam you mentioned and bingo youll be set. You can basically get good ideas from that build up even minus the heads add everthing else plus your as mentioned cam and youll be fine. A 302 small block will have to spin a little more RPMs to see most power gains A healthy 302 thats all done at 6000rpms is really not crazy at all! its about right. But thats were the gearing helps take avantage of the HP too, but mostly in the mud were keeping the tires cleaned out is important. I guess im trying to say is you could have a motor that takes full advantage of its power in all aspects of its rpm range. From low to high.

That's a really good point. It's easy to get caught up in peak power numbers. So you agree that with my lower rpm goals that I can just skip the heads?

 

[jagdprcp]

You could skip the heads now. Then if you were unhappy with the overall perfomance, you would have something else to upgrade... New heads would add more power but you might just be happy with using the existing heads.

Skeeeter

 

[broncobilly72]

From what I understand a 1972 302 had lower horsepower than a 1971 due to the fact that in 72 was the beginning of SMOG reduction so compression in the heads was lowered and EGR AND PCV VALVES WERE ADDED. I upgraded my 72 302 with new heads, new cam, performer manifold, 4 barrel carb, electronic ignition, headers, heavy duty oil pump, and heavy duty water pump. All this boosted the HP to about 285 over the old 140. Has a lot of get up and go....pulls my boat now without burning up clutches.

 

[broncnaz]

About 1/2 the HP differenace between 71 and 72 was in the way the numbers were attained. But yes the smog years they were detuned mostly with timing chain probably a cam change. There was very little compression ratio change something like .1. PCV valves were standard on ford engines starting sometime in the 60's. EGR valves didnt really take away HP. And some broncos cam with smog pumps even before 72.

 

[BluebroncoNC]

Just read the entire thread. Great read, a lot of good info here. Thanks.

 

[4x4livn]

Just read the entire thread. Great read, a lot of good info here. Thanks.

Glad my questions could help someone else. What are you thinking about doing?

 

[matts460]

Ya man ! Based on the 400HP stock 302 build up you can build a good condition 302 with mild cam as you described IDLE to 4800 0r 5500 rpm range. Decent long tube type headers, Good dual plane alum intake manifold, probly just a good 600cfm carb or slightly smaller as you had mentioned, good double roller timing chain set, Or at least a good straight up timed metal gear timing set from parts store (cloyes) brand. Cant go wrong with roller rockers too! Then if that wasent enough throw the AFR heads on it Bam 100 extra poneys by 6000RPMS. No matter what that motor is makeing power from IDLE through the end of the RPM range. Would be differnt if you were building a drag truck/car and the motor was build to start making power at 3000-3500rpm and was done making power at 7500-9000RPM. Then you would take the Automatic trans throw in a 3000RPM stall converter and 4.88 gear with 28 inch talll slicks And your were launching the vehical at 3200rpms at the starting line! LOL I think by now you get the point of it all and that nobady is steering you in the wrong direction. haha. DO you want most of us chiming in to tell you what we run in our broncos instead of all the What if this that and the other?

 

[4x4livn]

Definitely!

 

[BluebroncoNC]

Glad my questions could help someone else. What are you thinking about doing?

At the moment, nothing. My 33's and my 3.50 are keeping me happy. Mildly messaged my 302. New intake, 4 barrel carb, rv cam, split the exhaust through magnaflows (nothing to prove this, but my seat of pants experience, but it feels like I'm running around 180-200hp). I run between 2200 - 2400 on the highway. Still feels punchy taking off at lights. Oh, 3 speed auto.

So far so good. The 4.11 idea sounds interesting though.

 

[matts460]

OK i guess i can start since im still up and goofing off. Hehe. Basic 302 block. .30 over, flat top pistons. 1968 302 heads with the factory adj rockers (smaller combustion chambers= more compression) Cheap long tube headers with dual exausht and turbo mufflers, Edlebrock 289 streetmaster intake its an old school single plain intake with small runners works about as good as dual plain manifold. Old 1960's Holley vacuum secondary 4150 series 600cfm carb, Crane RV cam (nice little lopey idle) Factory dizzy with factory electronic ignition. Stock waterpump, 195 t-stat, Champion Alum radiator. Stock C4 with a shift kit, 4.57 gears and 31's. Overall the truck runs really well! Tends to get about 13MPG on road trips cruisen 60mph

 

[4x4livn]

At the moment, nothing. My 33's and my 3.50 are keeping me happy. Mildly messaged my 302. New intake, 4 barrel carb, rv cam, split the exhaust through magnaflows (nothing to prove this, but my seat of pants experience, but it feels like I'm running around 180-200hp). I run between 2200 - 2400 on the highway. Still feels punchy taking off at lights. Oh, 3 speed auto.

So far so good. The 4.11 idea sounds interesting though.

Which cam did you go with?

 

[4x4livn]

OK i guess i can start since im still up and goofing off. Hehe. Basic 302 block. .30 over, flat top pistons. 1968 302 heads with the factory adj rockers (smaller combustion chambers= more compression) Cheap long tube headers with dual exausht and turbo mufflers, Edlebrock 289 streetmaster intake its an old school single plain intake with small runners works about as good as dual plain manifold. Old 1960's Holley vacuum secondary 4150 series 600cfm carb, Crane RV cam (nice little lopey idle) Factory dizzy with factory electronic ignition. Stock waterpump, 195 t-stat, Champion Alum radiator. Stock C4 with a shift kit, 4.57 gears and 31's. Overall the truck runs really well! Tends to get about 13MPG on road trips cruisen 60mph

Huh thats interesting that you like 4.57 gears on 31s. I would think your mileage would be terrible with that gearing, but your mpg is far better than mine. Any idea what your rpm is?

 

[matts460]

At around 60mph Its about 3000 rpm Give or take. Just got home from a 160mile round trip for family get together today for Easter took one full tank 13gallons.It was very windy too! Thats what approx 12.3 MPG. cruisen 60-65mph.

 

[BIG_UGLY75]

Not positive on the mpg.... It was over 30...