Performance upgrades to my bronco

[hayes1699]

Hey guys. I'm pretty new to the bronco world, but have been constantly using this website as a reference. So thank you all for the help.

I haven't been able to find the complete answer to a few questions, so I thought I should finally make a post myself. It also seems that every truck is kind of unique, as are the drivers with their specific needs and driving habits.

He it goes, and forgive my ignorance. I have a 1976 bronco that's in the middle of a restoration. While the stock 302 engine is pulled, I'm looking to increase the performance of the truck, specifically my low end torque. But I don't want to have a loud or uncomfortable ride at 70mph. I'm putting on 33x12.5x15 all terrain tires. Upgrading to ceramic headers and a 2 into 1 exhaust (flowmaster 70 or 50 series). I'm mostly using the bronco on the street with moderate off roading (camping hiking etc)

I had a compression test done and all cylinders are hitting at about 125... One was at 117.

looking to get some answers about...

1) with 33's should I move to 4:11 gears? The 33's seem to be in a grey area as I've seen many differing opinions. I really want a smooth ride but def don't want the sluggishness that bigger tires can bring.
2) along with the gears, I figured I might as well throw in a four barrel carb and switch to a better cam.

I have no idea which carb to get, any recommendations (looking to not have to sell the house to get it in).

I've read that an rv cam is good, but again I don't want to kill my top end. Is there a good cam somewhere in the middle?

4) upgrade ignition? Any recommendations?

So gears, carb, cam, headers, exhaust, and ignition...

Any ideas on how much performance increase that would bring? I'm sure someone will post that I should toss in a 351w, but I'm looking to keep the original engine.

Final question, are of these upgrades really going to be noticeable, or are 2 or 3 of them really gonna put my 90% there?


Thanks again!

Jonathan Hayes

 

[moe d]

just install a blower..

33 x 12.5 AT's are a good choice, great tires.. I run BFG AT same size and love em.

Edelbrock 2121 manifold with a 4bbl carb 500 - 600 cfm with a mild cam and i think u will be happy. Also, bore the motor .30 over and yopu should be good to go.

MSD ignition is always a nice upgrade.

Welcome to your new addiction!

 

[SteveL]

Yes I'm a big fan of the 351w swap. For the 302 headers, a K&N air filter are a good place to start. If you're going thru the motor an rv cam would be nice. With 33's seeing lots of fwy time I had good luck with 3;73 gears. You can get more low end with the 4;11 but pay more at the pump with higher rpm on fwy. We have the flowmasters on our 66. They sound great but are loud. I ended up putting stainless borlas on my 72 to keep the noise down. For a carb the edelbrock/carters run good and dependable on the street. Plus they are easy to tune up. Their downside is they suck off road. I ended up swapping to a q-jet .for the carb. I run HEI ignition on both. Yoiu also may need to worry about smog legal dependindg on where you're at.

 

[broncnaz]

A cam and headers are your best bets the cam will be the key factor in making any power. Edlebrock performer cams are ones with siliar specs are commonly used. call a few cam comapanies and get there recommendations.
Intake is up to you its not really needed but I like 4v setups my self so as was said the edlebrock 2121 is a good choice. carb size I'd say no bigger than 600 cfm 500 cfm would be better. As for carb choice I like holley's there better all around. Edelbrocks are fine for the street but tend to have issues on hills while offroading.
Your 76 should already have a electronic igintion there's nothing wrong with it leave it alone. high dollar aftermarket igintions are really a waste of money and half the time they dont last nowheres near as long as the factory stuff. Just recurve the advance in your factory setup and it will be all you need.
Axle gearing is recommended but with the correct camshaft you can run the 33in tires and 3.50 gearing with no sluggishness. Plus that combo give you a slight OD effect for free.

All in all the upgrades should wake the engine up back in 76 the engine was rated for about 140 hp after the upgrades you might see about 200hp theres really no garruntee on that as it depends on the parts used but you will see a good increase in power.
A 351W swap would be a easy way to gain some torque but you still need to upgrade parts in it just like the 302 to make great power. I'd probably just stick with the 302. you can build up a 351W later on.

 

[trippin]

would you suggest running a higher octane fuel with the performance upgrades, or is regular unleaded still fine?

 

[bmc69]

would you suggest running a higher octane fuel with the performance upgrades, or is regular unleaded still fine?

Running higher octane than is required to defeat detonation at optimum ignition advance is actually a performance 'reducer'..

 

[bluebronco69]

for gears are you using an auto trans? stock 3peed or something with a low 1st?

if auto or a manual with a granny low (like NP435) i would stay with 355 gears,
if the 3spd. i would go with 411 gears.

depends on what kind of wheeling/driving you do though... need more info

 

[trailpsycho]

Forget the Flowmasters. They are really loud. In a previous incarnation, I had long tube heades, large SS Delta Flow 50s...it sounded bad-ass but very loud. I switched to a 2-into-1 with a super-sized Maganflow SS muffler and its about right...its still loud...hell, its a Bronco with a safari top...what do you expect, right?...But much more livable than the Flowmasters. I can now hear the phone ring...whether or not one can have a reasonable conversation is still in debate....but before no way in hell.

I agree with sticking with the factory Duraspark ignition...its dependable, readily available almost anywhere-if there ever is a problem....if you stick with the carb, that is.

As far as carb, I would say to look into something under 500 cfm. Maybe the Holley Truck Avenger 470. A friend of mine is running a 400 cfm carb on his Bronco and it scoots just fine.

I would think your compression ratio is a little tired. I would see if you could get away with going 10 or 20 over and throw a new kit in the motor. Otherwise, look into a long-block with some stock E7 Mustang heads (better than your stock heads) or, better yet, some aftermarket aluminum heads. A fresh short block with a full edelbrock Performer package (heads, cam, intake, carb) would be a nice upgrade. The Edlebrock 1406 carb is a good one for the street, but it does suffer off camber...the Holley TA might be a better choice all around, but I think the 1406 is a better street carb.


Definitely should consider a regear to 4.11s or 4.30s...depending on how much highway you will be doing.

Another thing that is unclear, how much driving time do you have in the truck? Really analyze what your plans are and what you want...it may be cheaper to buy a "crate" or "reman longblock" or a package like the Performer. As well, if you havent considered EFI, you might look into it. For the cost of a new intake and carb, you could be well over half-way to EFI. Are you planning on doing the work yourself? Keep us appraised of where you are, what your planning and just ask if you arent sure about direction...no shortage of opinions here, surely you will be find one to suit you.

Best

John

 

[Dan's73]

I did basically what TrailPsycho suggested with the 302 in my '73 & the full Edelbrock Performer kit: cam, heads, intake, & carb. I found that I didn't like the Edelbrock carb so much & swapped it out for a Holley 470TA. I like it a lot. Also added roller-tip rockers, a K&N air filter in the stock assembly, and some Motorsport wires (had 'em all so used 'em all). Put Duff's long tube headers on it, dual 2.25" exhaust running through stock-like mufflers & exiting behind the rear wheels. The motor had already been bored out & rebuilt by the PO,and was running the Duraspark ignition. I just wanted a little more oomph out of it & I got it.

Also, running the stock 3.50 gears & 33" tires with no issues or complaints. Am thinking about going to 4.11's someday but there's lots more I'd likely do before that.

 

[Ranchtruck]

Don't rebuild the 302. It's cheaper and quicker to start with 96-97 explorer 5.0 or a 88 or newer 351w. I would really recommend the 351w if you plan to keep the 3.54 gearing with 33's. The bigger displacement will have an easier time being loaded at lower rpms without bogging down. A 4 barrel aluminum intake will help offset the extra weight of the 351 a bit. Be very careful with your carb selection, many aftermarket carbs will not work well offroad, and may return poor millage but good WideOpenThrottle performance on the street. RV cams are fine, they're about what came stock from the factory and unless you have aftermarket aluminum heads (another weight offset for the 351w), the top end won't be killed by the cam because the heads couldn't keep up anyway.

Speaking of top end, a healthy 302 with gt40 explorer heads will push a 3spd 4.11 bronco on 31's past 110mph with ease at 5k feet altitude. It gets up there quick too. Oh, and that's with a Summit RV cam and an Autolite 4100 carb with stock exhaust manifolds and stock offset air intake and filter.

 

[Rustytruck]

Your biggest issue with the 76 302 is the factory 8.0 to 1 compression ratio. You can buy all the speed parts you want but if you keep the stock compression ratio you will not recieve the performance your paying for. Are you keeping the cats or is this an offroad truck. If your keeping the factory compression ratio then figure the need to go to 4:11 gearing at least.

 

[buckintone]

Gearing, exhaust and STOCK CAM. 4:11s will be good/ok with 33's and a c4, do not put another cam in it, the stock cam will provide you with the best low end torque, anything else will make your 33's feel boggy with a c4 and 4:11's(ask me how i know). If you're not worried about high rpms on the freeway, go with 456's you'll feel more torque on the bottom, or go with 488's and drive past any on ramp to a freeway you ever see Exhaust should be no more than 2" with a stock 302 and definitely use an h pipe or x pipe for the scavenging and back pressure balance(feels torqyer). This is what should give you the feeling of power you're after. Mid to hi end set up will never kick you in the ass like this will, unless you have a stahl converter and mash the pedal every time! which defeats the grunt and crawling ability of our beloved bronco's. JMO

good lucky buddy

 

[bmc69]

Forget the Flowmasters. They are really loud. In a previous incarnation, I had long tube heades, large SS Delta Flow 50s...it sounded bad-ass but very loud. I switched to a 2-into-1 with a super-sized Maganflow SS muffler and its about right...its still loud...hell, its a Bronco with a safari top...what do you expect, right?...But much more livable than the Flowmasters. John

I'll second that three times. My old school trail rig has duals with Flowmaster 40s...behind a 408 Cleveland. Being behind me on the trail is universally regarded as "hatefull".%)


I'm all about less noise and the simplicity of 2-1 single out exhaust these days...on practically everything we own.

 

[jw0747]

one of the earlier posts said to not rebuild the 302 but instead go with a used Explorer engine or a 351W that has most of the modern goodies like serp belt setup, efi and other stuff. if you give this some serious consideration think about this, would you prefer a rebuilt engine knowing exactly what was done to it and that most of the innards are new plus a new carb and cam? or do you want to buy an engine probably from a salvage vehicle that already has wear on it and you don't know its history. just sayin'
.

 

[hayes1699]

thanks alot to everyone for all the replies… it's really tuff because im kind of at the same starting point as before. everyone seems to have a different opinion/recommendation, and they widely vary!

from the forum and research, it definitely seems that the biggest problem with the 302 is the compression ratio. correct me if I am wrong, but boring the engine to .30 would help this yeah?

im looking now to:

1) headers
2) x-pipe exhaust (im going to go with flowmaster, but their most quiet series)
3) 4 bar carb
4) bore to .30

i really dont know much about cars, so some of the responses have been over my head, but thru some wiki articles, i am catching up! what else do i need to consider when changing the compression ratio?

thanks again guys, the response i have gotten is greatly appreciated.

 

[broncobilly72]

I had my 72 302 engine rebuilt with new larger valves heads, rv cam, heavy duty oil pump, heavy duty waterpump, new eldebrock performer manifold, new 4 barrel carb, shorty headers, and a petronix ignition kit. My horse power went from 140 to about 280 hp. my gas milage is about the same 15.8 to the gallon. No complaints!

 

[jw0747]

simply stated lower compression in the cylinders is generally caused by worn piston rings and valve seat wear on the heads. most times boring a block is done to correct worn or scored cylinder walls when an engine is rebuilt. some guys will bore a block just to increase an engine's bore size when building a performance engine. boring a block by itself doesn't improve compression. new piston rings and a valve job do especially when a performance job on the heads is done.

 

[Boss351]

Headers right off the bat performer intake 650 holley .456 lift cam new timing chain if you do a cam swap make shore you BUY the breakin additive or YOU WILL be doing the job again She will perc right up after that

 

[fetorino]

For what its worth JMO

thanks alot to everyone for all the replies… it's really tuff because im kind of at the same starting point as before. everyone seems to have a different opinion/recommendation, and they widely vary!

from the forum and research, it definitely seems that the biggest problem with the 302 is the compression ratio. correct me if I am wrong, but boring the engine to .30 would help this yeah?

No but when you are rebuilding it you can choose a piston to give you the compression you want based on the heads you use.

im looking now to:

1) headers
2) x-pipe exhaust (im going to go with flowmaster, but their most quiet series)
3) 4 bar carb
4) bore to .30

i really dont know much about cars, so some of the responses have been over my head, but thru some wiki articles, i am catching up! what else do i need to consider when changing the compression ratio?

thanks again guys, the response i have gotten is greatly appreciated.

1) headers sure the right ones can gain you some power, and some exhaust leaks also.
2) for a Bronco I prefer doing a 2 into 1 exhaust. You can buy headers and complete 2 into 1 from BC broncos. The headers are a little pricey but the 2 into 1 is pretty cost effective.
3) If you use a small Holley, an Autolite 4100 or a quadrajet then it may gain you a more responsive feel but at Bronco rpms the hp figures won't be all that different.
4) Do you know you need to bore it? If you are rebuilding it then it is likely you will bore it to clean up the cylinders. This will be driven by the condition of the cylinders and the availability of pistons in the size of the bore. If I were building a non FI engine I'd use a set of GT40 iron heads, get compression to 9.5 and run a replacement of the Explorer camshaft. Doing this you will need to run the later firing order to match the cam. You will also ned a steel or bronze gear on your distributor (send your stock distributor to be rebuilt and recurved ignition timing makes a big difference). The roller cam also requires a spider plate added in the lifter valley (cheap and easy during a rebuild). I would say this combo would give you good usable power in the rpm range a Bronco likes and will make the headers and 4bbl worthwhile upgrades. TMO

 

[broncnaz]

everyone seems to have a different opinion/recommendation, and they widely vary!

from the forum and research, it definitely seems that the biggest problem with the 302 is the compression ratio. correct me if I am wrong, but boring the engine to .30 would help this yeah?

i really dont know much about cars, so some of the responses have been over my head, but thru some wiki articles, i am catching up! what else do i need to consider when changing the compression ratio?

thanks again guys, the response i have gotten is greatly appreciated.

Yes opinions vary gives you a wide range of thought there are many different options although most of the opinions were based more on answering your orginal question directly. Some of the others were just different routes to take.
Comp ratio is sort of lacking in the mid 70's ford engines but its not a end all you just have to make sure the cam you pick willl work with your compression ratio. A .030 over bore only rasies the compression by .10 or so. Not really much of a gain in itself but pistons with different deck heights or dish volumes are availible and thats what changes the compression ratio. Higher compression in itself doesnt make very much power even going to 9-1 you'd probably only see a 10 HP gain but higher compression helps and allows bigger cams to be used which is where the power is made.

Since your new to engines and such I would still recommend just installing a cam and intake ect on your 302. It will give you a lot of insight and some experiance. Get a good repair manual and go to it. Then later on you can build up a 351 or whatever else you chose with more knowledge about what your doing.
Another thing to consider is cost of some of these upgrades and some fo the suggestions. gearing swaps tend to cost over $1200, where a simple cam intake and carb swap should only run about $600, EFI swaps about $1K + Explorer motor swap $1-2K. Sure sometimes things can be done cheaper if you happen to score all the right parts for next to nothing but in reality a lot of swaps cost a lot more than people admit.