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Discussion Starter #1
Ok.. I have read a bunch, and searched a bunch.. and learned alot.. but I'm still lacking.. so heres what i'm planning for some future work.
I have an 86 302 EFI Bronco, odometer says 39k miles.. when I pulled the valve covers, clean bronze color.. no crud.. 50psi oil pressure pretty much all the time. Seems to run a little lean (plan to remedy that in the next few weeks, but thats another issue.) So what I WANT is to get a little more umph out of it.. Not a race truck, not pulling anything heavy like a camper, just want it to move a little better down the road and pull my ATV better through the hills of NW Arkansas.. So, I have found a couple sets of GT40 and GT40P heads for about $150 a pair.. and I'm looking to do the swap with minimal headaches. :rofl:
This is what I know (hope I got it right).. The stock 302 intake will work, as I dont want the headache of swapping to the explorer intake. If I go with the "P" heads, I will need the Ford motorsports shorty headers (part number is all over the forums) for spark plug clearance. I plan on headers either way. And the Comp Cams 31-255-5 is a good choice for keeping vacuum on the Speed Density engines. And many people say its good to upgrade to the 1.7 rockers on the GT40/GT40P heads.

I'm good at turning wrenches and taking stuff apart and putting it back together.. I'm not good on compatability knowledge or engine building knowledge.. and knowing what will clearance and work together, and what wont
So here's what I dont know..
1. Which heads will I see better gains out of if I plan to do the headers, stock 302 truck intake, and the Comp Cam..

2. If I were to use the 1.7 Rockers, I heard there may be valve clearance issues.. Would one head work better than the other for this? (heard the "P" heads have a larger(?) combustion chamber? Would that matter? And all the 1.7 rockers I find have roller tips.. are those fine to use even though I dont have a roller engine?
Also, I'm sure the Cam would affect valve clearance also.. so would it be best to do one or the other? Cam or Rockers?

3. How would I know if I can still use my factory push rods.. Always heard if you change cams, you should change pushrods and valve springs.

Again.. I'm good at the grease monkey part... not so much at the knowledge part. I have done engine swaps.. but no actual engine building experience.
I just want to make sure I dont pull a no brainer and do something stupid to ruin heads, push rods, or anything else and waste a bunch of money.
Any info or advice is welcome.. Any changes to my plans are welcome as I havent bought anything yet.. So I'm seeking guidance and experience in this area from people who know way more about this than I do.. So, Please be gentle, I'm an engine building virgin. :beer
 

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Ok.. I have read a bunch, and searched a bunch.. and learned alot.. but I'm still lacking.. so heres what i'm planning for some future work.
I have an 86 302 EFI Bronco, odometer says 39k miles.. when I pulled the valve covers, clean bronze color.. no crud.. 50psi oil pressure pretty much all the time. Seems to run a little lean (plan to remedy that in the next few weeks, but thats another issue.) So what I WANT is to get a little more umph out of it.. Not a race truck, not pulling anything heavy like a camper, just want it to move a little better down the road and pull my ATV better through the hills of NW Arkansas.. So, I have found a couple sets of GT40 and GT40P heads for about $150 a pair.. and I'm looking to do the swap with minimal headaches. :rofl:
This is what I know (hope I got it right).. The stock 302 intake will work, as I dont want the headache of swapping to the explorer intake. If I go with the "P" heads, I will need the Ford motorsports shorty headers (part number is all over the forums) for spark plug clearance. I plan on headers either way. And the Comp Cams 31-255-5 is a good choice for keeping vacuum on the Speed Density engines. And many people say its good to upgrade to the 1.7 rockers on the GT40/GT40P heads.

I'm good at turning wrenches and taking stuff apart and putting it back together.. I'm not good on compatability knowledge or engine building knowledge.. and knowing what will clearance and work together, and what wont
So here's what I dont know..
1. Which heads will I see better gains out of if I plan to do the headers, stock 302 truck intake, and the Comp Cam..

2. If I were to use the 1.7 Rockers, I heard there may be valve clearance issues.. Would one head work better than the other for this? (heard the "P" heads have a larger(?) combustion chamber? Would that matter? And all the 1.7 rockers I find have roller tips.. are those fine to use even though I dont have a roller engine?
Also, I'm sure the Cam would affect valve clearance also.. so would it be best to do one or the other? Cam or Rockers?

3. How would I know if I can still use my factory push rods.. Always heard if you change cams, you should change pushrods and valve springs.

Again.. I'm good at the grease monkey part... not so much at the knowledge part. I have done engine swaps.. but no actual engine building experience.
I just want to make sure I dont pull a no brainer and do something stupid to ruin heads, push rods, or anything else and waste a bunch of money.
Any info or advice is welcome.. Any changes to my plans are welcome as I havent bought anything yet.. So I'm seeking guidance and experience in this area from people who know way more about this than I do.. So, Please be gentle, I'm an engine building virgin. :beer
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=812&sb=2

Looking at the cam specs, I would say that you dont need the 1.7 rrs. It has good duration/lift #s for a mild SD setup as is. Adding the rockers would increase the lift even more, and would be pushing the limit on the stock gt40/gt40p valvetrain.

I would just follow the KISS principle here, have the heads cleaned up/checked out, add some HD springs (if neccessary), bolt on the heads and cam, and let it eat.

As far as which head is better....
On a mild build they both are gonna be solid performers capable of supporting your setup, with negligible difference in performance between the two. I would go for the gt40 heads, for ease of installation, better ergonomics, and expanded header options as the criteria.

I am pretty sure your pushrods can be reused since you are staying with a flat tappet cam, but double-check me on this. Just visually inspect them for wear on the tips and roll them on glass to make sure they are true.

The above would be the best "bang for the buck" approach, IMO.
 

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Eric
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Responses in red:

... So here's what I dont know..
1. Which heads will I see better gains out of if I plan to do the headers, stock 302 truck intake, and the Comp Cam..

"P" heads flow slightly better, but, it's negligible. Maybe, 3-5 HP difference between the two sets of heads on your set-up. You, also, get a better burn from the revised plug angle. HOWEVER... the "P" heads do not have thermactor ports for use with your smog pump plumbing. This only matters if you need to pass emissions.

2. If I were to use the 1.7 Rockers, I heard there may be valve clearance issues.. Would one head work better than the other for this? (heard the "P" heads have a larger(?) combustion chamber? Would that matter? And all the 1.7 rockers I find have roller tips.. are those fine to use even though I dont have a roller engine?
Also, I'm sure the Cam would affect valve clearance also.. so would it be best to do one or the other? Cam or Rockers?

Keep the lift under .480" with the cam you choose and you will be fine with 1.7's. If in doubt, clay up one of the heads the check PTV clearance. You can get away with as little as .060".

"P" heads have SMALLER chambers (P's = 58-60cc / GT40's = 60-63cc). This will only increase your static compression ratio by ~.3-.5 points. Dynamic compression ratio is what's more important and this is gonna be way too low on your motor to make a difference either way.

Rockers will be fine as long as they're for pedestal mounts and not stud mounted. Pedestals are what both sets of heads have.

You can go with up to a .520" lift cam before stock valve clearance needs to be worried about with your motor as long as you have stock pistons with stock valve reliefs. If you have ever seen a valve-train at work, you will notice that the piston "chases" the valves closed on the compression and exhaust stroke, which limits the possibility of contact. Neither valve is fully open at piston TDC. You have more problems with cams which have a VERY narrow LSA and large lifts +.600" (read: race cams), which you are not running.

3. How would I know if I can still use my factory push rods.. Always heard if you change cams, you should change pushrods and valve springs.

Stock pushrods will be fine as long as you are running stock lifters. "P" heads have shit valve springs from the factory. If you run 'em, replace the springs. Not recommended to use anything over stock Explorer cam valve lift (.422"/.448"). Anything over .480" lift and you may experience coil bind. They, also, have a poor rate for poundage. You want a stiffer spring to take advantage of the new cam's ramp rates. GT40 heads handled a .479" lift. This was only at the valve, though, because the Cobra Mustang had 1.7 pedestal-mounted roller rockers produced by Crane and given a Ford part number. The cam was, actually, ground at a lower lift.
My $0.02,
Eric
 

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Discussion Starter #6
Thanks Eric.. So, If i understood everything right.. the Comp Cams 31-255-5 has .462 intake and .474 exhaust valve lift.. so it should be fine to run with the 1.7 rockers.. I would prefer to run the GT40 heads to avoid the header/plug issues. If I run the GT40 heads with 1.7's... I would need longer push rods right? Since the Cobra was the only one that used 1.7's? Not sure if i understood that right.
And then as a piece of mind.. once I get the cam in and get ready to bolt it all up, do a clay test to see if I'm having Valve to Piston issues? I'll have to do some reading on that process.
I just want to have the smoothest transition as possible between heads and cams.. Would the 1.7 rockers make any hp/tq gains that are worth the extra $200 and the extra trouble? What kind of gains can be expected out of the GT40 heads, headers and a good SD compatable cam? Truck already has free flow exhaust.

Thanks for all the input, Anyone else have any input? Or Agree/Disagree with anything thats been said?
 

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Thanks Eric.. So, If i understood everything right.. the Comp Cams 31-255-5 has .462 intake and .474 exhaust valve lift.. so it should be fine to run with the 1.7 rockers.. I would prefer to run the GT40 heads to avoid the header/plug issues. If I run the GT40 heads with 1.7's... I would need longer push rods right? Since the Cobra was the only one that used 1.7's? Not sure if i understood that right.
And then as a piece of mind.. once I get the cam in and get ready to bolt it all up, do a clay test to see if I'm having Valve to Piston issues? I'll have to do some reading on that process.
I just want to have the smoothest transition as possible between heads and cams.. Would the 1.7 rockers make any hp/tq gains that are worth the extra $200 and the extra trouble? What kind of gains can be expected out of the GT40 heads, headers and a good SD compatable cam? Truck already has free flow exhaust.

Thanks for all the input, Anyone else have any input? Or Agree/Disagree with anything thats been said?

If you run the gt40 heads w/ 1.7 rockers, it will be neccessary to upgrade the valve springs to handle the added lift. Stock gt40 springs (in good shape) could handle the cam's lift with stock ratio rockers.
The stock push rods will be fine. They would only need replacement if you were going to a roller cam/lifter setup, or if they are damaged/worn.
The 1.7 rrs would only gain you an extra 10 or so hp, so it wouldnt be worth the added expense or aggravation (to me), but its your coin.

Only to clarify: not all gt40 heads have thermactor ports for emissions (mine don't), so if that is a concern for you, you will need to make sure the set you get have them.
 

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Eric
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Responses in red:

Thanks Eric.. So, If i understood everything right.. the Comp Cams 31-255-5 has .462 intake and .474 exhaust valve lift.. so it should be fine to run with the 1.7 rockers..

If you do this, I would upgrade the springs no matter which set of heads you choose run. I would like to correct a previous statement by super-ceding it with the concept that you should change valve springs in the GT40/GT40P heads with any cam upgrade, to ensure that you remain on the safe side. This way you can swap in a different cam/rocker combo at any time in the future and not have to worry. The GT40P heads have a special "spinning" retainer on the exhaust valve spring that allows the valve to rotate, slightly, every it's actuated. This is to keep the carbon deposits from wearing down the valve seat.

I would prefer to run the GT40 heads to avoid the header/plug issues. If I run the GT40 heads with 1.7's... I would need longer push rods right? Since the Cobra was the only one that used 1.7's? Not sure if i understood that right.

The pushrod length changes in relation to length of the lifter. Roller lifters are longer than flat tappet because of the roller tip. This means that the pushrod needs to be shortened to compensate. The valve-train in the heads is a fixed geometry if you maintain the stock (or, stock replacement) direct-fit parts. Once you start playing with spring shims and valve retainer groove positions, you open up the world of custom length pushrods. In stock replacement applications you will be fine.

And then as a piece of mind.. once I get the cam in and get ready to bolt it all up, do a clay test to see if I'm having Valve to Piston issues? I'll have to do some reading on that process.

Use modeling clay and some WD-40 to spray the valves to prevent sticking when you mock it up.

I just want to have the smoothest transition as possible between heads and cams.. Would the 1.7 rockers make any hp/tq gains that are worth the extra $200 and the extra trouble?

No. You might see a single-digit HP increase, but, the most benefit will come from the friction relief of the roller tip and bearing fulcrum (~8-10HP/3-7 lb.-ft TQ over stamped rockers). This can, also, be had with a 1.6 ratio set of pedestal-mount roller rockers. You, only, really need to swap rockers if you want a slight power bump and don't want to pull the cam. We've swapped in higher ratio rockers on dyno pulls to meet certain performance goals. Later, upon rebuild, we selected a different cam grind and took the higher ratio rockers off.

What kind of gains can be expected out of the GT40 heads, headers and a good SD compatable cam? Truck already has free flow exhaust.

Do a lot of research and you will come up with an average. It will not be the same performance increase as with a carburetor, so, don't go by that. Just my opinion, I've determined around a 60HP/20-30TQ over stock on an SD 5.0L. Maybe, a little more with tuning, which is what I'm trying to determine with my thread you mentioned in post #2.

Thanks for all the input, Anyone else have any input? Or Agree/Disagree with anything thats been said?
Do your homework and you will be fine. Don't half-ass the build. You will regret it. Don't cut corners and think to yourself, "Meh... that's close enough."
There is "close" and then there's right. If something is out of spec, or, you don't think it's performing correctly, FIX IT.

Good luck with the build,
Eric
 

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Discussion Starter #9
thank you both for the reply and input.. I'm not worried about the Thermactor.. truck has no cats already, and the cross over pipe is rusted and leaking exhaust, so i'm not going to be heart broken if its gone.. Its not my daily, and will maybe see 5k miles a year on a good year..

well.. seems like I'd have to do a lot more learning and reading than what its worth for 8hp.. lol.. i'll just stick with factory 1.6 rockers.. and factory push rods. There is a local shop that is well known in the area for good head work, maybe (if I can afford it) i can have do some port work... I always see people talking about DIY port tuning.. but that seems kinda iffy to me.. I could probably polish them on my own.. but removing material doesnt seem like a good idea to do when you dont know what your doing.
Im in the planning stages, going to a few junkyards next weekend that have 5-10 exploders, gonna try to find some heads and EV1 DRI injectors.. Then I'll go from there.

Thanks again for the info.. Still open to input from anyone else.. tips.. "dont do what I did" advice from anyone who has already done this job and made mistakes.
 

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Discussion Starter #10
I noticed in Silver70's post.. people were talking about needing tuning.. If I go with the GT40 heads and a SD approved Cam... Am I going to need to tune the EEC? Or will it run good as is? I'm trying to do all this on a relatively tight budget and if its going to "Require" Tuning.. I may have to tone it back a bit. As I wont be able to spend another $500 for tuning, or however expensive it is..
 
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