Engine New Cam or Different Rockers?

93CalypsoConvert

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Nov 26, 2020
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I've been considering doing some power upgrades to the 302 and I'm debating weather to go with a new cam or go with 1.7 rockers... Its a carbureted '85 HO running flat tappet currently. Nothing is done besides emissions removal. I WILL put either a pair of GT40 or GT40p heads on before this. New valve springs too.

If I go with the cam, I would probably go with the e303. This means changing everything from flat tappet to roller and probably installing a new timing set.

The 1.7 rockers should be an easy swap without having to dig too far into the engine.

Lift on e303 is .498 and lift with 1.7s would be .472.

Should I even bother upgrading past the GT40 heads? What type of numbers should I expect with these upgrades? Thanks.
 
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HemiRick

I'd be looking at jacking under the house
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GT40 heads are only good good for about 30 HP....lotsa work for minimal gain compared to aftermarket heads.....
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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I think I've mentioned this before, look up the Engine Masters episode SBF head comparison. What it all boiled down to was budget, granted you have more head choices with a bigger budget but then you should have a detailed plan. Your reward will be more ponies but again, you spend more money, throw'n a set of gt40 or P heads on with a cam and a timing tweek yeah may only get you 30-35 (I believe it would be a few more, not many but a few more) ponies is a very good low buck modification.
Sure this can be argued, but it is still a very good low buck modification.
JMO, although I do have personal experience with this combination in a EFI set up, very stout driver.I
i will caution, with gt40P heads you may have ptv interference with the E cam and 1.7 rockers.
 
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mikestang63

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save up and do it right the first time. get either a good set of AFR or TW heads, cam, intake, carb, or bolt on decent Nitrous kit
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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Yeah and they make a 471 blower adapter for that sbf, you already have a carb.
go big or go home
i guess that's why I'm at home right?
 
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Mustang5L5

Put lubricant all over the balls
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What's your budget and goals?

I'd also say to save up and just start gathering parts, but but with better heads comes the needs for additional parts and scope creep will take over. Before you know it, a $800 GT40 head swap (total cost) now morphs into a $5K engine build.

My point is if you tell us you have a fixed $1K budget, than that changes the recommendations.
 
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93CalypsoConvert

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What's your budget and goals?

I'd also say to save up and just start gathering parts, but but with better heads comes the needs for additional parts and scope creep will take over. Before you know it, a $800 GT40 head swap (total cost) now morphs into a $5K engine build.

My point is if you tell us you have a fixed $1K budget, than that changes the recommendations.
Right now my goal is cheap power. I want to make this car not feel like a slug. Its not worth spending thousands on the engine considering the condition of the rest of the car, but I think $1000 could make it much more fun to drive.
 
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2000xp8

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I'd make sure an E cam clears on an 85, i'm pretty sure it doesn't on an 86 so...

While it's no secret i'm not a fan of gt40 iron swaps, if you are going to do it, it may just be easier to go out and buy an entire explorer engine. People seem to get them for $500 or less complete.
Do the springs, the cam on a stand. Sell the intake and add a good carb with intake on top.

On your current engine, if the cam is not possible (i do not know the specs of 85 pistons, the 86 are flat top), i'd scrap the whole idea. It's a lot of work for very little. Most likely your car will still be slower than a new camry.

1.7 rockers are hardly worth anything. I did them on E7's back in the day. I'd say they provide little to nothing.

I don't see where you mention what your car currently is.
Auto or manual? Gears?
If i'm not mistaken the 85 has a 7.5 rear, if that is true, i think i would do an 8.8 with 3.73 gears before tearing into the engine. Probably feel like an entirely new car, especially with a manual trans.
 
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Mustang5L5

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The '85 HO engine pistons have eye reliefs just like the 87+. Not sure if they are 100% the same however. E5 heads are also similar to E7 heads.

I'm not against GT40 head swaps (i had a set that i almost put on my car) but i do agree it's a lot of work for little gain. However if you are searching for a project, a head swap can be fun if it's your first time doing such a thing.

85-88 HO cam is probably the "best" factory cam put into a Mustang. I put it in quotes because the factory grind cams are all over the place and vary (according to one well-known cam grinder). Still, there was a very interesting thread on Corral.net referrencing keeping the HO cam and combining it with other mods. Impressive results. Most paired it up to at least a set of 1.7 RR's. But the cars idled well and drove like a stock Mustang. They may not have made as much potential power as the combo could have, but driveability was quite excellent. With a carb, you may not have the issues that EFI cars have with the Ecam or other camshafts.

WHy the Ecam? There might be other off-the-shelf choices that will be better, espeically with the carb.

I also second an 8.8 axle with 3.73's as a way to really wake the car up.
 
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Boostedpimp

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I'm not a fan of gt40 head swaps and it is simply because it isn't a big enough increase to warrant the job for me. You'll need to upgrade the springs off the bat and more than likey the heads have a ton of miles on them so a valve job, etc would be smart/a must. At the end of the day your slapping heavy iron factory heads from a ford explorer on a mustang looking for a sizeable increase in power. I would do like mentioned above and pickup a explorer or mountaineer engine, swap the cam, oilpan etc and sell off the other stuff and you have your swap the cheapest and easiest route.

And if you don't have ring and pinion upgrade already then that would be the first thing to deal with in my opinion
 

93CalypsoConvert

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Nov 26, 2020
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I'd make sure an E cam clears on an 85, i'm pretty sure it doesn't on an 86 so...

While it's no secret i'm not a fan of gt40 iron swaps, if you are going to do it, it may just be easier to go out and buy an entire explorer engine. People seem to get them for $500 or less complete.
Do the springs, the cam on a stand. Sell the intake and add a good carb with intake on top.

On your current engine, if the cam is not possible (i do not know the specs of 85 pistons, the 86 are flat top), i'd scrap the whole idea. It's a lot of work for very little. Most likely your car will still be slower than a new camry.

1.7 rockers are hardly worth anything. I did them on E7's back in the day. I'd say they provide little to nothing.

I don't see where you mention what your car currently is.
Auto or manual? Gears?
If i'm not mistaken the 85 has a 7.5 rear, if that is true, i think i would do an 8.8 with 3.73 gears before tearing into the engine. Probably feel like an entirely new car, especially with a manual trans.
I'm going to stay away from buying a whole engine. Mine was built not too long ago when it was converted from 4 to 8 cylinder... Only has 5k miles on it. Not worth swapping it again. Pistons do have valve reliefs, so cams shouldn't be an issue.

Its a 5spd with 8.8 3.73
 
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93CalypsoConvert

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The '85 HO engine pistons have eye reliefs just like the 87+. Not sure if they are 100% the same however. E5 heads are also similar to E7 heads.

I'm not against GT40 head swaps (i had a set that i almost put on my car) but i do agree it's a lot of work for little gain. However if you are searching for a project, a head swap can be fun if it's your first time doing such a thing.

85-88 HO cam is probably the "best" factory cam put into a Mustang. I put it in quotes because the factory grind cams are all over the place and vary (according to one well-known cam grinder). Still, there was a very interesting thread on Corral.net referrencing keeping the HO cam and combining it with other mods. Impressive results. Most paired it up to at least a set of 1.7 RR's. But the cars idled well and drove like a stock Mustang. They may not have made as much potential power as the combo could have, but driveability was quite excellent. With a carb, you may not have the issues that EFI cars have with the Ecam or other camshafts.

WHy the Ecam? There might be other off-the-shelf choices that will be better, espeically with the carb.

I also second an 8.8 axle with 3.73's as a way to really wake the car up.
The work isn't a problem for me... I'd gladly tear into it every spare second I have. I'm still undecided on the cam, but the cheaper ones are looking more appealing.

Lets set up four situations.
1. Head swap, everything else stock.
2. Head swap and keep the stock cam, but do 1.7s.
3. Swap heads and new cam, but forget the rockers
4. Swap head, cam, and 1.7s

Right now option 3 looks pretty appealing, but which one gives me the most bang for my buck? 1.7s give similar lift to a mild cam, but some say they don't make much different over stock rockers. What would you do?
 

Mustang5L5

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I’d do the head swap, stock cam, and good 1.7 RRs. There’s probably a few HP to be gained with the lower friction RRs over the stock stuff. Plus the idea of retaining drivability appeals to me
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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On a budget, with a carb, the E cam, considering you already have it right? And 1.6 roller rockers, the 1.7's if you clay them first, would be a very stout combo with a cool idle.
Oh, this is JMO
 

7991LXnSHO

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I'm not a fan of gt40 head swaps and it is simply because it isn't a big enough increase to warrant the job for me. You'll need to upgrade the springs off the bat and more than likey the heads have a ton of miles on them so a valve job, etc would be smart/a must. At the end of the day your slapping heavy iron factory heads from a ford explorer on a mustang looking for a sizeable increase in power. I would do like mentioned above and pickup a explorer or mountaineer engine, swap the cam, oilpan etc and sell off the other stuff and you have your swap the cheapest and easiest route.

And if you don't have ring and pinion upgrade already then that would be the first thing to deal with in my opinion
My, how that story has changed in the last 10-15 years.
Back then, to want a HD set of performance heads that flowed like Trick Flow TWs. I did not trust the aluminum ones when they first came out to not warp and blow a gasket. I have not looked in some time ar iron heads to know if World products are still making them and if they are price competitive.
@93CalypsoConvert, If you have more time than money, and want to have more fun with stock type reliability, go for the gt-40 heads, ported explorer intake (@tmoss ) headers, and call Comp cams for what custom grind they suggest, and what off the shelf grind is the closest match if you do not like the lead time. Crower and others will do this for you. Unless you want just the lope of an E, this will give you more bang and should not be expensive. The Crower cam custom for a flat six I have waiting was by far not the hardest piece to write the check for.
,
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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No, I don't own the cam.
Well then there are choices. Write down all the mods and the type of driving you'll be doing and pick a cam that works in that rpm range.
it is my understanding that a modern grind will use a 'duel pattern' that makes better low end torque than the old letter cams but I could be wrong.
 

7991LXnSHO

wanna catch the space herp
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Please enlighten me how tfs heads lack reliability?
First, I bet the 85 is carbed. What is the current manifold and the planned one? The EFI explorer manifold is not probably going to help. I have run the Edelbrock performer 302 intake and a Holley 1850 carb and was pleased.
I think iron heads are less likely to drop a valve seat or warp when run hot. Well made alluminum heads are not likely to do this anymore, but I still wonder about budget Al head’s manufacturing and machining.