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Discussion Starter · #1 · (Edited)
Hi all, I’m a new member but have been doing lots of reading/lurking. I was hoping some of the more experienced with the 302 could give me some advice. I recently picked the car up and would have done things differently if I did the build but I’m working with what I’ve got for now and trying not to spend money twice or blow up a fresh motor. Sorry in advance for the long post. Anyways, my current setup is:


1992 GT
Terminator X w/ 7” dash
Fresh 302 bored 0.20 over (400 miles on rebuild, runs strong)
TKX w/McLeod twin disc (swapping trans in this week)
Silv-o-lite Hyper pistons (coated)
GT40P heads w/upgraded springs
TFS cam (owner thought it was a stage 1, local builder thinks it sounds more like a Stage 2 from the idle)
TFS Street upper and lower
Accufab throttle body and spacer
BBK cold air intake
24lb injectors
Aeromotive Stealth 340 pump
Aeromotive FPR
BBK Shorties/Flowmasters back
3.73 gears
Stifflers Fit Kit
MM K-member brace
J&S weight jacker rear lower arms

I’ve got a brand new Vortech V3Si with Anderson power pipe sitting in the garage along with 60lb injectors, meth kit, 3 bar map, 12-15psi pulley setup, etc… I have been afraid to install it based on all I’ve read about splitting blocks and breaking hyper pistons. I understand that a good tune helps, but I know if you are playing fire you will eventually get burnt. Threads seem to be all over the map regarding the subject so I thought I would start here with my exact setup and proposed options. I also spoke to the machine shop who built the motor and they made a comment along the lines of “I set the ring gap for a strong NA street motor” which makes me think they may be on the tight side if you were building the motor intended for boost. That made me even more concerned about throwing boost at it with the hyper pistons. As I said, I’ve done a lot of reading here and there’s lots of good (and also conflicting) info. Anyways...

The motor just had $3k dropped into it by the previous owner on a top to bottom refresh (I have the receipts), only has about 400mi on it and runs great, so it would be a shame to blow it up. I’ve considered getting a different pulley and running more like 7-9lbs, but the pistons still have me concerned as I don’t want to break a piston and ruin a whole motor.

My overall goal for the car would be to capable of running low 11’s-high 10's with blower, or low 12’s if going NA (I am not interested in spraying, be there, done that). This is 95% a street car so I won’t be thrashing it and reliability is important to me and there will be times of sitting in traffic and so on.

My question(s) are:

1. Is my gut leading me correctly in being worried that throwing that Vortech on the current motor as-is may be pushing the limits/a time bomb with a short fuse? My plan would be a conservative tune, meth just for cooling and not for increasing timing), and dropping the rev limiter closer to 5600 or so. I could also spring for an intercooler most likely. I'm guessing my current compression with the GT40P's is in the low 10's and 92 octane is what's available in my area.

2. If not doing the blower, would it be worth looking into something like TF 170cc or AFR 185 heads? Would those (with say a Anderson N412 cam) get me into the low 12's on motor? I mentioned 185's instead of 165's as they would give me some room to grow in the future if I went stroker or 351.

3. What about doing the blower with new heads? Intent here would be to run a larger chamber (66cc-72cc depending on head) to reduce compression and improve flow/potentially reduce cylinder temps slightly. This would also give me a chance to go to ARP hardware and a better head gasket.

4. This was an option to "leave it alone" but I'd at least want to do some nice heads and a cam, even if I stay NA, so I pulled that option off the list.

Thanks in advance for any advice!
 

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I'd do number 4 in your shoes.......
I did not read through the OP's whole post and jumped straight down to your reply.
I was thinking I knew what #1 and a #2 was and was trying to figure out what a #4 was...Lol.
Then I read his #4 option and it became less confusing.
 
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Discussion Starter · #4 · (Edited)
To clarify on my orginal post a bit, I've been looking at doing some AFR 185's and going with a 72cc chamber to reduce compression to help preserve the block if installing the blower. I'll update the original post to clarify what I was thinking.
 

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If you plan on driving it within the next year, leave it as is and drive it.
Make a list of every single related part stock or aftermarket currently installed.
Make a wish list with prices.
Make a list of parts to be removed and sold with market prices.
Start saving money.
Put some mileage on and make notes of the dozen items that don't work or that annoy you.
Start shopping for good used stuff or new on sale.
Talk to people about what is missing in your plan and parts needed list. The little things will double your estimated cost.
Drive it some more and run it hard, you will find it's faults.
When ready to rebuild to your liking, ask the foxbody Gods for patience. Be prepared to spend way more than your budget.

Sorry, to answer your first concern. In my opinion, based on experience, hypereutectic pistons are the scapegoat for poor tuning. They have their limit, but will easily suit any factory 5.0 roller block. One of ma y combos I have done is 306/TFS 170/vortech 5-6&9/several chip brands all went 10k+ miles.
 

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Compression isnt really as much of a concern as people make it out to be. Sure.. if your 12:1 and want to run turbos, thats gonna be a problem without an alternate fuel but stock compression ratios on the 302ho arent really much to worry about even with P heads. I see you mention low 10s, high 9s for compression but how are you coming up with that. I looked up the pistions and they are not popup pistions and are flat top. I dont see a CC size listed but your average flat top pistion is around +7cc. They are not going to raise your compression ratio. A flat top pistion with +7cc means it adds 7ccs to your total chamber. If you have a 61CC head you have 67CC with the heads and pistons . You can achieve 500 whp with high comp 10lbs or low comp 13lbs, either way its making the same power, the fuel consumption is the same and I believe the over all cylinder pressure is the about the same. The main difference is lower compression means its more of a dog out of boost and more wear. If its around 9:1, dont worry about compression.

I put together a quick compression check and assuming your pistons are around 7cc, gt40p heads are 61cc or so, your compression is right around 9.0 using felpro 9333pt1 gaskets with a .047 compressed thickness and a 0 deck height.

Now the whole 500hp splitting the block in my opinion isnt really accurate. My low boost street tune is about 440whp which is around 505 at the flywheel. I drive it like that all summer. Now, if you have a block that has casting imperfections or something like that.. its got a much better chance of splitting or cracking but that is just that block. .The 500hp limit was something people came up with long before modern tuning was around. It was before people understood fueling, timing and tuning the computer. I guess what im saying, is its all in the tune. You can split a block with 400hp and detonation. Things to remember, with a blower, you put a lot of stress on the snout of the crank , the more boost the more stress and more parasitic loss from turning the blower. The crank snout takes a lot of abuse as does the #1 crank bearing. I would rather be high compression and lower the boost than run low compression with a lot of boost. Lower boost, lower stress on the crank. There is a reason the 03 cobra has a bracket to counteract the crank snout forces. My current car is 10.2:1 and I make 560whp using 91 octane on high boost which i believe was 9lbs, might have been 10, stock block.

Hyper pistons are fine at 500whp. I made 526 on a 308 with hyper pistons and drove it for years. Dropped a valve and took out that engine but the pistons looked perfect after taking it apart minus the #4 that ate a valve. If your really worried about exceeding 500hp, why not just buy a bigger blower pulley and drop the boost another 3 lbs. Its less stress on the crank anyway.
 
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Discussion Starter · #7 ·
If you plan on driving it within the next year, leave it as is and drive it.
Make a list of every single related part stock or aftermarket currently installed.
Make a wish list with prices.
Make a list of parts to be removed and sold with market prices.
Start saving money.
Put some mileage on and make notes of the dozen items that don't work or that annoy you.
Start shopping for good used stuff or new on sale.
Talk to people about what is missing in your plan and parts needed list. The little things will double your estimated cost.
Drive it some more and run it hard, you will find it's faults.
When ready to rebuild to your liking, ask the foxbody Gods for patience. Be prepared to spend way more than your budget.

Sorry, to answer your first concern. In my opinion, based on experience, hypereutectic pistons are the scapegoat for poor tuning. They have their limit, but will easily suit any factory 5.0 roller block. One of ma y combos I have done is 306/TFS 170/vortech 5-6&9/several chip brands all went 10k+ miles.
Thanks for the response. I've done a lot of that already (have my "to be sold" and "to be purchased" list all hammered out) and have all the current mods listed (not all above as some didn't apply). Money wise if I really wanted to I could pull the triggetoday on a 351 longblock from CHP along with mounts, dist, headers, etc etc... but "wanting" to spend that kind of coin unless I have to is another story. Previous to this car I always scrounged and bought what I could as I went, used, and so on. Now I'm a bit more flexible financially but that doesn't mean I want to spend it, haha!

So you mentioned the 306/TFS/Vortech combo an 10k mi. I'm running a Terminator so hopefully I could have a bit more control over the tuning aspect of things (as well as failsafes) vs. a chip and ideally make things last a bit longer (assuming conservative timing, rev limiter, fuel, etc...). I'm also planning to run a small nozzle meth to keep charges cool and considering going with an intercooler just to add a little more safety. On your past setups, could you tell me about what kind of whp they were seeing? Also, you mentioned 10k mi. Did the motors fail at that point with no setup/tuning changes or were they owner induced deaths etc...? Thanks!
 

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Discussion Starter · #8 ·
Compression isnt really as much of a concern as people make it out to be. Sure.. if your 12:1 and want to run turbos, thats gonna be a problem without an alternate fuel but stock compression ratios on the 302ho arent really much to worry about even with P heads. I see you mention low 10s, high 9s for compression but how are you coming up with that. I looked up the pistions and they are not popup pistions and are flat top. I dont see a CC size listed but your average flat top pistion is around +7cc. They are not going to raise your compression ratio. A flat top pistion with +7cc means it adds 7ccs to your total chamber. If you have a 61CC head you have 67CC with the heads and pistons . You can achieve 500 whp with high comp 10lbs or low comp 13lbs, either way its making the same power, the fuel consumption is the same and I believe the over all cylinder pressure is the about the same. The main difference is lower compression means its more of a dog out of boost and more wear. If its around 9:1, dont worry about compression.

I put together a quick compression check and assuming your pistons are around 7cc, gt40p heads are 61cc or so, your compression is right around 9.0 using felpro 9333pt1 gaskets with a .047 compressed thickness and a 0 deck height.

Now the whole 500hp splitting the block in my opinion isnt really accurate. My low boost street tune is about 440whp which is around 505 at the flywheel. I drive it like that all summer. Now, if you have a block that has casting imperfections or something like that.. its got a much better chance of splitting or cracking but that is just that block. .The 500hp limit was something people came up with long before modern tuning was around. It was before people understood fueling, timing and tuning the computer. I guess what im saying, is its all in the tune. You can split a block with 400hp and detonation. Things to remember, with a blower, you put a lot of stress on the snout of the crank , the more boost the more stress and more parasitic loss from turning the blower. The crank snout takes a lot of abuse as does the #1 crank bearing. I would rather be high compression and lower the boost than run low compression with a lot of boost. Lower boost, lower stress on the crank. There is a reason the 03 cobra has a bracket to counteract the crank snout forces. My current car is 10.2:1 and I make 560whp using 91 octane on high boost which i believe was 9lbs, might have been 10, stock block.

Hyper pistons are fine at 500whp. I made 526 on a 308 with hyper pistons and drove it for years. Dropped a valve and took out that engine but the pistons looked perfect after taking it apart minus the #4 that ate a valve. If your really worried about exceeding 500hp, why not just buy a bigger blower pulley and drop the boost another 3 lbs. Its less stress on the crank anyway.
Thanks for all the info! I will admit I was talking to a well known shop earlier this morning and they told me that I should be in the low 10's on compression with the motor as it is and the GT40P heads. I will be the first to admit I didn't do my own due diligence on that. and figured they would be giving me accurate info but in reality, it's my fault for not back checking it, not theirs. The pistons I have are Silv-o-lite 3165HC 0.20 over. The info on them is:

Alloy: 390
Bore Inch: 4.000
Bore MM: 101.6
Comp Ht. MM: 40.6
Comp. Ht. IN: 1.600
Compression Ratio: 9.1 (I did see this but thought there may have been some big increase with the GT40P heads based on talking with the shop this morning)
Crown CC: +5cc
Crown Type: DISH
Interchange: FM H654CP
O.E. Assembly: Similar to 3133H exc. rings.

As far as the snout forces go that is something I had a discussion about with a local guy. He basically said the same thing but it was more in regards to tightening the bejeezus out of the belt and putting a lot of strain on the crank. My current SC setup has a 3.12 upper pulley and a 6.87 lower which is supposed to be 12-15psi at 6000rpm. As you mentioned, I was thinking about changing the pulley setup and running a 7-9lbs pulley arrangement with reliability in mind.The other unknown is I don't know what head gasket they used when they built the motor as it wasn't line itemed on the previous owners receipt. Could be made of orange peels for all I know though the previous owner did seem to buy at least decent parts from what I see in the receipts.

So based on what you mentioned above, would you:

1. Throw the 60lb injectors in, re-tune it and run it as-is with a 7-9lb pulley and the unknown headgasket and forget about heads (just keep the GT40's and current cam).
2. Drop a little coin on some aluminum heads, ARP studs, known headgasket, etc... (mostly for reliability but less flow restriction and "easier" power don't hurt).
2B. If yes to a new head, and based on the compression data you gave me (thanks again for correcting me), which head would you consider? I was looking at the AFR 185's and they come in 58cc or 72cc chambers. I'm now thinking 72cc would be way too big, and 58cc may raise my compression though maybe not too much over the estimated low 9's it's currently at (not sure what the exact number would be with my +5's vs the theoretical +7's originally used above).

TLDR: Short version of what I'm after is, what would you consider to be the ideal top end setup to use with my bottom end/using the piston data above? Let's say $3k budget on top end parts without labor as I would most likely do it myself unless it's something you can't do without specialty tools, then I would send that out to be done correctly the first time. I don't want to touch the bottom end as it was just built and if I was going through all that hassle I'd just end up buying a 351 based block but that seems like it would be overkill for the stage I'm at, and to be honest, I just dropped a TKX and twin disc in it, not really wanting to drop $10k more on a 351 setup right now, lol.
 

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Discussion Starter · #10 ·
I’ve only had the car about 5 weeks and I’m in Seattle (rainy season) so there are no tracks open until spring (that I know of). With that said, I’m getting the car dyno’d on Saturday morning to make sure my Terminator tune is solid and see what my baseline numbers are moving forward. I like to be realistic so with my current setup I’m only expecting somewhere between 250-275whp.
 

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Thanks for all the info! I will admit I was talking to a well known shop earlier this morning and they told me that I should be in the low 10's on compression with the motor as it is and the GT40P heads. I will be the first to admit I didn't do my own due diligence on that. and figured they would be giving me accurate info but in reality, it's my fault for not back checking it, not theirs. The pistons I have are Silv-o-lite 3165HC 0.20 over. The info on them is:

Alloy: 390
Bore Inch: 4.000
Bore MM: 101.6
Comp Ht. MM: 40.6
Comp. Ht. IN: 1.600
Compression Ratio: 9.1 (I did see this but thought there may have been some big increase with the GT40P heads based on talking with the shop this morning)
Crown CC: +5cc
Crown Type: DISH
Interchange: FM H654CP
O.E. Assembly: Similar to 3133H exc. rings.

As far as the snout forces go that is something I had a discussion about with a local guy. He basically said the same thing but it was more in regards to tightening the bejeezus out of the belt and putting a lot of strain on the crank. My current SC setup has a 3.12 upper pulley and a 6.87 lower which is supposed to be 12-15psi at 6000rpm. As you mentioned, I was thinking about changing the pulley setup and running a 7-9lbs pulley arrangement with reliability in mind.The other unknown is I don't know what head gasket they used when they built the motor as it wasn't line itemed on the previous owners receipt. Could be made of orange peels for all I know though the previous owner did seem to buy at least decent parts from what I see in the receipts.

So based on what you mentioned above, would you:

1. Throw the 60lb injectors in, re-tune it and run it as-is with a 7-9lb pulley and the unknown headgasket and forget about heads (just keep the GT40's and current cam).
2. Drop a little coin on some aluminum heads, ARP studs, known headgasket, etc... (mostly for reliability but less flow restriction and "easier" power don't hurt).
2B. If yes to a new head, and based on the compression data you gave me (thanks again for correcting me), which head would you consider? I was looking at the AFR 185's and they come in 58cc or 72cc chambers. I'm now thinking 72cc would be way too big, and 58cc may raise my compression though maybe not too much over the estimated low 9's it's currently at (not sure what the exact number would be with my +5's vs the theoretical +7's originally used above).

TLDR: Short version of what I'm after is, what would you consider to be the ideal top end setup to use with my bottom end/using the piston data above? Let's say $3k budget on top end parts without labor as I would most likely do it myself unless it's something you can't do without specialty tools, then I would send that out to be done correctly the first time. I don't want to touch the bottom end as it was just built and if I was going through all that hassle I'd just end up buying a 351 based block but that seems like it would be overkill for the stage I'm at, and to be honest, I just dropped a TKX and twin disc in it, not really wanting to drop $10k more on a 351 setup right now, lol.
with a +5 CC piston, youre looking at 9.23:1 with the same specs as i listed above.

3k would buy you a really nice set of TFS 170 11r heads or even the cheaper 170 FAC TFS heads but dont forget you need pushrods and rockers and maybe valve covers (87-93 aluminum covers work with clearancing them inside. Those parts add about another 600. All of that would work great with the intake you have and not revving it to the moon. 58cc heads would put the compression right around 9.56:1 which is safe, but I think those heads would really like a better intake. If you really wanted to lower the compression, you could use a thicker head gasket. There are tons of fancy dancy ones to choose from in all different compressed thicknesses.

I wouldnt worry about headgaskets. the 9333pt1 is the most common gasket ive seen and also one of the cheapest. I think you can even see the part number on the front of the gasket that sticks out under the head. I think the part number is on the end. They might already be installed. As long as you dont have detonation, pretty much any gasket will hold up to what youre shooting for. Most of the time blown headgasket is due to improper tuning. If it blows a gasket, then you can replace them, or for piece of mind you could change them, I wouldnt. For the record, I use the 9333 gaskets.

If it were my car, Id put the blower on with it probably a bigger upper pulley, a set of injectors, pump and a good maf and see what it does. You already have it so why not just install it. I would make sure to take the smaller blower pulley with me and a belt to swap out if it wasnt making enough boost when getting tuned though. That would probably put you somewhere around 350-375 whp and probably around 375-400tq (low boost) and i think that might be conservative. There are plenty of people with that setup who are quite happy with it. The only thing that would really concern me is the ring gap. If the rings are gapped tight, I wouldnt run more than 8-9lbs on it. There are plenty of pistons missing the top ringland due to the gap. Ring gap is just as important as bearing clearance. If at that point, you arent happy with the power, you could up the boost or HCI upgrade, but youre gonna need to check/get the ring gap up to about .024-.026 top ring land and .002 bigger for the second ring if you want to add more power.
 
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Discussion Starter · #12 ·
with a +5 CC piston, youre looking at 9.23:1 with the same specs as i listed above.

3k would buy you a really nice set of TFS 170 11r heads or even the cheaper 170 FAC TFS heads but dont forget you need pushrods and rockers and maybe valve covers (87-93 aluminum covers work with clearancing them inside. Those parts add about another 600. All of that would work great with the intake you have and not revving it to the moon. 58cc heads would put the compression right around 9.56:1 which is safe, but I think those heads would really like a better intake. If you really wanted to lower the compression, you could use a thicker head gasket. There are tons of fancy dancy ones to choose from in all different compressed thicknesses.

I wouldnt worry about headgaskets. the 9333pt1 is the most common gasket ive seen and also one of the cheapest. I think you can even see the part number on the front of the gasket that sticks out under the head. I think the part number is on the end. They might already be installed. As long as you dont have detonation, pretty much any gasket will hold up to what youre shooting for. Most of the time blown headgasket is due to improper tuning. If it blows a gasket, then you can replace them, or for piece of mind you could change them, I wouldnt. For the record, I use the 9333 gaskets.

If it were my car, Id put the blower on with it probably a bigger upper pulley, a set of injectors, pump and a good maf and see what it does. You already have it so why not just install it. I would make sure to take the smaller blower pulley with me and a belt to swap out if it wasnt making enough boost when getting tuned though. That would probably put you somewhere around 350-375 whp and probably around 375-400tq (low boost) and i think that might be conservative. There are plenty of people with that setup who are quite happy with it. The only thing that would really concern me is the ring gap. If the rings are gapped tight, I wouldnt run more than 8-9lbs on it. There are plenty of pistons missing the top ringland due to the gap. Ring gap is just as important as bearing clearance. If at that point, you arent happy with the power, you could up the boost or HCI upgrade, but youre gonna need to check/get the ring gap up to about .024-.026 top ring land and .002 bigger for the second ring if you want to add more power.
Gotcha, thanks for your time answering my newb questions. So what I’m gathering from above is:

Get a bigger 7-9lb pulley and run it. I have a Terminator installed with a 3 bar map so no maf. Fuel wise I’m running an Aeromotive Stealth 340lph pump with 10ga power run straight to the pump. As I mentioned above, I’ve got 60lb injectors also ready to go in, along with a small nozzle meth kit.

What I think you are saying is to run the GT40P heads (with the added fuel) and I should see upper 300’s, maybe a little more, at 7-9psi. Is that correct?

I did look at TFS 11r heads but apparently they are hens teeth to get at the moment. Most places quoted me 5mo+ before arrival if I ordered now. I did find a set of AFR’s in stock however. I’d go for the 7/16 rocker studs and the upgraded springs (even though I won’t be revving that high I might as well get the better springs if I’m ordering new). From my limited reading it sounded like the AFR’s and the TFS were a toss up on performance? I also think (if I’m reading it correctly) those Silv o lite pistons have enough relief I wouldn’t need to fly cut the pistons on the AFR’s. I did consider the supporting stuff and would be looking at TFS or Scorpion 1.6 roller/rockers, ARP hardware all around, TFS pushrods, new lifters and an Anderson N412 cam. I’m not 100% sure what the existing cam is so I figured since I’ll be in there it would be better to just have a known good cam on hand in the event the installed one is smaller than expected, then just sell whichever I don’t use.

Using the GT40P’s is of course the easiest option and I could probably have the blower and injectors installed over the weekend easily enough. Do you not think there would be some level of additional reliability with the aluminum heads from a heat dissipation/less resistance to flow standpoint? In other words, making the engine work less to make the power and maybe a little gain on cooling from the aluminum.

Lastly, do you agree that for the blower and potential to go “bigger” on either a dart block or a 351 in the (hopefully distant) future I’d be better off going with a 170-185 head vs 165’s? Thanks again for sharing your knowledge, much appreciated.
 

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Discussion Starter · #13 ·
Ok, so what I’ve gathered from all of this is:

1. Go with a smaller pulley. My kit came with a 8rib 6.87” crank pulley and a 3.12” blower pulley. I ordered a 3.33” pulley this morning to drop boost a bit closer to the 9lb range instead of the 12-15lbs the 3.12 is supposed to run (6000rpm). Do I need a new belt for this or should it be close enough to use the belt the kit came with?

2. Hyper pistons should be good (assuming a good tune) for more power than I can make on a stock block reliably.

3. Run it with the GT40P heads since they are already on the car and see where power lands.

4. Upgrading the heads will reduce restriction and maybe make a bit more power but the small reduction in compression (going to a few larger cc chambers over the GT40P’s) won’t give me any appreciable increase in reliability/detonation prevention. Nor will aluminum vs iron give me a significant improvement in cylinder temps. Nor will the reduced restriction to flow make a difference on reliability. Basically better heads would be strictly for making a few extra hp.

Is that the general consensus here? Anything I’m missing to make this more reliable without getting into the rotating assembly? Thanks in advance for any info shared and for all the answers so far!
 

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You will need a different belt most likely. Aluminum heads dissipate heat faster but cylinder temps should be similar. I would say in general i agree with your statements.
 
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