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  1. #1

    Default Alittle insight into a possible engine combo. 85gt

    Alright fellas. Been at this 85gt for a long time now. Had a local mechanic do some work and it proved to be a mess. So I was lucky and got a real fox lover who rebuilds mustangs to take the car under his wing. It’s getting the full Monty now. 🙏🏼

    But we’re talking about economical ways to rebuild my 5.0 without breaking the bank (paint, body, and rust repair is eating a lot of my budget now). The car had the original 302/ manual trans combo. Already has AFR Renegades 165s, cobra 1.72 rockers, AirGap intake, headers, and a Holley carb. The new redo was planned to keep most of that but add a Holley Sniper to it. But after digging into the engine a bit, the last guy did some questionable work and the engine needs a rebuild. The block is good etc. So for a budget build we’re talking about having the block sent out , stripped, and cleaned up etc. Then rebuilding the internals with 87+ forged pistons and all the accompanying crank, bearings, etc etc. Then popping the AFR 165s, AirGap, Sniper, 1.72s, shorty headers, and full Bassani stainless w x pipe exhaust back on.

    What kind of compression, HP, and relatability and I looking at with this combo?

    I think it’s a good plan for a super reliable, good mannered car with a little bump
    In power without breaking my ever shrinking budget.

    Just for info my fox has been pulled into pieces. New roof skin w sunroof, new doors, hatch, fender aprons and core support (due to rust). Motor is out. New wiring harness, heater core, brake system with 94+ rear axle w disks and 87+front disks, new fuel system and tank for the sniper, etc etc etc.

    Thanks for the input.
    Joe E

  2. #2
    FEP Power Member richpet's Avatar
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    IIRC, the 1.72 rockers can put a little more side load on the valves and wear the valve seals more quickly if they are not set up very correctly. Rather than use the rockers to adjust lift/duration, bump the cam a bit and go back to stock ratio 1.6 roller rockers for long term durability. If you rebuild the motor it means a new cam anyway.
    A .030 overbore in the rebuild will help unshroud the valves a bit and improve flow. It also very very slightly changes the compression ratio to your advantage (up. Same stroke, more volume of air and fuel to compress).
    Not sure the chamber size on those heads, but if you can get a static 10:1 out of them that compression bump will boost torque and sound good to the ears, though it may necessitate mid or premium fuel.
    Just thoughts.

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    Last edited by richpet; 07-14-2022 at 07:31 AM.
    83 5.0 GT. Quicker than it looks! 10:1 (or just over) 306, Motorsport a332 cam, 140A alt, t5 conv, 8.8 w/ 3.27's, Edel rpm, alum rad, very worked e7's, Holley SA carb, etc... SOLD IT!!!!

    Now an 1981 Granada! .040 over 302, Edel E-street heads... Currently building a 347 because, why not?

    "Never underestimate the power of stupid people in large groups"

  3. #3
    FEP Super Member bwguardian's Avatar
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    What exactly is going on with the short block that makes you think it needs a bore and rebuild? The 85 5.0 has forged flat top pistons with moly rings and roller cam...first year for those. If you can get away with not having to bore it you will be better off. The 87 and up pistons have a center dish...about 4cc-6cc worth so they are really not flat tops. It looks like those heads are around 58cc-60cc combustion chambers so with that piston dish it should put you right above the 9:1 static compression ratio and I would target 9.5:1-9.8:1 static compression ratio. Holley Sniper and budget build don't belong in the same sentence and I would run the carburetor. You don't say anything about the cam so I will assume you still have the stock cam in the short block with 1.7 rockers. If you do keep the original flat top pistons with the carb, then look at a cam with around 110* LSA...the head specs don't say what the maximum lift is for the valve springs installed so you'll have to look at that in conjunction with the 1.7 rockers...
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  4. #4
    FEP Power Member richpet's Avatar
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    Has the OP been back?

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    83 5.0 GT. Quicker than it looks! 10:1 (or just over) 306, Motorsport a332 cam, 140A alt, t5 conv, 8.8 w/ 3.27's, Edel rpm, alum rad, very worked e7's, Holley SA carb, etc... SOLD IT!!!!

    Now an 1981 Granada! .040 over 302, Edel E-street heads... Currently building a 347 because, why not?

    "Never underestimate the power of stupid people in large groups"

  5. #5

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    Hey fellas. Sorry for the absence. Been on a family road trip the last week+.

    The car is in the middle of a 20k+ restoration. The gentleman doing the car is a serious foxbody guy. He’s built a bunch of foxes and I trust him 100%. He’s been working with me every step of the way and really pushing to keep my build on budget. That’s why I’m not going with a fancy engine build or turbos etc. The car is getting a ton of metal and body work. Replacing the roof skin, doors, hatch, cowl, radiator support, both aprons and repairing the floor pan. Most moving parts of the car are getting replaced etc. So I’ve used the vast majority of my budget making the car solid and family friendly.

    The engine was thought to be ok. So it’d just get a good tune etc. But after we pulled the frontt end off the car, it was an easy time to clean the block up and redo the bearings and crank. I already have a Ford B cam so I’m using that to keep my costs down. And that’s pretty much the point of the whole engine redo. Budget friendly and use the parts I have laying around from years of gathering. I’d love to go full out crazy w it but the budget doesn’t support it.

    Was just curious if anyone had a hold kind of like it and what kinda power it made.

    Thanks for the replies fellas.
    Joe E

  6. #6

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    Oh to clear up a few questions…..

    The car will run on 98 or 100 octane all the time. That’s what we have available around my area anyways so that’s not an issue.

    And the last time the block was worked on was back around 1998 ish. It got a ford factory rebuild the with OEM components. It’s been a DD for a number of years since then. A bunch of miles put on the car up to about 2006. The car basically sat from 2008 to 2019 when I finally saved up enough cash to start a rebuild. The first 2 mechanics were a mess. And the car sat 99% of the time between 2019 and 2021 with only a small amount of work actually being done on it. So it’s been a long long time idle and a podgework of repairs and additions made over the years. So I’m letting the current gentleman doing the car advise me on what he thinks is best at this point and for my future family weekend cruiser.

  7. #7
    FEP Power Member richpet's Avatar
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    Sounds like you're gonna have a great ride when it is done!
    I hope I didn't come across wrong when I asked if you've been back - I just get really curious about what different people decide to do. I guess I like 'closure' sometimes. Lol.
    That is super high octane fuel - are you planning a huge power adder or super high compression? If not, you won't need that kind of anti-knock protection. Higher octane fuel in a lower compression motor does not add power, it can actually reduce it. 93 octane is plenty for static ratios up to 10.5-1 or more with the right cam, maybe even higher.

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    Last edited by richpet; 07-19-2022 at 02:21 PM.
    83 5.0 GT. Quicker than it looks! 10:1 (or just over) 306, Motorsport a332 cam, 140A alt, t5 conv, 8.8 w/ 3.27's, Edel rpm, alum rad, very worked e7's, Holley SA carb, etc... SOLD IT!!!!

    Now an 1981 Granada! .040 over 302, Edel E-street heads... Currently building a 347 because, why not?

    "Never underestimate the power of stupid people in large groups"

  8. #8

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    No worries sir. It’s always interesting to hear about a build and why people plan what they plan. I’ve been a fly on the wall for literally 15 years here. Dreaming of this point I’m at now with my 85gt. Quick background here. My dad bought the car from a friend in 1993 in Florida. He drove it daily until 2003. I traded him for a Chrysler I was driving at the time and used it part time until 2009 when I moved over seas (my wife is from Europe). Now I’ve saved up enough money to get it cleaned up and ship it to a Copenhagen where I live. It’s on a be our family fun car. And my son will get it when he’s ready at some point. So the car has a lot of sentimental value to me. Way more than its actual value. Lol. So I’m upside down in this car many times over but it is what it is.

    European fuel starts at 95 octane and goes up to 100. So it’s nothing “special” just what I can get at every gas station around here.

    My hope if for a clean, rust free, trustworthy car. Not a racer or show car. I want it to start and stop every time I want. Dont want the usual issues Ive always had w the car…. Gassy interior smell, sorry brakes, hard starting, no AC, gangster lean seats, etc. lol.

    So that’s the deal. Just want my car back.

  9. #9

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    Octane ratings in the EU (RON) are not comparable to octane ratings in the US (AKI). If I remember correctly 97RON (EU) is only 91AKI (US), so 100RON would be about 95AKI.
    1985 GT 5.0 CFI / AOD
    All Original

  10. #10
    FEP Power Member richpet's Avatar
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    Quote Originally Posted by TxMike64 View Post
    Octane ratings in the EU (RON) are not comparable to octane ratings in the US (AKI). If I remember correctly 97RON (EU) is only 91AKI (US), so 100RON would be about 95AKI.
    Very true!
    When I had my Triumph motorcycle that was discussed in the owners manual.


    Sent from my Pixel 6 Pro using Tapatalk
    83 5.0 GT. Quicker than it looks! 10:1 (or just over) 306, Motorsport a332 cam, 140A alt, t5 conv, 8.8 w/ 3.27's, Edel rpm, alum rad, very worked e7's, Holley SA carb, etc... SOLD IT!!!!

    Now an 1981 Granada! .040 over 302, Edel E-street heads... Currently building a 347 because, why not?

    "Never underestimate the power of stupid people in large groups"

  11. #11

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    Then cool. I’m not just throwing money down the drain with gasoline that’s 100 octane lol.

  12. #12

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    I'll chime in, a little late, but anyway....

    I've been building my 84, went 306 from 95 Mustang with mild E style cam, basic rebuild, Edelbrock carb and intake, headers, dual exhaust, and stock heads. It's a 5 speed. I'm guessing I'm at stock 9:1 compression on this one, so likely 200 hp to the wheels. She runs great, same goals as you, just get it going and reliable. Gets 17 mpg. AFR heads are in the future as well as roller rockers. I wish I would have gone to forged pistons but that'll be next on the 331 build lol.

    So with your setup, if you keep the Holley carb you'll be doing better than me with the AFR's. Sniper EFI will not net you any big power gains, it will just run a lot better and cleaner and you can tune it easily. Those are big dollars though. I'd stay with the carb for now unless you have the budget. If you deck the block, shave the heads a tiny bit, and use thin head gaskets I think you could get close to 9.5:1. If you get new pistons just get ones that get you to 10:1, that's an easy hp upgrade. If you do it right you might be at 300 hp at the wheels when you're done, great cruiser. So your final comp ratio will depend on if you deck and resurface the heads or not and which piston you use. Ask your machine shop to get a base figure for you when they do the work.
    Last edited by slonomo; 08-02-2022 at 08:44 PM.

  13. #13

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    Alittle update from here. Firstly I really appreciate those of you who have replied. That’s why this forum is still so good while many of the same type of websites have dried up in recent years.

    My buddy got the engine pulled and started to clean it up for the machine shop. He found a spot that was alittle concerning around the water pump. The machine shop got into it and found the block had a small crack on 2 of the bolt holes for the water pump. They sent the block back to my buddy and said they couldn’t do anything with it. It fits cuz a past fella who worked on the car had a hell of a time installing a leaking water pump. So my stock block is a boat anchor now. 😞

    Fast forward a few days and my buddy had worked alittle magic. He had another customer deliver a 306 that had been recently re built but had an issue. Was rebuilt with 9.7:1 Wiseco Forged pistons a comp cam, etc. But the fella decided to go with a built 351 block instead and would sell me the 306 for a drop dead good price. So we will use this new 306 with forged pistons along w my AFR heads, 1.72s, AirGap intake, and Sniper EFI kit. We will use the good part off my 302 and instead rebuild the 306. So alittle more power and block that’s healthy. So let’s see what we end up with.

    The sniper system is getting a new fuel tank and all fuel lines as well. Plus we are swapping a 8.8 w discs into the rear instead of the stock 7.5.

    So lots happening. It’ll be great to hear the car run again tho.

    Thanks again

    Joe E.
    Last edited by joelliott; 08-10-2022 at 03:59 PM.

  14. #14

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    hey, just a few comments

    when you change the cam, pistons and rocker arm ratio... watch out for.....
    1) piston to valve clearance at max lift, you'll want some clearance (1 mm?) to prevent violent contact between moving parts
    2) valve spring solid height (height at full compression) at max lift. there should be at least 1.5 mm of spring compression remaining at max lift. if springs are fully compressed solid before max lift you'll snap your rocker arms. also be aware there will be slight solid height variations from spring to spring so each spring will need to be checked.

  15. #15

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    oh, and good luck with your project, joelliott. sounds like it'll be a fun driver

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