Results 1 to 21 of 21
  1. #1

    Default Head swap for budget build - lifters

    I'm pretty dead set on doing a head swap for my Fairmont Budget build. However this is 100% new to me. I've done some research, but it's really looking like it will end up being spring by the time I do this, but I have a question I need help understanding.

    Plan is to keep stock cam. Get some GT40 heads rebuilt at machine shop (3 angle valve job, surfaced as necessary, valve stem seals replaced). Keep stock springs as I'm running stock cam, but spend money on roller rockers.

    What would the risk/bad practice be if I replaced everything from the pushrod up, but not the lifters? Leave the lifters that are currently in car right now? I can see the obvious reason as to why to replace them, the current ones would have wear on them, and I'm down there, and it's good practice...but the other part of me sees it as why mess with one other factory part, and an opportunity to not fix something that's not broken and help me stay on track with the total budget if I don't have to buy something else.

    If you could help me put into perspective how foolish it would be to leave the stock lifters in place I would appreciate it.
    Last edited by Str8sixfan; 09-28-2018 at 08:10 PM.

  2. #2


    Being that you say the car is a Fairmont I'm going to assume that you have flat tappet lifters. Roller lifters can be reused without issue. For flat tappet lifters, I would take each one out at a time and inspect for wear. If they look good I'd reuse them.

    Don't forget to look at the lobes on the cam too.

    Previously owned;
    1979 Mustang, v6 swapped to EFI 393, custom installed m122 blower, 4r70w trans, Megasquirt II, T-top swaped in.
    1990 Mustang, 545 BBF, C-4 with brake, ladder bars.
    1983 Mustang, 1984 SVO Mustang
    1984 Mustang convertible, v6 swapped to 351
    1986 Mustang GT, 1989 Mustang GT convertible
    1992 Mustang coupe, 4 swapped to 302

  3. #3


    Jess you beat me to it. Rollers are fine as long as they are ok , but flat tapped lifters are actually rotated by the cam as well as going up and down. It's good practice to replace them with a cam change, as they "seat" to the cam.

  4. #4


    Hey thanks both of you for the replies. I assume too that it's not a roller equipped motor either. Eventually I'll get that confirmed for sure before I purchase anything. So a flat tappet lifter that has excessive wear, I assume that's a concave shape on the face of it?

  5. #5


    Yes. That's why non roller cams generally come with lifters. At least the ones I have bought did.

  6. #6


    Explorer GT40 heads do not have enough spring for a stock HO cam

  7. #7
    FEP Super Member bwguardian's Avatar
    Join Date
    Jul 2010
    Houston (Clear Lake), Texas


    Leave the lifters alone if good and invest in better spring pressure...however you want to accomplish that...
    '82 GT monochromatic (red) cloth

    '85 GT vert two tone (white on charcoal)...white leather
    '00 F350 two tone (white on silver)...gray cloth
    '00 Excursion Limited two tone (white on tan)...tan leather...wifes ride
    '08 Taurus Limited ice blue...tan leather...daughter ride
    '08 Edge Limited white sand tri-coat metallic...tan leather...other daughters ride

  8. #8
    FEP User bkm's Avatar
    Join Date
    Jan 2016
    House Springs MO


    Flat tappet cams and lifters have to be changed, and broken in as a unit. If you're staying with the stock cam, just bolt the gt40 heads on and go. I wouldn't waste money on springs or rockers for a 79 flat tappet cam.

  9. #9


    Quote Originally Posted by bkm View Post
    Flat tappet cams and lifters have to be changed, and broken in as a unit. If you're staying with the stock cam, just bolt the gt40 heads on and go. I wouldn't waste money on springs or rockers for a 79 flat tappet cam.
    That was my thought as well. Springs should be fine. Been doing some number crunching lately, hoping I can keep the GT40 heads in the build, but things are evaporating quick!

  10. #10
    FEP Power Member Ourobos's Avatar
    Join Date
    Apr 2008
    Waikoloa , Hawaii


    If you do remove the lifters to inspect, make sure you put them back in the exact same hole..

    You may need differently length pushrods, particularly if the heads get deck much. You can always measure the sweep with the ones you have to find out before you order different ones.
    1986 CHP SSP Coupe

  11. #11


    Thanks for the tips...makes sense about the lifters since they create their own groove. I'll probably leave untouched, but we'll see. Also i saw on how they make a push rod measuring tool.

  12. #12


    So here's where my list is at for the moment:

    AFR head bolt kit - $48.81
    Fel Pro Head gaskets - $47.98
    JEGS brand Push rods - $99.94
    Rocker channels - $22.97
    Roller rockers - anywhere between $143.99-$196.99

    So after $300 on machining (went to two different places and they quoted me about the same around here)...

    That's a total of $663.69-$716.69 on top of the cost of the heads. So curious where else you guys think I might be able to find other savings?

  13. #13


    Honestly....... even a Stock head with a decent intake and other parts is good for 6250 RPM. That will either hold or it won’t — considered sorta not recommended with stock rod bolts.

    Meanwhile the physics behind a 3” stroke says normal hardware is fine up to around 7000.

    Here’s the thing — Add more CFM with GT40 or other heads, and air pumps do what air pumps do — MORE and FASTER

    If you do t swap out the shortblock shut it down early because it will want to spin a lot higher than is advised. 7000+ if things are right with the CFM expected.

    You can choke that down with restrictive intake or exhaust but it negates the purpose of the swap. You can throw longer intake runners at it to create port velocity based limits. Those change slightly with things like unequal shorties on the exhaust side driving down port velocity. Long tubes long runner will go high on velocity first.

    More velocity adds area down low at the expense of upper RPM gains. Upper RPM is where the fun is at — that’s where the gains will be huge.

    All ARP in the bottom end if you do the Block swap is cheap insurance. Balance it too if you can...

    Everyone always talks about big power big displacement. Nobody ever talks about high power high RPM and honestly there are certainly good use cases for it. Street cars and road course cars that love RPM are THE BOMB when you drive them.

    Assuming 2.73 gear and a normal foxbody 3.35:1 T5
    5300 rpm rev cap due to breathing — 1-2 shift at 45, 2-3 at 70, 3-4 at 115, 4-5 at 150

    6250 RPM rev cap due to limiter — 1-2 at 55, 2-3 at 80, 3-4 at 125, 4-5 at 170 (lol)

    Then you throw a T5Z gear set at the 2nd motor
    6260 RPM rev cap - 1-2 at 61, 2-3 at 88, 3-4 at 134, 4-5 at 170

    These are about what they are..... tire size and other stuff factors in, use an RPM calculator and your gears

    Bigger than the top speed in each gear is where in the power band for the motor is when you pull the next gear and you’re running 1000 RPM more, etc

    Somebody forgot to tell my worn out E6 Head 302 in my 500K mile 86GT that it’s not allowed to make power up top. SO much fun. 0-60 comes in well under 5 seconds all in first gear......

    To steal a line from Steve — it dominates.

    you can shim the lifters or put in thread in oil galley plugs and jack up the oil pressure to avoid collapse. Valve control determines output and longevity.
    Last edited by erratic50; 10-03-2018 at 09:40 PM.

  14. #14
    FEP User bkm's Avatar
    Join Date
    Jan 2016
    House Springs MO


    Quote Originally Posted by Str8sixfan View Post
    So curious where else you guys think I might be able to find other savings?
    Use the stock rockers and pushrods. IMO, for such a stock build, it's money that can be spent elsewhere.

  15. #15


    On the pushrods - what’s the expected RPM range? Deflection kills power big time.

  16. #16
    FEP User bkm's Avatar
    Join Date
    Jan 2016
    House Springs MO


    Quote Originally Posted by erratic50 View Post
    On the pushrods - what’s the expected RPM range? Deflection kills power big time.
    Judging by the stock 78 cam, 4000 rpm probably. Personally, I think the stock stuff will be just fine unless there is a camshaft upgrade.
    Last edited by bkm; 10-04-2018 at 06:04 AM.

  17. #17


    I really appreciate your guys' input. Learning quite a bit. At the moment, the heads I purchased didn't come with rockers. I'm trying to unload them and start from scratch, but that's partially why I'm planning on buying rockers. I thought pushrods were fairly cheap reassurance since I probably am not smart enough/have a skilled enough eye to notice if stock pushrods were slightly bent or not, and also assumed that something about the pushrod length would likely have to be tweaked due to different heads (potentially some decking) and they're swapped all together...maybe buy a different head gasket thickness over stock by accident that it would just be best left to measure push rods and buy new.

    Also I'm really pushing the head swap for a few reasons:

    1) stock motor has such low compression, this is a great way to combat that
    2) it's out of my comfort zone so I believe best way to learn
    3) it's unconventional which I think makes for a better YouTube video, and am crazy enough to try it
    3a) want to demonstrate what someone can do with limited access to space/ I'm running the numbers I'm probably better off doing a motor swap after U-Pull-It runs a special weekend...but I really don't have the space for a motor swap, or an engine hoist. I know I could probably rent an engine hoist, but again trying to make it relatable to the driveway mechanic. It's like a half step past bolt-on king.
    Last edited by Str8sixfan; 10-04-2018 at 05:47 PM.

  18. #18


    Re - read all of this. The GT40 springs are plenty strong for a non-roller (flat tappet) HO style cam. The concern was with the lift and duration of a stock HO roller that the explorer springs would be too lazy to control the valves due to the added inertia of the roller lifter going up and down more.

    You will pick up a lot with a good intake and headers and those heads. Especially if you shave them down enough to get your compression up in the range of 9’s to low 11’s.

    Just keep your RPM down - at or under 5500 - so it stays together and you can enjoy it.

  19. #19
    FEP Member brianj's Avatar
    Join Date
    Feb 2012
    Raymond, New Hampshire
    Blog Entries


    If this is a flat tappet 79 motor, I believe you can also reuse the head bolts and save $50. They are not stretch bolts like newer ones. The original bolts from my '83 motor are happily holding the GT40P heads down on a '96 5.0 with 9 pounds of boost.
    1983 Mustang G.T. No-option stripper- I like strippers.
    5.0, GT40P heads, Comp Cams XE270HR-12 on 1.6 rockers, TFI spring kit, Weiand 174 blower, Holley 750 mechanical secondarys, Mishimoto radiator, Edelbrock street performer mechanical pump, BBK shortys, T-5 conversion, 8.8 rear, 3.73 gears, carbon fiber clutches, SS Machine lowers, Maximum Motorsport XL subframes, "B" springs.

  20. #20


    Hey, good pointer brianj...I'll have to confirm that somehow to move forward with it...but at least I know what to/how to double check to figure that out!

  21. #21


    The gt40 heads spring pressures may be too high for a hydralic cam as it was meant for a roller one would think?
    This is the budget build I should have done.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts