My new engine is a dog!!

Discussion in 'Classic Mustang Specific Tech' started by crushnut, Oct 6, 2004.


  1. crushnut

    crushnut New Member

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    What about the 260H? It also says the 268H would work, how much diff. is there between the two?

    It says they work well with engines that make 8:1 to 9:1 compression :shrug:
    #61
  2. D.Hearne

    D.Hearne Banned

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    Hard to say on the intake milling requirements. On the 5.0 I had the Canfield heads on last year, I milled the heads .060 and then needed to mill the Vic Jr intake .040 per side and .020 off the bottom to fit it. With these heads on the 331 I have now ( also a roller 5.0 block and it's had the decks milled .010 to clean them up) I used slightly thicker head gaskets ( needed to reduce the comp some) that are .009 thicker than the .039 Felpro's on the 5.0. With the same milled by .060 Canfield heads, the reproduction 3x2 intake needed no milling to fit, it did need the bolt holes ovaled slightly toward the center to line them up with the holes in the heads though. Milling the heads on a small block moves the intake bolt holes towards the center of the block slightly, hence the need to oval the intake's holes to make the bolts line up with the heads. Bottom line is even after milling, you may not need to mill the intak at all, only way to know for sure is to wait til you have the heads back on and torqued in place, then set the intake down and see how everything lines up before milling the intake. You might just need thinner intake gaskets after miliing the heads to make everything line up. Ford's recommendation on head milling is that you can mill the heads up to .040 before needing to mill the intake.
    #62
  3. D.Hearne

    D.Hearne Banned

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    I gotta go back to bed now, have to work tomorrow. your cam links didn't work. :( Do more research before making any changes that will be hard to correct, always pays to do your homework :nice:
    #63
  4. crushnut

    crushnut New Member

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    How much do you think it would raise my compression ratio if i had that done? And would it be cost effcient to do so? Or would getting a different cam, like the ones i posted earlier be cheaper?
    #64
  5. D.Hearne

    D.Hearne Banned

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    Can't tell on the comp ratio increase, it's impossible to figure with your heads. If you can reduce the head volume by 4 cc's then that will raise it back up to 9.0 to 1 . Milling an E7TE head .040 will reduce the chamber volume 6 cc's, milling your's the same amount, will reduce the volume by a lesser amount, due to the smaller chamber size. You could possibly get a 4 cc reduction with a .040 mill. That combined with thinner gaskets could get it closer to where it needs to be. A cam swap might be easier though. According to Comp Cams, the 260 and 268H will work with your comp ratio.
    #65
  6. crushnut

    crushnut New Member

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    If i do decide to do that, do you think my carb would be enough?
    #66
  7. mdjay

    mdjay Premium Sponsor

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    While I don't disagree with what you're saying may be a concern, crush posted that he pretty much just bolted it on. So checking the operation of the current carb is critical. The choke could be malfuctioning, the secondaries could not be kicking in, tiny jets, the springs on the metering rods could be too big and not openning, the float could be stuck or misadjusted, squirter pump etc. So check it!

    However, it's been my experience that with Ford motors, they do not like to be leaned out. Like you said, they may come off the line ok, if it's functioning properly, but they will run out of air/gas at about 3000-4k rpms. A stocker runs real nice with a Holley 600. A mild performance motor should be running a 600-650 carb. I have a close friend that runs two 500's on an edel dual quad intake, 302 with a large cam, and it runs clean and very strong.

    As I said, the cam selection concerns me but I still think it wouldn't run quite that bad. I also don't think it would run that bad with just the 500 unless something was wrong with the operation of the carb. Or it has small jets and large metering rods. So check it! But ulitmately, change it. I have found the demons to be superior.
    http://www.barrygrant.com/demon/default.aspx?page=5

    I agree to a possible change for the cam. Don't mill the heads. But first I would test and adjust the current carb, and highly consider testing a bigger carb. The recommendations for your intake are here:
    http://www.holley.com/HiOctn/ProdLine/Products/AMS/AMSM/8020.html

    Crush, starting at 600 cfm, it should come off the line strong with a very responsive bottom and middle end. Gradually moving up to 650, you will gradually loose the bottom end and gain on the top end. So depending on the cam you end up with, even current, move the size of the carb up. You selected a nice intake that's good to 6800 rpms. Give it the air/gas it wants!
    #67
  8. D.Hearne

    D.Hearne Banned

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    I don't disagree with anything you say, just that those who think his carb being too small is the problem are barking up the wrong tree. As you and I have posted, even with a too small carb it will still be responsive off the line and up to a certain rpm where it will run short of breathe. I think he needs to work with what he's got before swapping carbs. And I also agree on the cam swap over milling the heads, but he needs to make sure that the cam and/or the compression is the problem before changing or altering parts. :nice:
    #68
  9. Stang_1973

    Stang_1973 Founding Member

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    I remember when i swapped my stock cam to an "RV" Cam- 204 int and 214 Exh with lift around .448 and .472 @.500. The mechanic who did the work said it would be best to have at least 8.5 Compression, and a 600 CFM carb. When we firt started the engine we had the timing retarded for about 500 miles and then. even like this I could feel a huge difference. Then whe we advanced the timing, it was even better.
    #69
  10. ratio411

    ratio411 Founding Member

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    RV cams need less compression, not more.
    That is not his issue.
    He needs to start small and check one thing at a time before deciding that his rebuild was a flop and start changing major engine components.
    Make sure it has no vacuum leaks.
    Make sure you give it time to break in. Engines become stronger as they get some miles.
    Make sure the timing is right.
    Make sure you are using the right fuel. If you have low compression, do NOT bother with high octane fuel. Higher octane that what you need is BAD for economy and performance. Contrary to what gas companies will have you believe.
    Check the tuning and all the 'little' stuff before pulling the thing apart again!
    If you need ideas on everything to check, ask people and get a thorough list.
    Dave
    #70
  11. ratio411

    ratio411 Founding Member

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    Yeah, what he said!
    That is what I just posted, more or less... ;)
    Tune what ya got, down to the last detail, and find the problem before you change stuff.
    :D
    Dave
    #71
  12. D.Hearne

    D.Hearne Banned

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    How's things in P'Cola ? Have they rebuilt the I-10 bridge across the bay yet ? Better yet did they find the truck driver that dissappeared off it ? Also heard that on of the tunnels in Mobile was either damaged or flooded in the storm, that true ?
    #72
  13. Bad67MF

    Bad67MF New Member

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    My engine is a dog!

    You may have installed your distribitor 180* off. When you thought it was at TDC of the comp. stroke it was actually on the ext. stroke. The motor will run but you will have no power. Pull out your #1 plug hold your finger over (not in) the hole,have someone crank the motor (best by hand you may go to far by using the starter) until you feel comp. You can use a wooden dowl or some type of probe in the sparkplug hole to determine TDC.Then look at your timing marks they should line up fairly close to TDC. Then pull your distribitor cap and your rotor should line up with the #1 plug wire. If not rotate your dist. so it does. This will cure your lack of power. If it is lined up w/#1 then obviously this was not your problem. Hard to diaignose over the internet.
    #73
  14. rbohm

    rbohm Founding Member

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    actually that IS his issue. rv cams come in two flavors;
    1: designed for high compression engines so that you can maintain decent power while gaining fuel economy, and so you can run a lower grade fuel,
    2: so you can pump up a low performance low compression engine to improve performance and fuel economy.

    the cam he selected is the former. the large valve overlap conspires with the lower compression to essentially kill low end performance, and the moderate lift hurts the top end. a cam swap to something with wider lobe centers, and less valve overlap will trick the engine into thinking it has more compression than it really does by holding in cylinder pressure. more lift will help on the top end as well, and the comp cams he268h high energy cam does this nicely. the lobe centers are 110 degrees, and the valve overlap is something like 50 degrees. a tad large, but will help the engine at all rpm ranges. with a thinner head gasket, he can bump the compression to around 8.8 or 8.9:1, and that will also help. the carb is not the problem right now, the lack of compression, or the excess valve overlap is the problem.
    #74
  15. crushnut

    crushnut New Member

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    Can you recommend a cam that has less valve overlap than my current cam, closer to say 30 degrees? And still has good performance, mostly bottom end/midrange torque.

    Thanks :)
    #75
  16. crushnut

    crushnut New Member

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    rbohm.... how low do you think i could go on the valve overlap to help gain some power back, but not too low that it would cause problems with even a low compression engine like mine and not allow me to run regular pump gas, the cheap stuff 87 octane with pinging?

    Thanks again :nice:
    #76
  17. D.Hearne

    D.Hearne Banned

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    Crushnut-------- If you can find one of the Ford Racing flat tappet cams ( A311 or A312) thise will give you what you want. Both are ground with 112 degree lobe center angles and have short overlaps. How short is hard to tell at .005 lift , but the .050 lift figures , neither has any overlap, so thet .005 overlap will be very small, both are designed to work with stock, 8.5 to 9 to 1 comp ratios.
    #77
  18. rbohm

    rbohm Founding Member

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    d.hearne listed two good cams from ford. the ones i usually recomend are the he260h and the he268h cams from comp cams. crane has a couple of similar cams as does crower. the edelbrock performer cam(NOT the rpm cam) is also a good choice. these cams were designed with the lower compression engines of the 70's to the late 80's in mind.
    #78
  19. crushnut

    crushnut New Member

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    Thanks guys, i will look into those cams. Any ideas on where i might be able to pick up one of the Ford Racing cams? Ebay maybe :shrug:
    #79
  20. crushnut

    crushnut New Member

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    The specs on that Edelbrock Performer cam only give you the .050 timing and using those numbers the valve overlap figures out to 15 degrees. I know you said SAE timing was more accurate, so how would the 15 degrees at .050 relate to the SAE number for overlap?
    #80

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