massive lack of power
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  1. #1
    Rods 'n' Sods Junkie TheWebDesignCompany's Avatar
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    massive lack of power

    Hi I wanted to see what the general opinion was regarding a problem I've got with my car.

    I recently took my car to a mechanic to have a blown head gasket repaired. after discovering that one of my camel hump heads was cracked,
    I bought a set of Quantico Aluminium performance heads to fit instead. The mechanic told me that my cam shaft needed replacing as 2 of
    the lobes were worn. He also said that I needed new lifters as they were worn and two or three of them were jammed and crushed. I couldn't
    really afford this but he said the engine would never run if he just put the new heads on like I asked. So I had them all replaced, new hardened
    race lifters, new camshaft and new heads. The car should know have way more power.

    I originally had a Lunati 00010 Cam Shaft and replaced it with a Comp Cam XE268 cam shaft.
    The mechanic was trying to push me to have a full engine rebuild but I didnt have the money.

    The car has a high stall Torque converter and a limited slip diff and even before the head gasket blew it would spin the wheels every time I
    pulled away and leave 2 black lines on the road if I reved it. However after I got the car back it is gutless and even if I rev it before I pull
    away if doesnt leave black lines on the road anymore.

    When I picked the car up it had almost no oil in the transmission and a pot of transmission fluid was under the car. He wasn't supposed to
    touch the transmission and said it was leaking a bit because the dipstick holder was flopping about lose after the heads were removed.

    I asked why the car suddenly had no power on pull away and low end especially when the cam shaft was a very close match to the one we replaced
    and he said it is your heads. The old camel hump heads were probably much better.

    The new heads are 200cc aluminium performance heads with big valves. The old heads were rusty old camel hump heads with cracks in.
    Does that should possibly to you, or does it seem more likely that the torque converter has been nicked and replaced with a standard one?
    Last edited by TheWebDesignCompany; 12-10-2017 at 20:55.

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  3. #2
    Official RnS Addict rodster's Avatar
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    It sounds to me like its probably more of a problem with the engine lacking power, it could just be that its been timed up wrong, or are you confident the engine runs sweet?
    If quitters never win, and winners never cheat, then who is the fool who said "Quit while you're ahead"

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    Official RnS Addict cptpugwash's Avatar
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    Seems your old heads are around the 64cc mark.
    Last edited by cptpugwash; 12-10-2017 at 19:28.

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    highly experienced bodger draguar's Avatar
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    If the new heads a lot larger size it could lower compression and reduce power? Or You said about lifters but did he replace the push rods as some aluminium heads require longer ones so your valves might not be opening properly? Just a guess I’m sure someone will be along in a min to tell me I’m talking ****! Lol


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    Rods 'n' Sods Junkie
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    Not sure what motor it is, but I suspect there is a big mismatch in the parts now, as mentioned the head cc numbers are totally different so cr will be lower, coupled with the camshaft change the chances are the parts are not working together efficiently, possibly resulting in an apparent lack of power, not sure about the torque converter, is the build spec a recognised combination? Dave

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    Rods 'n' Sods Junkie
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    sebspeed is offline
    maybe the engine builder didnt dial the cam in.

  9. #7
    Rods 'n' Sods Junkie TheWebDesignCompany's Avatar
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    Yes the old heads were 64cc, it has domed forged pistons that have 10 to 1 compression.
    The new heads are Quantico Aluminium performance heads and the spec from their website is as follows:

    Technical Data

    Intake: 196cc
    Exhaust: 74cc
    Chambers: 68cc
    Stud Base Thread Drilled: 7/16"
    Plug:
    Straight
    Valve Guides: Bronze Manganese
    Suitable Valve Details
    Intake Valves: 2.02"
    Exhaust Valves: 1.60"
    Valve Stem Diameter: 11/32"
    Complete Heads:
    Valves: Stainless Steel
    Height: Standard + .100
    Spring including dampener
    Spring Diameter: 1.450"
    Max lift: .600"
    Seat Pressure: 130lbs @ 1.800"
    Open Pressure: 335lbs @ .600"
    Lift Coil Bind: 1.060"
    Installed Height: 1.800"



    So these are pretty similar in terms of chamber size 68cc rather than 64cc shouldn't these improve the power rather than lose it?

  10. #8
    Rods 'n' Sods Junkie TheWebDesignCompany's Avatar
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    When one of the old heads was cracked and causing overheating, I tried to replace it with the same head, but had trouble finding them.
    So I bought a set of aluminium performance heads instead thinking that with the new cam shaft it would give me more power.

  11. #9
    Rods 'n' Sods Junkie
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    Quote Originally Posted by sebspeed View Post
    maybe the engine builder didnt dial the cam in.
    Most likely this, or didnt re-install the dizzy correctly and re-set ignition timing.

    With a different cam etc fueling may be off too, but that's probably a less likely cause as incorrect cam/spark timing.

    Sounds like a better mechanic is needed. But for you now, ignition timing would be the first and easiest thing to check. Cam timing a little more awkward.

  12. #10
    Official RnS Addict mygasser's Avatar
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    the pistons will only give 10:1 compression with a given combination of deck height, compressed head gasket volume and cylinder head combustion chamber volume. plus of course bore and stroke too. with no other changes the new heads will lower compression which will hurt hp. however it shouldn't be as dramatic as you say so as others have said a good start would be having it set up properly, on a rolling road is best by someone who knows the engine type you have. it's generally no good asking someone who sets up modern efi 'sports' cars to sort your chevy v8. luckily Atspeed Racing are near you and come highly recommended by folks on here ATSPEED Racing - Rolling Road In Essex
    good luck with it, neil.
    need a job done on your project? i may be able to help.

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