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Mates worked 202 fails to make power up top, and i mean at all. It's fully rebuilt, blue/black internals in a red block, more than 10/1 comp, custom 12port red head, 35/75 camtech hydraulic and triple SU's. Everything's new and run in, carbs totally rebuilt, whole thing tuned, and it won't make power past 4100 rpm.
The power curve is sweet up till 4000, where it's got 105 at the wheels. This combo should see 6500 easy, but power drops at 4150. After all the usual checks i'm thinking it's weak spark. Fuel and air are plentiful.
Runs an HEI dizzy, but looking at it, a stock coil. 12V at the coil of course. Plugs are generic and running 26thou gap. Way too small but if that's what the tuner ended up with i assume it's all the ignition can support?
Thoughts?
"Silly modern cars" |
"Silly modern cars" |
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Rank: Veteran
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Joined: 25/11/2008(UTC)
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vac advance working ok? leads in good condition?
if he wants to upgrade his spark plugs then tell him to invest in a set of brisks, yes there expensive, but damn there good
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Rank: Veteran
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Joined: 28/03/2008(UTC)
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maybe just try a standard dizzy and coil for comparison?(they should rev up higher than 4100) if it doesnt(but i bet it will),then it should be fuel starvation ,3 carbs standard fuel pump usually enough fuel?as dave says leads ,vac, leaks(air)lifter failure?....just shoot at stuff...jim
Jim in Adelaide...Hindsight is bad vision! |
Jim in Adelaide.. |
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Rank: Member
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High pressure pump, regulator, new Top Gun leads.
Run without vacuum advance, but total timing should be the same if set right, right?
I had brisks, theyre brilliant. Will recommend once we sort the problem.
I gave him a spare GT40 coil i had, told him to fit and and see if it changes, then if itll support a bigger gap, around 45thou.
No noticable leaks, lifters all pump up and cycle.
Basically, its a strong motor, pulls harder than mine down low and ive got about 130rwhp. It revs beyond 4100 but just looses all power. Bit of a stumper.
Cheers guys.
"Silly modern cars" |
"Silly modern cars" |
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Rank: Member
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GT40 no good with HEI, but ok with standard. The advance curve could be off for the combo as well, coming all in too soon.
Another thought is that the exhaust could be a bit restrictive (or mis matched to the top end combo). I had a set of big pacemaker dump pipes with a "big torque low down" set up intake / carby / cam. Ended up with neither top end or big torque. Changed to tri-ys with balance pipe and suddenly big low down numbers. Could have the reverse here.
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Keep the shiny side up, and the greasy side down. |
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Keep the shiny side up, and the greasy side down. |
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Rank: Member
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Joined: 14/06/2007(UTC)
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Well hold off on the GT40 then, thanks. Ive got a sports coil here that came off a Holden V8 of some variety in good working order. More suitable?
The cars been dyno tuned, so youd think obvious points like timing and air/fuel would be as good as possible without dizzy re-curve.
Exhaust is pacemaker 2pc, twin 1 3/4 with single straight through mufflers and a balance pipe.
"Silly modern cars" |
"Silly modern cars" |
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Rank: Member
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Joined: 30/03/2005(UTC)
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red with triples and no power. what needles are in them. 1"3/4 hf series carbs i would think oa6 needles. put it back on the dyno and make sure the pistons pull all the way tp the top.if you cant sort it and the car is in brissy send me a message . i do this all day long. kel
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