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Adding cam and header to 1986 lg4

Old 09-03-2018, 05:54 PM
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Adding cam and header to 1986 lg4

I have a 1986 Berlinetta 305, Iím looking to put a set of headers on this winter and putting a xe256 or 262 in also to wake it up a bit. What kind of ccc carb adjustments am I gonna have to do for changing cam and headers? Iím new to the forum and all this computer carb stuff, runs fine as is with open air filter and cat back. Iíve had this car since high school and just recently got it back on the road. Any thoughts or experience would be much appreciated
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Old 09-03-2018, 06:53 PM
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Re: Adding cam and header to 1986 lg4

Use the 256, if the only other mods you have done, or are planning to do, are the ones you have listed. It's well and widely known to be a good match to that situation. No "adjustments' necessary other than advancing the timing. (which is necessary ANYWAY even with the stock cam... the factory's settings serve MANY masters, including emissions, gas mileage, emissions, all-altitude function, emissions, compatibility with cat-**** gasoline, emissions, ... and oh by the way, did I forget to mention emissions? that was the factory's BIGGEST priority back in the day, FAR ahead of anything resembling or otherwise related to "performance") Just do it.

The \strongest weaknesses keeping your car slow are the torque converter (1600ish RPM) and the gears (2.73). If you were to put 3.42s and a 2500 or so stall converter in it, a GOOD one not a cheeeeeeeepie, you might be AMAZED at how things other than the engine can cripple a car.

I'd also recommend a dual-snorkel (L69) air cleaner. Probably good for 5 HP easy over an open element.

And, another SURPRISING YUUUUUUUUUUJJJJJJJJJE power sucker: that clutch fan. Put an electric one, and a higher-output alternator, on it. There's another 12 - 15 HP right there.

There ya go: 20 HP without cracking the motor or draining any fluids. What's not to like about THAT?
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Old 09-03-2018, 07:54 PM
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Re: Adding cam and header to 1986 lg4

The 256 shouldn't upset the CCC. While you're in there, replace the valve stem seals, valve springs & retainers and a nice new set of standard rockers. You dont have to go with anything particularly special, a set of Z28 ebay springs will be better than the 30+ year old fatigued rubbish thats in there now.

I've got a 268H in my lg4 - non computer controlled and can definitely concur with Sofa that a 2200+ stall converter is a worthwhile investment.
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Old 09-03-2018, 08:01 PM
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Re: Adding cam and header to 1986 lg4

I was just gonna buy the xe256 kit with new springs, retainers, lifters, cam and timing set from summit or somewhere like $315? And it needs the valve stem seals anyways so figured be good to just do the whole thing and get that little factory cam out of there
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Old 09-04-2018, 12:12 PM
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Re: Adding cam and header to 1986 lg4

A quick look I found summit the cheapest for the K12-234-2 kit. Also free shipping.
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Old 04-12-2019, 08:01 AM
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Re: Adding cam and header to 1986 lg4

So last fall I installed my slp headers, and raised the timing up to 6 degrees. Since this is an 86 lg4 from what Iíve read it should have 9.5:1 flat top pistons? If I add that xe 256 cam what kind of power gains do you guys think would be expected? More or less is it worth tearing it apart to do it?
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Old 04-12-2019, 08:19 AM
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Re: Adding cam and header to 1986 lg4

I put a Summit K1104 cam, Edelbrock intake, Holley 650DP and headers on an LG4 and it turned 14.9s in the 1/4, In saying that my stock auto LB9 car with 2.73 gears and all turned 14.7s.
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Old 04-12-2019, 08:53 AM
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Re: Adding cam and header to 1986 lg4

So not really worth all the work then Iím guessing, not big horsepower gains prolly only 20-30 or so?
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Old 04-12-2019, 10:45 AM
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Re: Adding cam and header to 1986 lg4

Car went from 15.90s to 14.88 best. Daylight and dark but still not a huge improvement. I will never try to improve upon a 305 again myself. Gear change, TC, and a good shift kit goes a long way though. 350s are cheap these days id hold out for one.
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Old 04-12-2019, 10:54 AM
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Re: Adding cam and header to 1986 lg4

Ok I appreciate the help, by the time I get the cam kit for $350 dollars or so and replacement rockers and everything else while Iím In there, I could buy a used limited slip more aggressive axle prolly and be farther ahead. Just didnít know if cam would get me up to 250 hp region or not, I may work on the drive line improvements instead. Thanks for thoughts so Iím not wasting time haha
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Old 04-12-2019, 12:55 PM
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Re: Adding cam and header to 1986 lg4

That's what I did. Upgraded driveline first. Suspension, rear end, tc + shift kit etc. Then waited on a good deal on a 350. Getting 250 HP out of a 305 is possible but it would take probably flat top pistons, atleast some 081 heads if not 059s, a cam around 218-224 duration with a good intake. Your carb would probably support 250 HP, just may take some tinkering with. 250 or even 300 hp is easy to get out of a 350 though.
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Old 04-12-2019, 08:44 PM
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Re: Adding cam and header to 1986 lg4

Since I have added headers and raised the timing and have an ďopenĒ air filter with the factory base and hose setup, it still seems to run just fine driveability wise. After how much more lil mods does a person have to put different rods and hangers in the carb, should I look into that or should be ok yet with the very lil Iíve done? I donít know if itís up to L69 specs yet, I just donít wanna be running it lean.
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