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New personal best with the 'Bu and got a nitrous question

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Damon
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New personal best with the 'Bu and got a nitrous question

Post by Damon » Wed Nov 21, 2018 9:10 am

So, made it to the track with a buddy of mine who has been trying to get his turbo blow-through Chevelle into the 9s. He said I should bring my Malibu and take a few runs, too, so I did.

With the new, shorter blower belt on the itty-bitty Weiand 142 my belt slip issue is gone and I picked up just a smidge of boost on the top end. Good enough to run 11.8 @ 116 on a dead-hook launch with NO other changes to the combo- same as it's been for the last ~6 years. (My friend in the Chevelle was the next car down the track after me and he got his nine: 9.95 @ 137. I was on the return road getting my slip so I didn't get to see it, sadly.)

So, with that little issue fixed the quest for the 10s is now on for me. All my friends have turbo cars and I'd rather not be the slowest of our crew. At least not by a full second!

I don't have the time or money to do much, so the old plate nitrous kit I've got on the shelf is getting dusted off and installed over the winter.

My question relates to ignition advance. I've done blowers. I've done nitrous. But never together before (at least not on my own car). The motor is 8:1 compression and I run it with 28* of timing advance because these little 142 blowers are known detonation-makers if you get too greedy with cylinder pressure. Pump gas, obviously.

Now, if I throw a mild 100-125HP shot on top of the blower I'm wondering how much timing I should pull out. Normally a shot that small wouldn't require much if any but I'm a little concerned how it's going to interact with the boost. Anybody done something similar could get me in the ballpark with a recommendation?

Thanks in advance, guys.
78 'Amana White' Malibu- My grandmother's go-to-church car with 35K original miles. Out with the smogger 2bbl 305. In with a really mild 383 topped with ancient AFR heads, Summit's finest K1103 house brand flat tappet cam, a Weiand 142 "underhood" blower and a home-brew QJet. GN rear, DRs. 11.99 car with a 12.0 driver.

Damon
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Re: New personal best with the 'Bu and got a nitrous questio

Post by Damon » Wed Nov 21, 2018 9:17 am

I guess I can update my signature now. Heh.
78 'Amana White' Malibu- My grandmother's go-to-church car with 35K original miles. Out with the smogger 2bbl 305. In with a really mild 383 topped with ancient AFR heads, Summit's finest K1103 house brand flat tappet cam, a Weiand 142 "underhood" blower and a home-brew QJet. GN rear, DRs. 11.99 car with a 12.0 driver.

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StreetBu
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Re: New personal best with the 'Bu and got a nitrous questio

Post by StreetBu » Thu Nov 22, 2018 10:20 am

Well that's cool! Congrats! Now onto your question. IIIRC roots blowers need so much timing pulled because of the heat they generate, basically filling the cylinders with really hot air. Adding nitrous will help combat that issue and really pickup the performance. Obviously read up some more about it and don't take my word for gospel, but I'd only pull a couple of degrees for a 125hp shot. Bet you pick up close to 150hp with it...
'78 bu, 350/380hp, M-21. Now with a GN 3.42 rear and Detroit Tru-Trac, 18x9.5" wheels on all four corners with 275/35/18's, grey bucket seat Monte interior

Damon
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Re: New personal best with the 'Bu and got a nitrous questio

Post by Damon » Sat Nov 24, 2018 9:33 pm

Yeah, that's what I'm hoping for. The intercooling effect of the nitrous offsetting some or all of its typical detonation-inducing effects. Agreed, every time I've seen it run on a "hot air" blower setup, the nitrous hit is worth well over it's "rated" HP increase. That's why I'm gonna keep it in a modest 100-125HP range for starters.
78 'Amana White' Malibu- My grandmother's go-to-church car with 35K original miles. Out with the smogger 2bbl 305. In with a really mild 383 topped with ancient AFR heads, Summit's finest K1103 house brand flat tappet cam, a Weiand 142 "underhood" blower and a home-brew QJet. GN rear, DRs. 11.99 car with a 12.0 driver.

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prairiehotrodder
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Re: New personal best with the 'Bu and got a nitrous questio

Post by prairiehotrodder » Wed Dec 19, 2018 1:23 pm

those little blowers love nitrous.
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Damon
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Re: New personal best with the 'Bu and got a nitrous question

Post by Damon » Fri Aug 30, 2019 9:23 pm

So, a little update!

I yanked the engine earlier this summer and replaced the hypereutectic pistons with some cheap KB forged slugs, new rings, some fresh rod bearings (not that there was much wrong with the old ones) and, of course, new gaskets. Amazing the number of minor things you find wrong with an old engine you haven't had apart in years! Other than the piston swap, no changes. Didn't even remove the cam or crank from the engine.

Fired it off last weekend without issue. Would love to share the first-fire vid but for some reason this website won't accept a .mp4 video file??? Drove it around blower-only (exactly like it was before) to make sure it hadn't lost a step. It hasn't.

I have the Qjet-plated nitrous kit sitting next to the car right now, ready to install.
78 'Amana White' Malibu- My grandmother's go-to-church car with 35K original miles. Out with the smogger 2bbl 305. In with a really mild 383 topped with ancient AFR heads, Summit's finest K1103 house brand flat tappet cam, a Weiand 142 "underhood" blower and a home-brew QJet. GN rear, DRs. 11.99 car with a 12.0 driver.

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