73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: SUX2BU99 on September 06, 2008, 01:13:54 pm
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I was finally able to get my truck to the drags. First time since buying the truck in April 04, and first time back running at the strip since 2000. So, read my sig below and guess what I ran. My truck has power windows, locks, tilt, no cruise or a/c. 295/50-15 rear tires. My carb tuning is questionable and my 60' times suck since I get all giddy and nervous when the lights go green and in the moment, I can't even remember how I launch lol It's much different then when you are on the street and can control yourself. Anyway, what do you think? It's like Pass Time without the money ;)
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15.2???
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14.7
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14.4
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15.55
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1/8 or 1/4?
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If you were on sticky tires, I'd say 14.1 and if you were on street tires then 14.5.
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i say 14.3?
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So, how long do we have to wait to hear the real number? Suspense if killing me ;D
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^ :D Alright, well here's the scoop. I was hoping for mid-14s or less but I know my truck isn't that dialed in yet. My track is only 24 ft. above sea level and temp. conditions were mild. Not sure on barometric pressure. Anyway, tire pressure was around 32-35 psi and this was full 1/4 mile. I got two runs in:
15.111 @ 91 mph
14.994 @ 91 mph
So I was able to get into the 14s but I need it better than this. My MPH tells me it's not really making the horsepower to bring the times down which really disappoints me but there is work I need to sort out on my truck to make it quicker. Namley:
- carb tuning. I've always been suspect about the Edelbrock 1406 I have and how it's setup
- base timing. I think it can use more, which should improve my 1/8 mile times at least
- launch. I just torqued it up to around 1200 or so and then stomped it. With all of the excitement of racing against a pro tree light (all 3 yellows flash at once, it doesn't count down like a sportsman tree), there's little time to get myself setup and calmed down lol
- shift rpm. I shifted 1-2 at 5500 and 2-3 at 5000 or so. With my heads and cam, my engine should pull a little stronger than it does after 5000 so the carb issue might affect that and maybe I might need to change my intake manifold.
- exhaust. It's alright for now, dual 2 1/4" with H pipe and headers, no cats and Ultraflo mufflers but I think a dual 2.5" system would help my top end HP.
I'm sure there's more I can do but I'd really like to see mid-14s. Good guesses everyone!
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no one guessed the exact numbers >:(
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What rod/jet/spring combo are you running in you carb? A good baseline for your combo might be to set it up like a #1405 carb comes out of the box (a .070" x .047" rod in a .100" jet with orange springs). I've heard that if you are running anything bigger than an rv-type cam you should run the pink or silver spring, not sure how true that is, but you could play with it. Check your float settings mine were off by about 1/8" both in terms of drop and height; set them according to the manual. Also don't under-estimate the influence the idle adjustment screws have on drivability. I've found the best just-off-idle response by setting the screws for max vacuum in park at idle and then another 1/4 - 1/2 turn out (rich). Edelbrock/Carter carbs have to be the easiest, most fun carbs to tinker with, enjoy.
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thats not bad i ran 15.3 consistant,same carb ,30 over,vortec heads,performer rpm,same cam,i shift at 6000 1-2,but stock 350 turbo and 3.08 gears.i got a full sec.by putting premium gas and octane booster but i had to play with the timing.love your truck by the way
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Thanks, blue :) I know I can put some more timing in it. The only thing I regret about when I bought my heads was not getting the smaller chamber for a higher compression ratio. So it slows the velocity a little too much at lower rpms. Big chambers and lower compression can usually tolerate more timing so I've read so I'll try that.
Event, good info on the carb. I downloaded the owners manual for the Edelbrock carbs and have read through it a couple of times on my commute to work. The carb is definitely very tuneable and it seems relatively easy to do so. Before I bought my truck, it had been tinkered with to pass emissions and I suspect that has set it up strange. I definitely have a WOT stumble that I think is attributed to a weak accel pump or the plunger rod in the wrong hole. What's a kit cost for these things with different springs and rods?
A couple projects down the road would be exhaust like I said and, as much as I don't want too since it's a 'Dart' product, change out the intake to an RPM Air Gap intake since I read nothing but good reviews on them. The Dart II Sportsman dual-plane I have now is getting on about 10 years old and the new RPM Air Gaps just plain perform better apparently. The only negative I've heard is when cold, the idle quality and driveability really sucks since the vehicle takes longer to warm up.
Jefferias and his opening guess was pretty close to my first run!
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Here's the kit (http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D1487&N=700+115&autoview=sku) I have. If you want a bit more to play with, you could get this one (http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D1479&N=700+115&autoview=sku) plus a pair of 70 x 47 rods (http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D1451&N=700+115&autoview=sku) and just use the tuning guide for the #1405. You'll also need to pick up a set of air horn gaskets (http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D1499&N=700+115&autoview=sku).
The RPM air gap manifolds are nice, but I would probably keep the dart manifold, especially if cold weather driviability is an issue. You can always improve performance of the manifold a bit by port matching to the cylinder heads. Also note the center divider is cut on the edelbrock rpm air gap. I suspect that is where it gains some of its power over the plain rpm manifold. But I'd consult with a veteran hot rodder before cutting yours. Also you can play with open, four hole, or tapered spacers to fine tune the manifold.
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That's cool. I think I'll pick one up and play around with it. It's cheap enough anyway to do that and it get me some experience with tuning a carb.
The manifold thing will probably be on the back burner for a while. I'd like to get the motor tuned nicely and then maybe invest in a new exhaust system. Current is a 2 1/4" true dual system with crush-bent tubes, unknown headers, simple H pipe, Dynomax Ultraflo's that were take-offs from 98-99 Dodge Dakota R/Ts and Magnaflow 3" tips. It sounds nice but it's starting to corrode (especially where it's been wrapped with header wrap) and 2.5" should help it breathe better.