Track Trip
Thread Starter
Staging Lane
Joined: Jul 2008
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I guess when i get home this weekend I will throw the vacuum guage on it and see what's up with it, if i do think it is floating the valves would it be worth throwing new springs in it? Im bout to pull the motor but when i sell it i want it to run correctly.
What springs would you recomend?
What springs would you recomend?
Launching!
Joined: Oct 2006
Posts: 289
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That cam is very similar to a comp 268H grind. Comp recommends the 981 or 983 single spring (1.25 OD). Also, I looked up the 290HP motor and it is rated for power up to 5100RPM. That means you should be shifting at about 5400-5500RPM.
How many miles are on the motor? If there aren't many miles, and your vacuum gage shows what appears to be valve float, it could be the lifters also.
How many miles are on the motor? If there aren't many miles, and your vacuum gage shows what appears to be valve float, it could be the lifters also.
Thread Starter
Staging Lane
Joined: Jul 2008
Posts: 59
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it has about 15K miles on it, i went back and got dad to pull out the receipt and it is the 260hp model... hell right now it wont even make it to 5500rpms.
I thought about throwing some heads and a cam in it but idk if that bottom end would hold any power.
I thought about throwing some heads and a cam in it but idk if that bottom end would hold any power.
Launching!
Joined: Oct 2006
Posts: 289
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The 260HP motor appears to be a stout piece (4-bolt mains, cast crank, LT1 rods and decent pistons). I have a completely stock 1990 L98 short block in my IROC. It runs 11.60's at 117MPH and I have the rev limiter set at 7000RPM. That short block isn't as good as the one you have. That crate engine can take more than 260HP and 5000RPM.
The cam specs are real mild and the compression is pretty low on that crate engine. I think it will be all done by about 5000RPM. Super Chevy did a test with one of these engines. In base form it peaked at 264HP at 4400RPM. They then bolted a blower on it and made some serious power (383HP at 5500RPM on 7psi of boost).
If it were me, I would go over the motor good. Use your vacuum gage. Try to diagnose what is going on at the 5000RPM. Get the carb in tune and play with your timing. The secondary valve on the quadrajet (the plate that covers the top of the secondaries) can be a great tuning aid and there is power to be found there (you want it to open as fast as possible without bogging the motor down). Also, many smog era quads were limited in how far the secondary throttle blades could open. Verify that they are making it to full-open.
The short block is a decent foundation to build from. If you plan on keeping it, I would go with a head and cam swap.
The cam specs are real mild and the compression is pretty low on that crate engine. I think it will be all done by about 5000RPM. Super Chevy did a test with one of these engines. In base form it peaked at 264HP at 4400RPM. They then bolted a blower on it and made some serious power (383HP at 5500RPM on 7psi of boost).
If it were me, I would go over the motor good. Use your vacuum gage. Try to diagnose what is going on at the 5000RPM. Get the carb in tune and play with your timing. The secondary valve on the quadrajet (the plate that covers the top of the secondaries) can be a great tuning aid and there is power to be found there (you want it to open as fast as possible without bogging the motor down). Also, many smog era quads were limited in how far the secondary throttle blades could open. Verify that they are making it to full-open.
The short block is a decent foundation to build from. If you plan on keeping it, I would go with a head and cam swap.
Thread Starter
Staging Lane
Joined: Jul 2008
Posts: 59
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I've thought about building off it, i just didnt know how stout it was and also I bought a nitrous kit to spray it but with it acting up backed out... so i guess i will go over it and see what I can do with it.
Just a camshaft change w/ wake your motor up.Go w/ something like a Comp Cam 218/218-454/454 RPM range1500-5500.I think your over reving your motor which is not hard w/ the little cam that is in it now.
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Joined: Oct 2006
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If you are looking for something to just have fun with, stick with the shortblock you already have. Its free, has low miles and you know the history of it. Getting 1HP per cubic inch is pretty straight forward. I would look at EQ cast iron cylinder heads with 180cc runners and 64cc cumbustion chambers. This will bump your compression up. I would then throw a comp XE268 hydraulic cam in it. Get a set of 1 5/8 headers and dual exhaust (if you don't already have them). Put a high rise dual plane manifold on it (like a Performer RPM). Keep the quadrajet and the HEI. This should get you around 325HP and decent low end torque. I wouldn't be afraid to hit it with a 100HP shot of nitrous...just be careful with the timing (high compression/cast iron cylinder heads). You will also want a higher stall convertor (2800-3000RPM) and decent rear gears (3.55:1). Take as much weight out of the truck as possible and then plan on finding a way to hook it all to the pavement (Cal Track bars and new front springs and shocks). All of this will cost you money...but you can do it in steps. Thats the fun part! Going back to the track week after week and getting a little faster every time!
Thread Starter
Staging Lane
Joined: Jul 2008
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well i have the money to do aluminum heads, i was thinking AFR 195s, and id like to go with a cam with a pretty good bump to it... also i already have 1 5/8s headers, and 3.73 gears out back with a Torsen locker!
so do you think all that and a 75-100 shot would work on that bottom end?
how fast do you think it'd run in the 1/4?
so do you think all that and a 75-100 shot would work on that bottom end?
how fast do you think it'd run in the 1/4?
Thread Starter
Staging Lane
Joined: Jul 2008
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The truck is an 83' C-10 and it needs to be able to be weekend driven, i refuse to trailer it to a track, it weighs about 4500 lbs.
Im kinda leaning toward building a motor cuz i want something very reliable idk though.
Im kinda leaning toward building a motor cuz i want something very reliable idk though.
Launching!
Joined: Oct 2006
Posts: 289
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4500lbs isn't as bad as I thought. No reason you can't get it into the 12's. There is a guy with a similar truck at the track I race at that is in the high 12's. He has a 406 with iron heads and a mild cam. The truck also doesn't hook well (lots of tire spin!). I think the formula I gave you above can get you there with the short block you have. Suspension tuning will be the key. You'll want a tire in the neighborhood of 27" tall and as wide as you can fit/afford. I would put them on 15" rims (no bigger). You're going to want some sidewall flex to get weight transfer to the rear. I'm not sure if Cal Tracks are made for your suspension, but if they are, they work good. You could also remove a leaf or two from the rear springs (you wont be hauling anything with it?). For the front, find a lower rate spring (maybe from a 2wd with a 6cyl). You can also whim the swy bar at the track to get a little more front end rise.
Thread Starter
Staging Lane
Joined: Jul 2008
Posts: 59
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very nice, i think i will soon order AFR 195s, comp. 272H cam (or bigger?) thinking of going roller, recommend me an intake manifold and carb.
What kinda valve train set-up would u go with?
and Cal-Tracs are made for my suspension... like 85 bucks!
What kinda valve train set-up would u go with?
and Cal-Tracs are made for my suspension... like 85 bucks!
Launching!
Joined: Oct 2006
Posts: 289
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Looks like you are thinking of going all out. If you are thinking of a roller, I would look at the Comp XR288HR. You will have great flow with the AFR's. Just make sure you get them with a 64cc or 60cc chamber for good compression to go with that cam. Get yourself a performer RPM Airgap and as good of a carb as your budget can swing (something in the 750-850 range). The right carb will make this streetable (look into AEM...they have good stuff but it is pricey). This will all get you some major horsepower (probably in the 450HP neighborhood). Sell the nitrous kit to fund the carb if you have to.
