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I ran my vortec 350 last night at tri-state dragway and i'm in need of some suggestions on what to do next with my car. I only have a single 2" exhaust that being the most restricted area, which is over the rear end its crimped to hell. I also still have 2.73 gears and im debating whether to go 3.73 or 3.90. My trans is built and i have a 2200 stall, but its not shifting as hard as i want it to.
I only ran a 14.7 but like i said gears and exhaust are destroying me.
I foot braked it around 2200 right before the tires spun. I ran 1st gear to 50mph and left it in second the rest of the way. I'm guessing if i had my exhaust i would pick up loads of top end because of my cam being retarded and my open spacer i only got one run in because it started raining. A guy suggested letting it idle while you brake it and smash it right when you go bc it would get the torque converter spinning..
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1992 RS Heritage Edition /350 OE Roller Bored .060 over/Holley 650/Edelbrock Performer RPM/Vortec Shaved Heads 10.5:1 Compression/Beehive springs/Comp Magnum 1.52 Rockers/Speed Pro Flat Top Pistons/Comp XR 270 .502 lift
'10 best 13.1 at 106! Needs some minor tuning for 12s
Fix the exhaust before deciding on a gear ratio but you really need a better gear. 3.42 or 3.73 would probably work fine.
Foot brake racing usually only needs a little bit of throttle at the start line just to load up the driveline. Going too high will overpower the tires because the vehicle's brakes can't hold back the engine's power. With EFI, it's not so bad but if you were using a carb, raising the launch rpm up past an idle goes through part of the accelerator pump shot and when you go to WOT, it will have a lean stumble.
You'll probably launch better if you can bring the rpms up to around 1500 then when you see the last yellow light come on, let go of the brake and put the throttle right to the floor.
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Hardtail Racing
All engine, no power adders! Bests: 9.029@150.45 (at altitude)
Theoretical sea level performance 8.623@157.05
The exhaust will allow you to free up horsepower and let your motor breathe making more power and hopefully gaining better times.
The gears will take what you currently have and allow it to work more efficiently in the 1/4 mile. My guess is it would shave more time than exhaust.
One good thing about getting the exhaust done is it will make the car sound a lot better though. Both changes will probably end up costing about the same.
I would have to say between the exhaust change and gear change....I would go with the gear change. Changing to a 3.73 is whats going to make you feel like you have a car that works. Those 2.73 gears in there always made me feel like the car just doesn't work. Like it shouldn't be anywhere near the race track.
__________________ 1986 Camaro SC - SOLD
383/T-350/4.10'S/PUMP GAS
10.71 @ 126 W/ 1.52 60FT
Desktop Dyno said my motor should be making 398 horsepower with an open exhaust, and when i went to restricted it dropped to 308hp. That might be a little extreme but you have to look at how much top end my exhaust is holding back. it gets the air/fuel in fast but cant get it out quick enough. Both are probably going to drop my e/t .5 of a second or hopefully more. i should be running 13.0s-13.3s when its all said and done.. Theres a real close custom exhaust shop by my house i think im going to get the exhaust done first, what mufflers do you guys suggest or should i just run straight 2.5 inch without anything?
Fast i agree about the gears it just feels like im flying a plane or something it just has the same pull the whole time lol
So do you guys think im in the right et range without the other stuff done? i could probably run a 14.5 if i launched like stephen said, another guy at the strip told me the same thing... any other considerations would be appreciated.. thanks
I ran same setup as you. shaved heads and all. At the same track as you, and i can tell you, your top end is non existant. I see you say you need to tune your carb. Do that. Open up the exhaust. I had 2.5" off of dougs headers either open or through and x pipe. Should be trapping around 103-105 with that combo and gear i would say. What rpm are you shifting at also? Good luck, its a solid combo.
I ran same setup as you. shaved heads and all. At the same track as you, and i can tell you, your top end is non existant. I see you say you need to tune your carb. Do that. Open up the exhaust. I had 2.5" off of dougs headers either open or through and x pipe. Should be trapping around 103-105 with that combo and gear i would say. What rpm are you shifting at also? Good luck, its a solid combo.
well with gears and exhaust im hoping to pick up the extra 11-13mph. i have friends with stangs that picked up .8 going from 3.27-4.11 alone, and mines even more extreme going from 2.73 - 3.90. so i plan to pick up at least a second or more from gears/exhaust. my carb is fine actually i have bigger jetts in the secondaries and a bigger squirter. but with my current setup its probably running too rich. what do you mean you had 2.5" off of his headers? i have hooker headers that are 3" but it eventually goes into a y pipe thats 3" and then a 2.5" exhaust thats bent to hell over the rear end. thats where im losing my powerband, it just stays flat around 4000+. it doesnt really pick up after that. i shifted around 5600 rpms into second at 50mph and left it into 2 the rest of the way. thanks man alot of people have had good luck with my setup even with smaller cams so i want to run 13.0s some day or better.
ive got a vortec350 and i trapped 107 first time out w a 2.09 60ft on junk street tires. these vortec heads make very good power and i cant wait to see how she runs w my new hyd roller cam... since my flat tappet comp xe274 went flat on 2 lobes
also i was tryin to shift it at 6k but my limiter was at 5800 so it hit the limiter in evry gear but 3rd.
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08 best: 13.07@107 on street tires, untuned
1. Exhaust
2. 3:73 gears (better have posi)
3. Tires
To give you an idea how bad the gears are killing you, I'm going into 3rd just before I cross the 1/8th with my 3:73's.
Dan
__________________ 86 Camaro tired 305 low output only heaven knows how many miles on it. Lunati cam, Edelbrock torquer intake, Holley 670 Street Avenger Carb, Hei distributor, Headman headers, 373 gears, lock rite locker, shift kit, 2500 rmp stall converter. Best 1/8 mile time so far: 8.89
I would say that with the mods listed, you should be able to break into the 13s with a gear and exhaust. That gear is going to make your car a dog, and the exhaust isn't going to help much. Get some 3.73s, decent tires, and a bigger exhaust and you should see some 13s.
I changed the tv cable tension on my 700r4 and it launches WAY harder than it used to. the tension before was so loose that it would never downshift and it shifted soft. i tightened up the slack although i need the right brackets, and it took off harder. it downshifts now but not like it should, after 45 it wont ds into 2nd. so i think i couldve ran a few tenths faster if i wouldve realized that. desktop dyno says my single 2" is holding back 90hp which is alot of top end. its not hurting me as bad now because i have more low end which i need with the long gears. but i should be running 13.0s with 3.73s and some good tires once everything is done.
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1992 RS Heritage Edition /350 OE Roller Bored .060 over/Holley 650/Edelbrock Performer RPM/Vortec Shaved Heads 10.5:1 Compression/Beehive springs/Comp Magnum 1.52 Rockers/Speed Pro Flat Top Pistons/Comp XR 270 .502 lift
'10 best 13.1 at 106! Needs some minor tuning for 12s
Ok guys I finally got some exhaust work done and took my carb spacer off and took her for a run. They switched to 1/8 mile fore the dragsters on my best run so i dont know what i would've ran but i was a tenth faster than my 14.35 run. I'm spinning just a little off the line. I got true dual 2.5" exhaust put on with dual glasspacks and a crossover pipe. Do you guys think thats a pretty good timeslip with 2.73s? What should i run with 3.90s?
Its funny my worst run had the best takeoff, so maybe i shifted at the wrong rpm or something but i', guessing at best i could run a 14.1 with 2.73 gears and 245's. So could i run low 13's with slicks and 3.90s? thanks for the suggestions guys
If u change the gear set without a set of slicks.. u are probably going to run slower..
U already said u are spinning, the gears are only going to make matters worse.
I have 2.73 gears no posi in my drag car. It works good for me. I run high 10s with stock LT1 and 150 shot. The car goes straight, no wheel spin or funny business.
If u change the gear set without a set of slicks.. u are probably going to run slower..
U already said u are spinning, the gears are only going to make matters worse.
I have 2.73 gears no posi in my drag car. It works good for me. I run high 10s with stock LT1 and 150 shot. The car goes straight, no wheel spin or funny business.
thats why i said 3.90s with a set of slicks, it would probably be the same time with a higher trap speed lol, but i did some calculations and my gears with 3.90s would be like 1st - 35 2nd - 70 3rd - 109 at 5500 rpms
Thats perfect since most vortec setups are trapping 107. How much would i pick up getting roller rockers and deleting ac? oh and i found out my car weighs 3365 lbs.
I would say that it would depend on how your heads are setup. Overall the Vortecs are lower reving torqy heads so leaving the hole isn't as important as making up for the RPM loss, especially in a light uni-body car. In that case I would say 342's are perfect, 273 gears suck with the exception of gas mileage, umless of coarse you cruise under an ideal cruising RPM. If you have 2.02 valves and the springs set up for a high .500's cam I would consider the 373's, but remember that the gears would ideally be compimented with a higher then stock stall speed to level out the power curve. A general rule of thumb is to stick with 2'1/4 for 250-300 HP and 2/1/2 for 300-350 HP. Yes, your 2" is probably killing you, unless if you are still running the stock Vortec roller. The mandrell bent pipes are definately ideal but not as big of a factor as having the right size. If you get to large a size you will hurt your back pressure and loose some precious oompf off of the line. Remember also that the size depends on if you are running true dual or a single cat back system. True dual 2" will run like 2 1/4 cat back since you get the increase in flow. There are still many other factors such as are you carbed or FI? Do you need to rely on a computer friendly duration or can you get away with a single pattern cam? Hope this helps. Blocks-
If you read a little bit further down you would see i got my exhaust work done and i do have a .502 lift cam. I'm not sure what you mean about the 3.42's and 3.73s. My cams powerband is from 1800-5400 and i was shifting around 5500-5700. my exhaust is perfect it might be dual 2.5" but he had to make some bends so its more realistically like dual 2.25" which is plentiful. I picked up a tenth off my 60' and .5 possibly more off my 1/4.
Tech guys i also swapped my pump cam to the maroon one which was the biggest one and thats when i ran my best run. But i've heard a 750 vaccum secondary would help me better than a 650 mech. sec. with an auto trans.
I just got 3.73s installed last weekend. I'm loving the 3rd gear pull on the highway. first gear feels like a granny gear too haha. im running it this weekend and before i go im buying an accel spring kit to increase my mechanical advance
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1992 RS Heritage Edition /350 OE Roller Bored .060 over/Holley 650/Edelbrock Performer RPM/Vortec Shaved Heads 10.5:1 Compression/Beehive springs/Comp Magnum 1.52 Rockers/Speed Pro Flat Top Pistons/Comp XR 270 .502 lift
'10 best 13.1 at 106! Needs some minor tuning for 12s
Ran my car the last weekend the track was open. I broke 13s but im very dissapointed with my top end, something has to be wrong because most vortec setups are trapping 105-107. so please guys any ideas would be appreciated!
60' - 2.028
330' - 5.80
1/8 - 8.934
MPH - 78.41
1000 - 11.636
1/4 - 13.913
MPH - 99.25
I dropped my tire pressure and got the tires real nice and warm and it spun and grabbed at the same time for maybe 20 or 30 feet. it wasnt just going up in flames. but im not feeling the top end that this motor should have. and i noticed a hissing noise now out of my engine bay.. i even put bbk underdrive pulleys on it a few days ago minus the alt pulley. what could be wrong? i still have stock steel rockers but that cant make a big difference. i'm using a 305 harmonic balancer, could that be an issue? we have never been able to get my timing reading right but it seems fine no knocking and the dist. is in the right spot and it idles fine.. maybe my carb needs tuned too but i should at least be trapping 102.. im going to probably buy a 750 vac sec. carb
Yea the engine has the 305 harmonic balancer that originally came with the car. it that bad? The hissing sound sounds like the alternator fan or the pulley itself. yea i tried it without the carb spacer. I'm still using the 245 tires and my best run i launched at 1500 and it didnt spin bad, the other runs i tried around 2000 and it spun really bad the whole time so theres room for better timeslips but i should still be seeing alot more top end. i think my spark plugs are bad too.. it doesnt start that good like it used too and its running rough
Why aren't you able to get your timing reading right? You need to know what you're timing is set at, at least at idle. If you're serious about taking it to the track, it's a good idea to set it off total timing as well. Of course it's hard to say but aside from your tall gears, it really sounds like something is way out of tune somewhere. I'd start with getting the timing nailed down. If you have to change harmonic balancers to get the timing set, do it, there's no point in guessing and throwing parts at it. Also, if you do swap balancers, be sure and buy one with the timing marks on it all the way around so you can set total timing if you want to later.
Dan
__________________ 86 Camaro tired 305 low output only heaven knows how many miles on it. Lunati cam, Edelbrock torquer intake, Holley 670 Street Avenger Carb, Hei distributor, Headman headers, 373 gears, lock rite locker, shift kit, 2500 rmp stall converter. Best 1/8 mile time so far: 8.89
Correct me if im wrong, but if its internally balanced, the you would be fine to swap out the balancer. If its externally balanced, then you will have to have the rotating assembly rebalanced.
You can get timing tapes for your size balancer and marked covers.
Get your timing set (not by ear) and tune from there. The wrong timing can rob you of quite a bit of hp.
What about some new tires?
Did you say that you installed the cam retarded?
And I know you have the Beehive springs, but did you check for retainer to valve seal clearance?
Last edited by bluegrassz; 11-17-2009 at 07:09 PM.
Thanks for the input guys about the timing. I've had mechanics look at it before and the harmonic balancer doesnt give them the right reading. the line on it has to be off or something and the teeth on the tab aren't numbered. But I have the distributor set on the right spot and it idles relatively smooth. The guy that built the engine did say he cammed it 2 degrees retarded. what could be keeping the timing from being around 34 degrees?
Another thing i'm concerned about is the secondaries. How much are they supposed to open? on my 650 if they open past 45 degrees it clicks and opens to about 80 degrees. i havent had somebody check it but i might not actually be getting full throttle the way my pedal is set up
So you really dont know were your timing is at. That being said, you are leaving some hp on the table.
Have you tried a piston stop and remark your balancer? If its a 6 3/4 balancer, you can get a timing tape or cover that is marked. On the stock tab, for every ^ the point is 2* and every valley is 2* if I remember correctly starting at the deepest valley. The notch on the balancer should be lined up with the deepest valley on the tab at TDC.
Stock base timing for a TPI motor is 6*. With your setup you should start with a base of 10*-12* and aim for 32*-34* total all in by 3k. This will get you in a ballpark.
Last edited by bluegrassz; 11-18-2009 at 02:33 PM.
So you really dont know were your timing is at. That being said, you are leaving some hp on the table.
Have you tried a piston stop and remark your balancer? If its a 6 3/4 balancer, you can get a timing tape or cover that is marked. On the stock tab, for every ^ the point is 2* and every valley is 2* if I remember correctly starting at the deepest valley. The notch on the balancer should be lined up with the deepest valley on the tab at TDC.
Stock base timing for a TPI motor is 6*. With your setup you should start with a base of 10*-12* and aim for 32*-34* total all in by 3k. This will get you in a ballpark.
If the mark is off, the balancer is probably bad, it's probably slipped.
Another thing i'm concerned about is the secondaries. How much are they supposed to open? on my 650 if they open past 45 degrees it clicks and opens to about 80 degrees. i havent had somebody check it but i might not actually be getting full throttle the way my pedal is set up
At 80 degrees you're not really losing much airflow. By the time plate throttles are around 50-60 percent open you're getting 95 percent of the airflow.
My throttle bracket was loose. My secondaries were only opening about 25-30 degrees. I pulled it back and took it for a drive and i felt a world of difference! Haha
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1992 RS Heritage Edition /350 OE Roller Bored .060 over/Holley 650/Edelbrock Performer RPM/Vortec Shaved Heads 10.5:1 Compression/Beehive springs/Comp Magnum 1.52 Rockers/Speed Pro Flat Top Pistons/Comp XR 270 .502 lift
'10 best 13.1 at 106! Needs some minor tuning for 12s
My throttle bracket was loose. My secondaries were only opening about 25-30 degrees. I pulled it back and took it for a drive and i felt a world of difference! Haha
I had the same thing happen to me. I had to trim the black plastic sleave on the cable.
My throttle bracket was loose. My secondaries were only opening about 25-30 degrees. I pulled it back and took it for a drive and i felt a world of difference! Haha
Are u serious?! Your only problem was the throttle not opening?!
I took my car to a performance shop and they changed my spark plugs to the right ones, from .460 reach to the standard vortec .708. They also found TDC on my balancer and had to move my distributor around to get it right. They said its advancing now up to 25 degrees and running a heck of alot better than it was. They said it idles better and has better response than before. They're now going to get the additional timing around 34 degrees but they said my vaccum advance can isnt working. But I thought it only works under part throttle? They said holleys port on the carb still draws vaccum under full throttle which will help my timing go from the 25-34-36 degrees. Any truth to this?? They run some badass cars at the track and they have been very legit so far
I took my car to a performance shop and they changed my spark plugs to the right ones, from .460 reach to the standard vortec .708. They also found TDC on my balancer and had to move my distributor around to get it right. They said its advancing now up to 25 degrees and running a heck of alot better than it was. They said it idles better and has better response than before. They're now going to get the additional timing around 34 degrees but they said my vaccum advance can isnt working. But I thought it only works under part throttle? They said holleys port on the carb still draws vaccum under full throttle which will help my timing go from the 25-34-36 degrees. Any truth to this?? They run some badass cars at the track and they have been very legit so far
good to hear you're finally getting it right, the car i was talking about had the wrong head gaskets in it, they were the .041 compressed instead of the .028.....woke up a TON when we swapped them and put in the new springs. ran 8.2x on legit street tires......
They also found TDC on my balancer and had to move my distributor around to get it right. They said its advancing now up to 25 degrees and running a heck of alot better than it was. They said it idles better and has better response than before. They're now going to get the additional timing around 34 degrees but they said my vaccum advance can isnt working. But I thought it only works under part throttle? They said holleys port on the carb still draws vaccum under full throttle which will help my timing go from the 25-34-36 degrees. Any truth to this?? They run some badass cars at the track and they have been very legit so far
Holley's have both "full manifold" and "timed" vacuum ports, so it depends on which one you use. I prefer full vacuum for non-emissions applications, tends to improve idle.
M1tch, I just read through this thread. Sounds like you've made some progress and figured things out since last summer! I'm wondering why your cam is installed 2 degrees retarded..??? Even not knowing the LSA of that cam, I'd say performance will fall short of expectations until you get it degreed correctly. It should be at a 107 or less ICL.
I'll be out at Tristate when they open, with my Impala, and my daughter with her black 86 Fbird. Was at Edgewater Friday and Kilkare Saturday. What color is your car? I'll look for you.
Hey Pat heres a few pictures of my car, you might of seen me before. I'm not too concerned with the cam being a few degrees retarded it should help me a little top end wise anyways. But if all is well I will be at Tri-State this coming Saturday Hope to see ya there
Holley's have both "full manifold" and "timed" vacuum ports, so it depends on which one you use. I prefer full vacuum for non-emissions applications, tends to improve idle.
Holley's have both "full manifold" and "timed" vacuum ports, so it depends on which one you use. I prefer full vacuum for non-emissions applications, tends to improve idle.
THe mechanic i spoke to said that holleys vacuum port on the left side of my 4150 will still provide vacuum at WIDE OPEN throttle allowing the vacuum advance to provide the full 34-36 degrees of timing. Is this true? I've read religiously that you don't count vacuum advance at WOT because your vacuum drops to essentially 0. So I have my car back now and he showed me how its advancing with a timing light. He said it could be off a few degrees because they didnt use a dial wheel, only marking TDC on the balancer which is really close but not exact. I tend to think its a few degrees low because of how easy its starting after warm which is really rare. I'm only getting a reading of 26-27 degrees advanced mechanical with the base timing close at 8 degress, but i'm guessing its only around 5-6. If its false that vacuum advance won't provide any extra timing at WOT then i'm going to plug it up at the drag and increase my base timing about 6-10 degrees for the drag strip. Other than that its running better and smoother and its nice having new rockers on!
Most people hook the vac advance to the base plate source. You should be checking your timing with it plugged off.
What HEI distributor are your running. I run a MSD Probillit without the vac advance. I use a lighter spring to have all my timing in by 3k. You may need a recurve kit.
