Ok, so yesterday I took the GS ('71 GS350 convert) to the track. This is the first time I had the new motor at the track. Just got it broke it, changed the oil and drove to the track 80 miles away. about the motor- '71 block and heads, ported out by Burek to flow over 250 at 500 lift. poston S-divider intake, Barry Grant 850 demon, 10.1:1 compression 280 duration @.050, .520 lift cam, arp everything, MSD billet dist. (RTR, no box) 2004R trans, 4.11:1 gear, 30.5" x11 Gforce KDW street tires, global west supension, shocks tuned for drag racing. My first pass literally drove 80 miles to the track, signed in (in my car), staged and down the track. sucked. 15.11s @ 89 mph. not happy. I ran a couple more times, still 15s, these with the exhaust uncorked. I aired down the tires to 21 psi, shifting at 5500- 14.88@ 91 Shifting at 5800- 14.60 @91 Added 4 degrees of timing, shifted at 6200- 14.41 @94 The tires on the car are really sticky on the street, they hardly blow off at all, but at the track, it was like they were soaked in oil, spun through the 60-foot a few times. I tried it all- no burnout, roll 'em to clean them off, big burnout. Big burnout worked out much better than little or none. with no b\o, the car just sat there, smokin tires. I tried rolling the throttle, but my 60-foots were worse. I know there is 13-sec time on street tires in there, I just have to find it.
Can you please post the cam card for this engine? Was this engine on the dyno if so what where the numbers?
I don't have the cam card available, but it is the Poston 111, which is 302 advertised (280 @.050), .520 lift int and .523 ex. Dyno'd 396 hp @ 5390 414 ft\lbs @ 4300 I don't have the dyno sheet in front of me, but the torque curve is fairly flat.
Great job! How do your plugs look? Was there air fuel data from the dyno pulls? Have you looked into the pinion angle? Which header primary size are you using btw?
What were your actual 60' times? MPH seems alittle low for the power level you should have based on your dyno numbers. What rpm were you going through the traps? Your tire seems alittle tall for the car even with the 4.11s. I would tend to think you should be running a 26 or 27" tall tire. You need more RPM. If your peak power is really 5400rpm then you should be going through the traps at that number or a little higher to optimize your car. After typing all this I realize you mentioned shifting at a higher RPM and going faster, this is supporting the point even more. See if you can maybe borrow a buddies tires that are shorter and then see where your at. Good baseline you've got.
those were my thoughts exactly. The big tires look killer, but they are for the street, not the track. I definitely need to be running through the traps over 5000 and not 4500. My 17s are 26 tall, but they are really hard tires, the 30.5 are stickier. I blow the 17s off at 1\4 throttle, they would be nasty bad on the track. ou: A friend of mine has offered some 28 x 10.5s, those should fit under the fenderwells, i hope. I need some rims though, I don't have any 9 or 10" rims that have the right BP. I thought the 4.11s would be enough gear for the big tires, but apparently not. definitely too big for the track. I figure shifting higher (with the big tires) is putting the engine at around 4500, so that it is right in the peak of the power band. With a shorter tire, it won't have to spin as fast on the upshift to stay in the power band, therefore not working quite as hard. AND I can get the rpms up at the big end so I get the most of 3rd and the entire run. 60 foot times were between 2.171 (the 14.60 run) and 2.298 (15.11 run) I am running hooker super comps. I am either going to do run the full slicks or try to get some drag radials. I can't really fit tires in the trunk, so drag radials sound pretty good. I have to drive the car to the track. I am taking the car to get weighed tomorrow. I didn't get a chance to look at the plugs. I will bring an extra couple of plugs next time I go.
I'm thinking the GS350 111 cam that you have is more like 240 in/248 ex @.050". Probably the same specs as a GS105A but on 111 LC. If it had 280 it wouldn't idle below 1400 rpm and would be just about the biggest hydraulic cam put in any Buick engine. It probably still has a lumpy idle. Now that that is over did anybody notice that that cam in a 350 is making peak power way too low in the rpm band. I ran a program that shows peak power between 6000-6500 and peak torque between 4500-5000 rpm. His numbers are about 700 rpm low. His torque should be closer to being the same as his HP. A 455 would peak higher than that with this cam. Something's up there. Was this cam degreed in? Sounds like it is way too advanced. Maybe to try to make the idle better? The way it picked up by shifting higher indicates high rpm power but the dyno said otherwise. I would have thought that when it was dyno'd the operator would have said it was making power awfully low for such a big cam. Maybe it is the "mysterious" 350's only make good power with a single plane intake problem? This looks like a great engine to try out that theory once your launch problems are solved. Anybody want to volunteer one so that he can actually try it at the track on an engine that might actually require one? At the least I would get a 1" open spacer on that intake or is the intake divider cut down some? That might help. I'd get some MT Street Drag Radials 255-60-15(27") tall to get traction and to get the rpm up and they can be driven on the street. That should get you some traction. You might find at that time the engine feels a little doggy when launching if you don't have a high stall converter. You didn't mention one but I'll assume you have something in there but with that cam and carb a 3500 10" one wouldn't be too much. Tire spin covers up a lot of problems. Once you get traction off the line and if it does feel slow maybe a 1" 4-hole spacer would add some torque. It doesn't matter what tire size is on the back as far as shifting is concerned. The rpm drop from gear to gear is the same because that is in the transmission and this engine seems to need rpm so don't think about shifting earlier because of different tires. Of course things change and you will need to find the optimum rpm to shift at once everything settles down. What is the elevation of the track? It is important because that and the weather can make a big difference in performance. Overall I'd say just getting traction and your 60's into the 1.90's should get you into the 13's. Plus it will be alot more fun. There's nothing fun about having to feather the throttle off the line just to get going unless you just want to talk about how much power you're making smoking the tires. You might also pick up a few mph because while you're spinning your tires you're making the track shorter and giving yourself less space to get going. With your HP I'd say if you get around 105 mph you are in the ballpark but that is going to take some doing so good luck.
Agreed, Mike...the only Poston cam I see with that lift is the GS 105A with the specs you already mentioned, unless they did something different between the big/small blocks. Devon
The 111 is the biggest cam Poston made for the 350. It is 302 advertised with a 114 centerline. You are right it is 240 at .050, I had 280 in my head for some reason. I have rhoades lifters to make it idle. It will idle down to 750 warm, but I keep it around 1000 so it will start and run cold. I have a 2500 stall. I could use a little more converter, but that is what TCI spec'd for my combo. I have a 1\2" spacer and the intake has been whittled on a little. I can't fit a 1" spacer under the hood with an air cleaner. As it is, I have a drop-base and I bumped the hood with fresh paint and cracked it. I had a wing nut on the stud. Now I just use a nut. Jim Burek did the head work, put the motor together and dyno'd it. it does make power pretty low. The heads flow 243 at .500. My dyno program with all the right specs shows peak at 5500 of 408 hp and peak 430 ft lbs at 4000-4500, which just a handful off from the real deal. I think the tires are killing it. They are just too tall for the track, and they spin. I am looking at some drag radials, if I can get them in the next couple of weeks, I will run it again. we shall see.
ET is car setup, MPH is horsepower. Something is off with the low MPH, you are trapping 1 MPH lower than my best with a stock 82k mile longblock and a mild Comp cam. I'd look into the tune and see why the power has dropped off. 2 weeks ago I drove my car to Island Dragway in North NJ, 65 miles away and right off the highway clicked off a 13.96 at 94 MPH without so much as a cooldown.
I think Mike is right about peak hp happening so low. There is a cork in this thing somewhere in the combo that should have been addressed at the dyno. Peaking at that rpm is how near stock 350's behave. Do others get higher peak hp with the 350 S-Divider? Does it need a carb spacer like the big block version does to come together? I know it's not that simple, but... Devon
definately the tires are too tall. i would try the 17's you have just for the mph/rpm range, dont worry about et. that would give you an easy guesstimate on tire size. i would suggest 4.30's and a 28'' tire if your going to race more often. with that motor you want about 6000-6200rpm max thru the traps. also t/q about 3k. the motor doesnt recognize walking rpm's. 105 mph, i dont think so. maybe 102's. s/p vs d/p shift rpm loss is way different. hardly any loss w s/p. when we ran the glide in the hawk, the d/p drop was about 6-800 rpm, had to wait for it to reach rpm. with the s/p, loss was about 300 and it screamed right back to the top. what a sloppy reply by me.....
Johnny, please spell out SINGLE PLANE and DUAL PLANE or the new people searching the site will not know what the hell you're talking about! :error: Devon
I was trying to figure out what sp and dp was myself.... I am from Oklahoma. I agree that it makes power really low, but I am not sure what to do about it. I have a sheetmetal intake that I want to try, but I also want to keep the stock hood, and that ain't gonna happen with that intake. TA needs to get on the stick and get that SP1 for the 350. I really think that is what I need to get the power I am looking for. I spec'd the motor for 500 hp, but the stock valve size is hurting it (was done for a magazine article, it was necessary) and the s-divider intake is hurting it. Jim tuned it on the dyno, it has been tweaked since then. With a max-flow single plane, I think I would be making closer to 500 hp. The port work and the cam need air flow, the dual-plane (s-divider, which is not a true dual-plane according to Jim) is only good to about 350 hp, beyond that it starts hurting power potential. I need to get my intake done. All I lack is the final tig welds on a few areas and the water neck.
How is the cam degreed? Some info on similar combos, you need that single-plane intake!!!: http://www.v8buick.com/showthread.php?t=46831 http://www.v8buick.com/showthread.php?t=106735&highlight=dyno+350
