torque convertor,shim gasket only bump compresion max .5 if your luckey and at like 2% power gain with compresion change aint worth the time and money invested unless you comp is 8 to 1 change your fuel filter and check your tune/ carb / timing fine tuning will locate any other problems i would also check your fuel pressure under load to see if your getting enuff fuel for upper end rpm
Hey Kody.... Thats great you got it runing again....sounds like your valve timing is much more in line with the rest of the motor. If i were you I would now get that adjustable vaccum advance canister and also put the bushings from the kit to limit your mechanical advance to between 15-18 degrees and bump your initial way up to 18 start with that and then use the adjustable vaccum canister to limit that advance to where the ping is eliminated. One more thing Kody....I bet with that 800 carb your motor really isn't flowing what it can quick enough. Now might be the time to also put that converter in to get into the power band a little quicker. Mark
A little late for some of this, but a C110 should be great for 8.5 to 9.5 CR and seems to do fine on 8.0 cr 455's. We normally don't recommend this cam with more than 9.5:1 because of too much cylinder pressure. At .050" it has 1 degree overlap which helps with cylinder filling and cylinder pressure. Some say DCR is useful and some say it is worthless. I think using it to compare two cams - apples to apples is helpful. Advertised numbers are worthless, calculations should always be done at .050. I updated the cam specs in the new catalog trying to give more info on how to select a cam. It now lists overlap at .050 this will help you determine vacuum. I also updated the power ranges and the low number helps with selecting a torque converter. I was going to give DCR's but I was told more than once that it's not worth doing. The one thing that I need to add in the future is suggested initial timing, because most people are not addressing this. For this particular combo, we still need to know the rear gear ratio. Jack up the car, rotate the tire one full turn and count how many turns the driveshaft makes. If we are talking a 2.56 or 2.73 that is one problem. He says it is a `69 GS 350, just need to make sure it does have the TH350, if it is an ST300 there is another problem. If the gearing is 3.08 or less go with 2000 stall if gearing is more go as much as 2500. Most converters are rated on a SBC so should be good for this. He said advancing the cam 4 degrees made a difference (now he is at square one), he will have to get a feel for the rest of the power range, if he can live with peak power (hp) occuring slightly sooner, then upgrade the crank gear to a 9 keyway and advance to 8. We normally recommend 12 initial timing on a camshaft of that size, but up to 16 should do well without lugging the starter. You can run a few degrees of vaccum advance at idle to help with acceleration, but probably only 4 or 5 degrees. Get rid of the carburetor, try borrowing a 600 to 750 cfm edelbrock or holley from a friend and see what happens. The 800 QJ is too much for this set up and all too often the Q-Jets are not working properly. The Q-jet is the best all around carb, but if they are not right they suck and the average person can not get them dialed in. The 455 loves a big carb because of it's big bore, the 350 has an undersized bore and won't need 800 cfm until peak power approaches 6000 rpm. End results should be: minimum 4 degrees advanced on the cam. 12-16 degrees initial timing and 34 degrees total. Ported vacuum port on the carburetor should read 0 degrees at idle. Switching from park to drive should only drop 100 rpm. Manifold vacuum at WOT should be about 1".
Wow, thanks for all the help everyone. I want to thank Dave from TA for stopping by and breaking things down. All of this is great information and makes a lot of sense to me. Now my question is what order do i do it all in? Will 8* advance give me anouther noticable gain? Like 2 seconds off my 0-60 like i got when i advance it to 4*?
Another 4 degrees will do similar. How is the rest of the power range? I think if it was me and it is buttoned up and running, I would work on the tuning and other upgrade items. There should be more power to be had by getting it dialed in. I have a customer using a 284-88H in a `69 350 w/ 9.5:1 cr. Every few months he would call up and complain about it being under powered. We would go through everything and it was always coming back to the carburetor. But he would never make the change, I had written him up for a carburetor at least twice in the past and he cancelled. He was using a Q-Jet from a 454 Chevy and assumed it was an 800 CFM. But never knew for sure, I doubted it. I suspected the carb, because he could never get it dialed in like I recommended and his shops kept returning it to him not running right saying it wouldn't respond properly to changes. About a week ago he calls me all excited, he borrowed a 750 holley from a friend and the car runs great now, rips the tires off at a dead stop, never did before. Idles better, everything about it is better. Just another messed up Q-jet as the culprit. Some people fail to remember that these carburetors are 30 + years old, and so are HEI's, it is very infrequent these days that you can just slap them on and have them work right. Over the counter Q-jets are not much better.
How's it going ? Did you figure anything out ? I put my stall converter in, it runs very strong out of the hole now. Chris
Its running better. Mark is helping me out a lot. I got the cam right, and im running 19degrees initial timing. I can do crazy burnouts now. It lacks in 30mph plus so im gonna get a higher torque converter and a shift kit. Im also might try a 750 qjet. Overall its running better.
I am recurving my dist next. Keep tunin, it's fun isn't it ! I don't think I will ever be satisfied. My goal, is to break into the 13s. then 12s.I want to get a g-tek. are they worth the money? Chris
I just skimmed through all of this and am still terrified that there is no mention of what your fuel pressure is. I would have ruled out all the easy stuff first. If the thing lacks upper end power which you state, that could be fuel falling off. This might sound really lame of me to ask, but with 2 fuel pumps, are you certain they are both installed correctly? If the electric one was installed backward you would certainly have fuel pressure problems. I'd have a pressure guage rigged up right away and make sure it has something to burn when you're feeling the power fading.
The car feels to have more power with the electric fuel pump on. They are both installed correctly but im not sure what my fuel pressure is. I sent mhgs a private message stating that my 0-60 was 8.70 with my electric fuel pump on and 9.20 with it off. Mark (mhgs) stated this in his response to the private message i sent to him "As far as the fuel thing....wouldn't surprise me that with the electric fuel pump you are getting some higher line pressure and thus some running past the float stop.....but this would not be good in stop and go and to tell the truth not accurate as far as tuning either. might be telling us that your carb is in deed too big for the car at launch and over coming it with fuel which is the wrong way to do it as too rich is less power than ideal...." Im going to replace my inline fuel filter tomorrow, i wouldnt be surprised if its gummed up. I also think im going to remove the one in my qjet.
ou: You went through all this with the possibility of not just one but two plugged filters? If you run a decent inline filter just get rid of the small one in the carb. Devon
That's good news. If it ran better with the electric pump on, then there is DEFINITELY a fuel issue. I still cannot stress enough to just get a pressure gauge set up and see where it is at. You don't have to get a fancy Autometer gauge, just a cheap little hardware store gauge. Tee it into the fuel line at the carb and run some hose with clamps to where you can see the gauge while driving. Heck, duct tape the sucker to the hood or something, just long enough to do some tests. You could then drive around and see exactly what's happening. I concur with the abandonment of the carb's internal filter, so long as adequate filtration is provided elsewhere.
Oh also as far as the fuel pressure being too high, it would idle like garbage because of nozzle drip and I thought I read somewhere in here that your plugs showed no sign of running rich? An electric pump shouldn't put the pressure too high as long as it wasn't designed for an external regulator. Again, a pressure gauge will answer all of that.
One last thing, (gotta love my thread hogging huh?) I sound so passionate about this fuel problem because I fought the same thing for a LONG time. I found that my mechanical fuel pump had carved a deep groove in the eccentric reducing it's pumping capacity. I have never had a fuel delivery problem after switching to electric, even feeding the turbos.
Ok ill look into a fuel pressure guage. My car does idle rough and the tach bounces around at idle. I think im gonna try my 750 qjet after getting a gtech time today for my current setup. I will also change the inline filter.
