Author Topic: Freshly Rebuilt Roller 302, pics! (Read 1975 times)

apollard · « **Reply #75 on:** August, 27, 2010, 07:50:10 PM »

Pull the hose from the vac advance. If the drop changes, you have the vac advance hooked to the wrong port on the carb. If that doesn't change anything, you have a mixture problem. Generally, too lean a mixture will cause this. Here's a good way to set it:
http://www.chevyhiperformance.com/howto/45638/index.html
If you don't have the vac guage (they are cheap) - start with the screws 1 1/2 turns out, turn in until it starts to miss (turn 1/8 turn, wait 10 seconds, turn again). Note that setting. Turn out the same way until it misses. Note that, then set the screws 1/2 way between the two. That will be close. Then set the speed in drive. If it still revs up (more than 300 rpm or so), recheck for vac leaks. It can drive OK and still have a leak.

AzPete · « **Reply #76 on:** August, 28, 2010, 05:17:31 AM »

When warm and shut off, are the throttle plates completely closed. Look down the carb with a light. Just searching for possible things now.....

Midlife · « **Reply #77 on:** August, 28, 2010, 05:36:47 AM »

Quote from: AzPete on August, 28, 2010, 05:17:31 AM

When warm and shut off, are the throttle plates completely closed. Look down the carb with a light. Just searching for possible things now.....

The throttle plates are below the carb; don't be confused with the choke horn plate which is visible right on the top of the carb.

jonward786 · « **Reply #78 on:** August, 28, 2010, 08:03:56 AM »

Well i went and grabbed a vacuum gauge to test and the needle on the gauge was twitching so wildly it was impossible to get a reading. It was twtching from like 15 to 8. Yes throttle blades are closed. What does that mean?

AzPete · « **Reply #79 on:** August, 28, 2010, 08:39:32 AM »

As long as they are closed, you are actually running on the idle circuit of the carb. If they are open to much, you get into the transition from idle to main jets.

You might try a different setting for the timing....maybe 12 and reset things. Somewhere is the happy medium for that engine to run good all the way around. It is just trying the different combinations.

jonward786 · « **Reply #80 on:** August, 28, 2010, 09:32:28 AM »

Yeah thats going to be the last thing i try before asking the mechanic to help. This is the cam. Would you guess it wants more initial than 8*

http://www.summitracing.com/parts/CCA-35-421-8/

AzPete · « **Reply #81 on:** August, 28, 2010, 09:36:51 AM »

My last car had a radical cam and really liked the advance. I was running around 15 I believe. Ran like a top. Try it and see how it goes.

jonward786 · « **Reply #82 on:** August, 28, 2010, 10:02:55 AM »

Well it seems you were right. The rpm drop isnt as significant with the initial timing set at around 15. Thanks for the hint

Starfury · « **Reply #83 on:** August, 28, 2010, 06:34:29 PM »

I can't imagine you'd need 15*. I only run about 12-14*, and I have a lot more valve overlap than you do, even with my Rhoads lifters. I think maybe your idle mix is off. Increased advance will help hide that. If the vacuum is flickering around that much with that cam, either your mix is way off or your timing is erratic. More likely the mix. Tune the idle mix for highest stable vacuum, since you've got a vacuum gauge. Even I can get a stable (albiet a bit low) vacuum reading on my motor.

jonward786 · « **Reply #84 on:** August, 28, 2010, 06:43:39 PM »

Ill try again i guess. When i had the gauge on it, the needle was all over the place while it was idling in drive. I guess now that its got more initial the vacuum might be stable enough for the gauge tune to not be useless

Starfury · « **Reply #85 on:** August, 29, 2010, 08:25:26 AM »

With an aggressive cam, a mix even a little off can cause an idle misfire, which then throws off the vacuum reading.

Just start from scratch. Gently seat both needles, then back out 2.5 turns and go from there until the vacuum readings stabilize.

jonward786 · « **Reply #86 on:** August, 29, 2010, 11:50:58 AM »

The vacuum will not stabilize with the car in gear. It is however, pretty stable with the car in park. Here is a video i shot of what it does. i went from park, to drive, to park again. Its a youtube video so they might not be done processing, but when it comes up, tell me if that looks normal.

So i got the vacuum as high as it would go with the car idling in park, because as you can see, i cant even get a reading with it in drive.

Starfury · « **Reply #87 on:** August, 29, 2010, 12:08:27 PM »

Hrmph. The 16-17 @ idle looks good. But yeah, as soon as you put it into drive, something's off. Maybe you have a power valve rated at too high of a vacuum? I'm not super familiar with Holleys, so I'm not sure what else would affect the mix at low loads at low rpm's.

What's the base timing at ~700rpm? IIRC, that's about the rpm you should be shooting for in drive. 8* should be good at that point, but it might jump up a hair in park.

jonward786 · « **Reply #88 on:** August, 29, 2010, 01:13:16 PM »

Thats not 16-17, the gauge sweeps from the top CCW. Its only 13-14. I tried to have it at 8 degrees and it would not idle in drive unless the park idle speed was insanely high. thats why i bumped the timing up. ive been reading around and found someone else with the same problem, people were suggesting that his stock torque converter was too tight for his cam, i.e. it was stalling too early and putting a load on the engine too soon.

i would love for there to be virtually no drop in rpms from park to drive. like maybe 50-100 rpm drop. then id be happy.

apollard · « **Reply #89 on:** August, 30, 2010, 05:26:04 AM »

Quote from: jonward786 on August, 29, 2010, 01:13:16 PM

i would love for there to be virtually no drop in rpms from park to drive. like maybe 50-100 rpm drop. then id be happy.

From my experience with cams like that, you are unlikely to get only 100 rpm drop in gear. Heck, that's tough to do on a carb car with a stock cam.

jonward786 · « **Reply #90 on:** August, 30, 2010, 09:05:44 AM »

Good news! I took the car back over the the machine shop (cause he wanted to see it completed anyways) and showed him the vacuum at idle and told him about how the rpms drops so much from park to drive. he said that vacuum readings like that were normal for this cam.

The first thing he did was say "ok you cant have the choke hooked up to the coil, its robbing voltage and could even cause misfire at high rpms. i know its popular to do it, and i even did it when i was younger, but its incorrect. nothing should come off the positive side of the coil except distributor lead and ignition lead."

I told him i had initial timing at 15, he bumped it back to 12. He then proceeded to fiddle with the carb for all of 30 seconds and then said to put it in drive and wouldnt you know, it only idled down from 900 to 750. Praise the lord! Man i wish i had the magic touch some people have.

This is me trying to fine tune my carb :dh

RyanG85 · « **Reply #91 on:** August, 30, 2010, 09:12:59 AM »

Glad it worked out. I know what you mean about the magic touch with carbs.... I've fiddled, studied and attempted to tune with little luck. I can always make improvements but never get them perfect. Some guys can just listen and tune to perfection.

AzPete · « **Reply #92 on:** August, 30, 2010, 09:13:38 AM »

Glad you got it. Just takes a bit of adjusting and messing with it to get the proper balance of things.

Starfury · « **Reply #93 on:** August, 30, 2010, 04:48:56 PM »

Good to hear, Jon. When do you get back into town?

jonward786 · « **Reply #94 on:** August, 31, 2010, 08:21:47 AM »

Ill be back in town probably the 11 or 12th. We start on the 20th. And i have more good news! I am hearing the same sound that i was hearing last time my tranny mount rubber was cracked through, that sound at idle that you can hear the tranny gently knocking on the tunnel. This time its the motor mounts, woohooo. Passenger side mount is nearly cracked all the way through. Please tell me this is something that can be replaced with the engine in the car lol

Horseplay · « **Reply #95 on:** August, 31, 2010, 08:49:01 AM »

Yep. You'll probably scrape a knuckle or two and speak a little French but it can be done.

jonward786 · « **Reply #96 on:** August, 31, 2010, 08:51:21 AM »

I think what im going to do is unbolt the mounts from the block, get a floor jack and raise the engine up a tiny bit by the oil pan, just enough for me to get those babies out of there.

Horseplay · « **Reply #97 on:** August, 31, 2010, 09:10:12 AM »

If you no longer have a hoist, that is the shade tree way of doing it. Mind you, you'll mark up/dent the pan and will also be putting a whole lot more compression load on the pan gaskets. You'll want to make sure to snug the pan bolts again when you're done.