Did I over Carb?
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Posting Guru
Joined: Apr 2011
Posts: 1,636
Likes: 5
From: Orlando area
Hey, that sounds awfully conservative on the timing. Disconnect the vacuum advance and plug it off for now. Then advance the timing to about 10 to 14 degrees, even higher if it will take it. I believe you will notice a big difference. Advance it some, then find a big hill and nail it in high gear and see if the engine rattles. If it doesn't, advance it some more. Keep going till the engine rattles, then back it down a couple of degrees. After that, let it sit for 5 minutes and then see if it will crank over. If it struggles to crank, then back the timing down a little bit more till it turns over easily when it's hot.
You have to set your timing by ear, since you have changed everything around. After all this, you might need to then get an adjustable vacuum advance. If it pings and runs terrible when the vacuum line is hooked back up, you have too much advance with the vacuum , and I would leave it unhooked rather than back the timing down even more.
You have to set your timing by ear, since you have changed everything around. After all this, you might need to then get an adjustable vacuum advance. If it pings and runs terrible when the vacuum line is hooked back up, you have too much advance with the vacuum , and I would leave it unhooked rather than back the timing down even more.
Thanks for the advice. I think you're on to something.
I'll post back this weekend and let you know what I find.
Post Fiend
Joined: Jan 2000
Posts: 5,330
Likes: 17
From: Dryden, ON, Canada
The 870 take is a huge Carb, a good friend of mine tried running one on his very healthy al. head 501 Dodge, and he plain old could not get.it to run decent. It turns out it is built on the same center as a 1100 double pumper with the same size butterflies and venturis. He tried a 770 also and has ended up with a 670 to get good tune ability and drivability out of it. He had many hours in on the phone with Holley and many many hours tuning carbs. His engine is an easy 550+ HP and probably the same or closer to 600 on torque.
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