Engine Bog
- Thread starter Bennett
- Start date
Screaming Metal
Active Member
Hahaha, yea, its just a thing I got....some builders paint the inside of the motor, the lifter valley for faster oil drainback....its just a quirk of mine. Hey, they look good!
For anyone that wants to know, Holley started putting the blow out preventers in all carbs in '92. A really quick check on power valves, IF you can run your mixture screws all the way in and your motor dies, your PV is OK....unless MAJOR INTERNAL MODS have been made!
For anyone that wants to know, Holley started putting the blow out preventers in all carbs in '92. A really quick check on power valves, IF you can run your mixture screws all the way in and your motor dies, your PV is OK....unless MAJOR INTERNAL MODS have been made!
Carburetor age? The Tech at Summit (oh by the way I purchased the blow out preventers at Summit not Speedway, Sorry Speedway) said based on the carb numbers they are late 60s or early 70s. I didn't even know they made 390 cfms back then.
So I guess the Tech was blowing a little smoke.
Screaming Metal
Active Member
Yes, its hard to exactly pin down a Holleys exact age unless it had something else the others didn't have. I believe its a 70's model, because thats when the smaller motors with the small carbs were out...the little V6's and small V8's. They were popular on the Jeeps of that era.
Back in summer of 75', I worked alot of OT to get a TR for my early Nova with a 283. They has the 600 and the small carbs....I had to wait 2 months cause they were on back order.
Back in summer of 75', I worked alot of OT to get a TR for my early Nova with a 283. They has the 600 and the small carbs....I had to wait 2 months cause they were on back order.
Wild Mango
Member
I note the secondaries have the metering plates still. You can update with a kit to enable you to use screw in Holley jets in the secondaries, which will make mixture changes in the secondaries easy.
Replace the butterfly retainer screws and a dab of loctite when the new ones go in, your ones are chewed up by some lummox and could be damaged/weakened. You can do without your engine swallowing a butterfly plate screw after all this.
Replace the butterfly retainer screws and a dab of loctite when the new ones go in, your ones are chewed up by some lummox and could be damaged/weakened. You can do without your engine swallowing a butterfly plate screw after all this.
So here’s the update on the carburetor rebuild and how the engine runs now. Things are much better but still requires a bit more tweaking.
Starts and idles very nice even sounds better. Still has a bog which comes in at approximately 2200 RPM over the road in any gear. Once you get it past 2500 or so it goes away. If you pump the throttle one or twice and then lay into it, wheels break loose and it takes off. I’m thinking their not getting enough fuel at that RPM or throttle position…any thoughts?
I forgot to put a paper clip on the vacuum secondaries to see if they’re operating. I’ll try that tomorrow. It's getting dark.
Starts and idles very nice even sounds better. Still has a bog which comes in at approximately 2200 RPM over the road in any gear. Once you get it past 2500 or so it goes away. If you pump the throttle one or twice and then lay into it, wheels break loose and it takes off. I’m thinking their not getting enough fuel at that RPM or throttle position…any thoughts?
I forgot to put a paper clip on the vacuum secondaries to see if they’re operating. I’ll try that tomorrow. It's getting dark.
Yes, I would say that was a correct statement.
Don'tCallMeJimmie
Member
Sticky advance weights, or no weights are a typical culprit.
If you think you need more fuel earlier, you need to change the power valve from 6.5 to a higher number. I would go to a 7.5. If you want to take a manifold vacuum reading at idle in gear, it may verify your diagnosis. You can also vary the pv opening by running an air filter making it open sooner or removing the filter making the pv's open later. I doubt the secondaries are an issue at 2200 rpm part throttle bog, but a passenger can watch the linkage for you. If you get a chance, how about some pics of the set up after the re-do.
This morning I checked to make sure that everything under the distributor cap was moving freely. Everything was free however the centrifugal weights looked like they were dragging a bit (rubbing and scraping debris evident). I gave them a small squirt of WD40 to test the theory. It definitely made an improvement. The bog became less. Earlier some of the other guys on this site had suggested that I replace my ignition system with a HEI distributor. I'm an Engineer by trade so I like controlled experiments but the evidence is mounting and I guess it's time to take their advice. The new ignition may not totally fix the issue but the bog is becoming less with most every improvement I make.
A new twist: In gear from a stand still, it will backfire if I wing the throttle. This is a lean fuel condition...Correct?
I didn't get to do much more road work....It's now raining
Here are few post carburetor rebuild and set up pictures.
Ignore the dirt...I got caught in the rain on the back from the test run.
Let me know if you want to see a pictures of anything else.
2old2fast
Active Member
Easy way to check if the PV's are in play is to connect a vacuum gauge & drive "into" the problem & see what the gauge tells you.
dave
Random thought, sounds "maybe" as if it could be going lean when it runs out of pump shot ??? If that's the case then larger pri. jets would be in order...
dave
Random thought, sounds "maybe" as if it could be going lean when it runs out of pump shot ??? If that's the case then larger pri. jets would be in order...
Timing set @ approximately 12 * BTDC (Vac Plugged). I think the cam is stock or very mild. I haven't checked compression. will add to my list.
Forgive me I don't understand the following question "How much total adv.[initial+mech.] & when is it all -in?"
I will try this ("Easy way to check if the PV's are in play is to connect a vacuum gauge & drive "into" the problem & see what the gauge tells you.on the next test run.") What should I be looking for in regards to a vacuum response?
2old2fast
Active Member
Initial timing is what you set it at idle [12 is probably O.K.] mech is how much mech adv. adds to initial {usually 20-24 degrees] . When it's all-in is where the max. combined timing occurs[ anywhere from 2000 -3000 rpm] GENERALLY on a performance engine, getting the timing all -in by 2000-2500 rpm is desirable [depends on the cam&compression RATIO . On MOST SBC , it's generally accepted not to exceed 34-36 degrees of total timing to stay out of detonation [vacuum adv. is additional & not part of this equation because it only occurs under "no-load" conditions...
You're looking to see what the vacuum reading is when the bog or flat spot occurs, if the reading is above the PV #[in your case 6.5] then the PV's have no bearing on the problem.
O.K. ,now my fingers tired....hope this helps
dave
You're looking to see what the vacuum reading is when the bog or flat spot occurs, if the reading is above the PV #[in your case 6.5] then the PV's have no bearing on the problem.
O.K. ,now my fingers tired....hope this helps
dave
Similar threads
