New heads and intake, now engine bog off the line - Page 3 - Chevelle Tech
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post #31 of 45 (permalink) Old Jul 4th, 19, 1:02 PM
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Re: New heads and intake, now engine bog off the line

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Originally Posted by hjdca View Post
Here is a pic of my 15 year old un-modified Holley 750 Double pumper zinc body (116-112). I broke the ear off tightening it, so, it is garbage now. You can see the big hole in the middle with the air channels. This is the perfect size for the idle-ease. This is an unmodified throttle body. If you buy a new aluminum 116-112, it will look exactly the same, except the hole will be half the size or smaller, which gives you less tuning ability. Fortunately, the air channels are the same size, so, you can just drill out the hole to the same size as the old zinc baseplates. This is what I did, and I ended up using the "whole hole" for the best tuning of my cam - idle-ease turned counterclockwise all the way.

I have fixed 2 of those broken baseplates. I drill holes where it's cracked and add small pins for both sides then I JB weld them together. I bolt it to an old intake manifold so it stays flat. Both Holley's are still going strong today.
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post #32 of 45 (permalink) Old Jul 5th, 19, 12:20 PM
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Harry
 
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Re: New heads and intake, now engine bog off the line

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Originally Posted by 68Chevele View Post
I have fixed 2 of those broken baseplates. I drill holes where it's cracked and add small pins for both sides then I JB weld them together. I bolt it to an old intake manifold so it stays flat. Both Holley's are still going strong today.
Great idea. Mine looked like it had some internal "gaps" where it broke. I am using it for parts now. I also stripped the threads for the bowl screw on a zinc HP body. I like the new aluminum parts better, I think they are stronger and much lighter and less chance of breakage and screw stripping. Since I changed to the Aluminum ultra XP body and aluminum base plate, my carb. is a lot lighter than the old zinc stuff.

Note: That hard core grey coating on the aluminum ultra XP bodies is also really nice. Very smooth and I would not be surprised if it helps with carb. cooling.

Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers
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post #33 of 45 (permalink) Old Jul 5th, 19, 6:37 PM
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Re: New heads and intake, now engine bog off the line

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Originally Posted by hjdca View Post
Great idea. Mine looked like it had some internal "gaps" where it broke. I am using it for parts now. I also stripped the threads for the bowl screw on a zinc HP body. I like the new aluminum parts better, I think they are stronger and much lighter and less chance of breakage and screw stripping. Since I changed to the Aluminum ultra XP body and aluminum base plate, my carb. is a lot lighter than the old zinc stuff.

Note: That hard core grey coating on the aluminum ultra XP bodies is also really nice. Very smooth and I would not be surprised if it helps with carb. cooling.
To fix that main body mix up some JB Weld and put some in the hole, take the bowl screw and put teflon tape on it, screw it in the hole and wait until its semi hard unscrew the bolt and let it sit 24 hours and it should hold great. I tried to fix one with the helicoil and it worked like crap now I just use some kind of epoxy.
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post #34 of 45 (permalink) Old Jul 16th, 19, 8:44 AM
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Steve
 
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I am currently running a Holley 670 SA vac. secondaries. I have Holley 770 SA vac. secondaries which I took off because I thought it might be over carbed causing the off idle stumble. I haven't had much time to play with it lately though. I do need to get it dialed in over the next four weekends before the big Dream Cruise here in Michigan.
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post #35 of 45 (permalink) Old Jul 17th, 19, 8:14 AM
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Rick
 
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Re: New heads and intake, now engine bog off the line

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Originally Posted by 68elky396 View Post
I am currently running a Holley 670 SA vac. secondaries. I have Holley 770 SA vac. secondaries which I took off because I thought it might be over carbed causing the off idle stumble. I haven't had much time to play with it lately though. I do need to get it dialed in over the next four weekends before the big Dream Cruise here in Michigan.
Either carb on a 396 should work fine. Just need some carb and ignition tuning.


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post #36 of 45 (permalink) Old Jul 17th, 19, 8:40 AM
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Steve
 
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Thanks mrpaticular, I appreciate your advice. I will try to tune it this weekend starting with timing. The 670 SA is performing well except for the off idle bogg. I will give an update with my results sometime this weekend. Here are a couple of photos of my '68.
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post #37 of 45 (permalink) Old Jul 25th, 19, 5:44 PM Thread Starter
Mike
 
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Re: New heads and intake, now engine bog off the line

Just wanted to update the guys that reached out to help me. I replaced my carter afb with a quickfuel 670 brawler and the bog I was experiencing when stomping the gas wide open is now gone. The new carb has vacuum secondaries and seems to run great right out of the box. I'd like to get it on a chassis dyno and a/f sensor to see if the jetting can be optimized but I am very happy with the way its running right now. Would be nice to make a few runs at the dragstrip also. Best run with the old 350 in it was 15.07 @ 93.7, hoping it would be in the 13's now. Thanks to everyone who helped me out and gave me advice much appreciated. I don't believe the problem was the air gap intake. I think I just opened up the engine with the heads and intake and the little carter didn't have enough accelerator pump shot.
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post #38 of 45 (permalink) Old Jul 27th, 19, 7:46 PM
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Re: New heads and intake, now engine bog off the line

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Originally Posted by MNmalibu View Post
Just wanted to update the guys that reached out to help me. I replaced my carter afb with a quickfuel 670 brawler and the bog I was experiencing when stomping the gas wide open is now gone. The new carb has vacuum secondaries and seems to run great right out of the box. I'd like to get it on a chassis dyno and a/f sensor to see if the jetting can be optimized but I am very happy with the way its running right now. Would be nice to make a few runs at the dragstrip also. Best run with the old 350 in it was 15.07 @ 93.7, hoping it would be in the 13's now. Thanks to everyone who helped me out and gave me advice much appreciated. I don't believe the problem was the air gap intake. I think I just opened up the engine with the heads and intake and the little carter didn't have enough accelerator pump shot.
Glad to hear someone got a Quick Fuel VS to work. Looks nice, let us know how the adjustable sec. screw works to dial it in.
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post #39 of 45 (permalink) Old Jul 27th, 19, 9:08 PM
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Re: New heads and intake, now engine bog off the line

Thanks for the update.

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post #40 of 45 (permalink) Old Jul 29th, 19, 1:42 PM
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Re: New heads and intake, now engine bog off the line

Glad to see your 400 is running good with the new vacuum secondary Carb.

Louis
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post #41 of 45 (permalink) Old Aug 2nd, 19, 7:27 AM Thread Starter
Mike
 
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Re: New heads and intake, now engine bog off the line

15mph rolling start, no bog, block long one wheel wonder burnout.
Time for a posi upgrade
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post #42 of 45 (permalink) Old Aug 2nd, 19, 1:04 PM
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Re: New heads and intake, now engine bog off the line

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Originally Posted by MNmalibu View Post
15mph rolling start, no bog, block long one wheel wonder burnout.
Time for a posi upgrade
Well, you could always go on the other side of the road and lay down the another black mark to match it to look like it has a posi. LOL.
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post #43 of 45 (permalink) Old Aug 2nd, 19, 1:22 PM
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Chris
 
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Re: New heads and intake, now engine bog off the line

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15mph rolling start, no bog, block long one wheel wonder burnout.
Time for a posi upgrade
Eaton for the win!
Dino oil only.
Been beating the crap out of mine for almost 18yrs!

73 nova,3515#(all steel)Pump gas!(91octane)406ci N/A, best 1/4,1.45 '60,[email protected],10.6 @ 122.38, short shifting,NO tuning!


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post #44 of 45 (permalink) Old Aug 4th, 19, 10:41 AM
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Well, here's the latest update on tuning the off idle stumble out of my Holley 670SA. This carb is on my 396 now 402. Yesterday I changed the 6.5 PV to a 9.5. It has 17 inches of vac at idle, and 15 to 17 at cruising speeds. I changed the sec. spring from silver to purple, float adjustment is correct, a/f mixture screws are one turn out, stock 65 main jets, changed the stock 31 main squirter to a 35 and installed a black pump cam on the number 2 hole. It is way better now, the stumble is almost completely gone. I still need to recheck the timing. I think it's around 18 initial and 39 total. Lot of good info on this thread and others. Thanks to everyone.
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post #45 of 45 (permalink) Old Aug 28th, 19, 8:26 PM Thread Starter
Mike
 
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Re: New heads and intake, now engine bog off the line

I installed a lock right locker in my open diff and I'm really happy with it. Now I have uncovered a new problem, wheel hop!! lol

and on and on it goes....it's all good though, I love the car and I love chasing more and more performance.
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