Cam break in is done, time to tune. ** Uh-OH !!! - Moparts Forums

Register Log In Moparts Forums Moparts Question and Answer Cam break in is done, time to tune. ** Uh-OH !!!

Print Thread

Page 2 of 14

1

2

3

4

…

13

14

Re: Cam break in is done!....Now more questions! [Re: cjskotni] #1492844 09/01/13 05:53 PM 09/01/13 05:53 PM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	Cj, I am amazed that your engine doesn't rattle to death with that cam! The whole reason I switched to the bigger cam was to reduce the cranking compression and cylinder pressure. You must have ideal quench to pull that off! I wish I had gone that route! The gas here is "Up to 10% Ethanol." Some guys on the board suggest to UPsize the jets to account for the Ethanol. That is why I went from the 85/92s to 86/93.

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492845 09/01/13 09:22 PM 09/01/13 09:22 PM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	*****UPDATE***UPDATE*****UPDATE****** I got the wideband guage installed. I haven't jumped into tuning much yet, just wanted to pop in to post this: Engine as is without touching anything: 9 1/2 inches idle vacuum at 1000, 4 in gear at 700-800. Idle mixture screws were only 1 1/4 turns out from being seated. IN GEAR the guage reads between 15.0 and off the guage which tops out at 18.0. When I revved it above idle, it pegged past 18.0! I had a feeling it was lean! I seated the idle mixture screws, then backed them out a full 2 turns. Idle vacuum went up to a solid 10+ with 5+ in gear. At idle, the guage reads between 14.0 and 15.0. It still pegs when I lean into the throttle. Here is a thought: The primary side is running lean with the 86 jets. Being that I have 5.0" of vacuum and a 6.5 Power Valve, I think the PV may be covering for the UNDERjetted primaries. When I rev the engine, there is no additional fuel to keep the Air/Fuel ratio in check. Sound right so far?

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492846 09/01/13 10:00 PM 09/01/13 10:00 PM
Joined: Jul 2007 Posts: 1,526 North Carolina cjskotni pro stock
cjskotni pro stock Joined: Jul 2007 Posts: 1,526 North Carolina	If my motor has awesome quench, it's purely by chance. I wish I could claim to have planned it that way. When I did my build, I was aiming for a street motor. Mine hits peak torque at a whopping 4200 RPM and peak HP at 5200 or so. Gobs of torque down low but I know I am leaving high end on the table but oh well... Quote: The primary side is running lean with the 86 jets. Being that I have 5.0" of vacuum and a 6.5 Power Valve, I think the PV may be covering for the UNDERjetted primaries. When I rev the engine, there is no additional fuel to keep the Air/Fuel ratio in check. Sound right so far? If your vacuum is consistently low in the range of 5 inches with a 6.5 PV, this would actually cause a rich condition as the PV would 'think' the engine was under a load and stay opened allowing more fuel. If you can't get much more than 5" in gear, I would recommend going back to the 3.5 PV. Having a A/F ratio of 18+ is WAYYY lean and definitely going to be a contributor to the pinging issue. I am surprised that you aren't getting popping back through the carb with that kinda mix going in. Since you did a cam swap and presumably pulled the intake...I might just double and triple check for a vacuum leak maybe. Going to bigger jets also is the common sense approach here but yours seem kind of big to me already but I guess every engine is different. My engine is also quite happy with the idle screws only 1-1/4 - 1-1/2 turns out. I saw above where you mentioned the gaskets being BG. I would think they would work fine but maybe something is blocked off or something clogged with debris? I would say to get the blue Holley gaskets and swap those in to be sure. Also, how is the fuel pressure when it leans out? Have you checked the floats to make sure they aren't too low?

Re: Cam break in is done!....Now more questions! [Re: cjskotni] #1492847 09/01/13 10:26 PM 09/01/13 10:26 PM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	Hello again! I switched the 3.5 PV back in. The idle readings went down to 13.0 to 13.6. Kinda odd for it to richen up when I went to a smaller rated PV. I turned the idle mixture screws in to where they sit at 1 1/4 turns out again and the A/F reading came back to the 14.5-14.9 range. NOW it goes off the charts lean when I put it into gear or hold the brake and ease on the throttle. I thought I knew a little about carburetors, but tell me if i have this right: * The IDLE circuit works when the primary throttle blades are closed. The main jets are NOT in play when in the idle circuit. * The primary jets begin to function when the engine is put under a load and the primary throttle blades open. If the above is true, would that mean that my primary jetting is still too lean? I understand that you are supposed to make only one change at a time which is why I only changed the power valve when I had the bowl off. Looking at the gaskets I used, they actually are fine. They are a rubber like red gasket that came in a Demon rebuild kit I had.

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492848 09/01/13 10:30 PM 09/01/13 10:30 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	Spray brake clean or carb cleaner all around and see where the vacuum leaks are??? I use silicone on both sides of my intake gasket. where did you install the sensors for the O2??? Do you have another carb to try I think this one is wacked?? was it new or jerry rigged by someone?? You probably need a faster. Try holding you hand over cab to see if it idles better Maybe ulta lean had been your problem all along. Last edited by Dodgem; 09/01/13 10:37 PM.

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492849 09/01/13 10:34 PM 09/01/13 10:34 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	Air bleeds too big! Internal leak in the carb?? gasket under carb leaking?? intake leaking. is the cap on the big vacuum line at the back of the carb??? Your idle rally falls off N t D maybe needs lighter advance springs?? Last edited by Dodgem; 09/01/13 10:35 PM.

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492850 09/01/13 10:37 PM 09/01/13 10:37 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	Air bleeds too big! Internal leak in the carb?? gasket under carb leaking?? intake leaking. is the cap on the big vacuum line at the back of the carb???

Re: Cam break in is done!....Now more questions! [Re: Dodgem] #1492851 09/01/13 10:41 PM 09/01/13 10:41 PM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	Quote: Spray brake clean or carb cleaner all around and see where the vacuum leaks are??? I use silicone on both sides of my intake gasket. I used "Gorilla Snot" gaskacinch. where did you install the sensors for the O2??? I have a bung in each header collector, but only one sensor came in the guage kit. Do you have another carb to try I think this one is wacked?? was it new or jerry rigged by someone?? The carb ran fine before I pulled it off for the cam swap. I only changed the 4 jets and Power valve. You probably need a faster. ????? Try holding you hand over cab to see if it idles better Okay, but it seems to idle fine. Its when I put a load on it that the guage goes LEAN. Maybe ulta lean had been your problem all along. It looks that way. I'm going to UPsize the primaries to 88s and report back

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492852 09/01/13 10:48 PM 09/01/13 10:48 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	squiters working right I think that 6.5 power valve must have be defective. This has me scratching my head. There is a transition from idle circuit to jets that is where the power valve is supposed to come in. You have the mufflers in I take it?? Last edited by Dodgem; 09/01/13 10:49 PM.

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492853 09/01/13 10:51 PM 09/01/13 10:51 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	Without mufflers you get pulse reversion and the O2 sensor wont read right needs 18 to 20 inches of pipe behind it!

Re: Cam break in is done!....Now more questions! [Re: Dodgem] #1492854 09/01/13 11:27 PM 09/01/13 11:27 PM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	I have a full exhaust, tailpipes and all! The 88 jets now have the IN GEAR AT IDLE A/F at 16.0 to 16.8 but it still goes off the guage when I power brake up the rpms. I haven't taken it on the road since yesterday. I figured that if it pinged on the light duty testing I'm doing here, it would be worse on the road. I'm amazed to think I'd need primary jets bigger that 88s.

Re: Cam break in is done!....Now more questions! [Re: Baxter61] #1492855 09/01/13 11:54 PM 09/01/13 11:54 PM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	Quote: Are you sure its not just out of fuel? I've done that before!

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492856 09/02/13 12:02 AM 09/02/13 12:02 AM
Joined: Jan 2003 Posts: 5,443 Indiana Y YO7_A66 master
YO7_A66 master Y Joined: Jan 2003 Posts: 5,443 Indiana	""The 88 jets now have the IN GEAR AT IDLE A/F at 16.0 to 16.8"" The jets do not control the In Gear Idle A/F. You are lean on the idle/transition circuits which consists of the Idle Air Bleeds and the Idle Feed Restrictors. The jets will affect the A/F further up the rpm range (cruising speeds)depending on how the carb is setup, not in gear at idle. You need to forget about the jets and concentrate on these two circuits before you burn up your motor. Once you get the idle circuit a little richer, then you need to concentrate on getting the off idle and low speed cruise richer too. Then once you get that under control, then revisit the main jetting. ""The gas here is "Up to 10% Ethanol."" You may want to aim for around mid to high 13's at the in gear idle with E10. 1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)

Re: Cam break in is done!....Now more questions! [Re: YO7_A66] #1492857 09/02/13 12:16 AM 09/02/13 12:16 AM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	" You are lean on the idle/transition circuits which consists of the Idle Air Bleeds and the Idle Feed Restrictors. The jets will affect the A/F further up the rpm range (cruising speeds)depending on how the carb is setup, not in gear at idle." So, could the lean readings I get when pressing the gas be attributed to the accelerator pump shot being too weak? I have a package of new pump cams I could try. I have a Holley book here but it appears to be written for the guy that already knows carburetors better than I do. Am I to understand that any and all jet changes shouldn't affect the guage readings at idle in Park? I wish that I had some specs of what others used for their jetting. Cj wrote that he had 84/88 and the A/F ratios were right where he wanted them. My engine has a bit more compression and a lot more cam, so isn't it fair to think I'd need bigger jets than he used? Last edited by Frankenduster; 09/02/13 12:20 AM.

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492858 09/02/13 12:21 AM 09/02/13 12:21 AM
Joined: Jan 2003 Posts: 5,443 Indiana Y YO7_A66 master
YO7_A66 master Y Joined: Jan 2003 Posts: 5,443 Indiana	What carb are you using? 1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)

Re: Cam break in is done!....Now more questions! [Re: YO7_A66] #1492859 09/02/13 12:33 AM 09/02/13 12:33 AM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	I have a Barry Grant 850 Vacuum secondaries. It has a 4 corner idle circuit. I currently have all 4 corners adjusted 1 3/4 turns out from seated. The fuel pressure is holding steady now that the engine is running cooler. I installed a fan shroud the other day.

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492860 09/02/13 12:33 AM 09/02/13 12:33 AM
Joined: Jan 2003 Posts: 5,443 Indiana Y YO7_A66 master
YO7_A66 master Y Joined: Jan 2003 Posts: 5,443 Indiana	You need to start at the beginning on your tune. Since you have an auto, you want the most vacuum that you can achieve at your in gear idle rpms. With the brake applied (emergency brake or someone pushing on the brake), adjust your metering screws to obtain the best vacuum reading. Do no worry about the vacuum reading in N, you want the best vacuum reading in gear with the brake applied. You may need to work with your initial timing to get this vacuum reading up. Once you have your in gear idle vacuum reading at it highest, look at the A/F reading. This might be as rich as the 13's. After you get this set, then take it for a drive and watch the A/F readings at light throttle and cruising up to around 55-60 or so. Write down the A/F readings at the following: In gear idle (with brake) A/F= 30mph A/F= 40mph A/F= 50mph A/F= 60mph A/F= 70mph (if you drive at this speed) A/F= (If you are anything leaner than 15, then take it easy on the throttle so you don't hurt it!) Once you take note of the A/F readings at these speeds, then you will be able to watch what happens at these same speeds when you make a tuning change in the future. Taking notes is the best way to keep track of your changes. 1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)

Re: Cam break in is done!....Now more questions! [Re: Kern Dog] #1492861 09/02/13 12:35 AM 09/02/13 12:35 AM
Joined: Jan 2003 Posts: 5,443 Indiana Y YO7_A66 master
YO7_A66 master Y Joined: Jan 2003 Posts: 5,443 Indiana	Does this carb have screw in bleeds or are they just holes? 1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)

Re: Cam break in is done!....Now more questions! [Re: YO7_A66] #1492862 09/02/13 01:19 AM 09/02/13 01:19 AM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog OP Striving for excellence
Kern Dog OP Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	Quote: Does this carb have screw in bleeds or are they just holes? Sorry, I'm not sure what this means. If you mean the idle mixture screws on the sides of the metering blocks, there are 4. One on each side of each metering block.

Re: Cam break in is done!....Now more questions! [Re: YO7_A66] #1492863 09/02/13 01:32 AM 09/02/13 01:32 AM
Joined: May 2003 Posts: 6,560 Downtown Roebuck Ont Twostick Still wishing...
Twostick Still wishing... Joined: May 2003 Posts: 6,560 Downtown Roebuck Ont	Make sure you have no leaks UPSTREAM of the sensor. Any header tubes that might be leaking or flange gasket leaks will suck in air and give you a lean reading. I don't recall your cam specs but if it has a lot of overlap, exhaust reversion will cause random misfires (that choppy idle sound)and the O2 sensor will read lean even if it is actually rich. Misfire = no oxygen was used so it get pumped out past the sensor which does its job and reads it. Get the engine to sound happy first and then use the readings to tell you what changes to make. They will not likely be where you expect when you are done at least as far as idle and cruise go. Kevin

Page 2 of 14

1

2

3

4

…

13

14

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1