Your donations help keep this valuable resource free and growing. Thank you.
|
258 / 4.0 Head / 260H Cam |
Post Reply | Page <123 |
Author | |||
Heavy 488
AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3557 |
Post Options
Thanks(0)
|
||
Yeah, costs a few $ up front but not all that bad when you consider how much time spent that you'll never get back from trying to wrestle the pig to the floor. I put one in my daily driver (injected). If I don't see 14.7 rolling or 12.8 working it, I know theres a problem.
|
|||
tloftus
AMC Nut Joined: Mar/18/2008 Location: Sioux City, IA Status: Offline Points: 296 |
Post Options
Thanks(0)
|
||
I have seen those wideband O2 sensors.. definitely something to consider. Pulled the lid off the carb today -- floats are close, but slightly off. Primary jets are larger than factory settings. Assuming the secondary jets are also, although I can't see a number on them to confirm so may just get a set of those also to be sure. On one hand I'm glad to have found something wrong, hopefully it explains my flooding issue. On the other hand if a guy tells you a carb is new when you buy it, it should be new (no one on this forum). The question about fuel pressure... it is widely accepted that 5.5 is the absolute max for an Edelbrock. When my fuel pressure gets above 4.5 is begins to bounce, so I turned it down to 4. In troubleshooting this issue I turned it down to 3. I will probably turn it back up to 4 as it doesn't seem to have affected the issue. Also something I read is that the fuel filter with the return line -- the return line should be clocked to the 12 o'clock position. Mine is not, but I will do that when I get everything put back together just to be sure. After the idling I've done (cam break in, troubleshooting, etc) I did pull plugs and it is certainly running rich. I cleaned them off and re-installed them. Hopefully this jet, metering rod, spring issue takes care of things. If not, I have not had exhaust work done yet so maybe I will have them weld in a bung for a wideband. Thanks, Tom |
|||
1966 AMC Rambler American Rogue - 232 I6
http://theamcforum.com/forum/1966-amc-american-rogue_topic20995.html 1978 AMC AMX - 258 I6 http://theamcforum.com/forum/1978-amc-amx_topic62333.html |
|||
Heavy 488
AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3557 |
Post Options
Thanks(0)
|
||
Are you absolutely sure it's flooding? Black smoke? Drop the largest metering rod you have in the hole and leave the springs out. Now you have no enrichment to interfere besides the pump shot. FWIW, summit lists the Eddy carb as 6.5 max.
|
|||
Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
Post Options
Thanks(0)
|
||
I feel like there should be more than 11"-13" of manifold vacuum, even with the 260H cam. Maybe something more on the order of 16"-18"? Does anyone else around here run that cam that can chime in on what kind of vacuum reading they see?
|
|||
1968 AMX 390 w/T5
|
|||
232jav3sp
AMC Addicted Joined: Jan/09/2013 Location: Texas Status: Offline Points: 2451 |
Post Options
Thanks(0)
|
||
I have that cam in the 232, in my Javelin, with a Clifford single plane, 500 Eddy, and a homemade header. From memory, idle RPM is 750 and vacuum is 16. Been quite a while, but I think that's pretty accurate.
|
|||
tloftus
AMC Nut Joined: Mar/18/2008 Location: Sioux City, IA Status: Offline Points: 296 |
Post Options
Thanks(0)
|
||
I have the dual plane, I'm not sure if that makes a difference. In any case, I replaced the jets with the factory spec defaults and it is running pretty good now.
I did order a wideband O2 to play with so we'll see what that says, but first order of business is getting it to the exhaust shop to have a new exhaust system put on -- no more muffler hanging from clothes hanger!
|
|||
1966 AMC Rambler American Rogue - 232 I6
http://theamcforum.com/forum/1966-amc-american-rogue_topic20995.html 1978 AMC AMX - 258 I6 http://theamcforum.com/forum/1978-amc-amx_topic62333.html |
|||
billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
Post Options
Thanks(0)
|
||
Nope, go ported. That Edelbrock instruction is dead wrong. Whoever wrote that has no clue why or when it was even invented. It's ZERO to do with emissions - period. There were no emissions thoughts in the 1930s and 1940s when Chrysler, then Ford, came out with it. PERFORMANCE, correct timing at the correct times. I even studied it in college - the why and how it works and why ported. You lose the impact of the vacuum advance, the WHOLE REASON for it to be there when you run manifold vacuum to the advance. Vacuum advance was originally INVENTED by Chrysler in the late 1930s to cover a stumble or loss of "umph" when taking off - you boost the timing when the mixture is lean to help compensate for the lag.
So vacuum advance's whole purpose was to run with PORTED vacuum and help cover that lag. You negate the whole purpose of having it by running manifold vacuum to it. IGNORE what people say out there about it needing manifold vacuum and that it's for emissions and all of that BS - if you read the engineering behind it (and I don't mean that fake Chevy guy who says he was an engineer and talks about vacuum advance being for emissions - that's one of the biggest crocks I've seen related to timing) you'll see how it works, why it works, and why ported. Edited by billd - Jul/15/2020 at 8:44am |
|||
billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
Post Options
Thanks(0)
|
||
It may help but that's NOT the purpose, that's not why it was invented or why it was used. NO ONE cared about MPG in the late 1930s. It was for performance, to help with in-town driving, stop and go, to help cover the lag when you take off - advance the timing just as the mix turns lean. Sorry, but I guess no one studies automotive history these days I guess - and there's no formal training on combustion, ignition timing, etc.
|
|||
tloftus
AMC Nut Joined: Mar/18/2008 Location: Sioux City, IA Status: Offline Points: 296 |
Post Options
Thanks(0)
|
||
Sorry I should have mentioned that also. My initial timing is set to about 14 degrees. I did move my distributor advance to PORTED vacuum. With the mechanical advance in the distributor I got about 32 degrees at 2400 RPM.
|
|||
1966 AMC Rambler American Rogue - 232 I6
http://theamcforum.com/forum/1966-amc-american-rogue_topic20995.html 1978 AMC AMX - 258 I6 http://theamcforum.com/forum/1978-amc-amx_topic62333.html |
|||
billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
Post Options
Thanks(0)
|
||
"most engines" - and it varies "somewhat" depending on stroke, rod length and other factors, but most should see peak combustion pressures at about 14-16 degrees ATDC. My college texts and papers say 14, I've seen some say as late as 16.
So whatever timing works to achieve that - because BURNING (and this is a controlled burn, not an "explosion" as people keep calling it) burning takes TIME. Higher RPM means less TIME to burn, since you want peak pressures at about 14 ATDC, you have to start the process sooner to be finished in time. Typically, total advance, everything all in - about 36 degrees total at 3,000 or so RPM. Sounds like you could be close to that - assuming the mechanical advance isn't yet all in at 2400 RPM. My 360's HP peaked out with a total advance of 38. I could see in the dyno sheets that they started with 36 degrees total and then later bumped up to 38 and saw more HP and torque - but if you achieve peak combustion too soon, you LOSE power. so those who say you need more timing - well, won't say what I may think of that because more timing can FIGHT you - you get too much pressure at the wrong time - even before the piston is all the way up to TDC, or even when it's just past TDC and has no mechanical advantage over the crankshaft. Think about cranking on a Model T - where do you have the best advantage to spin that engine using the crank on the front? With the crank at 12:00? 6:00? OR, is it somewhere closer to 12:10 or 6:37? |
|||
Post Reply | Page <123 |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |