JeepsAndGuns
update at the bottom
I just got my 401 in and fired up last night. One thing I was wondering is about the intake. I have a holley street dominator intake on it now. Its the one with the small runners. I was wondering if this is the best choice for a intake for a 401? Or do you think a edlobrock preformer would be better? The runners on it are the same size as the ports on the heads, where as the runners on the holley are about half the size. I heard that the smaller runners give better low end power. The 360 I used to have this intake on would stop pulling at about 3k rpms but had good low end power. I havent got onto this engine yet (cause it is still new and not broken in) but it feels the same.
Only problem I am haveing is the idle, and I am not sure I got the timing set right. The idle is not smooth, the tach kinda jumps up and down and the engine shakes just a little (but not too mutch) I tried the vaccume timing method and also tried to adjust the carb too. I have it running pretty good but the needle on the vaccume guage is also jumpy. But I will be first to tell you I cant tune a carb verry good. I am more of a fuel injection guy. But I have adjusted the float levels and the mixture screws as per holleys instructions. Carb is a brand new truck avenger 670cfm. I still dont have the smoothest idle. Any input?
Lifted79CJ7
:-| Not sure about the running rough part - I have always been bad at diagnosing those things. As for the intake, the smaller the runners, the less air and fuel can get through it. Kinda like a garden hose vs a fire hose...
jeepsr4ever
The dominator and sp2p are the economy intakes. A performer will give you alot more power. What kind of mileage do you get now and can you afford to have your mileage suffer?
JeepsAndGuns
I have no idea what kind of mileage I get. I only just got the engine installed and broken in sat night. I probably dont even have 50 miles on this thing yet. Since it is not my daily driver I usally only drive it on the weekends. When you say suffer, just how mutch? Like 1 or 2 points? or like 5 or more? Surely not that mutch. :-|
Also any idea about the bumpy idle? I reset the timing at 10* as reccomended by someone on IFSJA and it seems to run a little better. I set the idle at around 650-700, but it is still a little bumpy. Does it just need driven/broken in more? I am thinking hard about the edlbrock intake.
jeepsr4ever
If you do decide on the edelbrock I have a new one sitting here I will sell you for $185... A customer bailed on it and edelbrock has a shitty return policy.
I will add this without bias..
You can definately tell the difference between performer and street dominator..big difference.
JeepsAndGuns
jeepsr4ever wroteIf you do decide on the edelbrock I have a new one sitting here I will sell you for $185... A customer bailed on it and edelbrock has a shitty return policy.
I will add this without bias..
You can definately tell the difference between performer and street dominator..big difference.
Sent you a email. Looking to hear from you.
adba22
If the intake is non EGR, I'll buy it. I'm starting a 360 build. Any other parts I might be intrested in?
JeepsAndGuns
Well I just got the edlebrock preformer installed and as of now I am not real happy. I dont really notice mutch any diffrence other than it almost feels like my throttle is not as responsive. I installed it last night but just started it and run it around a little. I got home today and started fooling around with it. I run it down the road to warm it up then got back and hooked up the vaccume guage. The needle was jumping from one side of the guage to the other really fast. It would not hold still. I adjusted the mixture screws both lean and rich with no change. I got out the timing light and checked the timing at it was still at 10* where I had it before. It ran good with the other intake, but with this one It was kind rough. I started adjusting the timing with the vaccume guage and after screwing around with it and the mixture screws and driveing it around a little bit. I have the the idle the smooth out for the most part. The tach needle dont jump like it used to. but the vaccume reading is still pretty jumpy. I have got it down to where it jump back and ourth between about 15 and 20. it jumps REAL fast between the two, and no matter what I do I cant get a even reading. I checked all vaccume lines and ports, I sprayed some carb cleaner around the base gaskets and everywhere else to check for leaks and didnt find any. I hooked the vaccume guage (guage/pump) to the vaccume advance and started pumping it. when I am pumping it will go up but as soon as I stop it starts going down. Is this normal. I had one bust on my once, and replaced the whole dizzy with a rebuilt one (this one) and its hardly a year old. I am almost starting to regret doing this. No noticeable change in power, cant get the thing tuned throttle seems not as responsive. I am almost tempted to go back to the holley intake. How do you know when you need to change jet sizes? and what to change them to? I dont know sh*t about carbs and am getting mad. :(:
jeepsr4ever
NOT happy with a performer...hmm thats strange you would have those symptoms :-|
What cam were you running?
JeepsAndGuns
Comp 256H. You reccomended it to me for the best low end/midrange.
I dont know. just from what I can compare off the top of my head, it almost feels like it ran better with the holley intake. also it almost feels like it doesnt pull as hard as it used to. ??
jeepsr4ever
:-|
Goose
Far be it from me to stick my nose in..but, I would be looking for the cause of the Vacum gauge dancing like that.. Usually pulsations like that are caused by valve issues or extreme timing problems. Like a valve not seating/sticking or lifter pumping up etc..
To be quite honest with a fresh motor the "seat of the pants" difference is going to be tough to feel in an already overpowered truck.. you should feel some but how exactly is "Some" defined.. :-|
tufcj
A dancing vacuum gauge isn't right, unless you have a VERY radical cam.
This article explains it pretty well.
http://www.centuryperformance.com/vacuum.asp
Bob
tufcj
JeepsAndGuns
Well I called a local guy at a performance shop here and talked to him for a litle while. I told him about my engine what I have done to it and what its doing and whatnot. He said the jumpy vaccume guage is from my cam. I read off all the specs from the card that came with the cam and he said its a big cam (??) and that I wont get a good steady reading with it. I really called looking for someone to tune the carb for me, but they didnt do that. He told me a couple things to check and to check the plugs. I go out and pull one of the plugs and look at it and it does have a blackish color to it. Not real dark, but a blackish tint none the less. So I guess that means I am running rich. He told me to set the timing back to around 8-10* cause if I kept it as high as I had it I would run into pre ignition problems. I run it down the road to warm it up and break out the timing light. I set it best I can see (I have the AC compressor, so its a real PITA top see) to about 9-10* The idle changed a little bit but stayed mostly even. drove it down the road and it seemed to do ok. Funny cause when I first started last night it was at 10* and didnt want to run good. Now it seems to be ok. But hell I cant remember mutch now.
So now I am looking for "holley tuneing for dummies" This will be the first carb I have worked on. (other that changeing gaskets and adjusting the mixture screws) I have never re jetted a carb and dont know where to start. One question I do have, the mixture screws. Most call them the idle mixture screws, so does that mean they only affect the fuel mixture when the engine is idleing? Or does it affect mixture through all range of useage? How do I know what size jets I need to go to. I need help.
tarior
First thing I would look at is whether the dizzy is off a tooth, second I would pull the plugs and compression test all 8 cylinders, next, pull the valve covers and see if any of the rockers are too tight, next, pull the timing cover and check your cam timing. Those are most of the things that I have encountered that cause a bouncy vacuum gauge, and in ascending order of PITA to do.
Mudrat
Nice Bob :t:
I like the last line too ...
"Always remember to use the right tool for the job!"
So that means I need different sized hammers, for the different sized problems? 111!!!
tarior
Yes, good article. When I bought my vacuum gauge froma Matco, it came with fairly detailed (for stock engines) instructions. I have a large selection of hammers, too.:mrgreen:
wolfe_man
I had a motor do that (chevy) after putting on a new intake....I could not find the vaccum leak to save my life. Come to find out it was leaking from under the intake in the lifter valley, I replaced the gaskets and used some RTV (god help the person who has to pull it off again) and all was good.
Gabe
jeepsr4ever
I am very suprised that the edelbrock intake didnt out perform the holley street dominator. ...something is wrong here. I wonder if the power developed better between the dominator and the cam vs. the performer and the cam.
JeepsAndGuns
It seems to run a lot better after I re jetted the carb. I was running way to rich and droped two jet sizes and am running better now. I also changed accel pump cams and it feels better too. I tried to set the mixture screws best I could cause I still cant get a even vaccume reading. I used some spray copper sealant (same I used on my head gaskets) on the gasket before I put it on, and rtv around the water ports. When I tightnd the bolts I started in the middle and worked my way around from side to side makeing my way to then ends. Just like you do when you tighten a head. So it should be tightened evenly. Is there ANY way to check for a leak on the valley side?
