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Topic Review (Newest First)
10-03-2012 04:57 PM
dave1969chev Checked for leaks around the manifold/carb, none reset the valve lash and I'm pretty sure its running right now. Took it down the road at 34 total timing and I'm pretty pleased but the heat is still climbing. Thank you for helpin me out
10-02-2012 08:07 PM
Choctaw Bob Think you may have a vacuum leak. a really lean engine will run hot. Stick with working on the things you changed to get it in this condition. The single plane will raise the power band substantially.


Quote:
Originally Posted by dave1969chev View Post
The headers were fine when I was running the Sr torkers. So I swapped the the strip dominator for the air gap, reset the initial timing to 14btc and I'm getting 35 total, threw the avs back on and its noticeably better but its surging at idle. Checked the vacuum, its 13 by but shaking alot then I ran it down the street. No power at take off, but its a Damn rocket at 3500 rpm. Parked it, pulled off the vacuum caps at the tree and idled up and quit stumbling at idle. Ran it down the street, now low end just stumbled, caught up and was a rocket at 2700 rpm. I also noticed that the temp was rising pretty fast. I also noticed that the carb was hard to adjust the air to fuel. I ended backing them all the way for the best idle. But all and all it would run alright at idle and then start ****tin itself in gear. Why would it run better with vacuum leaks? Makes no sense
10-02-2012 06:51 PM
RWENUTS More timing! Try 22* initial.
10-02-2012 06:35 PM
dave1969chev The headers were fine when I was running the Sr torkers. So I swapped the the strip dominator for the air gap, reset the initial timing to 14btc and I'm getting 35 total, threw the avs back on and its noticeably better but its surging at idle. Checked the vacuum, its 13 by but shaking alot then I ran it down the street. No power at take off, but its a Damn rocket at 3500 rpm. Parked it, pulled off the vacuum caps at the tree and idled up and quit stumbling at idle. Ran it down the street, now low end just stumbled, caught up and was a rocket at 2700 rpm. I also noticed that the temp was rising pretty fast. I also noticed that the carb was hard to adjust the air to fuel. I ended backing them all the way for the best idle. But all and all it would run alright at idle and then start ****tin itself in gear. Why would it run better with vacuum leaks? Makes no sense
10-02-2012 11:15 AM
vinniekq2 Its way more important that you get the correct size headers than a truly tuned exhaust system.With the correct headers you will get the same increase of power as using the correct intake,perhaps more.as most race cars make more power with open exhaust the easiest thing for a person to do is put the least restrictive system on after the headers as money allows.You can go into pages and pages as to shape/length of pipe after the headers round Vs oval.reducers for velocity,tapered expansion exits and a lot of other things that make a slight difference at a high cost. What old said is true and complicated.

for your application I think the old smaller heads with dual plane intake and 1 5/8 headers will make it easier to tune.If you want the bigger heads then consider what old said about adding a pressurized intake system.If you want normally aspirated and only race high altitude(you didnt say how high?) then more CR would help and a higher RPM cam to take advantage of the bigger heads and intake.Your 1 7/8 headers are way too big. I use 1 7/8 headers on a 434 with 10.75:1 with a 256/264 duration solid roller cam ,its lift is .420X1.6/1.5
10-02-2012 11:02 AM
lmsport
Quote:
Originally Posted by dave1969chev View Post
It will idle extremely rough and die unless I hold the throttle, no power at cruise, alright at wot but still not as much as I thought a head swap would give me. I tried throwing a 750cfm on it and it just blew rich smoke and wouldn't hold an idle. But I figured that was bc of the high alt. With my old heads I never had a issue with running a single plane, it behaved on the street.

You have a basic problem like valves too tight or firing order wrong, etc. If the heads are too big, which I doubt, it will just be lazy at lower RPM. It should idle at least as good as it did, especially with more compression.
10-02-2012 10:43 AM
AutoGear Bogie;

I appreciate each and every one of your posts, but please explain why you are advocating the balance pipe (H-pipe) over the X in this case. PM me if you think it will water down the current thread.
Thanks!
Nate
10-02-2012 10:42 AM
dave1969chev I do have a brand new set of 4.10 gears and a dual plane rpm air gap hanging on the shelf, will this help? I also threw 2 1/2" baffles inside the pipes.I just want my set up to be a screaming street machine.
10-02-2012 10:09 AM
oldbogie
Quote:
Originally Posted by dave1969chev View Post
Hello, I'm having some serious issues getting my buildup to run right. I have a 383 4 bolt .040 over with flat tops. Sportsman 2s with 64 cc chambers, strip dominator(also have a air gap on the shelf) . I'm in high altitude so I'm running a avs thunder 650cfm. Lunati voodoo hyd flat tappet 268in/276ex 110lsa. Scorpion 1.5 in/1.6ex rollers. 1 7/8" sidemount headers with 4" pipes. Hei dist with a 7 amp module. 11mm livewires. Bm holeshot 2400 stall converter. Built th350 with shift kit. Independent 3 series Posi with 3.55 gears. I put in premium unleaded but I can't get it to run right. It ran strong with the 69cc chamber Sr torkers, decided to move up to 200cc intake runners. I'm running 36 deg total timing. What am I doing wrong?
Thanks
Dave
Ports are too big for the altitude air pressure. Solution is:

1) Go back to the SR Torquers with the 170 cc port to get the intake port velocity up.

2) Stiffer gears to get the engine wound up to where it can get the velocity in the 200 cc ports moving again.

3) Put some form of a supercharge on it.

4) This is important your exhaust system is too big. Reduce the size of the exhaust system from the header tubes back so there will be a harder pull from the exhaust during the overlap. 1-5/8ths header tubes into 3 inch collector of at least 20 inches. 2-1/2 inch head pipes to mufflers 2 to 2-1/4qtr tail pipes. Connect the head pipes just behind the collector with a 2 to 2-1/4 inch H pipe cross over. Do not use an X pipe. It might be necessary to use terminator boxs behind the collectors. You'll have to build the system then see how it runs then if necessary trim it to get the return waves when the engine needs them the most.

The problems of high altitude all come from the lower air density. This drops the velocities in all the porting systems intake and exhaust. It lowers the true compression pressure regardless of compression ratio, part of the solution here is less cam duration with more lift and more ignition both in terms of advance and volt/amps, a multi-strike can be helpful. The smaller carb you have was a step in the right direction as that keeps the venturi vacuum up which improves metering. The 11 mm wires are a great idea as the dielctric (insulating) value of materials goes down with altitute so a thicker jacket is needed to keep high voltage in the wires. A coil pack per cylinder is a massive help as it keeps the high voltage runs short and eliminates high voltage from the distributor cap where it leaks all over the place between terminals.

Bogie
10-02-2012 07:48 AM
Choctaw Bob How much vacuum at idle? 750 CFM isn't too much. You probably found another problem in the carb itself.. Are these carbs Edelbrocks/carter or Holley type?
Edelbrocks need about 12 inches of vacuum to seat the needles at idle and also affects the cruise settings. Did you change the cam at the same time? If this is the problem, you can tune it out with a jet/needle/spring change and the time to work through it.
If Holleys, older power valves are susceptible to blown power valves.
Your combination doesn't seem to be excessively mismatched. If the carburetor isn't the problem you will have to check everything. It almost sounds like it could have jumped time one cog. Bring the engine to TDC and look to see that the timing mark is where it should be.Check all the vacuum hoses and manifold for leaks.

Quote:
Originally Posted by dave1969chev View Post
It will idle extremely rough and die unless I hold the throttle, no power at cruise, alright at wot but still not as much as I thought a head swap would give me. I tried throwing a 750cfm on it and it just blew rich smoke and wouldn't hold an idle. But I figured that was bc of the high alt. With my old heads I never had a issue with running a single plane, it behaved on the street.
10-02-2012 07:11 AM
dave1969chev
383 issues

It will idle extremely rough and die unless I hold the throttle, no power at cruise, alright at wot but still not as much as I thought a head swap would give me. I tried throwing a 750cfm on it and it just blew rich smoke and wouldn't hold an idle. But I figured that was bc of the high alt. With my old heads I never had a issue with running a single plane, it behaved on the street.
10-01-2012 11:37 PM
vinniekq2 headers are way too big for that little cam.decent heads,big intake,small carb ,cam matches the stall but the intake does not.
when you say its not running right,what are the issues that you have?
10-01-2012 07:16 PM
RWENUTS Welcome Dave!!
You could get a better answer over in the engine section of the forum.
But I'll take a stab at it!
36* total timing?
What's your initial timing? At high altitude you should run it with 22-24 degrees initial. 12* mechanical and all in by 3400rpm. Add 10 degrees with the vacuum advance.
Got a pic of your ride?
10-01-2012 06:39 PM
dave1969chev
383 problems

Hello, I'm having some serious issues getting my buildup to run right. I have a 383 4 bolt .040 over with flat tops. Sportsman 2s with 64 cc chambers, strip dominator(also have a air gap on the shelf) . I'm in high altitude so I'm running a avs thunder 650cfm. Lunati voodoo hyd flat tappet 268in/276ex 110lsa. Scorpion 1.5 in/1.6ex rollers. 1 7/8" sidemount headers with 4" pipes. Hei dist with a 7 amp module. 11mm livewires. Bm holeshot 2400 stall converter. Built th350 with shift kit. Independent 3 series Posi with 3.55 gears. I put in premium unleaded but I can't get it to run right. It ran strong with the 69cc chamber Sr torkers, decided to move up to 200cc intake runners. I'm running 36 deg total timing. What am I doing wrong?
Thanks
Dave

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