Take a guess where the bottle neck is!

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20K miles.. I'd have a couple valve springs tested for tension and double check the lifter preload. One of my assumptions was the parts and assembly was good. With that many miles and that cam they may be getting tired.
 
One thing to check is your throttle cable. Have some one get in the car and push the gas all the way to the floor. Then go over to the carb and make sure you cant rotate the throttle bracket any more. If you can you are not getting full throttle. That can make it fall on it's face up high too.
 
moper said:
20K miles.. I'd have a couple valve springs tested for tension and double check the lifter preload. One of my assumptions was the parts and assembly was good. With that many miles and that cam they may be getting tired.
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The springs have that many miles, the cam doesn't. It like the rest of the engine only has about 300 to 400 miles on it.

Burntorange70 said:
One thing to check is your throttle cable. Have some one get in the car and push the gas all the way to the floor. Then go over to the carb and make sure you cant rotate the throttle bracket any more. If you can you are not getting full throttle. That can make it fall on it's face up high too.
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I have a Lokar throttle cable and kickdown cable on the car and I am not happy with it at all. I have had tons of problems trying to get a consistent idle out of it. When I change the intake, I'm definitely going back to the factory stuff.

ta3834bbl said:
Sounds like an ignition limit to me, what's your total timing advance ?
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32 degrees all in by 2500 rpms.
 
My friend swapped a low rpm chip in my msd one time. Took me a while to figure it out because I knew I had put a 6000 in it. Do you have a rev limiter? anything like that possibly? Just trying to throw out ideas.
 
Lars said:
The springs have that many miles, the cam doesn't. It like the rest of the engine only has about 300 to 400 miles on it.



I have a Lokar throttle cable and kickdown cable on the car and I am not happy with it at all. I have had tons of problems trying to get a consistent idle out of it. When I change the intake, I'm definitely going back to the factory stuff.



32 degrees all in by 2500 rpms.
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Where is the lokar hanging? Idle, I can see that, due to bracket. Top end????
 
Ok. But the springs are the wear item. As for the cam, if preload wasn't checked when you assembled it, check it. That's what I was referring to.
 
green1 said:
Where is the lokar hanging? Idle, I can see that, due to bracket. Top end????
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Yeah at idle. I haven't checked it in a while, I "used" to be OK at WOT, but it probably has shifted.

moper said:
Ok. But the springs are the wear item. As for the cam, if preload wasn't checked when you assembled it, check it. That's what I was referring to.
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How do you set pre-load? With shims under the springs? It is a pretty mild hydraulic flat tappet cam, those are relatively maintenance free aren't they (that's why I chose it)?
 
No, you should not need shims for anything if the valve job was done properly. You set lifter preload with pushrod length. Pushrods are always the dead last item I order for a new engine. In most cases, lifters have a pretty big window in terms of preload where they will work properly. The higher rpm you want, the more precise the preload needs to be. It wil not change much once the engine is run and broken in. But it gets important during the assembly.
What we call preload is the amount the plunger in the lifter is pushed down into the lifter when the rocker asembly is installed. You are looking to measure the distance between the top of the plunger (the part that has the cup the pushrod seats in) and the bottom edge of the plunger's retaining clip. I use a wire-type feeler gage for it but you could even eyeball it if you have to using normal feeler gages. It doesnt have to be perfect, it does has to be close to perfect. That distance should be anywhere from .010-.045" depending on the lifter type and manufacturer.
 
moper said:
No, you should not need shims for anything if the valve job was done properly. You set lifter preload with pushrod length. Pushrods are always the dead last item I order for a new engine. In most cases, lifters have a pretty big window in terms of preload where they will work properly. The higher rpm you want, the more precise the preload needs to be. It wil not change much once the engine is run and broken in. But it gets important during the assembly.
What we call preload is the amount the plunger in the lifter is pushed down into the lifter when the rocker asembly is installed. You are looking to measure the distance between the top of the plunger (the part that has the cup the pushrod seats in) and the bottom edge of the plunger's retaining clip. I use a wire-type feeler gage for it but you could even eyeball it if you have to using normal feeler gages. It doesnt have to be perfect, it does has to be close to perfect. That distance should be anywhere from .010-.045" depending on the lifter type and manufacturer.
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Comp should have the exact specs for me since I'm using one of their cam and lifter kits then right?
 
You will need to know what lifters you run, but yes, Comp can tell you what lifter is included with the cam and lifter kits, and give you the specs for them.
 
Valve springs use shims to correct the installed height of the spring.

When the valve is in the closed position,the valve spring is still holding a certain amount of pressure on the valve to keep it shut.
The amount of pressure the spring is giving to the valve retainer in this state of being closed, is determined by it's installed height.\\\\ This is the amount the spring is being crushed when the valve is closed.

If you have a valve job done on a set of heads,the valves will be sink in the head a small amount.
This makes the installed height of the spring increase and become taller.
This in turn gives you less spring pressure when the valve is closed.

If you do not make sure that the installed height,after a valve job, is not correct,and you do not have the minimum crush that the springs where designed to have,you will not have the correct holding power for the spring to work through the entire rpm range.
The result is VALVE FLOAT. OR A BETTER WORD IS>> VALVE BOUNCE.


I am not suggesting that this is your problem,but it could be.
Ask the person who did the heads if he checked the installed height when he did the heads.
I can't see a valve job being done without shims, unless bigger valves where installed and the minimum crush in foot pounds was good.

PS>>>>>IF IT IS THE VALVE SPRINGS,IT WOULD HAVE ALWAYS DONE THIS FROM THE DAY THE HEADS WHERE INSTALLED ON THE ENGINE WHEN GOING PAST 5000 RPM'S.
You said you have 20 thousand miles on the heads.
Valve springs last almost for ever in mild performance engines.
Think of it this way.
If it's a NEW PROBLEM, then it's most likely NOT A STEEL PART.
It's in the IGNITION OR CARB.
GOOD LUCK.........:thumbup:
 
If I ever get the free time I'm going to look at the ignition first since I've had this problem before. If I can't turn anything up then I'll look at the valve train.
 
Is the engine popping or missing in high gear? These guys are on target with their suggestions on valve springs and fuel delivery. Ask yourself "how big are the fuel lines and how good is the fuel pump? Is the fuel filter too restrictive? And what's the fuel pressure at the top of second and third gears?"

If the engine has more than 1000 street miles or 20 or so full-throttle passes, then you need to have a couple of valve springs checked. Unless they're really high-quality springs, they go away really quick.
 
torquehouse said:
Is the engine popping or missing in high gear? These guys are on target with their suggestions on valve springs and fuel delivery. Ask yourself "how big are the fuel lines and how good is the fuel pump? Is the fuel filter too restrictive? And what's the fuel pressure at the top of second and third gears?"

If the engine has more than 1000 street miles or 20 or so full-throttle passes, then you need to have a couple of valve springs checked. Unless they're really high-quality springs, they go away really quick.
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No popping, doesn't feel like it was missing. Has the factory 5/16's fuel line up to the fuel pump, then from the fuel pump to the carb is -6an braided lines. Heads had about 20K street miles on them from my truck, 360 was freshened up in early 07. I've put about 350 miles on it since then. Springs are Comp cam springs match to the cam (which is an XE268 iirc).
 
I still have the stock sender in my tank(5/16)then run 3/8 line all the way to carb. so don,t think it,s a fuel delivery problem.(my car runs in the 10,s)I think it,s a problem with your dizzy or wrong convertor for your cam/rear gears setup.JMO
 
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