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Old 09-01-2008, 07:47 PM
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I have a 48 Chevy that I have Street Roded or at least I am trying to. I am very new to rodding I put a 350 that was bored 30 over new flat top pistons and a performance cam I am not sure of the cam size but I think it was 4.65 x 4.65 if that sounds right. it has roller rockers, an Edelbrock performer manifold a Holly street advenger 670 a HEI distributor with vacum advance. My problem is that it has no top end if I nail it it seems to flatten out at around 2700 RPM Any sugestions?

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Old 09-01-2008, 08:44 PM
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First, welcome to Hotrodders.

When you say 'flattens out' do you mean that it stops revving?
Does it do so with popping and carrying on?
Does it do so on a free rev?
Are you getting full throttle?
Is it running on all 8?
Any black smoke?
Who assembled that engine?

Once you have RULED OUT carb and timing and it is still a slug, check the cam chain/sprocket installation.

Give us all the info you can.
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Old 09-02-2008, 08:43 PM
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no power

Hey I just went through this same thing with my hot rod, It also is a 350 bored 30. I agree with what was said previously.
1).Go through your firing order and Triple check timing. If your in doubt reset #1 to TDC and start over.

2). Make sure all your components are working. Just cuz thier brand new doesn't mean they're working. especially electronics. You can check your wires with an ohm meter or I just pull the plugs out of the block, leave it in the boot and hold about 1/8-1/4 inch away from a ground (the block) and spin it over a few times (get A buddy to). you should see a bright blue spark jump from the plug tip to the ground. If not there is a problem somewhere. I typically go through the process of elimination. first try a new plug, if that doesn't work, try a new plug wire, then go to the dist cap as you could have a bad point. If all these yield nothing i'd get a new dist.

3). Check you throttle cable, make sure your carb is being opened all the way by the cable. I Just went through this. I couldn't figure out why my 4 barrel wouldn't open when using the pedal, turns out i had to much slack in my cable, easy fix but a big head scratcher.

4). while you have the plugs out go ahead and check the pressure of each cylinder, to save some trouble later, they should all be within ATLEAST 10% of each other. ex: if #1 is 100 PSI none of the others should be greater than 110 or less than 90. The closer they are to each other the better.

5). Check for any vaccuum leaks and fix them. make sure your carb is forcing a good spray down the intake. Check the accelerator pump lever, at an idle it should be just barely touching the activation lever

Once you do all these things, if you have a good engine, it should go way above 2700 rpm's. You may have to play around with the advance to find the sweet spot but these steps should get you pretty close. Let me know if i can be of anymore help, i'm no pro, but i've been around the block a time or 10 with these SBC's 350's.
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Old 09-02-2008, 09:17 PM
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after all else fails, check for a flat cam.
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Old 09-02-2008, 10:49 PM
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I forgot to tell ya to make sure the engine is on the compression stroke by blocking the #1 plug hole with your finger. When air pressure pushes your finger off, you are on the compression stroke. I usually go to TDC by hand with the balancer bolt from there. thats just me.
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Old 09-03-2008, 02:09 AM
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Originally Posted by 406 bug
after all else fails, check for a flat cam.
Times 2 on that Kemosabe.
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Old 09-05-2008, 04:44 PM
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Pop the dist. cap and make sure the mechanical advance weights can move freely.

I put a distributor together once and the weights got fouled up somehow...the symptoms were very similar to those you describe
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