I recently put on a new carb, intake, cam and rockers. Now when i punch it from a stop it has no power and slowly builds up. Then once i get to higher rpms there is this almost rattling noise but i think it is a popping noise. I was thinking the vaccum advance could be bad i have an original distributor. Or maybe the fuel pump. I have a 67 327 by the way. Any help would be great.
Thanks, Tim

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1967 camaro 327 coupe
Performance engine looks great, cherry red all flush

Sounds like either serious valve float or detonation...either way, the engine isnt going to last long. Did you start out with a stock motor, and what parts did you add? Give a little more info and myself or someone else can help you get your combo tuned in.

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375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova

ya i started with a stock engine, but the compression was good and eveything sounded good. I put on a 208/216 durstion 426/454 lift crane cam, performer rpm intake, summit roller tip 1.5 rocker arms, pushrods, summit double roller timing chain, edelbrock 600 cfm carb. What could i do to fix this problem????

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1967 camaro 327 coupe
Performance engine looks great, cherry red all flush

Could be a timing issue. What is your initial set at? Try setting it around 12-14 degrees and see if this wakes things up. Also, you may need to do some serious carb tuning...get the edelbrock kit and follow the book on how to fine tune your carb. The performer rpm intake seems to me to be much more finicky than the regular performer style intake. I run the same 600 edelbrock on my current rpm equiped engine and had to change several things to get it to run right, even though it worked great out of the box on my previous engine. I had to fatten the primary and secondary side 1 step each, step up to a 7" enrichment spring, and put the accel pump rod i the middle position. This was after steping up from a 210/210 cam to a 224/230, going from a weaind low rise dual plane to a performer rpm vortec, and swapping the ported 882 heads for vortecs.

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375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova

Yes,it sounds as if the timing is out.Double check it making sure if you have vacuum advance,it is unhooked.12 to 16 deg initial is a good place to start.I figure the timing is retarded a mile.If you find it hard to set at these settings,you may have to recheck TDC on the compression stroke and re-install your distributer at #1.Good luck.

Sounds like a cam problem to me. Sometimes a new cam, usually if it's not broken in right, can toast a lobe. But more likely is that your valve springs aren't up to the job with your new higher lift cam. Could one be broken? You should really replace valve springs when you replace a cam, especially if you don't know what type of springs you have or what wear is like on them.

I'm assuming that you've checked the obvious, like two plug wires switched, or the + and - wires on the coil switched, etc. When you tear apart a motor to that level it's easy sometimes to get something switched when you put her back together.

i think eric68 is on it. plug wires switched is the first place to check. and valve springs are next up. ive broken valve springs before, didnt notice much difference at low RPM but higher up it sounded almost like a rod knock.

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ya i am pretty sure i broke the cam in right, i waited a while before i punches it. The negative and positive wires are right, the sparkplugs are right. I am not sure about a broken valve spring, but everything looked good when i did the engine. I am pretty sure that my vacuum advance is not working. I accidently left it unpluged yesterday and it ran the same. I was gonna try replacing the distributor and see where that takes me. And i will look into the broken spring.Thanks guys

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1967 camaro 327 coupe
Performance engine looks great, cherry red all flush

You can quickly check your distributor advance curve with a timing light, a dial back light works best. Just put your timing light on and slowly rev the motor from idle to about 3000 RPM. You should see the mark slowly advance as RPM increases. At about 3000 RPM you should have around 34 - 36 degrees total advance (that's with everything hooked up). If the mark jumps around or you're only seeing like 25 degrees advance at 3000 - your vacuum advance could be bad.

[This message has been edited by Eric68 (edited 04-01-2001).]

I'd say you need to replace those springs. I got a gut feeling that's what it is. If you have a points type distributor it wouldn't hurt to replace it but I'd bet the valve springs aren't up to par.

You car can run fine without vacuum advance if the intial and centrifugal advance is set right. Try 12 intial and 24 centrifugal and see but I wouldn't rev it out til you replace the springs since they are probly the stock ones.

I can run no vacuum advance if I don't punch it too fast. If I do it'll bog down but that can be solved by running a little more intial.
Good Luck

Ya i will definetly look into replacing those springs. I think they are the stock ones. I was gonna go talk to my mechanic friend this week and see what he thinks. I will keep you guys posted. How hard is it to replace valve springs. Just take off the valve covers and change them. Won't the valves drop into the cylinders. Well thanks again. Any more ideas would be well accepted.

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1967 camaro 327 coupe
Performance engine looks great, cherry red all flush

I was talking to his one mechanic i know and he thinks that my jets are wrong. He told em to get a strip kit and adjust the jets lower. I hope it works.

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1967 camaro 327 coupe
Performance engine looks great, cherry red all flush

If you get an air fitting that is set up for the sparkplug hole, you can charge the cylinder with air from a compressor and change the valve springs with the heads on the car

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Bob
Garnet Red 69/SS396/TH400/355 Posi
94 HD Dyna Wideglide