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Discussion Starter · #1 ·
I have a 91 RS. It was a 305 TPI. (I am old school. My last Camaro was a vintage 67 with a 302. All stock.) I installed a stroked 383 in my new 91. Stock heads, moderate cam, Holley 750. I am running a Summit HEI Distributor. Wires are new and plugs are in good shape. She runs low 12s. When I accelerate hard, she misses just a little. As if she is breaking up a bit and I know that is costing me power. This happens during street driving where I get on it a bit. I also notice that this happens more on cold days where she runs under 180 degrees. Also she backfired two times when I passed 5,100 at the track. Don't worry, I know better than to run her with that happening. She is off the track until I solve this.

I think I have two problems:

First: I think my distributor isn't up to the job. It's a $159 Summit HEI, nothing fancy. It is relatively new, but I'm wondering if stiffer advance springs are in order or if an MSD will help solve the lower RPM problem by controlling timing advance better. On the other hand it may not be timing advance at all. It's very suttle and most people wouldn't even notice it. She idles real nice and I recently adjusted my valve lashes so I know that's good. I'm open to ideas!

Second: I'm pretty sure I am floating my valves past 5,100. That I understand how to solve. Either new heads or stiffer springs.

Now here's why I think it may be ignition related. Back when I had my 67 RS (way back in 1970. I told you I am old school:yes:) that car did exactly the same thing. That car had a stock distributor with stock points and springs. A dual point would have solved that back then as I think I was floating the points.

Well, thats my dilemma. Any ideas?
Thanks
Dave
 

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Carb? timing or carb not letting motor breath. I personally think its related to timing.
 

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As suggested, I'd retard total timing a bit to see if it cures backfiring at high rpm.

If you have the stock 305 heads on now, I would say its a good indication weak springs. You can get an on-head spring tool and install a spring shim under the the spring to increase spring seat pressure, say 0.030".

Just my thoughts.
 

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Discussion Starter · #6 ·
Thanks for the responses. I figured I would have to pull the heads and change springs completely.

Everett Writes:
You can get an on-head spring tool and install a spring shim under the the spring to increase spring seat pressure, say 0.030".

Everett, Where would you go to find the tool and shims. I have been out of the game for a while. Also, will the tool allow me to remove the springs and do I have to pressurize the cylinder like we used to back in the day?

Thanks
Dave
 

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the distibutor from summit ok I have a mallory hei for $144 its great just get a if u have 50,000v coil already get one also get for $80 in summit mag is a msd module called man-made lighting it spark consistently up to 9000 rpm
 

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