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-   -   th 350 "rattles" under hard acceleration (http://www.hotrodders.com/forum/th-350-rattles-under-hard-acceleration-119626.html)

accidntprone 07-07-2007 12:32 PM

th 350 "rattles" under hard acceleration
 
hello. ive got a 69 chevelle with a 350 tranny, 307 block. stock. problem being that when i accelerate semi-hard, i hear a grinding, rattling noise. it doesnt do the noise in park. its not a hotrod, but itd still be good to get a nice pick up without her sounding like shes choking. any help?

Deuce 07-07-2007 12:48 PM

Could be the engine spark knocking ... :D

Check your timing ... or increase the octane rating fuel you use.

In the timing area ... a bad vacuum advance will do that ... or the timing set too high.

jakeshoe 07-08-2007 03:06 AM

Could be the sun shell rubbing the case. They get bell mouthed when abused and worn bushings give it even more runout and they do get into the case sometimes.

31choptop 07-08-2007 09:15 AM

I tend to agree w/ Deuce. back off your advance a little and or add octane boost. Brian

accidntprone 07-08-2007 01:54 PM

thanks. illl check my timing, and re-adjust ( if needed) the carb also, thanks chop top and duece. but... whats the "sun shell rubbing the case, bell mouthed and abused when bushings go out". ? im a starter to this. i coulda sworn id adjusted the idle/mixture screws on the carb (original two barrel) previously. and i could have sworn ,but i have to look into it somemore, that i threaded them out 2 & 1/2 turns, but like i said i coulda sworn. also. another thing thats off subject. my uncle just gave me some used headers, and two of the pipes are smashed in, semi. not eccesive, but still. will this be a problem? or should i try and pull the dents out a little? cutting and welding is no problem, but looking to see what you guys think about a semi-imperfect exhaust. thanks

31choptop 07-08-2007 09:47 PM

I dont think the flow being reduced on a stock motor would be that big of a problem, but if you want to cut and weld new sections in why not! the sun shell refers to auto trans internals.. if it was the shell rubbing on the case it would likely cause severe vibration when ever the planetary was in motion plus there would be a lot of noise. the idle mixture screws are for idle only, wont have any effect on high speed system. but the main jets would! Brian

accidntprone 07-09-2007 01:11 PM

coool. ok. so... any advice on tuning the main jets? and how about the vaccum advance? im a new to this, but taking the car to a doctor is only for major works, so any "how-to" advice would be coool. thanks!

Greg T 07-09-2007 09:35 PM

You may want to check the flexplate. It may be cracked and distorting under a hard pull.

31choptop 07-09-2007 09:50 PM

I dont hook up my vac. advance it is really to improve fuel mileage more than anything else. tuning the main jets is time consuming. you need to start with a couple sets of fresh plugs, a lonely stretch of road. you will want to check the high speed system without the secondaries coming on, and with the secondaries open. normally if you dont have any backfiring, popping or miss, or loss of power under accel or hrd cruise the carb is probably fine. unless you like tinkering for tinkerings sake :thumbup:


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