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Discussion Starter · #1 ·
Hey Ya'll, I just bought a 1975 Chevy Cheyenne it was an orig. 454 truck but someone pulled it and put in a late model 305 stocker. My problem is this when i set the timing the valves rattle under a pull well they rattle pretty much anywhere you set the timing. It is a center bolt valve cover engine. A friend of mine said the cams are different but i dont believe that i read on 3rdgen.com that the HEI dist. are different on the early and late model engines. ohh and im guessing it was TBI engine they changed to carb. I need to know how i can tell the difference in the Dist. or do i need to run the #'s on the engines any help would be appreciated. Thanks
 

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The distributor has nothing to do with lifter noise. If the cam has been changed, you need to find out if it's a solid or hydraulic cam. If it's a solid cam with solid lifters, it will have lifter noise due to valve lash, it's designed that way. These are mostly used in high rpm engines to help control valve float. If you have a hydraulic cam & hydraulic lifter, you can adjust these so there is no noise but you need to know the proper procedure and specs for either. Without knowing exactly what you have, it's tough to give you much more info.
 

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Discussion Starter · #3 · (Edited)
This is a stock engine thanks for your reply but yes if this was a factory fuel injection engine and they changed it to carb. the dist. should be different than a factory carb. dist. engine and im not sure if its a hyd. roller cam or a reg. hyd. im not sure what year they changed them over im guesstimating it to be a 1990 or a 1991 engine. ohh you got a nice s-dime i had a 85 and a 88 good little trucks
 

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possom83 said:
Hey Ya'll, I just bought a 1975 Chevy Cheyenne it was an orig. 454 truck but someone pulled it and put in a late model 305 stocker. My problem is this when i set the timing the valves rattle under a pull well they rattle pretty much anywhere you set the timing. It is a center bolt valve cover engine. A friend of mine said the cams are different but i dont believe that i read on 3rdgen.com that the HEI dist. are different on the early and late model engines. ohh and im guessing it was TBI engine they changed to carb. I need to know how i can tell the difference in the Dist. or do i need to run the #'s on the engines any help would be appreciated. Thanks
I guessing you mean it pings or detonates under load rather than having noise from the valve train????

What a down trade 454 for a 305, this means the 305 has got to work a lot harder than the 454 did for the same road speed.

If the 305 was originally an injected engine that was converted to a carb, then the distributor also needs to be back dated to a pre-electronic fuel injection HEI because the EFI distributor gets its advance from a computer you don't have. An old fashion coil in cap HEI with a mechanical and vacuum advance will be proper. You need to be careful with the distributor gear as well, if the 305 has a roller cam, then the gear on the distributor needs to be a factory Melonized gear, the gear an old HEI used against a flat tappet cam will wear very quckly when run against a roller cam. Check the block casting number 10243878, 14093627, or 14103058 are roller blocks.

Then of course the engine will have to be tuned, which also includes the carb.

Bogie
 

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This sounds like a case of spark knock and if it is it has nothing to do with valves and lifters. It is common for someone to mistakenly refer to the pinging sound as "valves rattling" when it actually is detonation in the cylinder that is making the noise, does retarding the ignition relieve this sound? Lifter noise would be more of a pecking sound and would most likely be noticeable at idle but spark knock would be more noticeable with the engine under a load while driving and probably not at all at idle.
 

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Discussion Starter · #6 ·
yea thats what its doing sorry i didnt put that more clearly. it pings like crazy when its under a load ive got the timing jacked way down to ease it up a little its still annoying and it kills the performance of the engine. i set the timing when i first got it and drove it about 5 mile and couldnt take it anymore the dist. thats in it has a vacuum advance on it i just dont know the difference between the old and new HEI's im just hoping i dont have to change the cam. whats the easiest way to tell them apart. ohh and yea it was a downgrade from the 454 the bad part is with the timing down like it is im probably getting worse gas mileage than the 454. im trying to get the 454 from the guy but his son has it in his work truck. thanx for all of your help
 
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