383 question Rockers

[velrob]

My motor is in process of getting machined. Needs to be bored out 060 and crank 020

The shop the motor is at said I should get adjustable rockers. They're like 3x the price of non adjustable. What's your opinion?

I'll be using xe268h cam with edelbrock intake and Holley 4160 carb

I'm not looking to race just street cruise and sometimes letting it rip

 

[lewtot184]

i wouldn't worry about using stamped steel rockers with that cam. the fly in the ointment will be if the heads and block are milled increasing the preload on the tappets. even at that adjustable push rods or custom length push rods would work and be more economical. typical machine shop to me; their big ideas with your money. another thought is; adjustable rockers sometimes will have a higher than advertised ratio making retainer to seal/guide clearance too tight (heads will need machined for this).

 

[texas69bee]

Needs to be or is going to be bored .060 over? Recommended is .040. What's your thought lewtot184?

 

[velrob]

alright ill pick up regular rockers then that will let me dump the extra $$ into something else

its already 040 and needs to be bored to 060

thanks alot

 

[mopar 3 B]

alright ill pick up regular rockers then that will let me dump the extra $$ into something else

its already 040 and needs to be bored to 060

thanks alot

383 all ready bored to 040 and now needs again? Better fix the oiling system to fix the cylinder wear problem. Cylinder wear in a 383 is not a connon problem or is this a million mile motor?

 

[lewtot184]

Needs to be or is going to be bored .060 over? Recommended is .040. What's your thought lewtot184?

i would sonic test at .060".

 

[lewtot184]

alright ill pick up regular rockers then that will let me dump the extra $$ into something else

its already 040 and needs to be bored to 060

thanks alot

run a dial bore gauge thru each cylinder to find out exactly what you have.

 

[moper]

If this is a mild build I wouldn't panic over +.060. That was done very often "back in the day" regardless of the service manual specs. In regard to the rockers - Mopar's shaft rockers require a very accurate valve job to get the geometry right. Some shops like to think adjustable rockers or shims will help that, but it's all in the valve job. The cam does not require dual valve springs or anti-pump-up lifters, either of which would mandate a better set of rockers. Stamped will work fine. I have a #s matching 383 in an Ebody RT that is +.060 and runs the XE268 cam. Stamped rockers, and custom pushrods (I run those on everything I build) and it's been running very strong for 16 years.

 

[velrob]

Should i be worried if hes asking me to get adjustable rockers? Does that mean he does poor valve jobs?

how much horse power will i be able to achieve with 060? will pushing 400-500 be a problem? i plan to do mild at start then go from there and increase the power over time

 

[velrob]

run a dial bore gauge thru each cylinder to find out exactly what you have.

im hoping the machine shop already did that to figure out i needed 060

the pistons already in there were 040 but im pretty sure i saw 030 as well.

 

[miller]

Another 'back in the day' thing is, used to be able to buy pistons at every .010 oversize. That would give you +.040 - +.050, next size up. But, guess that came to a stop.
One critical thing to be looked at is correct push rod length. Don't assume you can use stock push rods (unless using adjustable rockers), because new tappets are not made the same.
My 'stock' push rods were .020 too long for the tappets I got, since the cups were not cut as deep as the stock tappets were.

 

[moper]

A dial bore gage will tell you if the current bores are round or tapered. It will not tell you if the walls are thick enough to make some real power or avoid heat transfer problems. For that - you have to sonic test them. I do not feel it is needed at the 400-450hp level. With an expectation of above that, it probably should be sonic tested to make sure it will live. Or, assume down the road you will be doing another one for the higher power level. That would be my first choice there. If you want big horsepower, and big numbers to last, the every first thing you have to have is the thickest cylinder walls you can get.
If he's asking you to go with better rockers - ask him why. "Because I said so" is not an answer. Nor are internet guys (myself included) really an empowered group - he has your block and has to stand behind the work. We don't. I wouldn't use anything exotic, but he may be thinking the expected power output will mandate the rockers in the future, so why spend, or spend twice. Again we get back to the money vs two builds deal. You need a bit more IMO for a 383 making 1.3hp/inch vs one that makes 1.04hp/inch. More money & better parts.

 

[velrob]

I guess i will look for a 440 in meantime to build out after the car is on the road.

i will ask him about the adjustable rockers when i drop off the pistons and such so he can begin machining