383 Engine rebuild

[BBodyBarrett]

I am planning on rebuilding a 1969 383, performer intake 906 heads, stock pistons using a 292-292, 509 cam balanced assembly, 4 speed, 3:91 8-3/4. Do I need to cut valve relief notches in the pistons. Thanks in advance for input.

 

[BSB67]

I am planning on rebuilding a 1969 383, performer intake 906 heads, stock pistons using a 292-292, 509 cam balanced assembly, 4 speed, 3:91 8-3/4. Do I need to cut valve relief notches in the pistons. Thanks in advance for input.

Can you give us the details of your "stock" pistons? Are they factory original stock, or stock replacement, like the 2315?

If you have either of these, you will likely have piston to valve clearance issues unless you fly cut the pistons.

Don't know where you are at in you build, but consider a different piston if money allows.

 

[PurpleBeeper]

That cam is right on the ragged edge of hitting pistons (I ran one for years). At the very least, you will need to use clay on the pistons & check your piston to valve clearance if you have flat top piston. On factory original '69 383 pistons, the valves would hit.

These days, you "could" run some very thick head gaskets, but you'll lose quite a bit of compression. You might want to consider different pistons or a smaller cam.

 

[superbeedave]

The KB400 dome pistons made for the 906's should work out perfect for you if looking to replace the stock pistons. They also have valve reliefs to allow
for up to .565 lift I believe.

 

[beanhead]

The clearances have to be measured to be sure. It's not the max valve lift but the longer durations (where the valves are as the piston moves through TDC) that get you into trouble. I know it sucks because you can't measure that or mock-up and do the clay measurement for valve clearance without having the engine mostly together and having the cam installed..How far down the pistons end up will be a factor and 383s were apparently all over the place depending on which one you have..

https://www.forabodiesonly.com/mopar/threads/383-stock-piston-depth.301012/

https://www.forbbodiesonly.com/moparforum/threads/383-piston-height.163771/

 

[BSB67]

The clearances have to be measured to be sure. It's not the max valve lift but the longer durations (where the valves are as the piston moves through TDC) that get you into trouble. I know it sucks because you can't measure that or mock-up and do the clay measurement for valve clearance without having the engine mostly together and having the cam installed..How far down the pistons end up will be a factor and 383s were apparently all over the place depending on which one you have..

https://www.forabodiesonly.com/mopar/threads/383-stock-piston-depth.301012/

To be clear, non of these dimensions in the linked forum #1 post are what you would find from the factory.

If I was going through the effort to put new pistons in, the Diamond piston would be my first choice, probably followed by the new Icon, IC687/KTD

 

[beanhead]

To be clear, non of these dimensions in the linked forum #1 post are what you would find from the factory

Really? Ok...my apologies for re-posting wrong information that was given as accurate..other people had posted what they've found also. The main point was, you must check and verify what you have..

 

[BSB67]

Really? Ok...my apologies for re-posting wrong information that was given as accurate..other people had posted what they've found also. The main point was, you must check and verify what you have..

Sure, and I believe that if you read through it, some other posters chime in qualifying the numbers. Just didn't want some one to read the first post and draw an incorrect conclusion. What is posted are Ma Mopar NHRA blueprint specs. And your point is spot on.......check/measure.

Even if someone thinks they know what it should be, 1969 was a really long time ago. Someone has probably been in the motor, and possibly several times. Milled deck, milled heads, valve grinds, head gaskets after market piston CD (stock CD piston not available for 40 years) will move the valve closer, or further away from the piston. You just don't know until you measure.

 

[lewtot184]

I used a racer brown ssh44 (for all practical purposes identical to a 292/509) in a '68 383 with 10:1 stock replacement pistons and had to notch the pistons. I've bent intake valves with a stock cam/valves (actually broke a head one time) with lifter pump up in a factory stock '68 383. piston to valve clearance with a flat top piston in any 383 can be an issue. as for the ssh44 cam; it took a nice running 383 and turned into a total turd. there's also some serious retainer to guide/seal issues with that cam and stock iron heads. if your not sure about what your doing and tuning abilities are limted choose another cam.

 

[BSB67]

I used a racer brown ssh44 (for all practical purposes identical to a 292/509) in a '68 383 with 10:1 stock replacement pistons and had to notch the pistons. I've bent intake valves with a stock cam/valves (actually broke a head one time) with lifter pump up in a factory stock '68 383. piston to valve clearance with a flat top piston in any 383 can be an issue. as for the ssh44 cam; it took a nice running 383 and turned into a total turd. there's also some serious retainer to guide/seal issues with that cam and stock iron heads. if your not sure about what your doing and tuning abilities are limted choose another cam.

There's some really good advice.

 

[BBodyBarrett]

Can you give us the details of your "stock" pistons? Are they factory original stock, or stock replacement, like the 2315?

If you have either of these, you will likely have piston to valve clearance issues unless you fly cut the pistons.

Don't know where you are at in you build, but consider a different piston if money allows.

They are the factory stock flat top pistons. I have removed the heads but haven't removed the pistons from the block at this time.

 

[BSB67]

They are the factory stock flat top pistons. I have removed the heads but haven't removed the pistons from the block at this time.

So you plan is to rebuild the motor, but use the 50 year old used pistons and not bore and hone the wore out block?

 

[BBodyBarrett]

I used a racer brown ssh44 (for all practical purposes identical to a 292/509) in a '68 383 with 10:1 stock replacement pistons and had to notch the pistons. I've bent intake valves with a stock cam/valves (actually broke a head one time) with lifter pump up in a factory stock '68 383. piston to valve clearance with a flat top piston in any 383 can be an issue. as for the ssh44 cam; it took a nice running 383 and turned into a total turd. there's also some serious retainer to guide/seal issues with that cam and stock iron heads. if your not sure about what your doing and tuning abilities are limted choose another cam.

The engine is a matching number to the car. After reading the comments I am leaning towards replacing the pistons and using a cam similar to the 284-284, 484. That would eliminate any issues with the pistons and valves. Its been 32 years since I have tore down an engine/ rebuilt a BB Mopar. After talking with the machine shop today, let them assemble the motor due to my time restraints. They will set the cam and check all the clearances.

 

[BBodyBarrett]

So you plan is to rebuild the motor, but use the 50 year old used pistons and not bore and hone the wore out block?

Heck No!!!The engine was rebuilt stock in 2002, with only 46,000 miles.The car has been in storage most of its life. It was running fine when I pulled it, leaking a lot of oil and needed hardened seats The cylinder walls look good, the machine shop will take care of what it needs. I would like to have a little more horsepower and love the sound of more than stock cam.

 

[lewtot184]

The engine is a matching number to the car. After reading the comments I am leaning towards replacing the pistons and using a cam similar to the 284-284, 484. That would eliminate any issues with the pistons and valves. Its been 32 years since I have tore down an engine/ rebuilt a BB Mopar. After talking with the machine shop today, let them assemble the motor due to my time restraints. They will set the cam and check all the clearances.

i'm familiar with the 284/484 and it has it's place, but I think it's still a step too far. the 284/484 (the one I measured was actually 286/486) is ground on 108CL and will have about 72 degrees of overlap at the seat. of course a lot of this depends on what you plan to do with the car, race it or street cruiser. I think you'd be much happier with something like a comp cams 280/480 ground on 110CL; about 60 degrees of overlap. cams with higher overlaps aren't real happy with cast iron exhaust manifolds. my car was a '68 road runner 4spd car I bought new in '68. I specifically remember that the more I cammed the worse it ran; on the street and track. the best dual purpose cam I ran was a crower 201hj; no longer available. my car wasn't sloppy tuned. the engine just didn't like big duration with high overlap. even with some of the smaller performance cams your tuning abilities might be challenged with a 383.

 

[Don Frelier]

.455 cam

 

[BSB67]

Heck No!!!The engine was rebuilt stock in 2002, with only 46,000 miles.The car has been in storage most of its life. It was running fine when I pulled it, leaking a lot of oil and needed hardened seats The cylinder walls look good, the machine shop will take care of what it needs. I would like to have a little more horsepower and love the sound of more than stock cam.

We seem to be talking in circles. If the motor was truly rebuilt in 2002, it does not have stock pistons. Someone may have told you that it has stock pistons, but the truth is that it has similar to stock pistons, but they will not have the 1969 compression distance of 1.932". There were several stock like pistons available in 2002, and ALL of them had lower compression ratio than the 69 piston. Therefore, back to my original question, exactly what pistons are in it? If you want the motor to run as good as it can, and want to pick the best cam you must first understand what pistons are in it.

Or just fly cut the pistons and put it together the way you want. But, expect to get you butt whipped by minivans if you have a 7:1 CR 383 with the 509 cam.

 

[lewtot184]

8:1 383 will have the pistons .070", or more, down in the hole. they are just miserable contraptions.

 

[fratzog lover]

.455 cam

Great street cam. 221/221 gives him no clearance issues and runs strong on the street with manifolds. Will also surprise you with the MPG you get. Often overlooked because of it's relatively "tame" numbers.

 

[Bee1971]

Back in the 90s when I rebuilt my 383 Magnum I went with

Speed Pro Forged 2315 - .030 Flat Tops with no valve reliefs

Compression height 1.920

If I remember right , they where something like .017/.020 in the hole when I changed out the factory heads a few years back with Edelbrock E Street Heads

Was running the Mopar 284/484 Cam and lifters at the time of changing heads

Just changed heads nothing else , same but new Fel Pro .039 Head gaskets

Motor ran awesome for about two weeks , right up until I kissed some pistons with the intake valves on two cylinders

Motor loved the new heads in the RPM range and of course larger intake and exhaust valves with the E Street over factory heads

Anyways

Took out the cam lobes , lifters , pushrods and of course had to pull those same heads and have my machine shop go through those new heads again

That same 383 Magnum is now a 432 Stroker