383 build advice

[1970Bee]

I’d have thought a larger displacement motor would want more cam timing to operate at a given RPM? Ie- what is mild in a 440 would be more radical in a 383

 

[RemCharger]

Yes the same cam will be about 400 rpm higher in a 383

 

[BSB67]

The power band is done by rpms so it would be the same for both 383 & 440 by my thoughts, just different hp levels by number of cu. inches.

This is incorrect. Everything else equal, the rpm will be proportional to the cubic inche difference

 

[BSB67]

OP, care to share the cranking cylinder pressure. Hard to imagine a flat top 383 pistons with valve notches and 452 heads and a cam to be anything but dismal in cylinder pressure.

 

[1970Bee]

All of the cylinders were about 110, +\- 5 psi. Which seemed low in my experience, but were at least consistent. In full disclosure, the lifters were out when I did this; I just wanted to be sure I hadn’t bent a valve before proceeding (using the best compressor $20 can buy at Auto Zone )

 

[496 polara]

If those heads from Hensley run anywhere as close to the ones they did for me they will outperform stock stealth heads. I had mine on a 440 and then put them on my 496 with a small solid cam (239/243) and it had no problems turning 6000 rpm and beyond with a 4.15 stroke. I wish I still had them.

I would call @PRHeads and tell him what you have and what you want. You can look at some of the Howards grinds as well.

 

[BSB67]

In full disclosure, the lifters were out when I did this;

So, you did cylinder pressure test with all the valves closed. You have $1,500 receipt for head work, but no info as to what was done.

Honestly, I’m at a loss as what to say. I have nothing helpful to offer other than good luck.

 

[1970Bee]

that’s good to hear! If it hasn’t broke a lifter, I’d have been in no hurry. After it did, and going thru it found it had such a radical cam, it occurred to me it might work better as a street car with less cam and a dp intake.

 

[1970Bee]

Yes and yes. Not sure what else I should have done? Headwork was done 3 owners ago. Test was done to convince myself it hasn’t bent a valve.
“At a loss” suggests I’ve done something I should not have?

 

[BSB67]

I’m at a loss to make any recommendation because you have no idea what you have. I think slapping it together as cheaply as possible and driving it probably makes sense. Just don’t have any expectations.

 

[1970Bee]

You may be right, but what information am I lacking? What was precisely done to the heads besides larger valves and cc-ing the chambers, I don’t know. The paperwork doesn’t specify.

I know the CR pretty precisely. Stall, gears. What other information am I lacking in asking for help with a cam selection?

 

[BSB67]

I’m suspicious only because I’ve seen these things play out before. What a guy thinks he got is way different than what he’s really got. So, I ask you this for the things your believing to be true, do you have documentation?

Can you post pictures of the Hensley invoice? Where did the 9.5 cr come from? Do you have the measurements to make that determination? Do you have the piston part number, and how far down in the hole on the build. Head gasket thickness

Why would you post that the cylinder pressure is fine when you really didn’t measure it.

A roller sh*t the bed. Why? You thought it was hydraulic.

Yes, I’m suspicious on what you think you know.

 

[1970Bee]

I ran a rudimentary compression check to ensure a valve didn’t get bent. Consistent measurements on all 8 make me feel confident that there is not another catastrophe going on.

I did not know it had a solid roller cam because I purchased the car from my brother and it broke a lifter driving it cross country. I didn’t look at the historical documents on the motor because I didn’t have ready access to them and the price was such that it was a good deal if there was no motor.

I do have the documents but not right in front of me. But assuming zero deck on a 4.315”bore and combustion chamber volume of 83.4cc’s the result comes out to about 9.75. It’s likely a few thousandths below deck, and there are valve relief notches, so 9.5 sounds pretty right to me. Let’s just say I have no reason not to trust what I’m reading.

It ate a lifter because 19 years ago somebody built a street strip car. The subsequent owners bought a cruiser. The valves had not been adjusted in 5 years, I’m fairly confident. Also, a SR cam as aggressive as what was in it likely should have had springs replaced some time ago.

Is there something besides intended use, bore, head type, valve size, combustion chamber volume and professionally calculated CR for a ball park cam recommendation?

 

[PRHeads]

Low-230’s @.050 is what I’d be looking for.

 

[1970Bee]

Thank you very much! Sorta what I had in mind, but didn’t want to assume too much.

 

[oldkimmer]

I’d have thought a larger displacement motor would want more cam timing to operate at a given RPM? Ie- what is mild in a 440 would be more radical in a 383

Very true. Kim

 

[oldkimmer]

All of the cylinders were about 110, +\- 5 psi. Which seemed low in my experience, but were at least consistent. In full disclosure, the lifters were out when I did this; I just wanted to be sure I hadn’t bent a valve before proceeding (using the best compressor $20 can buy at Auto Zone )

I fail to see how u did a compression test without the valves opening and closing. Please explain what u did. Kim

 

[1970Bee]

“Compression test” isn’t an accurate term; I just used a cheap tester to convince myself I hadn’t bent a valve.