906 heads on a 516 engine?

[Zwap]

My 516 closed camber heads needs a rebuild but I've got a pair of 906 open camber (from a 383 Magnum -70) in good condition.
Is it possible to use these 906 heads on a stock 383 -66?
The service manual say 9.2 to 1 compression ratio on that engine.
I think the 516 have 6cc less chamber volume than 906.

What do you think?

 

[detmatt]

The 906 will work just fine. A little less compression but better flow and larger valves.

 

[1978 NYB]

Yep, no problems with the swap.

 

[Landyacht]

You can do it with no problem. You will loose some compression but that is not necessarily a bad thing. With less compression you can get away with running lower grade fuel.

 

[Zwap]

OK, thanks!
How much do you think the compression ratio will drop?

 

[1978 NYB]

A little less than a full point.

 

[Landyacht]

OK, thanks!
How much do you think the compression ratio will drop?

Probably not enough to effect the performance of your engine. There are online compression calculators availableCompression Ratio Calculator Engine Compression Calculator You will need to know some basic info on your particular engine such as bore , stroke , piston to deck height , head gasket thickness , and combustion chamber volume.

 

[70bigblockdodge]

I would guess 1/2 to3/4 of a point because of smaller bore and sroke in a 383. If this is a 2 bbl engine you probably don't have 9.2 to begin with.

 

[Zwap]

The service manual and other sites I've been looking at says 9.2:1 2bbl and 10:1 4bbl for a 1966 383, and yes mine is a 2bbl engine.
Is there any reason why this is'nt correct?
What is the difference between the 1970 383 2bbl with 290 horsepower 2bbl and 8.7:1 compression ratio and the 1966 2bbl with 270 horesepower and 9.2:1 compression ratio?

 

[detmatt]

Better heads.

 

[Landyacht]

The service manual and other sites I've been looking at says 9.2:1 2bbl and 10:1 4bbl for a 1966 383, and yes mine is a 2bbl engine.
Is there any reason why this is'nt correct?
What is the difference between the 1970 383 2bbl with 290 horsepower 2bbl and 8.7:1 compression ratio and the 1966 2bbl with 270 horesepower and 9.2:1 compression ratio?

The 906 heads were used on the 1970 383 engine which had better flow characteristics than the 516 heads used on the 1966 383. I've heard from several different sources that the compression ratios listed in the service manuals are inaccurate . For example the 8.2:1 ratio listed for the mid to late 70s big blocks is actually closer to 7.6:1

 

[Zwap]

OK, that make sense, I then drop from 9.2:1 to closer to 8.6:1.
I ran the numbers in the comp calc and asuming the piston to deck hight (the only value I didn't got) is 0.073 to get 9.2:1 and when I put in the cc value for the 906 I got 8.7:1 (actually the 1970 383 2bbl listed comp ratio), 1/2 drop of a full point.
Let's asume that the piston to deck hight is more like 0.106 and my engine have 8.6:1 to begin with, then it should be a drop to 8.1:1 with the 906, is it OK or is it too low to run OK?

 

[detmatt]

It'll run fine especially if you're just looking for a good cruiser.

 

[70bigblockdodge]

The compression ratios you are reading in a book are what they are supposed to be I have never seen a set of untouched heads that cc out to number that Chrysler listed, most have to be milled a good amount to get to those numbers. I personally would rework the 516 heads and use them compression will be slightly higher but close combustion chamber with create better quench/swirl and tolerate higher compression ratio. If the engine you are working with is a 2 bbl you don't have 9.2: 1 to start with.

 

[Zwap]

OK, the engine is a 2bbl but has been upgrade with Mopar M1 dual plane intake, Edelbrock 600 carb, electronic ignition and HP manifold with 2 1/2 - 2 1/4 - 2 inch dual exhaust.
Would that work together with 906?
The reason I want to use 906 is that they are in very good condition and would be bolt on with no need to rework.
I'm not looking for performance but I don't want it to have less performance then it got today with the worn 516.

 

[cbarge]

Dude,the 906 heads will be perfect for the combo you already have.
The engine will be much happier now it can breathe.
The 516 heads worked fine but were restrictive in the flow department.
I putt 452 heads on a 66 383 which are essentially the same as 906 heads with hardened valve seats.
Make sure you block off the heat crossover ports from the intake. A cooler denser fuel charge helps.

 

[livininharrow]

in my opinion the 600 eddie carb is too small. anybody?

 

[Zwap]

Dude,the 906 heads will be perfect for the combo you already have.
The engine will be much happier now it can breathe.
The 516 heads worked fine but were restrictive in the flow department.
I putt 452 heads on a 66 383 which are essentially the same as 906 heads with hardened valve seats.
Make sure you block off the heat crossover ports from the intake. A cooler denser fuel charge helps.

That sounds great!
Yepp, I've blocked the heat riser with the Fel Pro 1214 valley pan and going to use the same when I switch the cylinder heads.
Is there any issues with the rocketarms, push rods or hydralic lifters when I go from 516 to 906?

 

[detmatt]

There was a different pushrod style used for a short period about that time that is obsolete with replacement lifters. They had a noticeable taper on the ends, otherwise all parts are the same.
I bought the 750 Eddie for the 440 on my Imp that I had just rebuilt with 915s with oversize exhaust valves and an hp grind cam and pulled it off in favor of the 600 cfm Eddie. The engine woke up with the 600 cfm carb and has much better throttle response.

 

[65Fury440]

I put a 600 Eddie on in place of a 750 for a minute on my built 440, lots more responsive. I just put on of these Street Demon 625cfm in place of a 750 Eddie on my stockish 440, like night and day better driveability.
Factory Refurbished Street Demon 1900 625CFM 4bbl Carb