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I have a 396 that is bored 60 over with stock heads. I am thinking to change to aluminum heads. There is NOTHING radical about the engine. It is a 396!
The 60 over 396 is what I have and what’s in the truck. Mild Edlebrock RPM cam. Pretty much bone stock. Just looking to liven it up a bit.
Is it even worth changing the heads and how do I determine my pushrod length.
Welcome to CHR! I would say it's definitely worth changing the heads if you go with a set offered by a quality aftermarket supplier. You'll get improved flow, plus they'll dissipate heat quicker allowing you to run a bit more timing without fear of detonation. You can get an adjustable pushrod from Summit or JEGS to determine needed length, if the head supplier doesn't provide the info - https://www.summitracing.com/search/...rder=Ascending
Some of the other guys have recent BBC experience (Glenn Sexton?, Ryan/40FordDeluxe?) and can probably point you toward some specific heads.
Welcome to CHR:
If you have stock cast iron oval port heads, aluminum heads can definitely make a difference in the performance of your 396 (now a 408). Depending on your budget, heads can be responsible for 50+ horsepower with no other modifications. Budget is the key here. If you have $2,500, you can purchase AFR 265 heads. Allow another $4 - 500 for incidentals – gaskets, oil, antifreeze, and new head bolts, etc.
The internal combustion engine is a big air pump and these oval port aluminum heads flow an amazing 354 cfm at .65 lift which is huge improvement over stock. Typically aluminum heads will allow a bit more timing as they dissipate heat better than their cast iron counterparts.
I’m assuming that you will be living in the 1,200 – 5,500 RPM range where these heads are a perfect fit. In addition, you’ll save about 35 pounds per head. If you’re going to invest $2,500 in heads by all means, use new head bolts (ARP 135-3703 - $125). Use FelPro 1017-1 gaskets (another $100 per pair).
As to the pushrods – stock intake on 396 is 8.280” and exhaust is 9.250”. Not knowing if your block was decked when bored we can’t determine if different length pushrods were used in reassembly without measuring them. We also don’t know if you are using the stock 1.7 ratio rocker arms. Pushrods should be the last thing you buy. Put the heads on and then use a pushrod checker (as per Roger’s post). New pushrods are available from all the major suppliers in .050” increments. Resist the urge to use anything other than stock rocker arms.
There are less expensive aluminum heads and others will chime in here. If/when you get serious about a purchase; it would also be helpful to know just what camshaft and carburetion you have. If it’s still undecided, I’m a big fan of dual plane, i.e., Edelbrock Performer RPM (or similar) with a big ol’ 800cfm Quadrajet. Nothing is quite like the sound of those secondaries opening up when you stomp on the gas.
Once again, welcome to CHR. More details about what your desired outcome is will help to refine this process. One constant is that building horsepower costs lots of money.
Regards,
Glenn
A big thank you to both of you. Edlebrock manifold, 800cfm, as well as Edlebrock RPM cam I already have. As well as Comp roller rockers. Next I will look into those AFR 265 heads. Again thanks and I will be posting pics of my build as I progress.
Do you already have the cam and the roller rockers? If so, what are the part numbers as some of this stuff doesn't always play nice together.
Also, is this an automatic or stick shift truck?
Cam part #7162Quote:
Originally Posted by glennsexton
700r4 auto
So just to clarify - the 7162 cam and roller rockers are installed and currently running in this engine?
No!Quote:
Originally Posted by glennsexton
Nothing is assembled! Theses are parts that I am accumulating.
Well, this could be an interesting build.
In my opinion, the 7162 could be problematic for several reasons. First off, with modern oils, flat tappet cams require following a very precise break in process. It is essential that you run the engine at 2,000-3,000RPM for at least 20 minutes using a factory recommended 30wt break-in oil that has a zinc additive. The oil should be changed after 200-300 miles and closely inspected for any metallic particles. Even the best engine builders cringe a bit went installing a flat tappet cam for a street engine. I’m far from a professional and I won’t build another flat tappet engine.
I also think the duration and lobe separation on this cam is too much for the street as it comes to life about 2,500 RPM and likes to see 6K+ as an upper limit. It will also have a rough idle. It will need 14 degrees of initial timing to idle (probably 1,000RPM) and maintain enough vacuum for power brakes.
The 700R4 will spend a lot of time in 3rd gear unless you have a 3.93 or 4.11 rear end. You’ll be unhappy with a stall converter under 3,000 RPM.
If you haven’t yet purchased this cam, I’d recommend you consider a roller cam kit like this one from Clay Smith:
https://www.speedwaymotors.com/Clay-...454,80449.html
Duration is a bit less (229/240 versus 240/246 @ .050) but more significant is the lobe separation of 109 degrees will bring the power curve down so that you’ll start to really pull at about 1,800 and see great power at 4K. It would be very comfortable with a 2,500RPM stall converter and would idle well at 700 RPM with an initial timing of 12 degrees and provide more than enough vacuum. Yup, it’s expensive but rollers are, in my opinion, the best way to go for non-professional builds.
Roller rockers are a waste of money for 90% of all street engines – and again, resist the temptation to go beyond 1.7 rockers.
No offense is intended – this is my opinion. I’m hoping Jerry Clayton chimes in here as he is truly the master dragster/racecar builder. If Pat McCarthy (https://www.facebook.com/McCarthyPerformance/) is still reading now and again maybe he will comment. He’s who I’d use if I needed a big block built - I have nothing but the utmost respect for Pat and his knowledge.
Regards,
Glenn
I really do appreciate this information. These are parts I inherited with the motor. Will have to look up the specs on the rockers. I have been hearing a roller cam was the way to go. I will definitely be looking up roller cams and following the pointers you are giving. Thanks a whole lot. Just looking to build a strong reliable 396.
I agree with everything Glenn has said. I'd just like to add that from my research and findings are that 396s and 402s love big cams and more air movement with better cylinder heads. I had a 396 in a chevelle with a .650" lift circle track cam and a 4 speed. That car ripped and I drove it every day. It may not have been as fun without the 3.73s and 4 speed. :LOL:
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