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Discussion Starter #1
So not to go too deep in the weeds, as I have been building my 406 Small block and 200R4 set up, a few things about that engine and trans (tech spec) just never sat well with me....And eventually in my drooling on line, I came across a 454 and HD Th400 set up. The price was more than right, and I just couldn't resist.
ANY how. So now I am BACK to square one, and I'm trying to figure out my build. One thing I do know, is it will be a 496. Whether it's a stroker or not...Im not real sure just yet. (2 bolt main) Shooting for the 6-700hp range. But quite honestly anything over 500 and I won't be let down. And I would guess that a solid 496 with good compression is still going to run like a scalded dog, even if it isn't stroked. I also know it's exponentially more expensive to build a BBC vs a SBC from what I have found so far.
One major weak point for me in design is heads. There is just something about figuring out heads that makes mine spin.
compression height, closed chamber, open chamber... I have read and read, and somewhere, something just never clicks for me. So I'm looking for some guidance.
First off, my dream build, accurate or not, is a $10K engine. I don't have 10K...And as most of you know, you really can't just start at the bottom and build. Gotta have a lot of parts ahead of it all, just to get $500 worth of machine work done. lol. So you are pretty much all in on the long block from the get go.

I have the peanut heads. Not real desirable for top end performance, but contrary to what a lot of folks say, torque range...I think they would be a great street rod head. Lotta low to mid range torque...just falls off fast in the upper RPM's.
SO my thoughts are, keep the peanuts for now, get better rockers/springs, definitely increase the compression with maybe flat top or a mild dome piston. But what I don't want to do is chase this route, then decide to up the heads later and find I can't due to the piston and head/valve clearances...and I'm stuck with the existing heads without changing pistons, because that becomes another major orchestration.

I've read that the peanuts have a 112cc chamber.
If I did a dome piston of 20cc, @ 60 over, peanuts...I believe that puts my compression around the 10.4:1, which is good. I could be wrong on that though. Please feel free to laugh at me, but by all means correct me.
If I remember another calculation, I would want 1.6:1 rockers as well, to accommodate the cam lift.
My question is, stroker or not, is there a magic number to stay under to ensure clearance, and keep compression in the green? Or maybe someone has a great piston, and cam combo...tried and true with the peanuts, that they would recommend. I am thinking that if I stay in the .500s lift, I should be safe in the flow ranges. I know .600 is going to probably start feeling the limitations of the peanut ports more significantly.

Thanks,
Willy
*SOMEDAY this car will see the road again.
 

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DC PIT CREW BOSS
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You got me on this one. I never understood big blocks. Small blocks yes but the biggies never
 

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I'm not an expert but I've built and driven a couple of big blocks. Use the information below to spark your own research, at least it might give you concepts to look at. I've owned a big block 69 435H Corvette. High compression, big port heads, three duces, all that stuff. Tried the L88 cam and a couple different intakes. That makes me a 396-427-454 guy, consider that the 496 might have completely different characteristics than the smaller stroke big blocks. Also not familiar with what your calling peanut heads. I assume they are the newer version of the smaller round port heads?

Are you planning on running pump gas or high octane racing fuel? Aviation fuel works great if you can an airport that will sell it to you. 10.4:1 comes with a high detonation risk if your running pump gas and iron heads. Aluminum heads help this quite a bit as they dissipate the heat much quicker. A much more realistic compression for pump gas is around 9.4:1 - 9.6:1 depending on heads. You will have to measure the volume of the chamber (CC) in order to calculate the actual compression ratio. Guessing is just that, a guess.

The round port heads build better torque through faster air flow earlier in the rpm curve. The big port heads don't really allow enough air flow volume to atomize fuel very well until you can sustain the higher rpm range. They are great for the drag strip or road racing applications. Once up there they run well but not very practical for a street engine.

Let's talk about the combustion chamber a little bit. Typically the big open chambers were for the lower compression engines. The smaller chambers (heart shaped) usually had a flat area on one side and the actual chamber on the other. These aid combustion by squench (Smokey Unick's term), forcing the air fuel mixture out of the flat area into the chamber causing further atomization of fuel as nears the peak of compression. At a safe compression ratio I think you're going to have some trouble meeting your HP goals with open chamber heads. Even open chamber heads with pop up pistons for what ever reason don't seem to produce the higher HP numbers without forced induction.

Think about the difference between quick and fast. Would you rather run a 12.5 second quarter at 94 mph or a 12.5 second quarter at 110 mph. Street driven cars IMHO should strive for the quicker side. Serious drag racers want to do both..... quick and fast. Higher torque with excellent mid range cam is where the quickness comes from. The huge cams that build HP at higher rpm levels have limited flexibility in their application. If all your gonna do is drag race, go for it.

As for the 1.6 rockers. I put a set on my intakes and couldn't feel/tell a difference. IMHO they are not worth the risk of hitting a piston with the valve. You should check piston to valve clearances regardless but if you decide to run 1.6's it's an absolute requirement.

More important than 1.6 rockers is matching engine parts to perform with the same goal in mind. For instance: mixing a giant cam with small port heads isn't going to work very well. Either would a high torque 4wd cam in a drag engine. Matching parts for your overall performance goals means understanding how the parts work together. It seems you have a pretty good handle on that. Putting all that effort into building an engine then changing heads or cam or compression ratio can drastically change how the components work together. If you decide to go a different direction perhaps it's better to spec out all matching parts and rebuild. Maybe leave the first one alone and start a whole other engine or invest in the parts you want to start with.

How you intend to use the vehicle, budget, space, time all play a part. Lots of research to do.......

Good Luck
 

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over the years Ive build MOSTLY BBC based engines
if you wade through the links and sub links you'll be far ahead of JOE AVERAGE in skills research and knowledge








 

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Discussion Starter #5
7TRoadster. Thanks! I appreciate any and all kinds of input to try and get over this knowledge gap.

lol...like most here I'm sure, as soon as I saw Grumpy chime in, it was a thankful welcome, but "oh ****, I have some serious reading ahead of me!" ;) Diving in.
 

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Save your money and get a set of AFR 300 oval port heads....you will drop a ton of weight out of the front end and have all the street able airflow you need for that engine.
 
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