Thread: 406

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right now i have come up with my combo for my street/strip 406. its going into a 68' camaro with t350 and with a 12 bolt with 3.90 gears. i don't have a lot of money(just like everyone else)so i'm using what i have laying around. my vortecs have very small intake port volume of a 170cc and still have 1.94/1.50 valves. i know that volume is too small, so i'm going to gasket match and try to open the port to 180cc and add bigger valves(2.02/1.60). i'm going to run a solid cam with 232/232 dur. .480 lift in/ex. this should give me power to 6000rpm. i do have one problem, but not serious. my 400 crank turns out to be turned down 383 stroker crank, which means it has 350 mains size (2.45) compared to a 400(2.65) so i'm thinking of using a 377 stroker main bearing spacers, but is it worth it? or should i just buy eagle 400 crank? the running 1 5/8 headers with 750cfm holley vac sec carb. the intake is a edelbrock rpm. and my cmpression is 10.25:1 which is borderline, but i think i can get way with running pump gas. if anyone has suggestions or comments, your imput would be appreciated!

Those 377's crank but I'll take cubes any day.

I would suggest using an Eagle crank over the stock. Chances are it is on the wrong side of the fatigue line especially if it has already been pounded on pretty hard. $200.00 is a small price to pay for peace of mind. Make sure to get the crank that is designed for whatever rod length you are using.

Also, leave those heads alone. They will do fine in stock form. Unless you have a flow bench, you can hurt those Vortecs' flow rather quickly.

I would not use spacers at any price. And certainly not if it is going to cost me cubes. That is going the wrong way, in my opinion.

Keep in mind that your compression will change, even while using the same heads, by going from a 377 to a 406 or the other way around.

Originally Posted by camaro_fever68

Make sure to get the crank that is designed for whatever rod length you are using.

Ok, tell how how rod length effects which crank you buy. In other words, what does it matter if you use a 5.7 rod or a 6 inch rod on a crank. I know that the piston has to change, but the crank?

The counter weight design and bob weight.

Here's a list of EAGLE CRANKS that specify what rods lengths and balance procedures go with each part no.

Originally Posted by camaro_fever68

The counter weight design and bob weight.

Ok, but couldn't the balancing shop take care of it in any case? I know one can specify different cranks which make it easier when balancing the rotating assembly, but with a good shop, any crank should be able to fit the bill.

Also tell me the difference between counter weights and bob weights. Isn't the bob weight a tool which the shop uses to balance the crank and the counter wieght the part whcih is part of the crank?

So in essence, the counter weight is the only thing that is different from one crank to another, depending on the rod one chooses? Yes?

I MAY NOT KNOW IT ALL BUT I'M WILLING TO LEARN AS MUCH AS POSSIBLE......

Bob weight refers to the mass located on a single crankshaft rod journal. This is two pistons, pins, locks, rings, both the reciprocating and rotating portions of the connecting rod and the rod bearings. To calculate bob weight, you must measure each individual component.

If you don't follow the bob weight the manufacturer suggests, heavy weight will have to be added (mallory) which is very expensive. If you use a light weight crank and regular weight rods and pistons, you may never be able to get it balanced.

On most cranks, the counter weights are designed to be used with certain length rods and internal or external balance. Refer to the link above.

Thanks for that detailed post. So the only difference from one crank to another, are the counter weights seeing as the bob weights are a measuring tool for the machinist.

Back in my machine shop days, used to have cutomers bring in all the parts they bought themselves and saved so much money on.....only to find out the mallory metal need to correct the imbalance was about $300.00, if their mess of parts could be balanced at all..... Pretty much killed the money they thought they saved.

I would suggest either consult with the shop that will be doing the balancing, or buy a balanced assembly.... Will probably save yourself $$$$ in the long run....

Originally Posted by TyphoonZR

Thanks for that detailed post. So the only difference from one crank to another, are the counter weights seeing as the bob weights are a measuring tool for the machinist.

Until you get into the drilled crank pins, knife edged counterweights, etc.

Originally Posted by vortec king

right now i have come up with my combo for my street/strip 406. its going into a 68' camaro with t350 and with a 12 bolt with 3.90 gears. i don't have a lot of money(just like everyone else)so i'm using what i have laying around. my vortecs have very small intake port volume of a 170cc and still have 1.94/1.50 valves. i know that volume is too small, so i'm going to gasket match and try to open the port to 180cc and add bigger valves(2.02/1.60). i'm going to run a solid cam with 232/232 dur. .480 lift in/ex. this should give me power to 6000rpm. i do have one problem, but not serious. my 400 crank turns out to be turned down 383 stroker crank, which means it has 350 mains size (2.45) compared to a 400(2.65) so i'm thinking of using a 377 stroker main bearing spacers, but is it worth it? or should i just buy eagle 400 crank? the running 1 5/8 headers with 750cfm holley vac sec carb. the intake is a edelbrock rpm. and my cmpression is 10.25:1 which is borderline, but i think i can get way with running pump gas. if anyone has suggestions or comments, your imput would be appreciated!

The engine might pull to 6,000 but I would guess it would make max. hp around 5,600.
Keep in mind this is a 406 and I would guess the cam will start 300-400 rpm's earlier and also end at 300 to 400 rpm's sooner.
I would try and run a 2,000 stall.
If you can't hook the car up you might find the 3.90 to be a little to much gear.

He did not say anything about building a 377 . He is wanting to know about the spacers to use a 350 main size crank in a 400 block. I have known several circle track guys that have used the spacers with no problems, and they were turning their motors way higher than you will. I built a 406 5 or 6 years ago and used a stock crank turned 10/10 and shifted at 6500 to 6800 without any problems.

Use a good harmonic balancer and a good machine shop and you should be fine. I do agree that I would run the vortecs just the way they are other than maybe machining for bigger springs, but with the cam you said they should be allright.

My 406 was in a 72 Monte, t-350, 3k stall, 373 gear, drag radials. The motor was pretty mild, solid cam can't remember the duration somewhere @250, 501/508 lift, 10.5:1, perf rpm, out of the box 750 vac. secondary, but it did have Canfield aluminum heads. It ran 12.20's at an NMCA race with a 1.69 60'
the car weighed 3800lbs. I don't miss the car much but I do miss the motor.

thanks Ron B. for recongnizing the crankshaft confusion! people, i'm not using a 350 crankshaft! it's a 400 crank with turn down mains, meant for a 383 stroker. the spacers i mentioned are for the gap between cranks main(2.45) and the blocks main (2.65). i only said 377, only because they mostly use the spacers on the 377's.
anyway, back on topic. are my heads going to be sufficeint enough for my 406? will the bigger valves help any? i can buy a set of aluminum heads with 190cc intake port, that flow 255in/190ex, but i want to see if my heads are sufficient before i hand over big bucks for aluminum heads. i'm hoping to make 450hp and 490ft torque, and would love to see low 12's possibly high 11's.if my vortecs can't do this, then i need to know before i invest money in them. and by the way if you have something write thats not relate to this post, then don't write it,it's annoying when two people have huge arguments thats not directly related to the topic, especially on someone elses post, if you want to argue, start your own post

Originally Posted by vortec king

thanks Ron B. for recongnizing the crankshaft confusion! people, i'm not using a 350 crankshaft! it's a 400 crank with turn down mains, meant for a 383 stroker. the spacers i mentioned are for the gap between cranks main(2.45) and the blocks main (2.65). i only said 377, only because they mostly use the spacers on the 377's.
anyway, back on topic. are my heads going to be sufficeint enough for my 406? will the bigger valves help any? i can buy a set of aluminum heads with 190cc intake port, that flow 255in/190ex, but i want to see if my heads are sufficient before i hand over big bucks for aluminum heads. i'm hoping to make 450hp and 490ft torque, and would love to see low 12's possibly high 11's.if my vortecs can't do this, then i need to know before i invest money in them. and by the way if you have something write thats not relate to this post, then don't write it,it's annoying when two people have huge arguments thats not directly related to the topic, especially on someone elses post, if you want to argue, start your own post

Well, the 190's would not hurt you any.
The exhaust to intake flow is better.
The 190's would also give you more flexibility if you ever wanted to go hyd. roller or mech. roller in the future.