406 -10: block

[dfhotlm33c]

So the final decision has been made.

We are running a 13:1 (ish) 406 with roller cam that will be matched to our set of Brodix -10 SP 40/60, 2.125" intake valve, 233 intake runner 23 degree heads. We will run lightweight, balanced rotating assembly.

Choices for block:
511 4-bolt block;
817 2-bolt block the way it sits;
spend $$ to upgrade the 817 to splayed caps.

We have these two blocks already. We aren't going to go aftermarket block. The 817 is already prepped, minus the final hone for pistons, and the possible splayed caps.
Opinions?

[Lizardracing]

Just some thoughts here but I think at your power level neither one of those blocks will give you much problem in a modified. I'd vote for 817 and splay the bottom. Or sell both and put toward an aftermarket stuff. Late Models tend to be harder on engines it seems because the increase tires and weight loads them a bit more. Slick vrs tacky track might also sway the decision.

[Brian Gray]

run the 817 the way it is it will be fine. learned a long time ago the 2 bolts hold up just fine. you will weaken the thing by drilling it for the wider caps.

trash the 511 or sell for what you can get out of it. dont build any kind of race engine out of the 4 bolt 400's

[DirtRacer9x]

Curious who has actually had failures??Did the block crack or possibly the caps??Im building a 11-1 406 in oem block now for my IMCA modified. Im using a stock block wanting to stay at the same over all weight as the crate Ive been racing.If I was running alum heads and roller cam I know I wouldn't consider a oem block.

You're trying to stay the same weight as your crate? How?

[charlie115]

cracked mine from center of mains to the cam. first time ive seen it happen

[Brian Gray]

That happens a lot with the 4 bolt blocks. I have had 0 failure with the 2 bolts. Untill someone puts caps on it

[stockcar5]

If your machinist installed splayed caps on a 400 block and made it weaker, i would find a new machinist asap.

[charlie115]

2 bolt block flat top 2 valve relief, vortech bowtie heads not shaved. block was decked to piston height. 7200 chip, I don't like turning my motors hard. no light weight stuff. lasted 13 nights

[charlie115]

and of coarse we were leading the feature with two laps to go,,, lol go figure

[charlie115]

scd do you do sport mod rear ends?

[fastford]

cracked mine from center of mains to the cam. first time ive seen it happen

your crack probably started in the cam tunnel and went down, we found years ago these blocks were weak there, for some reason the 2 bolt blocks were stronger there , as far as splayed caps go, it has a lot to do with how much power your planning on making, our rule of thumb is under 600 hp, 2 bolt caps with good studs work fine.

[dirtplay18]

Always had good luck myself running the 817 2-bolt blocks. I did have one split the #3 main cap (which I caught in time thank god), but I'm pretty sure it was caused by running the feature with a vibration in the car. Came to find out the RR axle was bent. Had to get the crank mains turned .010, but that's all. This engine was .040 over also. Is a 12.5 : 1 with dart heads, made about 550 hp. On the other hand, if you can afford an aftermarket block, I would go for it, esp if you have a nice rotating assembly. JMO, good luck!

[dereksehi]

We have had good luck in our shop running the 509 2 bolt block and putting splayed steel caps on the center 3 and the steel strap across the rear main cap with arp studs we have had 406's and 377's running 13:1 and have never had a block failure.

[dereksehi]

With mild compression and limited rpm you will probly be ok how many rpm are you planning on running?

[dereksehi]

Now that I think about it thats probly right my theory was with the fairly long stroke of the 406 the harder you run it the more force you will be putting on the block also.

[dirtrace09]

The ones I have seen break have been due to heating/cooling issues.

[dave41]

how do you strap the rear main cap with oil pump mounting

[dereksehi]

They make two different rear straps one for dry sump and one for wet sump. The dry sump strap is just solid steel whereas the wet sump has an oil passage cut in it just the the rear main cap does. If I recall right the straps are .625 thick and that amount has to be cut off the bottom of the rear main cap in a milling machine you will have to drill the dowel holes a little deeper and you will want to do this first. The dowels for the oil pump will have to be longer as they will locate the pump and the strap also if you stud the block the main stud under the oil pump has to be a special length with 12 point head to clear the pump.