I'm ready to make the order just want last minute do's or dont's. I have a 406sbc, weiand x-celerator intake, M-21, pro-billet, 6al and looking for a nasty pump gas street/strip car(on a budget). Heres where you guys come in before I order this stuff Brodix ik200's (will make me 10.0/1comp), holley 750dp, comp magnum 280h or 292h?, and headgasket thickness? I also have 1.52 roller tip rockers, can I use these with new pushrods and lifters? Any help is greatly appreciated.Thanks

Get some figures on current piston deck and head cc and we can provide correct head gasket thickness. Why dont you just tell us what you have and someone will ddyno it.

you could go with either cam.

Check the details on pushrods and such with your head manufacutrer, some alluminum heads need longer than stock pushrods. At least at summit, the guy on the other end of the phone will know if you call the order in.

Some if not most alluminum heads need particular ARP headbolts, usually small washer head, with ground flat washers.

It would be real nice to know the deck hieght.

motor currently has the stock cast 400 crank not sure what rods but stroke is stock length with .030 bore. 2 bolt main studded and head studs aswell. Pistons are pn#l2352 forged -14.0cc, .083 dish, w/4 reliefs. Bottom end only has about 2k miles on build so I want to leave it alone.Thanks

YES!! Try to make it right at 10 to 1 CR. so you can run good pump gas.

Depending on head chamber and piston dish cc's, DITH of your pistons, (stock is about .025" down) and thickness of headgaskets!!

I personally would go w/ the 280 cam b/c I have a 292 in my about 9.5 to 1 406 now and it's soft down low until about 25 to 3,000 rpm, then hang on!!

pdq67

PS., M-20, 3.31 posi and 26.5" tall tires!!

The .015-.017 steel shims would be good for this DITH .025 avg, to make about /035-.045 quench.

YES!! Try to make it right at 10 to 1 CR. so you can run good pump gas.

Depending on head chamber and piston dish cc's, DITH of your pistons, (stock is about .025" down) and thickness of headgaskets!!

I personally would go w/ the 280 cam b/c I have a 292 in my about 9.5 to 1 406 now and it's soft down low until about 25 to 3,000 rpm, then hang on!!

pdq67



^^ I think it was soft partially because that CR is a bit low for that cam! :)

I had a 292/244 cam w/ .507" lift in a 327 + .040 and it was pretty rumpy but I loved it! it did come on at like 3500, so in a 406cid it would certainly be quite a bit lower.
You could run 10.0 or even 10.5 compression ratio and be safe. (I'd do 10.5 and I assume you'll run Premium always)

Are you sure you want the double-pumper? Just curious. I'm admittedly biased for the vacuum secondaries. :p

^^ I think it was soft partially because that CR is a bit low for that cam! :)

I had a 292/244 cam w/ .507" lift in a 327 + .040 and it was pretty rumpy but I loved it! it did come on at like 3500, so in a 406cid it would certainly be quite a bit lower.
You could run 10.0 or even 10.5 compression ratio and be safe. (I'd do 10.5 and I assume you'll run Premium always)

Are you sure you want the double-pumper? Just curious. I'm admittedly biased for the vacuum secondaries. :p

Remember too that altitude will play a part in this compression game. Plug in number in this program and see what is acceptable.
http://www.hotroddersauctions.com/DynamicCompressionRatioCalculator.php

which accelerator intake do you have? the low rise one with curved runners is ok, but the tall one that uses the removable plenumn divider is not very efficient. if you haven't got the intake yet, look at the professional products "hurricane" that resembles a super victor. just a few more bucks, but way better design.

I figure that you will need to hand trim the .015" thick shim headgaskets b/c I did Mr. Gasket's .020" ones years ago that I used on my 406.

I just mocked it up and reached up inside and scribed a line on each cylinder where it overhung into the chamber and filed/ground them back!!

Worked fine but it is a pain. That and I also drilled them for steam holes too!!

Just set them on the block and set a stock 400 headgasket on top of them and then very carefully drill holes in them where needed!! I want to say 1/8" and 3/16" holes here??????

Then use them as templates to drill holes in your heads if they don't already have them?

pdq67

Remember too that altitude will play a part in this compression game. Plug in number in this program and see what is acceptable.
http://www.hotroddersauctions.com/DynamicCompressionRatioCalculator.php


You're right, I wasn't even thinking about altitude. My Bad!!

Excellent 'calculator' there, I think I'm gonna play with that a bit! :thumbsup:

I'm still confused on the head gaskets and shims, still learning, I don't know anything about quench and all that but when looking at prices I see for example.039 compressed or .041. etc. I don't have the heads yet but I read that I need to have steam holes drilled, not sure what that is but I'm sure I'll figure it out.Thanks

quench and all that is pretty easy...

"Quench" is a fancy term for piston to head clearance. We're talking about the flat parts of both, not the chambers. The idea is to leave a space that is so small any mixture in it will not combust. If the "quench" area is too big, the mixture in there can burn, and it does it in a hurry, promotes pinging.

But you can't get too close, or the piston and the head will try to occupy the same space, not a pretty thing.

.030" clearance is generally the minimum with steel rods.

.040" is about max for good quench.

Since the bottom of the head is flat, the quench or clearance area = the thickness of the gasket, plus or minus how close the piston is to the top of the block deck at TDC.

This could be anywhere... at least in theory, a "factory" engine has the pistons .025" below the deck at TDC, but there is a tolerance here. Add in a 30 or 40 year old engine that has been refreshed a buncha times and maybe been decked more than once... or better yet, throw in a bunch of aftermarket parts, crank, rods, pistons, and you really do not KNOW where that piston stops on the way up.

You HAVE to check it, and it's easy. Bolt a peice of flat steel across a cylinder, put the piston at TDC, and try to get a feeler guage between your peice of steel and the piston. (if you're being real persnickety, check all 4 corners) Whatever fits is how far "down in the hole" your piston is, and that measurement plus your gasket should add up to .030" to .040".

Thanks, now I got to see if I can find my feeler gauges. I'll see what I come up with

Slide the feeler gauge on top of where the pin is b/c if you slide it 90 degrees from the pin, the piston may be cocked a bit due to skirt clearances sorta deal..

pdq67

does .032 sound normal? that shim felt like it had a slight rub to it. Hopefully I'm doing this right, because it seems easy enough.

Here is AFR advise on adding steam holes.

Steam holes are recommended for all 400 block applications (GM blocks only). Use a 400 Gasket as a template and drill the three holes, nearest the spark plug side of the head, straight down. The other three which are very near the head bolt holes should be drilled at a 30° angle away from the bolt hole. The center hole will intersect water about 1" down and the two outboard holes to a depth of 2 1/4". Use 1/8 drill.