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406 ss monte 09-01-2008 10:23 AM

vortec heads on a 406, can it be done on pump gas?
i have a 406 with forged flat top pistons that i was going to put a set of afr 195 cc heads on with 75cc chambers. i'm selling the afr heads because i need cash to finish my garage, so now i need a set of heads. i have a set of 906 vortec heads, but they are 64cc chambers. i'm figuring 11.52, this is how i'm figuring it.

4.155 bore
3.75 stroke
4.200 gasket bore
.040 gasket thickness
5cc valve reliefs in the pistons (could be more or less)
.005 deck height.

is this to much for 93 octane? i'm thinking of a cam in the lines of 240-250 @.050 with anywhere from a 106 - 110 lobe separation.
the heads being cast iron is what worries me. aluminum would probably work, but i don't know about cast iron.

DoubleVision 09-01-2008 11:13 AM

With a tight quench, timing slightly on the low side, a slightly rich mixture, and coolant temps in the 180 degree range you might pull it off, but I wouldn`t hold my breath, especially if it has the stock 5.565 rod lenth.
In many cases, and this arguement has went on and on, it doesn`t detonate in the low rpm ranges so the driver thinks it don`t in the upper rpm ranges, but they don`t understand, the cam is bleeding off a lot of the cylinder pressure during low rpm use, then there isn`t the time for it to in the upper rpm ranges, so the engine could be detonating and due to the noise of the engine, exhaust and etc. It`s very difficult to hear. By the time it`s figured out the engine is usually gone.

406 ss monte 09-01-2008 11:19 AM

it's a 5.7 rod motor & the pistons i'm useing are sealed power L2489F.

how did people get by with double hump heads? i've seen plenty of flat top 406's with double hump heads. i've used 67cc heads before without any issues, but i figured it up at 11.52 with 64cc heads.

DoubleVision 09-01-2008 11:24 AM

You may pull it off then if you followed the guidelines I said. However, I would get more opinions from others in here that may have already did the same combo.

ScoTFrenzel 09-01-2008 12:25 PM

There is no practical difference between iron and aluminum for heat dispersion. Dyno tests prove it. A few milliseconds is just not enough time for heat to transfer. MOST of the heat goes out the exhaust.

Remember roller cams lose 8* due to lash.
Keep that LSA down to 106*.
.040-.050 squish distance is critical.
Soft-edge everything in the chamber/piston.
Timing curve will be critical as will mixture control.
Water injection is a good idea.

I ran an 11/1 '70 350/350 on 91-93 with water injection. Vortec heads are better.
You could also take some meat out of the chambers.

I suggest looking into the "head grooving" threads on this forum. It works. Automotivebreath is the "expert".

Remember the higher the rpm, the less "clock time" for detonation to occur.
Good luck, be prepared to buy race fuel.

Enginequest makes replacement Vortec heads in different sizes. Check that.

406 ss monte 09-13-2008 08:00 PM

How did people run double hump heads on 400's? Their 64cc chambers & need a lot more timing. I've seen several over the years with flat tops & double hump heads & run on 93 pump gas. what's the difference?

just so everyone knows. i already have the vortec heads. their not costing me a cent other than springs & having guides machined. that is the only reason i want to use them. FWIW, i took the exhaust valves out to check the seats to make sure their not the one's with the big seat that restricts flow & their not.

CNC BLOCKS NE 09-14-2008 05:19 AM

Here is a similar link with some good info.

406 ss monte 09-14-2008 10:31 AM

that would be me too. :D

i'm about ready to pull the 406 short block, & put in the factory vortec short block & use with the vortec heads. i would hate to screw up my 406 pistons from detonation. the 350 would be better suited with the heads anyways :confused:

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