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drill · 08-18-2002, 07:07 PM

how do tell the difference between 6x 4 , 6x 8 heads if the heads r still bolted down , ive got a 350 y9 block with 6x ? heads thinking of taking of and putting on a 455 6h heads as a start,

drill · 08-18-2002, 07:07 PM

how do tell the difference between 6x 4 , 6x 8 heads if the heads r still bolted down , ive got a 350 y9 block with 6x ? heads thinking of taking of and putting on a 455 6h heads as a start,

Brian Baker · 08-18-2002, 07:33 PM

On the side of the head there are bosses that would serve as a mounting point for any A/C compressor brackets. Look at these bosses from the side, there will be a machined surface with either a "4" or an "8" stamped (not cast) onto the boss. If the heads are on a 350, they should be stamped "4".

drill · 08-19-2002, 09:42 AM

Brian if the heads r 6x4,s {havent had chance to check yet} would they be worth pulling of the 350 and putting on the 455,

drewhelm1974 · 08-19-2002, 11:57 AM

I would say, YES!!!! 6X-4 heads are a very good head to put on a 455 and get right around 9.5:1 CR with no milling. I was going to use a set, but got a great deal on a set of 6X-8 and will have to mill about .060 off to get that CR.

larry davis · 08-19-2002, 07:33 PM

If ya can get them cheap, YES! But ditch the 350.

Will · 08-20-2002, 02:05 AM

Wait a second, that 350 has a few good parts on it if it's a complete motor. The timing cover, oil pan, distributor, and crankshaft are all worth saving (especially the crank as it's basically the same as a 400 crank). The rods might also be worth something as cores if you need a set of stock rods, or they may be perfectly good as-is.

hobbygto65 · 08-20-2002, 09:26 AM

Do you identify 4X heads the same way?

drewhelm1974 · 08-20-2002, 12:32 PM

Yes, you identify the 4X the same way.

Hold onto that 350! LOL I noticed someone in the Hot Rod Engine building Challenge is building a 350 PONCHO!!! All the parts are interchangeable with a 400. Hell you could bore it .125 and viola! You have a standard bore 400!

drill · 08-20-2002, 05:15 PM

had a good look for the 4 stamped on the head but cant find anything cleaned one {passenger side}all up took air con and brackets off still cant see it!is it on the front machined face as your looking at it or on exhaust manifold side ,or may be forgot to stamp it its a 77 y9 block

Taff · 08-20-2002, 06:34 PM

You can't bore just any 350 out to 400 size,the bore walls would get too thin. 350 blocks with casting numbers ending in -168 may be bored to the 400 bore size, I believe. Bruce at R&R engineering recently made 540hp with a (certified) stock bore/stroke 350 motor,so don't chuck away that old 350 quite yet.

johnta1 · 08-20-2002, 06:59 PM

On the side.

Will · 08-20-2002, 08:45 PM

There may come a time when 350 blocks are worth saving, but I don't think that time has arrived yet. There still seems to be a good supply of 400s out there.

If Bruce can make over 500 horses with a 350, just think how much he'd have made spending the exact same money/effort on a 400.

hoffman7476 · 08-20-2002, 09:38 PM

Or a 455

drill · 08-22-2002, 02:59 AM

JOHN THANKS FOR THAT PICTURE FOUND THE 4 STAMPED ON IT , MUST OF BEEN THE ONLY PLACE I DIDNT LOOK, THANKS AGAIN , WELL NOW IKNOW WHAT THE HEADS R WHAT DO U SUGGEST FOR A GOOD CAM AND INTAKE MANIFOLD,TO GET IT AROUND 450 HORSES [img]smile.gif[/img]

PONTIAC DUDE · 08-22-2002, 07:40 AM

Tell me more about the -168 code and having the capability to be bored to 4.120?????
That's quite a stretch for me to believe how it can go that far?
Unless it's a factory different core design.

hobbygto65 · 08-24-2002, 11:01 AM

I have a set 4X heads marked 1H what does that mean.

ddab3 · 08-24-2002, 09:31 PM

If they are unmolested(stock) they should be 2.11/1.66 valve, 112cc or 114cc(found conflicting info) chamber heads.Probably from a 73 or 74 455

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