[67Fbird]

Got a bit of a delima here.
So i will be building a SIMPLE old 455. fact
The assortment of parts I have varies but I have a HEAD problem (maybe)
The 7m5 (114 cc) heads from the 455 do NOT have the outside edge exhaust bolt holes The other heads I have ar 1974 4X (small valve) @ 98 cc and #62 @ 74 cc. This is a super budget build (using oem pistons as bore is within .005).
PROBLEM: I have never had manifold nor do i really want them. My 1.75" headmans have served me really well and I would like to use them BUT without enough screw holes (no material even there) I do not see how this is going to work.
Swapping to the 4x heads with 1.96 valves would be like a choke an even a 301 much less a 455.
Using the #62 would be GREAT except for the 11:1 compression on a cast piston motor = NO TIMING ALLOWED...

So I am open to creative suggestions???? HELP

[MarkS57]

Why not put 2.11's in the 4x's? Bumps the compression a bit too.

[steve25]

You can drill and tap the needed holes in the end head bolt bosses.
Tap the holes for fine thread and use a stud of the needed length.

This work needs to be done with a lot of care to get the studs in at the right angle so if you go this route you might want to have a shop do it.

The other and better choice that you have to me is to get a valve job done on those smaller chamber 4X head and fit them for the bigger 2.11” intake valves.

Exh valve wise its been proven that for the average street 455 running only up to 5200 rpm that the 1.66” exh valve makes more average power.

The 4X heads fitted with 2.11” valves are a win, win , win if they pass a Mag test .
1) more needed compression.

2) all needed exh flange bolt holes are there.

3) the chambers are not as deep, so the intake valve is less shrouded.

The 2” ID Headers you want to run are a problem to me big time, as you will drop off a bunch of street happy torque with those overly large tubes.

If your set on running these big 2” headers then I would consider the benefit of the 4X heads higher compression mandatory !

[74Grandville]

Ames = FN396SH

Probably easier to find usable 6x-8 heads


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[400 Lemans]

https://www.ebay.com/itm/28414056016...4AAOSwajVUNU47

[67Fbird]

corrected post those are NOT 2" headers...they are the 1.75"...
I haven't priced what it takes to go bigger valves in the 4x. ANY head going on will be getting new valves anyway so I figure stepping up in size should NOT be a big $$$$ what maybe 2 throat cuts before they do the seat angles...?"

[67Fbird]

hahah...figured I was NOT the first to run into this...

[Sirrotica]

Those heads come with, and without the boss cast in the place of the 2 outer bolt holes. If the cast iron is present you can drill and tap the location in the heads, I have done this before on a drill press, it requires some set up to get them in the correct placement, but is achievable if you take your time.

If the cast iron isn't there you need the brackets that have already been referenced.

The late model 6X, or 5C etc. 400 heads will give you all the bolt holes needed, and as has already been said, it will increase the compression to the point you'll need to run premium fuel in a 455. If running premium fuel is of no concern than changing the heads is probably the easiest venue. You'll also reap some performance increase over the OEM heads. While you have the engine apart a suitable cam is pretty easy to swap out at the same time.

Take it from me, DON'T try to use the 62 heads unless you want to destroy the pistons in short order, been there and done that. Race gas is the only way you'll be able to run that combination. I tried it on an oval track 455 and broke numerous pistons on an otherwise good 455 in one night of racing. Back in the late 70s race gas wasn't easily available and I tried cheating running pump gas with octane booster, major meltdown.

Nunzi was the person that told me to get a set of late model 400 heads and use them on a 455 to get a workable compression ratio. I found a set of 71 #96 400 heads and problem solved, they already have the 1.77 exhaust valve if you feel the need that you must have a 1.77 valve. I've done street 455s and used 5C heads with 1.66 exhaust valve size and never missed the bigger valves. If I remember correctly the #96 heads had the cast iron boss there, I just had to drill it and tap it so I could use headers.

[b-man]

Just run the 4X heads with the 1.96 intake valves.

The ports are essentially the same as ones equipped with the 2.11 valves. They won’t choke off performance to any great extent, the engine might make 10 hp less and you’re not going to notice that.

I read here on the forums where Cliff R ran some small valve 1969 #46 heads on a quickie 455 build and it ran really hard.

Super budget build.

https://forums.maxperformanceinc.com...69&postcount=8

[steve25]

Well if you gotta go for new valves and a valve job anyway then it may cost you nothing additional to pick up more power!
I once had to use a machine shop to do this recently while my seat cutting motor was waiting on parts and all they charged me was 10 bucks more !

That cost is equal to two cups of fancy coffee these days, lol!

[ta man]

Originally Posted by b-man

Just run the 4X heads with the 1.96 intake valves.

The ports are essentially the same as ones equipped with the 2.11 valves. They won’t choke off performance to any great extent, the engine might make 10 hp less and you’re not going to notice that.

I read here on the forums where Cliff R ran some small valve later #46 heads on a quickie 455 build and it ran really hard.

Super budget build.

x2 it is a basic build..no sense getting carried away. Just the compression increase is worth it. There are ways to trick those smaller valves..swap the valve springs and run 1.65 rockers..or a slightly higher lift cam or more duration..the thing about adding compression it opens up a nice performance option when it comes to cam choice.

[67Fbird]

Yes ...any head going on this will have NEW valves, liners, full valve job and of course springs for the cam. So Here is what i'm looking at 4x heads with required work to be good to go. ( will do some bowl work and basic porting...nothing dramatic.) Open push rod slots, run my HS 1.65's and the tried and true RAIV FTH cam. I'm 50/50 on IF i can get the Holley Commander ecu to communicate with anything I have computer wise...if NOT... the ole 850 Q-jet on top of the RPM intake. Should be a simple motor, effective and fun with the M21 and 373's .

[NeighborsComplaint]

Put a set of 2.11 I/1.77 valves in. Be sure to get the longer RA IV length.

The seats can be cut for both at minimal cost without installing hardened seats as the seat area is induction hardened out beyond the oversized seats.

[Formulabruce]

Or toss a set of # 15 heads on, you can find them pretty cheap.