Ok Im starting to loose my nerve here... Was there 2 different casting numbers for the 781 heads? Im all worked up now about the short valve spring height. Is there anyone else who has experience with these heads?? I have been talking to rustbucket79 but I think he is on a different time zone so communication is slow. Please help. Are ceratin ones of these heads junk? I dont want to be jimmy rigging the heads to make them satisfactory. Thanks!

Hey Badazz....I've just pulled the covers off my heads to find out they are the 336781 series heads. I was tickled at the time, but now I'm also concerned. I am looking at putting the XE274 comp cam kit (which includes springs)in mine. Are the springs that comp cams sends with this cam possibly not gonna work? Please let me know if ya find anything out. Thanks.

Not to bust stones.....but have you called any machine shops to find out their 2 cents as far as these head differences and what they can do to correct it ? I'd be interested to hear a few different opinions on them myself....

JMO I though there would be more knowledgable people here.

Ok I have talked to a very reputable machine guy down town.. heres what he told me..
Its true valve spring selection could be a problem, but he said he has never had a problem fiding valve springs for them. I guess the rotator under the exhaust F's-it all up.

Got some more info....Seems like all the 781s and 049s have this situation. hmmm dont know

<font face="Arial,Verdana" size="2">Originally posted by badazz81z28:
Got some more info....Seems like all the 781s and 049s have this situation. hmmm dont know</font>

If I recall I have these on my 049's as well. When I brought them to the machine shop, the guy said they were probably from a truck in referance to those things. I didn't realize they might affect spring selection. I have aftermarket springs on the heads now.

I think someone mistook the 3 an 8. Sometimes in the casting process the metal gets shaped funny around the numbers and it looks like a 8 or a 3 but it is an 8. Look a little closer, as there was not a 386781 casting number.

336781.....73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports

I thought the same thing too Dave, but after looking on the net some I found BOTH of them, and they are slightly different, especially in production years.

I once had a set of '781s that I had a machine shop install larger valves and new springs. I gave them the springs that came with my Comp Cams K-kit for the 280 magnum cam. They wouldn't fit. He ended up ordering a set of Crane springs for the heads and it worked fine. Don't ask me which ones, that was 14 years ago http://www.nastyz28.com/ubb/smile.gif . I have since read that some sets of '781s have a different seat depth or something that prevents a standard aftermarket spring from working.

Yes, my '75 P/U 454 -781 heads have valve rotators under the exhaust valves too.

Just buy a rotator spacer "SHIM" kit.. Or fix the one's you have so they can't rotate!!!!!!

AND yes, there are -781 heads that install at 1.88" spring height stock AS WELL AS 1.80" stock spring height so you have to match BOTH retainers AND springs to get the height to make sure you get what you need!!

The later, '80's, -781 heads are generally the 1.80" tall heads...

Crane know's all about this b/c I used to have their part numbers for BOTH installed heights???

pdq67

[This message has been edited by pdq67 (edited June 01, 2005).]

DO NOT !! And I repeat DO Not use the supplied springs for the Comp Cams XE274.These springs have contributed to 2 BB engine failures & 1 was my 427.The other was a 396.The springs in the kit do not have enough pressure to control the valves & SEVERE valve float occurs @5000 RPM. It is as if someone turns off the spark to the engine.And yes the springs were shimmed to the right height.Use the next recommended springs in the CC line. Believe me you won't be sorry.

------------------
'79 Z28 ZZ454 4-speed 3.42 Black w/tan interior.Goodmark Cowl hood, 17" TT2's, Flowmasters.

J-24-73
this is the date code for my 781s hopefully when I tear them down they dont have the 1.800 springs

They should be the tall springs..

pdq67

You guys are getting me kind of worried too now...
I just finished pulling my 454/TH400 out of a 75 C20. I haven't taken anything apart or measured anything on the engine yet. I merely removed the valve covers long enough to confirm the casting was a 781. Based on the above discussion I will assume there is only one 781 casting (I'm at work now, so I can't just run out and check anything).
My plans have been to put in the 2.19/1.88 valves along with an Eddy Performer cam and its recommended matched springs.
I haven't spoken to a machine shop about this yet, should I be worried about something in this combo not working?

<font face="Arial,Verdana" size="2">Originally posted by Wpg79Z:
You guys are getting me kind of worried too now...
I just finished pulling my 454/TH400 out of a 75 C20. I haven't taken anything apart or measured anything on the engine yet. I merely removed the valve covers long enough to confirm the casting was a 781. Based on the above discussion I will assume there is only one 781 casting (I'm at work now, so I can't just run out and check anything).
My plans have been to put in the 2.19/1.88 valves along with an Eddy Performer cam and its recommended matched springs.
I haven't spoken to a machine shop about this yet, should I be worried about something in this combo not working?</font>
My machine shop said everything is workable and the parts can be found. JMO though I would reconsider the eddy cam.. There are far better ones out there

[QUOTE]Originally posted by pdq67:
[B]Yes, my '75 P/U 454 -781 heads have valve rotators under the exhaust valves too.

Just buy a rotator spacer "SHIM" kit.. Or fix the one's you have so they can't rotate!!!!!!

AND yes, there are -781 heads that install at 1.88" spring height stock AS WELL AS 1.80"

The later, '80's, -781 heads are generally the 1.80" tall heads...

It would be good if we could reference the date codes to the irregularities...

I have 781s on and off of my motor currently. And no prob with the running ones for six years with CROWER springs 130-140# closed and 330# open, Was leary when I set up because the springs are HYD and the cam is Solid...thats a "no no" but hey no prob so far. Will check relating info on shelfed heads. LETS get date codes.

Awesome idea! Something that could have helped me out before.

[/QUOTE]
JMO though I would reconsider the eddy cam.. There are far better ones out there

[/B][/QUOTE]

Sorry to take a tangent, but I'm just curious now... what cam would you recommend with similar duration that's better?

Once I get the heads to the machine shop and measured I can post the date codes and spring heights - but it probably won't be until fall or winter.