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I have stock Gen IV 454 & 781 Heads, Compression ????

70K views 59 replies 11 participants last post by  wild_man84 
#1 · (Edited)
Im going to be working with stock 4 bolt main 454 Gen IV bottom end.. ( in vehicle) I have a set of stock 781 heads.... I'm ready to send the heads off to a machine shop for work ( if needed/recommended) for new parts to match cam and for port&polish job.

Ive been searching and it looks like the cc's of the 781 are 115-118 cc's. not sure on the valves.

The cam im looking at recommends CR to be 9:1+.
Can I and how do I get my CR up without bottom end work?

Should I get the bigger valves 2.19 and 1.88?
What should I tell the machine shop to do with my heads ( mill? cc? P&P )
Should I use 0.020" shims (read that) Port match gasket?
The the cam recommends 2 different valve spring sizes, how Would I determine the answer. so in the future, I can figure it out for myself instead of having to ask. here is what it offers/recommends for the cam

Single Outer Valve Springs: 1.524" O.D., 1.110" I.D. OR
Dual Valve Springs: 1.509" O.D. Outer, .697" I.D. Inner On a guess, Id say the Dual valve springs BC of High RPM and my cam is .51 lift int & exh. and my rocker ratio is 1.72? is that right


Not a daily driver.. Looking to get high tq. rpm range (2200 to 5800)

Any input/advice/direction would be appreciated.... thanks in advance
 
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#52 ·
wild_man84 said:
Unfortunately, the heads are already at the machine shop. I will be discussing work and prices tomorrow. If it gets too close to $2,000 then, Im just going to have them basically worked and just keep on hand for a back up. And just buy Aftermarket, again, as ya'll tried to tell me lol.... Mistakes/learning curves always have a price tag. Ill be getting those books Thursday and Friday.
if the guides are ok, you can still put the bigger valves in and get them dressed up for cheaper than a new set
if the guides need changed also, that will probably make it close to buying a new set, for not a lot more money :thumbup:

and when its all said and done, if put a lot of money into those 781s, its OK because they are/and you will have, a good set of heads :thumbup:
 
#53 ·
Its been forever but Im finally back

Ok so... Im not sure if anyone is familiar with Steve Schmidt racing. but thats where i had the heads worked. This is the parts and total....
Competition valve job
mill heads to 110cc (.045")

comp cam K-kit,heads worked and assembled, shipping,valves, rockers..

3,500.00.... ouch. but honestly if you subtract parts. only have 1072.00 in labor/head work

The new spec's are.....
781 heads cc 110
valves int2.250" exh1.880"
overall length int5.244" exh5.422"

spring
installed height/pressure===1.920"/150lbs(+.050 lock)

I know Ive got lots to learn. and Im trying to. I haven't installed these heads yet. Im planning on it by next week. (im off work for a few weeks) So, I dont have an exact on the piston/valve measurement yet. Im starting to think Im going to have to have the bottom end worked. Im trying to get out of that for now because im already pushing my budget.

Can someone help me out on seeing where im at for compression. If Ive paid attention. Im showing 8.2:1.. Thats not enough. I need a min of 9:1. IF!! Im wrong, and I hope I am haha, that my compression is already above that. Than, Im golden. If not!!!! then whats my cheapest way out? changing the pistons myself with domes or new crank. Just please take into consideration Ive performed top end work. Ive been around bottom end work. But never done it myself. I have read the books and reread them. But its a lot to risk, so the worry is up on the scale. lol

I know these heads or going to be nice. This valve and bowl job is at its max. I didnt get a flow rating though smh

The engines out. but I haven't started any work yet. Im at the point of decision making.

If you want to know what my budget is left.... Im wanting to get away with oil pan gasket and seals replaced.. Thats where I want to be. Very max...1200-1500 that's including any labor and work. but that's taking away from the accessories parts I need as well. I hope this is enough information to get some ideas going. I need all the help i can get.

btw---I haven't ordered the rockers yet.
cam specs are
11-432-8 - Xtreme Energy

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=444&sb=2
 
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