Another question on 440 heads

[motorhead440]

If you have your valve seats enlarged for the bigger valves, do you need larger valve seats? or will the stock seat accomodate the upgrade?

[Richard Reardon]

Motor,

I'm not 100% sure on this, but seeing no one else has responded yet, I'll give it a shot!

If you're talking about 440 heads where the stock intake is 2.14" and you're going to 2.19", I don't see why you'd need new seats, assuming the stock ones are okay to begin with. There is only 5 thousands (.005)difference so you only have to take off .0025 on the seat to make 'em fit. (Remember, you're taking "meat" off opposite areas of this "round" hole so you must divide by 2. If you took .005" off the entire circumferance, your hole would be 10 thousands bigger overall)There must be some "rule of thumb" (weird phrase!)that machine shop people are probably familiar with where the line is drawn between use as is or install new. I don't know what this is.
On the other hand if you were talking a 360 head w/ 1.88" intakes and you wanted to go to the 340 head valve which is 2.02" I'd guess you'd have to buy new seats as well as valves.
I'll guess you can go with the stock seats in this instance.
Let's see if one of the more knowledgable guys respond to this.

Richard

[Old hippie]

If you are refering to machining out the old seat and pressing in new ( ie...stellite) seats then the answer is no.....maybe. Do the valve seats have damage to them due to excessive valve seat degredation (fancy word for wear or compression) or just too many valve jobs? If that is the case then the machining process for the bigger valves will likely eliminate that damage and you will be good to go. If you have the heads down for this modification then you should have them pocket ported. Its not all that expensive and you will pick up a lot of very usable flow over a bone stock set of heads. Remember one thing. Remember it well, not only you but the others who look to us veterans for some advise. Simply installing the large valves with out doing any other work except enlarging the seats will do nothing for flow. ZIP, ZILCH,NOTHING,AND NADA!!!!!!!! You will have spent money for nothing to paraphrase Dire Straits. The thing that makes the big valve modification work is the additional work done below the seat. The last set of bb heads I had done, my machinest did a 70 degree throat cut down into the bowl quite a ways Thest heads were using stock valve sizes. Then I just spent about 15 minutes per chamber blending this cut into to the bowl area. I also spent another 15 minutes blending the guide boss. This work is basicly the same work that is done by using the mp porting templates except for the guide boss blending. The performance increase was astounding. These heads went on a very mild 400 that I had swaped into my '78 dodge pu. I had to swap cams to take advantage of the heads and jet the hell out of the carb to boot. My daughter had a real good time playing stoplight bingo with all these wanna-be cowboys and thier cameros (this according to the local police). Guess I should not have told her all the old "war" stories. Sage advise from The old hippie hisself.

[Christopher]

Again,correct advice from Richard and the Hippie hisself.The exhaust seats do not need to be replaced when enlarging valve size.The 70 degree cut is a MUST.Also do not use the M-P porting temlates when using the oversize valves on a big block,as you will really screw them up.Do it to it like the Hippie sez,and you can't go wrong.

[motorhead440]

Richard, the valve size i'm referring to is the 2.08, 1.74. Theses are the stock sizes to the best of my knowledge. I would like to upgrade to the 2.14, 1.81 this winter. The heads are 69 440, so i'm gonna say they are 906's. I have a 73 400 sitting hear that i could use the heads off of, but i'm not sure if they the 452's. Given the option of modifying either set, which is the best from your experience? I don't think that either set has been cut. The 69 set has only 59,000 miles on them, while i don't know the wear on the 73's. Thanks for the replies, MOTOR