2.25 intake valves

boss · 11-04-2009, 10:17 PM

Has anyone out there put the bigger 2.25 int valves in there factory C heads?. I am wondering if the seats must be changed out?.

I guess what I am wondering about is the original version of the boss heads back in 1969 came stock with the 2.23 int valves, then afterwards they installed the smaller 2.19 int valve in these heads... So are all the int seats used in these heads still for the original design 2.23 valve?, I have not been able to find any info on this.

Kato Engineering · 11-07-2009, 01:50 AM

I do not understand what you mean by using the word "SEAT".,

or maybe it is just that I want you to clarify what you mean.....

since the original cast iron that the head was made out of was what the valve itself sealed against....

there was no "insert" of material as is/ what is done with a aluminum head,
allthough any common iron head can have a seat REPLACED with a STEEL or cast iron composite or even berryilum-copper type material seat....

some of the heads actually have what was referred to in the day as a "induction hardened seat area... this was able to be identified on a virgin new head by the bluish discoloration of the cast iron right in area under where the valve would seal....
and this process was done on EVERY iron head from about 1972...maybe 1973 and onward even today,....due to at that time there was the removal of a valve guide and seat area lubricant called Tetraethyl lead...aka..." LEAD " from the gasoline ...... also was the era of the first smog requirements and air injection pumps that also made the exhaust port and seat area carry more combustion heat and thus EROSION of the non hardened or replaced seat material...
most all of the "replacement seats" today will be of a material matrix that willl easily controll erosion due to the elevated heat and such of unleadded gasoline....
if your heads have a insert seat, then someone installed them.
if you have a 2.190 valve, and wanna put in the 2.250 units, then just open up the throat area in the head under the valve where the new one seals...
it is only a .060" change.....

I ran a legit original BOSS 302 head along with a number of 351 C and legit BOSS 351 heads that I employed both sizes along with even SMALLER valves ...

low lift airflow was able to be increased with the larger valve,...but ultimate flow was not gained unless the head was ported or changed dramitically...

in fact, .... I usually enlarged the exhaust valve and gained a bunch of torque / power with most of the work in the exhaust port...

pick the combo that I used a lot,..
either I shifted it at about 8800 to 9200,....and spun it untill it stopped gaining rpm,
or made it run at a measily 7400......

....next question...???

.

boss · 11-07-2009, 06:31 PM

Sorry I should have been more clear, looking to pick up another set of factory C heads here that I was told had new seats put into them with 2.19 valves, so if I can just open them up as is for the bigger valve that would make it easyer. For some reason I thought the original 69 2.23 int heads had some type of separate insert/seat under the valve, no wonder I could not find any info on this lol.

Now that you mentioned the exhaust valve that was going to be my next question on these 4V heads, anyone out there put bigger exhaust valve in and how big were they?, I think I heard someone mention a long time ago 1.80+?, how big can you go keeping the stock 2.19 int. I heard doing this was a good option to aluminum high port plates?.

The idea for all this was for a 7500rpm max stroker, no 9000rpm for me lol.

Kato Engineering · 11-07-2009, 10:30 PM

without altering and moving the valve guide spacing,
and using the original 2.190 intake valve,
the largest exhaust can be in the neighborhood of 1.95 / 2.00 inch
the valve head itself can in fact be larger than this, but then you get into a second issue with fitment because BOTH valves have to clear each other, during camshafts "overlap" period..... since with the cleveland design of the intake valve is canted inward, towards the exhaust,.... when the intake valve is open a certain amount, it can touch the exhaust valve when it is closing.....

unless it is a race deal, there is no need to change,..especially if you still are overall restricted by the KINK in the exhaust pipe in a fox or similar platform / shocktower / frame confinement issue and fitment of the required 2 1/8" pipe.....

the other issue

boss · 11-09-2009, 07:23 PM

Thanks for the info, Im not 100% sure but years ago a guy here told me I think, he put in 1.88"? exhaust valves in his 4V heads. Makes sence about only using big tube pipes for this mod. I think I will just stick to putting the bigger int valve in these heads when I get them.

BlackSDnotch · 11-10-2009, 12:29 AM

On the factory iron 385 ford stuff the guy that did my dove-c heads said to keep the total valve area under 4in to avoid valve clipping, I have no issues and I'm running 650ish lift mid 250 intake, a little more on the exhaust(with worked on dove-Cs w/2.25-1.74) and it runs good so far, but I have the car apart as I'm switching to a stick shift( I hate automatics). This is my first 460 based engine and theres alot of ppl here that know alot more than me but I've had some really knowledgeable ppl help me not make any bad mistakes on this engine as I can't afford to do it twice. My next endeavor is gonna be a 351c,I can't wait, Ive never built one and dont know much about them but Im learning, I'm pretty excited about it and I have a 20k mile 85 gt body that's waiting for it, it'll be a stick shift as well. Good luck on your project.
Jr.