Big intake valves
 

I just read it is possible to use a 1.72” intake valves and 1.6” exhaust.
I thought 1.6” on both was max.
My 41 Merc blick is rather ported but I’ll seen bigger and its still has the 1.5” valves.
I can’t see on my block how a ring that wide can has a material under in the runner ?
Here is a picture on 1.72-1.60.

Re: Big intake valves
 

You need to use a block that does not have valve seat inserts fitted

Re: Big intake valves
 

I thought 1.6" fit with the stock seats after a modern valve job. Is that not correct?

Re: Big intake valves
 

They still take quite a bit of cutting to get from 1.5 to 1.60 and put the seat in correct location. Seems I have been doing this once a week lately.

Re: Big intake valves
 

I have owned this one block for 35 years out of an only Bonneville car ported to the max 3.375 x 4.250. It has 1.775 intakes and 1.675 exhaust. The valves an almost touching each other.

Re: Big intake valves
 

Wow thats a cool set up !
I think I might stay at the 1.5” as it might be issues.
Just checking.

Re: Big intake valves
 

I have just built 3 in a row with 1.6 intakes and 1.5 exhaust.

Re: Big intake valves
 

So bring it up to 1.6 from 1.5 on intake might be a idea.
So are you replacing the std rings doing so ?
Its 0.05” radially open up.
I has little hard to beleive its worth it as this ports is not ideal.
I guess the port work is more important than inlet area on valve.
But I cant tell as no experiance.
All I know my bock is really way bigger than std.
What get me worry is 1 cylinder has a crack welded up, its really nice done and comes from the exhaust port ( classic crack place )

I heard a Bonneville no blower not bored over or stroked and both at 1.6” really pirted up and tri-Y headers and .520” roller cam made 400 HP at sealeval.
Sounds tuff but car was fast.
If I go over and get my carbs to Uncle Max I hope visit him talk FH.

Re: Big intake valves
 

There is a lot more to good breathing Flathead then just big valves….
A roller cam with high lift and very good ports are needed.
Then small displacement and the engine will make power at 6k rpm , nothing below 3k and
Idle at 1500 rpm . Sound like the perfect street engine….. :-)

Re: Big intake valves
 

I would want to see a dyno slip with those HP numbers before I believed that the engine described above made that much power. Seems like a bench racing tall tale to me.

Re: Big intake valves
 

Me too :)

Re: Big intake valves
 

Hank wrote
I heard a Bonneville no blower not bored over or stroked and both at 1.6” really pirted up and tri-Y headers and .520” roller cam made 400 HP at sealeval.
Sounds tuff but car was fast.

Ron says
There's no way that kind of power can be made with a normally aspirated stock block Ford flathead burning gasoline using 1.6 valves. If it was true where's the results in the form of a time slip?
Ronnieroadster

Re: Big intake valves
 

Yes it sounds incredible ( my bad notes mentioned it )
I never been a dyno dude, but spend time there most doing nothing on ET ( in my stockers )
Then jetting will nver be there anyway and headers can't realy either be told and then its the dyno settings, dyno room, air inlet etc etc.
This is 'just' numbers ( for me )
Don't take this to serious, but the car ( Merc 49 ) was anyway going over 150 MPH 30 years ago at the salt and transmission and rearend eat allot of that HP.

Re: Big intake valves
 

I've got some ocean front property in Arizona .......

Re: Big intake valves
 

Everyone ever used a dyno know a dyno is a dyno.
Scoreboard to tell.

Re: Big intake valves
 

I suspect the car that 3W Hank is referring to is Kenny Kloth's Mercury sedan that raced at Bonneville in 1991, you can see the car at the 30:23 mark in this video: https://www.youtube.com/watch?v=zFIF7bQuv_s


Everything I have ever read about the car is it just cracked 140, and was running a very breathed on 267 cubic inch flathead. It was much more modified than the statement above would indicate. The engine was discussed a bit in this thread and was estimated to make 220 to 240 horsepower, which would still be an impressive feat for a naturally aspirated flathead.

Re: Big intake valves
 

38 coupe, that's correct.
Out of topics but fun.

I has not seen the timeslip but record might be 140 but I think he went over 150, but whatever 150 or not, 400 HP or not this guy I take out my hat for.
A very clever guy installed a 55 mm fatcam for big profile and made own roller lifters and over .500" in lift, thin rings and milled and tested own chambers and this is 80's or early 90's.
He was over 6.000 RPM and this was not bored or stroked.
This is a very heavy car and aerodynamics is not really there and take that to over 7.000 foot and over 100 F and bring on not HP friendly transmission and rearend and 'say' it went +150 ( as I heard ) it can be calqulated what HP it need.
As I said I'm not a dyno guy and I know a Swede that builded a Chevy BB low compression street motor in a Master Challange category ( he won ) many years ago, but he died in cancer after that and he always said a dyno is just get a number in apples or pears nothing more. I agree.

But back to a FH capable doing that speed one can calqulate HP, even at 'only' 140 MPH, I'm impressed and HP must be over 200 but not maybe 400 even in a dream dyno.