C-1 Intake valves

[Mike B.]

C-1 1961 with 2x4's 270hp Head # 3774692. I am not an engineer but I am told that it is possible to change the intake size of .172 and with machine work to the head to accommodate .194's. Is this possible??? Someone suggested it since I have to do valve job anyway. Any ideas on the subject other than not being truly original anymore. Thanks, Mike

[Terry D.]

Re: C-1 Intake valves

What are you trying to accomplish? A bigger valve by itself is not going to give you any noticeable power increase.

[Domenic T.]

Re: C-1 Intake valves

Mike,
I did that from 194 to the 202 and then did some porting and it worked out great.

I used my valve seat replacement tool to start the size then used a air grinder to port and get rid of the edges.

I'm sure it will work but it's important to keep all the ports the same when changing size. It took a few days to do it right.

I did it on 461 castings and then on the 400 SB heads holding my breath that I didn't get into the water jackets.

DOM

[Duke W.]

Re: C-1 Intake valves

1.94" is pushing it on 283 heads, but the 1.84" valve from 305s should work out okay on most. That's what Mike McCagh did on his 283/250FI cheater motor that got a Duntov.

If you really want "more power" massage the heads and use a Felpro 1094 .015" head gasket (as long as the block deck and heads are not warped) to keep from dropping the already modest compression ratio, which will probably run okay on regular unleaded. Since all the modifications are internal, no one but you and me and everyone on the TDB that you you have a cheater motor.

All this is in a Corvette Restorer article that was published prior to you joining.

Use the "send email" function to contact me and I'll send you a pdf of the article.

Duke

[Domenic T.]

Re: C-1 Intake valves

I think that Duke has the easiest way to go by doing some grinding.
If you look at the ports there is a lot of restriction and you can open them to equal the next valve size opening that is untouched.
We opened a set of 461 intakes and got better flow than the 202 intake that was untouched.
Don't forget the exhaust.

DOM

[Larry B.]

Re: C-1 Intake valves

The 1.850 valve is the way to go on the early heads. Get the valves with the .oo15 or .003 larger stems, then ream the guides and you have fixed the guides ware to.Take the heads to a shop with a Newen or Serdi valve machine .They can cut the seats to fit the valves then polish the bowls. Be careful on the short side radius bigger runner does not always mean more airflow. Don't forget the exhaust, if it can't get out it won't get new air in.