Would putting 2.02in 1.6ex valves on aluminum L98 heads be worth it? I asked a porter for his input and here is what he had to say: 'HOWEVER, with the LT1 and L98 chambers, you aren't going to get much improvement from going larger. The chambers are fairly small and even after fully porting them, they are shrouded (with the 1.94/1.50 valves). So, as I said, I can do it but I don't suggest it.'
What do you guys think?

 

i'd open the ports up before i worried about bigger valves. if you have to buy replacement valves anyway consider the manely pro flows, or race flows, whatever they're called

 

Im getting the heads fully ported and I asked the porter if he could install bigger valves and he gave me that reply. I was plannig on having the Manly proflos installed if I went bigger or not. So will it be worth the extra money?

 

Did you ask the guy doing the work if he could unshroud the valves? I have a set of 305 HO heads with 2.02 in 1.60 ex installed that have been unshrouded. According to the guy that did them he says they have found you need at least .050 in clearance between the valve opening and the wall of the bowl. He said it makes the heads around 62cc instead of 58cc. He also says they have flowed them and got between 20 and 30 more cfm of flow from adding the bigger valves. Of course the originals are 1.84 in intake.

Anyway these are all just things I was told. Maybe it was just a sales pitch. My engine definently has more power now, but that could be because of the 45 ci. increase to the 350, the 270HR cam and Hedman headers.

Also I chose to get bigger valves instead of porting because it was about half the price to have done. I'm sure the porting would have been the best option if I had already had the 1.94 in intake valves.

 

depending on how you define worth it (yeah my last name is clinton) and if you opened up the chamber around the valve a little there's just about got to be a gain to be had. the point is what are you willing to spend for how much of a gain.

 

PP,

Not to offend or challenge anyone, but I've ported LT1 heads. If your porting person is comparing L98 heads to LT1 heads as similar, she needs to do a little more careful measurement and observation. A much more fair comparison would be between the LT1 and Vortec heads, which seem to be very similar in design. The LT1 heads are substantially different in port runner design from the L98 and most other SBC heads. They also respond very well to careful port reshaping and larger valves.

One thing to consider is that the size of the valve is only part of the equation. The real number to study is valve free area. If your porter knows that your cam is about as big as it can be (around .600" lifts), or that the profile is so small that such a small increase is not worth the cost and effort, or that the duration is so short that "size doesn't matter", she may already have calculated that increasing the valve face diameter isn't going to gain anything in your situation. She may also have considered you other intake tract restrictions, so I'm not saying that you necessarily need to find a new port person.

However, making a broad statement such as that is ill-advised, since there are a lot of LT1 heads in the world that are flowing better with port work and valve replacements than with the stock configuration, mine included. As for the shrouding, any competent machinist should be able to performn some judicious flycutter work and/or grinding to alleviate any valve shrouding from 2.02/1.60 valves in a 350 chamber. There's a lot more room than you might guess. There are also other methods to improve flow around the valve margin areas, so that shrouding becomes less of an issue.

Before the port person gets crazy on your heads with a grinder, you might want to do a little more homework, lest you end up with a big pile of aluminum chips and worthless heads.

 

The largest valves that can be installed in L98 heads, are 2.00 & 1.56 unless you change the seats. Do you really want to go to that expense?

 

I did not know this. This is supposed to be budget performance so I will prob keep stock 1.94/1.5 and use the money for suspension or something. Another question, summit wants only $120 for the Manley Street-Flo valves and he wants $250, if he won't let me buy the valves separate and him install them should I still get them? I currently have stock valves from the zz3 with a stated 2000miles on them.

 

I'm glad Vader pointed out the difference between the LT1 and L98 heads. They are totally different animals.

There has been sucess in the past from cutting 2.02/1.60 valves in to 1.99/1.56 It definitely isn't worth the money to open up the seats in the heads because there isn't a huge performance gain from doing so.