How much difference in power/performance between the 2? The 265s are out of my price range for the fact that you have to upgrade to the custom Jesels, so I'll probably stick with the 255s, but just curious how much I'm sacrificing using the 255s as opposed to the 265s. This will be on a naturally aspirated 415 cu. in. L92.

What's the difference between the 2 heads? Why does the 265s required custom rocker arms and the 255s don't?

Is there any other head manufactures that I should consider over the ETPs?

 

Anyone?

 

The diffrence is in the .500" lift plus area. The 265's only out flow the 255's by a few cfm below that, but jump to 15-20cfm above that. High end flow ='s high end performance. If the car is severly limited by the intake, you won't see much diffrence, but on a car that is not restricted, you could see 15-20 hp on the big end. Don't forget that the Jesels aren't the only custom piece. You have to have custom Valve covers ($400), and longer plug wires as well.

The diffrence in the 2? One is 10cc's bigger than the other. The 265's require the rockers because the intake valve is offset to allow for a bigger valve, similar to the LS7. The 255's keep the stock valve spacing, so normal rockers work on those. No other manufaturer offers a head with the options that ET has right now. You could have some LS7's re-worked to flow in the range you want, but that would stack cost on top of a expensive head as well. Worked over L92's could be an option as well. Both heads would require work after purchase.

 

At .600" lift, the 265 40 heads put out 352 cfm while the 255s put out 349. That's a difference of 3 cfm. At .650" lift, the 265 40 heads put out 365 cfm as opposed to the 255s at 357. That's only a difference of 8 cfm.

What I meant by, should I consider another head manufacturer, was someone like Trick Flow, AFR, etc.? I know ETP heads are really popular, just wasn't sure if there was another head manufacturer I should consider over ETPs.

The L92 heads/L76 intake seems like its going to be a hot combo, but with intake not being readily available, its hard to consider it as an option right now.

 

Your right, I was looking at the 4.1" 265's. The only gain you would see by using the 4" 265's is if you planned on running a large solid roller that is over .700" lift. The 255's stop at .675" were as the 265's pull on up to .750"+. Even then, I'd still run the 255's because of the price. You can consider whichever heads you want. You can put extra work in to any of the above castings and make them do what you want. You can also change valve angles to make them flow better up top, but you'll likley sacrifice on the other end. You should make you a list of all heads being considered, along with there info. Then do some reasearch and write down the pro's and cons of each head. It'll help you to determine which one fit in your criteria and which don't.

 

ET all the way. this heads are the ****!!

 

Well I don't know what you consider large solid roller, but I had planned on a pretty aggressive solid roller. I had a T-ReX in my old motor/setup and that was big for what I had, being there was only like 60-70 thousandths clearance. So going from that setup to a setup like I plan, I don't know how much the lift is going to increase. I'm not a cam expert, so I wouldn't know how to choose my cam. I have no clue what range of lift its going to have, so its hard to say what heads I'll need. I guess if I can't afford the 265s and the 255s is what I'm going to use, then I need to have a cam designed around the heads and intake right? I know nothing about any other heads. Seems like ETPs is what is most talked about on here, so I just figured that's what's best.

 

You deffinatlly work on the cam last. Find the heads and intake you want, then find the exaust your going to run. All these things can play into camshaft selection. You can find a nasty solid roller to base around the 255's. You could also have the seat cut to 55* to pick up top end flow like I was saying earlier. Your not limited to what you read. Head companies have a gillion options to choose from and it's hard for them to list them all. Best thing to do is contact a few of your top picks and talk to them about what you want. They can clue you in on what all they can do to help you get exactly what you want.

 

Thanks a lot. You've been a great help.

 

I have a set of practically new Kooks stainless steel 1 7/8" headers with 3" collectors. Will that not be a sufficient set of headers for a 415 L92 solid roller? I was hoping to reuse them.

So if I can't afford the 265s and have to opt for the 255s, and if the cam ends up having more lift than .675", does that mean I have to forget about using them? Or, do that cut things you mentioned about? What's that all about?