Ya I did it ran like 4300rpm and was doing 50mph with a 21p the rest I am going to dig out papers I have and be back soon thanks and srry was half a slep when I stared on this form.

So, your new motor in front of a 1.5 geared Alpha, ran 4300WOT at 50mph with a 21P ?

A 21P what kind of prop ?

BTW: Awaiting what kind of prop, that's basically what a stock 260HP 350 will do with that gear and prop. or little better.

comp cams part /12-240-4 cs xm 270h-12 grindcs xm270h 12 valve lift int .480 exauust .489 duration .06 tappet lift 270 int open 286 exaust close lobe lift .3200 int lobe lift .3260 exaust lobe separation 112.0 i dont know about the piston but i know there flat head piston eldebrock carb 600 cfm eldebrock performer intake holly fuel pump with all these modification still cant get over 50 mph why please help me

Should not have made a gear change, but regardless your not making power.

Who put it together? I ran into something like this with a friends boat. He did a cam swap and it was installed retarded. So even with giving advanced ignition timing it ran like a dog. Also, did you do an exhaust upgrade? Just wondering.

Do you have a fuel pressure gauge on it? I have also seen engines run out of steam because the fuel pump was getting weak at WOT.

My migrain is back.

Please, I wanna help - I beg you - normal communication please.

About your cam - with 350cid's you really need 9.5:1 or preferably more to make it work well.
Also, stock exhaust will have a hard time with that cam.

The XM270H has 226, 236 at .050" / 112LSA and if installed to Comp's specs, only installed on a 110ICL.
It'd s lot of cam for an other wise mild build.

Too much cam for what you probably have, but have yet to answer those other pertinent questions.

You need to answer exactly what else you have for us to further help.

Impossible if you don't know what you have for us to see if it's an engine build issue or a possible tuning or engine health issue.

It would be like me asking everyone why I haven't scored Pamela Anderson yet.

Because you have respect for your dick and a desire not to get a big ole antibiotic shot in the ass??

Hell no !

.554/.557 On that cam....I think an exhaust upgrade is a must. That thing can't breath

Not on the XM 270H for small block. It's under .500"

Anyway, cam is way wrong for a mild 350 build.

Your right, sorry. I looked up xm270h and I found a big block cam with that grind # on the comp website.