Building a 408w for towing

[BLstangin]

oh wow so it gained 4 ft lbs and 35 hp with the bigger head?? That's awesome! Looks like maybe I should use the bigger head then? what do you think?

[Carnut1]

Last dyno had 10.5 comp. 9.4 is too low with that cam. The bmep was sad.

[Carnut1]

It needs some work. I like the bigger heads with more compression and a smaller cam on a tighter lobe center.

[BLstangin]

wonder how much compression I could run safely on pump gas and still tow without worrying about rattling the thing? That's my biggest concern. It has to be safe to. so did it kill it bad with the 9.4:1 and the bigger heads?

[Carnut1]

wonder how much compression I could run safely on pump gas and still tow without worrying about rattling the thing? That's my biggest concern. It has to be safe to. so did it kill it bad with the 9.4:1 and the bigger heads?

I would say yes. Look at my 355 curve ran it on 87 since I built it nearly 20 years ago. Now that I live in Florida I will run it on 93 due to the insane heat.I will try to do a few more sims for you tomorrow.

[BLstangin]

thanks I think I will go with the bigger head what compression ratio are u running?

[Carnut1]

thanks I think I will go with the bigger head what compression ratio are u running?

My 355 is about 10:1 with iron heads

[Walter R. Malik]

oh wow so it gained 4 ft lbs and 35 hp with the bigger head?? That's awesome! Looks like maybe I should use the bigger head then? what do you think?

Probably ... at WIDE OPEN THROTTLE.
Are you gonna drive this or race it and always be at wide open throttle ...?

[BLstangin]

im gonna drive it walter but you know how it is, to much is never enough lol! I have a tendancy to build everything radical and rev it up and I'm having a hard time restraining myself when I run a 210cc head on my 302 but of course I shift that at 8000 rpm! Your probably right and smaller is probably better in the case. IDK?

[induction apprentice]

The shorter duration cam is probably a no brainer. The 205 isn't that much too big for a 418 incher. If we could split hairs. I bet a 195 afr would size well on that and still give good cruise and throttle response.

[wyrmrider]

Back off at least one size each- this is not a "wide open" heads up build
you need velocity as well as flow

[Walter R. Malik]

My 408W uses X305 heads, dish piston for 9.7cr, Eddy air gap , 735 CJ 428 carb and the Ford F cam with a 1.7 Cobra bolt down rocker. No mods to the heads except a REAL valve spring ( 130 seat pressure) and ti retainers. 482 HP and 523 TQ on 87 Arco gas with 34*s timing. It's an animal in my daily driver '67 Ranchero. 12.40's at the track by adding a drag radial only.

The later X306 heads come with 64cc chambers, Comp #26918 BeeHive springs and 10 degree locks.
That "B303" camshaft is a single pattern - 284@.006" - 224@.050" - .300" lobe lift - 112 separation; ground 107 intake centerline.