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WIZ1 04-11-2017 09:13 AM

408 stroker build question
Hello Gentlemen,

My first post here but must admit I have been a lurker and reader for quite some time.

I am just a few days from ordering parts to make my 351W a 408 and I am curious to know if my parts list and conclusions will work like I think. Any insight or information will gladly be accepted with thanks.

To start the engine will be going into my aluminum fishing style jet boat replacing my old tired factory 240hp original. It is a low RPM engine but will hold RPM for quite some time 4500RPM max with most sustained runs around 3500RPM for a cruise speed.

I have acquired some parts already so they really must be used to take into consideration. I have a set of Ford Racing X307 aluminum heads with 58cc chambers 194/164 valves, a Edlebrock performer intake, Holly 650 carb and pertronix marine distributor with coil.

I plan on ordering this 408 kit from Summit:

Along with this cam kit:

According to my calculations I should be around 9.73:1 depending on what the deck clearance comes out. I want to be able to run regular 87 octane pump gas but if not I can live with it.

I am a little concerned about my cam choice however. I do not know what the stock cam is in the engine to start with as well. There is some issue with water manifolds and below water line exhaust that lobe separation becomes an issue. I do not want a wild cam at all as I do not need any "lope" per se' but would like a good improvement over stock. The complete donnor motor is from 1978 if that makes any difference.

Thank you for all your help,

GT350HR 04-11-2017 10:43 AM

Re: 408 stroker build question
Your combination should be fine. One word of caution, Boats have cold water pick ups for cooling the engine , not radiators like cars. Because of this the water temps are FAR lower than a car. This keeps the block from expanding as much yet the pistons are seeing temps like normal. The piston to cylinder wall "should" be increased by an additional .001 over what the piston manufacturer recommends for car use. With nearly double your former HP , you should get to that "secret" spot quickly. 9.7 is perfect for 87 octane. Keep the timing around 32-34 "total" , no vacuum advance.

WIZ1 04-11-2017 04:47 PM

Randy, thank you for the response. As you mentioned I had already considered piston expansion. I run a 160* degree thermostat and with a closed loop cooling system it is always right there.

I needed another Ford guy to confirm I was not overlooking something on my build. I was thinking 350ish HP when done looks like you think perhaps a tad more?

Once again thank you sir!

GT350HR 04-12-2017 08:54 AM

Re: 408 stroker build question
My 408 is pretty similar . Compression is the same , cam is close , heads the same , I am using the air gap intake with a 735cfm CJ carb. Mine made 480 hp and 520 tq on 87 Arco gas. You should make 400 easily. Nice work. 1 hp per inch is an easy number with today's parts.

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