Sbc 350 opions

[delawarerick]

Warm 350 autolite 25's(medium heat) ok,thermostat 125 140 160, timing to start with? Sierra 25-40 good oil or synthetic blend? Upgrading to a dual plane intake manifold spacer needed?thanks Rick

[Dave S]

Warm 350 autolite 25's(medium heat) ok,thermostat 125 140 160, timing to start with? Sierra 25-40 good oil or synthetic blend? Upgrading to a dual plane intake manifold spacer needed?thanks Rick

HAAHAA Replace with a Hemi.......

[delawarerick]

Somebody must know small blocks want this thing right for the keys run. thanks Rick

[wired247]

Maybe a little information on the motor? 350 SBC covers 40 years and more than a hundred iterations.

[Dave Strong]

Maybe a little information on the motor? 350 SBC covers 40 years and more than a hundred iterations.

For sure, what heads, cam specs, ign. type, etc.

Dave

[mrcrsr]

Rotella 15 w40 for starters if is raw water cooled 140 degree fwc is 160 degree. If motor is stock 32-34 degrees timing (total) plugs are ac Mr43t if short reach mr43lts if long reach

[delawarerick]

Thank you it is a warm 350 30 over short duration cam stainless valves 3 angle cut just a nice engine when tested had no idle but from 3-6k was very fast. I think I have a vacuum leak and not sure of fuel delivery. Picked up a new dual plane manifold and I think an electric fuel pump will aid in delivery of fuel. This is the longest I have been off the water and want to make the keys run. I have a cross over cooling system but since I need to run alot of no wake zones I am going back to a circulator pump.

[Zoomba]

Thank you it is a warm 350 30 over short duration cam stainless valves 3 angle cut just a nice engine when tested had no idle but from 3-6k was very fast. I think I have a vacuum leak and not sure of fuel delivery. Picked up a new dual plane manifold and I think an electric fuel pump will aid in delivery of fuel. This is the longest I have been off the water and want to make the keys run. I have a cross over cooling system but since I need to run alot of no wake zones I am going back to a circulator pump.

I seem to have luck with the stock spreadbore manifold, which is dual plane. SBC 5.7 runs great at idle, have you rebuilt the carbs and adjusted the choke, is it a Merc Rochester Q jet setup? I run a stock gm w the t bolt 4 ignition, I would try putting a vacuum gage on it but first change wires and ignition components out. Don't think changing manifold will do much, unless the gaskets are leaking. I would go thru the basic tune-up first, and look for 18-22" vacuum at idle. set timing on conservative end of stock specs ore even a couple degrees less, these things like to detonate with pump gas as they are heavily loaded.

In my experience carbs, for whatever reason, seem to like a rebuild every 6 seasons or so, both holley and rochester. Can't figure out why ever but they always work better afterwards.

I would replace cap and rotor as well. Stock fuel pump should be fine. my 5.7 merc has run well for the last 20 years with a closed cooling system on a 21' wellcraft merc alpha.
Dave

[Zoomba]

Actually wife hates my 2 stroke stuff and loves the SBC boat. Rumbles and chugs @550 rpm all day long, kinda like sailing..a Harley!

[NHGuy]

Shoot carb cleaner around suspected leak points. If the motor runs better you found your vacuum leak.
If it's not that, it could be in the primary side of the carb.
Here's how to do it.
Get one of those spring-flex carb adjuster tools with a few tips, they cost $10.
Warm the engine, shut it off. Gently seat your idle screws then back them out 2.5 turns. Start it & set idle to 675 in neutral, which is like 625 in gear. Turn each mix screw in til it stumbles, then out til it sounds wrong then back to 1/3 up from the stumble. Do both sides, keep the engine speed down during all this.
If it just won't idle, you could have clogged jets or idle tubes. Once you have the top off the carb the jets can be removed with a straight blade screwdriver and cleaned. The tubes require a ground down deck screw to remove, but nobody pulls them so they could easily be your culprit.
Also test the vac break/choke pulloff. Just push it in and put your finger over the hole. If it springs back out it's no good and a vacuum leak.
If you end up needing idle tubes I'd call Cliff Ruggles at cliffshighperformance.com, he will send em right out. Good guy.
I agree with fresh plugs and wires, 32 to 34 total timing. Which is 11 or 12 BTDC at idle on most Mercruiser Thunderbolt IV systems.
After it runs right check your plugs again, might need less idle fuel, I always seem to.