whats a good compression ratio if you plan on a Supercharger

[tyler93]

Im going to be building a 331 stroker motor for my mustang. I Chose 331 instead of 347 becuase i here the 347 wear down very very fast and actually that the rod puts pressure on one side of the piston and pushes it agains the cylinder wall.

Anyone have a 5.0? Is that true sounds like it could be. But anyway i want to be able to have alot of straight motor that i dont have to depend on the charger. I plan on running 9-10lbs of boost.On a vortech s trim.

whats a good compression ratio for this setup. Iam also wondering if i shouls go for x-303 cam b 303 cam or e 303. Or something else? what heads should i use.

 

[RangerFabWorks]

typically, 8:1 or 8 1/2:1 is ideal for a turbo or a supercharger. but with only 10 lbs of boost you could probably run 9 1/2:1 and just run a higher octane to prevent detonation. you should be good.

 

[Zachalanche]

Wear aside there is an advantage to having the bigger stroke. When stroking an engine the larger the stroke, the shorter the piston rod. the result of this is on the downward stroke the piston acelerates away from the head quicker which reduces the chance for detonation. on the other hand I have heard good things about the 331. I think a supercharged 331 would be an excellent engine.

as for boost I would agree with blackwidow.

 

[mentalbreakdown00]

whereas I would disagree here and say 10:1 and no more than 10 lbs of boost.

 

[RangerFabWorks]

whereas I would disagree here and say 10:1 and no more than 10 lbs of boost.

you could do 10:1 but the fear of detonation becomes more of an issue. 9.5:1 gives you some comfort room, plus he has the choise of running more boost if he likes.

 

[JP85prerunner]

I have had good luck with the 347 and it is my stroker of choice, but the 331 is a good choice. What really matters is what combination of parts you chose. A well planned, matched cam and set of heads are important. When boosting an engine I have always found that a fairly mild cam yielded the best results. I have had good success using the E303 cam but found it difficult to tune. The B-series suited me well a number of times.

A stroked engine loves boost.

I would not recommend going over 9:1 on the compression. Mostly because heat is the enemy, and I always wanted my engines to be long lived and reliable. also I didnt want to limit my self on gas grade. If you haven't already I would consider some engine bracing, such as an engine craddle for the bottom end, and cross deck supports for up top.

Hope this helps and happy building

 

[mentalbreakdown00]

None of us have ever built an engine with less than 9.5:1. The better you make it run without the boost the better it will run with it with tuning. Yes detonation can be a problem with over 9.5:1, but I ran my 351/ 408 for 5 yrs with 11:1 and 12 psi. Now, I did have to run 93 octane, had to have 10.5 non-w tires and stock suspension in my class too.

 

[shadetree]

When stroking an engine the larger the stroke, the shorter the piston rod.

Stroking requires a longer rod, not shorter.

Keep the boost under 8.5. You can get into trouble going higher if the tune gets off. Lower compression will allow you to raise boost, and experiment if you need to.

You want cams with narrow lobe centers, else all your mixture gets blown out the exhaust.shady