318/390 Stroker

[716PKRT]

I'm thinking of pulling the 318 from my 1972 Satellite Sebring and building a 390 stroker. Has anyone built one before? I would use one of the available stroker kits with a 4.00" crank and 0.30 over pistons. Seems like a fun little project. If anyone has input to some decisions like cam, heads, intake manifold, do's, don'ts, I appreciate it. Also any experiences with the motor like how it pulls, revs, low end torque, etc. Thanks!

 

[davek]

hope this helps https://www.hotrod.com/articles/mopp-0409-318-engine-build/

 

[Kern Dog]

I have a 318 sitting in my shop that runs but smokes. I have thought of doing a 390 build as well. I have nothing to put it in, it would just be an engine that I'd have, waiting for a car....

 

[HawkRod]

I am in the midst of building a 340 stroker. With the big bore of the 340, it will displace 416 cubic inches.

I didn't want to dramatically increase the cubic inches without addressing the heads. Since an engine is essentially an air pump, you need a lot more flow with a lot more cubic inches. I have elected to go with aluminum heads that flow much better than the 340 ported heads I have. In your case, assuming you have standard 318 heads, they would be very restrictive. I would highly recommend a good set of aluminum aftermarket heads. If not, then you should at least open up the intake and exhaust valves on your heads to the 340 valve sizes (2.02 and 1.60, if memory serves). You should port the heck out of them too. Getting airflow into and out of the now 390 engine will be critical to make power.

I am trying to do my 340 stroker build on a bit of a budget. My engine will be for street use on an air conditioned car, so I am building it for low end torque and reliable power with good low end vacuum. I purchased a Scat stroker kit with .030 pistons. It has a cast crank and hypereutectic pistons. It is still good for way more horsepower, torque and RPM than my street engine will see. My engine target is upper 400s for horsepower.

Overall I am happy with the kit so far. They seem to be nice components. My only gripe so far is the rods were slightly over spec so I will need to tighten them up.

I have not yet purchased my heads nor made a cam selection. This is still up for discussion with my father-in-law. However, we have decided that the cost of roller rockers is not worth it - I will go with a flat tappet cam (again, I am doing this as a budget build). The flat tappet will work fine, just need to be sure we break it in carefully.

Finally, I think stroking these small blocks is really cool. My engine will go back into my 1973 Road Runner. With aluminum heads and intake, it will make for a lighter, more nimble car that will still have lots of power!

Good Luck!

Hawk

 

[ACME A12]

I went this route with the engine in my wife's Swinger. .030" 318 block with a 4.00" arm. Turned it into a little torque monster. I used forged, dished KB pistons, a SCAT crank, and 340 con rods. 3418915 J Heads w/ 2.02" intake valves. Comp XE268 cam with 1.6 roller rockers. It's a fun little package. My guess is that it would make a small block in a B-Body a helluva lot more fun as that is a lot of car for a little 318 to pull around.

 

[YY1]

Interested in this as well.

I've got an LA roller complete but with bad rings.

I've seen 390/392 kits.

Wonder the cost effectiveness with machine work vs buying a 408/416 crate engine?

 

[716PKRT]

hope this helps https://www.hotrod.com/articles/mopp-0409-318-engine-build/

Interesting reading. Thanks.

 

[716PKRT]

I am in the midst of building a 340 stroker. With the big bore of the 340, it will displace 416 cubic inches.

I didn't want to dramatically increase the cubic inches without addressing the heads. Since an engine is essentially an air pump, you need a lot more flow with a lot more cubic inches. I have elected to go with aluminum heads that flow much better than the 340 ported heads I have. In your case, assuming you have standard 318 heads, they would be very restrictive. I would highly recommend a good set of aluminum aftermarket heads. If not, then you should at least open up the intake and exhaust valves on your heads to the 340 valve sizes (2.02 and 1.60, if memory serves). You should port the heck out of them too. Getting airflow into and out of the now 390 engine will be critical to make power.

I am trying to do my 340 stroker build on a bit of a budget. My engine will be for street use on an air conditioned car, so I am building it for low end torque and reliable power with good low end vacuum. I purchased a Scat stroker kit with .030 pistons. It has a cast crank and hypereutectic pistons. It is still good for way more horsepower, torque and RPM than my street engine will see. My engine target is upper 400s for horsepower.

Overall I am happy with the kit so far. They seem to be nice components. My only gripe so far is the rods were slightly over spec so I will need to tighten them up.
View attachment 1073257

View attachment 1073258

I have not yet purchased my heads nor made a cam selection. This is still up for discussion with my father-in-law. However, we have decided that the cost of roller rockers is not worth it - I will go with a flat tappet cam (again, I am doing this as a budget build). The flat tappet will work fine, just need to be sure we break it in carefully.

Finally, I think stroking these small blocks is really cool. My engine will go back into my 1973 Road Runner. With aluminum heads and intake, it will make for a lighter, more nimble car that will still have lots of power!

Good Luck!

Hawk

Thanks for the info. Mine is a budget build too. I'm definitely planning 340 heads, but will be 1.88/1.60 (340/360) heads. We'll see how that does and then go from there in the future. Just want to do something different and play with it, probably improve it over time.

 

[Babyblue66]

Thanks for the info. Mine is a budget build too. I'm definitely planning 340 heads, but will be 1.88/1.60 (340/360) heads. We'll see how that does and then go from there in the future. Just want to do something different and play with it, probably improve it over time.

Even a 340 reproduction cam would run nice in that. Would be smooth and make plenty of torque, easy on the stock rockers too. With 4 inch stroke it definitely could handle more duration than a stock cam. Just depends on how you want it to run. If you're on a budget, summit sells a decent cam cheap (6901). I used one in a friend's 340, runs really nice. Comes on pretty hard as rpms increase. So in a stroker it'd have more torque and I think it'd still pull some rpms.