Low Compression N/A Build opinions
 

I am considering doing a N/A 454lsx engine. Eventually in a few years I want to do a F/I setup, but for the meantime a N/A N20 build will suffice.
This is my question, if I build the motor to something like 8.7:1 compression ratio for the future F/I build will this work fine minus the roughly 3-4% loss per compression point?
For example i see alot of 454lsx motors putting out 550rwhp, will my 3 pts of compression really kill around 60rwhp? I have heard other issues such as torque loss etc..
Plans are E85 tune, Big Cam, good flowing heads, 2" headers etc...
Whats your input?
I hate to lose all that hp, but pulling out the motor in a couple years and rebuilding for low compression doesnt sound like much of an option.
:chug:

E85 and low compression are not good bed fellows.

If it were me. I would build to about 10:1, run gasoline for now and when you get ready to boost the motor, switch to e-85. Optimal for neither, but compromises rarely are.

Or if you want run a smaller combustion chamber on your heads for now and when you get ready to boost the motor, pull the heads and replace with larger ones.

These are just options. You need to figure out hom much you want out of it after it is boosted. When you really turn the wick up, ring selection changes. Like I said earlier compromises are never the best for either of the things compromised.

Can you use boosted rings for non boosted applications? Or is that a dumb question? They prly wouldnt seat well i would imagine.

Might have to consider switching pistons at a later date and run close to 12:1 compression now....

It is not necessarily the rings, it is the gaps that have to be opened up when running FI or N2O.

I think ring material has something to do with it also.

But I have been wrong before.

I was talking to them and Wiseco has this piston available which could set you up in NA form at least. You'd probably need a real blower piston if you want to make big power later but of it's for a few years I would rather have the right pistons for NA during that time.

""The k462f185 piston has a -3cc .215 tall solid dome and nets about 12.0 with a 70cc head and the typical 4.185 bore/4.125 stroke. That same piston with the dome leveled off to flat top nets -7cc. That's an 11g difference in gram weight and wouldn't affect balance badly, but would drop the compression about 1/2 a point without affecting the strength of the piston.""

If not probably as Stang's Bane said you could do something that would be somewhere in between.




Starting with a 72cc chamber shouldn't be tough to find and would net a 11.9 ratio to start and 11.4:1 after the mill. There are quite a few people running boost w/ e85 at 11 to 11.5:1 with no issues.

How much boost have you heard that you can safely run with e85 and compression that high?

Oh I would drop the compression to maybe 9.5 to 1 for boost and run a different piston but I know you can run a little more that that with E85 although I would just keep that as detonation insurance and not go crazy on the boost compression.

From what I have seen, E85 is safe at 1.0 to 1.5 higher than gasoline at the same boost levels. ON top of that, it makes more HP out of boost due to the higher compression. If you have access to it, e85 is great HP fuel.

E-85 is about 103 octane. That particular piston is .250" thick in the crown and 2618 alloy. It will take Nitrous or boost well.

So cant i put in a real blower piston now? Ill be shooting it with plenty of N2O.

Yes you could you will just have lower power on motor with the low compression but besides that you'd be fine.

Ill take 480-500rwhp for now!