smart to build a high compression hyper 306?

[IndyBlk5.0]

Well its been awhile for an update.... so... bought 3 core radiator, sn 95 dual speed fan... should work well... as for engine, short block went to the machine shop... originally was going to use my same pistons and everything (standard bore) until i found that cylinder number 6 and 7 were off .012 from standard bore... So scratch that cheap idea ... So..... i plan on building a high compression hyper pistoned 306... What would be the best compression ratio (preferrably highest) that i could go that would still be streetable and a daily driver? I was thinking 11:1, but now think probably 10.5:1 is better, what is your thoughts? Remember, this is a budget build... i am paying a tad over 1000 for a compretely redone shortblock (timing chain oil pump etc...) built complete... Block is getting decked... heads milled... blah blah... So my question, is it safe to do a high compression hyper pistoned 306? if so, what is the highest compression ratio you guys would go with a streetable daily driver motor? Thanks!!!

 

[kndyblucapri]

yea u can get hypereutectic pistons up to 11.1:1 compression those pistons can take up to 400 hp and u can get a set pretty cheap but your compression could vary depending on your heads the machine shop or who ever is gonna build the engine can figure it out with the set of heads u got.

 

[IndyBlk5.0]

stock ported e7's, they are getting milled too along with the block is getting decked...

 

[kndyblucapri]

summit sells a set of keith black pistons with a .200 dome for 222 bucks u could find them cheaper speed pro sells some cheap pistons

 

[IndyBlk5.0]

yeah im not going to run any type of boost hense the compression, no need.. breaks things...

 

[90stangLX302]

I thought this might help with figuring out the compression
http://www.prestage.com/Car+Math/En...tors/Calculate+Compression+Ratio/default.aspx

 

[IndyBlk5.0]

i will have to ask my machine shop what the specs are on my block etc... might find that out tomorrow... still need a good answer, what is better to do? 10.5 or 11:1 on daily driver?

 

[IndyBlk5.0]

bump

 

[eric88gt]

I would stick with 10.5:1 compression since you're going to be running cast iron heads. The gain in power from 10.5:1 to 11:1 wouldn't be worth the added hassle of dealing with the strong possibility of detonation.

 

[90mustangGT]

I've heard that 11:1 is pushing it, especally with iron heads. Stock heads are 61cc chambers, while most aftermarket heads have different combustion chamber volumes, so if you went in the mid 10's in compression now and then got some of these heads you would be near 11:1.

A question I have, what kind of increase in tq and hp would he see by replacing the worn factory shortblock with a new, higher compression shortblock assuming everything else stays the same?

 

[eric88gt]

If you go from 9.0:1 to 10.0:1 you probably wouldn't gain a lot of HP, maybe 10-15 at peak. You would however fatten up the torque curve before and after the peak HP and TQ occurred. You would also notice a little quicker throttle response with the higher compression motor.

Oh and yes you'll be fine with 10.5 to 1 with hypers. Just be careful with detonation, hypers won't take as much as a forged piston would.

 

[giddyup306]

Stock heads are 61cc chambers,

They're 64cc.

 

[billetunderwear]

The irons won't dissipate heat as well. They will be more detonation prone. Just keep that in mind.

 

[custom90GT]

heh, im running about 11.2:1 compression on Hypers and GT-40s (yep, the orig iron ones). Just add some Tolulene every fill up. I wanna get out of it though and run AFRs, but I'd like to boost compression up to 11.5:1 when I do that.

 

[IndyBlk5.0]

well i told my machine shop to build me a 9.5:1 motor, he said any higher i would have problems with ping on pump gas.

 

[Silentst2000]

well i told my machine shop to build me a 9.5:1 motor, he said any higher i would have problems with ping on pump gas.

I'm not trying to start a flame war but what allows the RSX type S to run 11:1 compression on pump gas? Why couldn't we use colder plugs and an MSD ignition to help with pinging at 11:1? Or a lower temp themostat?

I don't dig Honda's. I'm just trying to figure out the enemy works.

 

[NKau]

well i told my machine shop to build me a 9.5:1 motor, he said any higher i would have problems with ping on pump gas.

Good move. If you ever drive any place that only sells 87 or 89 octane, your engine will thank you.

 

[IndyBlk5.0]

anyone know what the stock compression ratio was for our stangs? and did the forged pistons compared to the hyper pistons in 93 make any difference in compression between the two? He is putting 9.5:1 pistons in it, but my heads have been milled twice and my block got decked, so i could be seeing more of a 10:1 compression range... Question - how much hp would a full point of compression be worth? Thanks

 

[HemiChallenger]

It all depends on what kind of pump gas is readily available near your house. 93 is the normal here, 91 is normal in other states I know. People who live in the city by me, and have a pump with race gas will always build high as hell compression engines because the fuel is readily available. I wouldn't push it any higher than 10-1 or 10.5-1 with any sort of common premium pump gas.