mulalleybs

My forged 427 ls7 is no longer among the living, so I am debating a new short block. I can't decide if I want to go with the 440 (4.000x4.185) or 454 (4.125x4.185).

Is there much of a gain in hp/tq from one to the other? gains over the 427?

I was wanting to go with ERL and their dry sleeved block. It seems like their quality is top notch and the longer sleeves would be better I'd imagine. With the longer sleeve would there be a wrist pin issue and premature part wear associated with stroker set-ups?

I don't do anything specifically. I did a few drag runs and autocross races with my old motor. I wouldn't ever be doing any type of race full time, but I would like to be able to do any type of racing if I felt like it.

6XX rwhp is where I'd like to be for the time being. Maybe if I ever got bored later down the road I would add something to it.

Brett

atljar

Bigger bores allow your heads to breath easier as the valves arent as shrouded by the cylinder. So on a NA motor, thats the way I personally would go if Im not immediately concerned with piston weight differences

(Edit, Sorry I had the bore/stroke flipped. I now see both options are the same bore size)

WhiteDiamond

I know it doesn't bother some on here, but I didn't like the distance between bores getting so close on the 4.185" bore with my ERL build. Stayed at stock stroke and a 4.155" bore: 434.

double06

I have a 454 ERL I would go with that. Or you could go with a smaller bore like guy said above and do a 447. Do not take crank any longer than 4.125 on stock deck height. The biggest thing I saw going to the 454 was the tq at the low end. You will get a few hp on top but the tq down low is more of the difference. I have like 500-510 ft pounds at like 3,000 rpm - at the tire. Is there anything salvageable from the 427?

Millenium Z06

My reasonings too, ERL 4.155 and 4.00.

4.185 leaves too little room between the bores and too little room for future rebuilds. ERL said they didn't really like the 4.125 stroke and recommended the 4.0 to slow the piston down, reduction in side loading of the piston and better rod gemoetry.

Whis9

Sub'd

Michael_D

Those are very good reasons, and why I often reduce stroke. 377 cid is one of my favorite SBC's.

Those arguments are also why I'd keep the OEM Ti rods whenever possible.

Da Z06

Specially if its an NA build!

Millenium Z06

Ti rods and the stock LS7 reciprocating assembly are very underappreciated. A forged LS7 bottom end will cost you 20+hp over a stock LS7 bottom end. The only bad part is the LS7's thin sleeves.

RamAir972003

Look at my build to give you an idea......let me know if you need help...the most you can stroke a ls7 4.130 so just see what you want personally I would just use a 427 block they ate underrated....

Da Z06

....and the glass pistons.

Michael_D

Pistons are not a weak point. They are actually a very nice piece, and probably one of the best OEM piston I've ever ran across. They are not forged though....

This engine was not designed for boost, so a forged piston was not needed. One thing about forged pistons, is they need more clearance. Not a big deal, unless it's a passenger car that might be owned by persnickety individuals who don't want to hear piston rattles/knock while the engine comes to temp.

The cylinder sleeves are not what I'd consider thin. I've seen them thinner. It is the alloy they were manufactured with. It is brittle and prone to cracking with the presence of detonation.

Unreal

Agreed with Michael.

Walls are not much thinner than ls2/3. Pistons are great for what they are designed for. The fact that they don't take much boost is more a function of the great flowing heads and displacement than weak parts.

Stock displacement, stock crank, stock block, and focus on the top end and rest of the car if you want a fast NA z06 IMO. Without getting into crazy race car stuff (tall deck center balanced solid roller, etc. )

Frans96ss

Neither.... Ive never seen an NA car make more power with bigger cubes ... a CORRECTLY build 427 will make all the power you need.

Unreal

Only exceptions to that IMO is the crazy builds like CMS car, or the vengance car that are crazy high dollar setups.

mulalleybs

Very informative thread guys! I appreciate the insight.

Frans96ss

Yes.... If you have something bigger than a 427 and it doesnt make 640+ its build wrong. It should make 1.5hp per cube when built correctly IMO..

MTPZ06

Out of curiosity what failed on your forged 427, and how did it fail?

mulalleybs

spun bearing and the cylinders are out of round. 4.175 would correct that I'm told.

Josh B.

I would keep the factory crank and rods unless you are planning higher hp levels. If you decide to resleeve and install aftermarket pistons, I researched several piston offerings. The most appealing for was Mahle, the 4032 material is a nice intermediate between stock cast Mahle and the traditional 2618 forgings, although Mahle also offers a 2618 piston. The Mahle standard ring pack is nice, and is even available with a 1,1,2 thin ring pack. LS7 pistons are very good for what they were designed for. They are quiet and run with tighter tolerances than comparable forgings, resulting in better ring seal and less "rock" as the piston leaves BDC. The Ford Boss 302 roadrunner engine as well as the 2015+ Coyotes use a very nice 4032 Mahle piston from the factory. Lucky guys. Too bad their oil pumps shatter.

I stayed stock bottom end for my personal LS7 build. I initially planned to use either an RHS block with a larger bore or a ERL block with a similarly larger bore. So now I just installed ARP Rod bolts in the Ti rods. I took the money I would have spent on sleeving/machine shop costs/pistons/balancing costs and applied it elsewhere in the combo. Time will tell if my approach leads to better hp/$.