I've been looking at a 427 using a C5R block (4.125 bore, 4.0 stroke)
I can't seem to find any flat top pistons for it.
Do I have to order custom?

C5R block 4.125 bore
Flat top pistons (.005 out of bore)
AFR 76/75 cc
.041 gasket

For a 11.44 SCR

Any ideas?

 

Why not just get some flat tops with valve reliefs and use a smaller head cc. AFR 225 heads are more like 72cc from what I know. It cost me an extra 200 dollars to get a custom set of pistons and a long wait.

 

Trick is I would like flat tops and stay at or under 11.5:1
This would be street driven with up to a 200 shot dry, so no valve reliefs.
Hmmm,

72 cc
.045 gaskets
.005 out of hole
4.125 bore
4.0 stroke

= 11.67 SCR (I could live with that)

So custom it might be (most likely)

Ross or Diamond ??

 

I don't see what a -2 cc valve relief would do that would hurt performance. With the -2 cc you would be at 11.4-1 and could have some extra room for a high lift cam.

 

Carbon build up and hot spots, and flame travel distortion.
I any case, most of the off shelf pistons I'm seing fot a 4.125 bore are like 16>18cc reliefs. (on the websites anyways).
Regarding the cam, it will be relatively mild (but the biggest I can fit with very comfortable PTV tolerances)
This will not be a max effort set up, but a reliable, non sleeved Alum 427 with LS1 tuning tech already on market (HPT).
Something I can stick in my C5 to rival the new Z06 and Vipers, not to mention some modified Porche and AMG Mercs.
450>470 rwhp and 420+rwtrq NA
Yet all this has to sound as close to tame as possible.
Basically a monster Stealth

 

I know those reason are the hypethetical theory behind the flat top preferrence, but I really don't believe it has that dramatic of an effect. My friend runs a -2cc valve relief piston on a 383ci with a 250 single stage shot right off the line with no issues and good timing. Most of the off the shelfs will be a -16+ because most of the stock heads are in the 60-64cc range. I see what your trying to do, but I think a smaller cc head with a dished piston would work just as well as a flat top with high cc head. I have run both and am now using a -19cc dish with a 56cc head. Will be trying out some 50cc heads soon. You should have closer to 480+ torque with that combo even with an average size cam. I put down 490rwtq with a 242 single pattern cam on a 422ci.

 

I already have the AFR 225's.
They were supposed to go on a 382/383 but I'm re-evaluating the set up judging that I'm whipping 383's at the track with my puny 346 and a 200 shot dual dry.

Although sleeved would be more cost efficient, I can't deal with any issues such as Evans cooling system and God forbid leaking or walking sleeves.
so C5R block it is.

I'm kinda like a Stealth addict, I'm thinking of putting in a G5x2 in there on a 114.
G5X2 specs - 232/240 .595/.608 114 LSA

Am I nuts ??

 

yes good luck with the setup

 

Don't know what the max bore of the c5-r block is but if I was you I would take it to just under the limit. If you like stealth and want to make hella power the biggest motor you can make is your best bet. It costs no more money to run a 4.125" bore verses a 4.155" bore. As far as pistons go I wouldn't worry about valve reliefs or dishes causing any flame propagation problems. One need only look at the engine masters motors to understand that the small combustion chamber and dished piston is the way to go. With a 200 shot I'm sure any piston you have will stand up just fine to that level of the juice.

I've got a 38cc chamber with a 4" crank and 4.155 bore going in my motor. I'm using custom turbo pistons and will at some point spray a similar if not smaller shot to my motor, I was assured it would be more then up to the task. Give the guys at HPE a call, I think you'll be suprised what you can run given a competant engine builder.

Good luck with your setup.

 

use ET heads with small chambers and dish/reverse dome piston. 11-degree heads rule.

 

That would be a good alternative, (yet to be fully tested).
But as I said, I already have the AFR 225 72 cc.
I'm curious however to see what Tony "Blue Pill" Mamo will put in his 415 Cid camwise, he is not a "bigger is better" guy, His specs should be interesting.

 

Whoops. Didn't read that part

Just put a stock LS7 cam in. That should be pretty stealth.

 

If I were you I wouldn't buy a c5r block. World products should have a block out soon, and will be much cheaper. That cam will work if you want near stock idle quality, but you'll be leaving a good 30 hp on the table. I think the old mti s1 was pretty tame at 244 on a 112 or 114 lsa and .612 lift.

 

A 244 duration cam in a 427 is like a 222-224 in a 346. A 232 would be like a 214-216 or so.

Remember, a 427 is quite a bit larger than a 402/408, or the difference is about the same as to what a 402/408 is to a 383.

C5R can be bored out to 4.130" max.

Why do you want 11.5:1 CR? You have 98 octane there. I'd run flat top (I'd go with CP Pistons--hell of a strong piston for boosted/nitrous apps) and mill the heads down to 68cc for 12.5:1. Even with a dry system. If you are going to do a C5R block with a thick AFR head, run a dual stage dry shot with a progressive controller with a separate propane fuel system like the Viper guys. Run a dual 200/150 stage that way.

 

Guys, all this is well, BUT...

I do not want a max effort motor.
I want a DD, tame as wolf in sheep skin, mellow idling with tons of trq below the curve. (and I mean tons).
The nitrous is just icing on top.

C5R is available yesterday, I'm not gonna wait ions for a new product to come out. (been there, done that)

Also, 4.125 bore is plenty, plenty room to rebuild in the future. My C5 is a keeper.

I've seen 408 with a 224 cam and trq output was higher than Hp. something like 420+ hp and 440 trq
That iron block propulses a stripped Nissan Patrol 4x4 with a 200 shot into the low/mid 10s. That guy drives it daily with the aircon on.

That is in my book.

Just a question:
I know there is a few Special Edition 427 F-Bodies, done by specialised dealerships. I'm sure their cam is nowhere 240+ durations.

anyway TTT, which would you think is better ROSS or Diamond for pistons.
(Once we answer this then it is time for rods, {very light ones})

 

I like the diamond better than ross. They were lighter, and the rings that came with them are really nice high tension. I liked the oil rings also. My JE pistons are even lighter, but I had to wait 6 months to get a custom set. That mti 244 grind is a really tame cam in a 427. You could go with the lg cam if you want like a 750 rpm idle. You can get up to a 4.160 bore on a c5r. A 4.125 will definitely give you plenty of meat for a future rebuild.

 

Predator, just curious but why spend the money on a C5R block. Re-sleeved LS2's are alot cheaper.

 

Yes I agree, (another but),
Being so far away, I can't deal with walking sleeve issues or leaking issues or Evans Cooling issues.
C5R block goes through 3 screening at least to ensure all is done right.
An LS2 is resleeved.
It is a big expense, but at the long run, it is worth it IMO.

 

check out the ls7 crate... im sure you've read about it... but it is tame and loads of power with nice interneals and heads....

just for thought... c5r you need a new intake... either sheet metal or ITB

 

Only if you use C5R heads, I'm putting AFR 225's. It will have FAST 90/90 or BBK SSI (if those sackapusses ever bring it on the market {I already have a 80 mm BBK TB})

See I want an easy 1>1 swap, no harness, pcm etc.... Just plug n play.