I finally picked up my 454 (.030 over). I ran it down to the engine shop and we looked it over. The pistons in it now are TRW L2465's, but with my GMPP aluminum rectals (118cc chamber), would end up with 8.5:1 compression. That's no good. I'm going to have to go with a new piston, and figured I may as well get some serious compression out of it. I've got to order them in the next day or two. I would like to go with 13-13.5:1. What would you folks recommend for a compression for a strip only motor?

My question is this: Obviously the SRP pistons are a great piece, light, able to handle the force of high compression, etc., but they are expensive as heck. Is there another brand you folks could recommend to me that is a little easier on the pocket book, but would work well for me?

Here's the motor as it sits...

Motor:
-454 cid block .030 over
-GM forged steel crank
-GM forged steel rods
-pistons???
-Lunati solid 402A6LUN 255 263(@ .050), 288/296, 0.612 0.630, 110 LSA, 3000-7200 rpm’s
-Cloyes true roller timing chain
-Melling oil pump
-GMPP rectal aluminum heads
2.19/1.88 Manley severe duty race valves, 11/32 stem
-Crane Gold roller tipped rockers
-Crane pushrods
-Edelbrock Victor Jr. rectal intake
-Moroso seven quart oilpan
Moroso windage tray
CSI SFI approved dampner
SFI approved flex plate

Sean,
I used SRPs in my 540. Awesome product! graemlins/thumbsup.gif
With all the other good stuff you're putting in that motor, I'd spring for a quality piston. Worth every penny, I believe I bought mine here...
http://www.flatlanderracing.com/srpjebbcpistons.html

I can never remember...what's the bore/stroke on a 454?

Originally posted by SS_Sean:
I can never remember...what's the bore/stroke on a 454? 4.250 x 4.00 Or in your case if it is bored .030" over,...
4.280 x 4.00
BTW, BRC makes a quality, lightweight piston

Please consider ROSS Racing Pistons!!

I went with them in my 496 and to me, they are nice looking, spec'ed right for my application and of good dollar value...

pdq67

2465's are dome pistons, no? :confused: The catalog I have says 10.8 with 119cc chambers.

http://www.flatlanderracing.com/trwchevy454.html

That's what I'm showing, also. I'm going to call this guy back and find out WTF...

SS_sean, Somebody seems to have given you some bogus info. The 2465+.030 listed in your chart has a compression ratio of 10.86-1 with a 119 cc combustion chamber which should work fine with the listed camshaft and 93 octane pump gas. The only drawback is that the TRW piston is quite heavy as is and most good aftermarket pistons will be 100-150 grams lighter.

P.S. The correct TRW piston number is stamped on the piston top so you can verify that someone hasn't sold you the wrong one by mistake. It should have a .226 dome according to your list.

Sean,you don't want or need that kind of compression.

Heres your pistons:
http://store.summitracing.com/partdetail.asp?part=TRW-L2465F30&N=120 4294925232 4294922410 301942

Specifications:

* Bore: 4.280 in.
* Stroke: 4.00 in.
* Rod length: 6.135 in.
* Compression ratio: 11.31:1 (100.9cc heads), 10.68:1 (106.9cc heads), 10.44:1 (109.4cc heads), 9.78:1 (116.9cc heads), 9.61:1 (119cc heads)
* Head type: .226 in. dome
* Oversize: .030 in.
* Ring size: 5/64 in. top/second ring, 3/16 in. oil control ring
* For use with open chamber heads only.

I'd use 'em,and spray the snot out of it :D

The TRW L2465F-30 has a .226" dome which has a volume of 25.7cc.

Using this volume, and with the piston .020" in the hole, 118cc head, .041" gasket the SCR calculates out at 9.80:1.

Originally posted by mr 4 speed:
Sean,you don't want or need that kind of compression.

Why wouldn't I want that kind of compression, if the cam I'm selecting needs it?

Here's a little something I found out. The Edelbrock, aka: GMPP heads have an oddball chamber shape, and don't work with standard higher compression pistons. SRP designed a special dome so the valves won't smack the dome. The compression would be roughly 12.7:1.

http://www.jepistons.com/pdf/2002-srp-chevy.pdf

I think 9.8:1 is way too low for what I'm doing with this motor, and the cams I'm looking at to get me to my goal won't run well on such low compression.

Again, I'm not interested on whether the motor will run on pump gas, or not, but am interested in getting that compression up there to squeeze some performance out of it.

I called Lunati and spoke with one of Harold's henchmen, nice guy. He and I talked for about a half hour and we both came down to the 402A6LUN or the 402A8LUN, depending on if I want a lower end power or higher end power.

I don't think that cam needs 13 to 1 or 13.5 to 1 compression.Remember,this car will probably weigh about 3400 lbs w/o a driver..and done right,it will could be a 10 second terror.I don't know too many cars that run that kind of compression (13 to 1) that runs in the 10's or even high 9's..what is your ET goal again? did you say this was already a low 11 second motor with amild cam and 781's or 049's? :confused:

I can't see you could justify that kind of compression in a 10 second or 9 second car,unless its some wacky small block and weighs nothing :D

Believe me,I'm not knocking You,just not sure what you're trying to accomplish with that kind of compression.

Originally posted by mr 4 speed:
I don't think that cam needs 13 to 1 or 13.5 to 1 compression.Remember,this car will probably weigh about 3400 lbs w/o a driver..and done right,it will could be a 10 second terror.I don't know too many cars that run that kind of compression (13 to 1) that runs in the 10's or even high 9's..what is your ET goal again? did you say this was already a low 11 second motor with amild cam and 781's or 049's? :confused:

I can't see you could justify that kind of compression in a 10 second or 9 second car,unless its some wacky small block and weighs nothing :D

Believe me,I'm not knocking You,just not sure what you're trying to accomplish with that kind of compression. The only SRP piston I can get for my heads (Edelbrock/GMPP's) are the 12.7:1 pistons I linked above, as I understand it. I just got off the phone with SRP and verified this as fact. I HAVE to run this piston (12.7:1 on 118cc chamber), or I have to have JE make me a custom setup.

I believe the 9.6-9.8 compression TRW's I have are too low for the cam I'm going to run, and a high 10's car. I'm looking for some help in getting a combination together that will work well.

As far as weight, you may be right about 3400#, I'm not sure. I suspect it would be 3400 with me in it, however. These Malibu's are lighter than Chevelles, and I've done stripped everything I can out of it.

As far as what the previous owner ran with this motor, I'm not calling him a liar, but I have a hard time seeing low elevens with the setup he had. He claimed 11.14@125 with a relatively small hydraulic.

You're a sharp guy, Chris. I trust you. Wouldn't you say 9.6:1 is a bit low for a goal of 10.xx@125?

Originally posted by SS_Sean:
Wouldn't you say 9.6:1 is a bit low for a goal of 10.xx@125? Sean,
I've gotta agree with Chris.
Most of the Chevelles (and MC) I know of around this board that are running in the 10.XX @125 range are 10.5 CR MAX and weighing 400 lbs more than your estimated 3400#.
Wouldn't it be simplier to just cut the heads down to say around 110 cc?

Sean,I think if you decked the block,and got closer to 10 to 1 or even left it as is compression wise you won't be disappointed with the performance.The weight of the car will be a the ultimate equalizer.Look at other peoples's 10 second combos,and notice what they have for compression,its not that high,11 to 1 tops (mostly up to about 10.7),and they aren't light weights either,as most A body big block cars thats are running 10's weighs at least 3700+ w/a driver.
remember you have a g body-they are lighter graemlins/thumbsup.gif
Todd G's Malibu/G body is a one impressive combo,and remember,he's running a 414 BBC and not 13 to 1 either.I don't own a 10 second car,but I know enough people who do and have seen enough to understand whats needed to get at least in the ballpark.Remember less is more :D
And thanks for the kind words.
(musta been typing the same time as Bill)

Done:

9.8:1 it is.
I just ordered a 402A8LUN, springs, retainers, Manley severe duty valves, SFI Balancer, and flex plate. Grand total: $1,000.

This a race only car, correct. You will not believe how much harder a 13to1 motor runs than a 10to1. If you don't want to run race gas use 10to1 but it will be much faster with 13to1.

each point of compression is ???%%% I can't remember but its miniscule compared to other mods that can be done. It doesnt hardly seem worth it to run anymore than 11-1 to me,unless you're running alkiehaul smile.gif

6% per point of compression is what I've been told...

With aluminum heads you can always figure about one full point of compression over cast iron heads, to make up for the thermal loss of the aluminum. For a strip only motor, 13.5 to 14.0 is common for a hard runner. 12.5 is about all you'd want with iron heads. If your going to spend the money for race gas you might as well go the max on compression.

Originally posted by SS_Sean:
6% per point of compression is what I've been told... =
Sean,
6% is a pretty good number when going from say 8 to 9 but as you go up in compression it drops off pretty rapidly. It is not linear problably more like 3-4% from 10 to 11 & 2-3% from 11 to 12.
None of this is written in stone except you will make more power with more compression if the fuel will support it period.

I gotta go with Mike Feudo on this. If it is a race car put some compression in it.

Are you getting the A6 or the A8??
The A8 cam is in my opinion just too big for 9.8 compression.
I think it would be much happier at 11.0 & even better at 12.0

Originally posted by SS_Sean:
I just ordered a 402A8LUN, springs, retainers, Manley severe duty valves, SFI Balancer, and flex plate. Grand total: $1,000. http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=2;t=024446

This has been an adventure. The best I can figure is that with these heads, GMPP sig series 118cc chamber, 2.19/1.88 rectals, the chamber design presents a problem to most pistons. SRP makes a piston that's 12.7:1, and JE makes a 10:1 pistons for these heads, and that's about it. I ordered the 12.7:1 pistons, since that's about the only choice I have. The TRW's won't work, I'm being told by SRP. The dome doesn't have a cutout to accomodate the centered spark plug in these chambers. The 10:1's are too low, and the 12.7's too high, for what I'm trying to do. Not to mention the fact that my engine builder called and said the cylinder walls would need to be bored to .060 over. The TRW's weren't going to work, regardless.

As far as cams are concerned, I didn't talk with Harold directly, but the cam suggestion I was given by his henchman, Steve, is the 402A8LUN, and that was giving him a compression figure of 12.7:1. He seemed to feel this cam would operate just fine at this compression...I understand what you're saying about the A8 looking too small for that compression.

This situation really kind of ticks me off. The compression I really need is about 11:1 from what you guys are telling me, and I would agree wholeheartedly. There are several advantages to and 11:1 compression. I got these heads at a great deal, $900 new, never used, but if I'd have known then what I know now, I think I would have re-thought my purchase. Good heads, but very limiting on pistons selection.

So, that's where I sit. I'm going to have 12.7:1 compression. There's one thing for certain, this thing will make power, and lot's of it. I have never had to deal with high compression motors, so other than really expensive fuel I'm not sure what to expect.

I would imagine tuning, spark plug indexing, and timing will now become critical, in order for this thing to run properly. I invision that this will be an extremely touchy engine.

I don't think it will too bad. With the right fuel, it will be like most any other performance engine. Comparing 9.8:1 with 12.7 is a 2.9 ratio increase that is almost a 12% increase in power. Give 500 to start with that's almost 60 HP more with just the compression increase. You'll love the sound of a high compression engine. It will let you know when the exhaust valve opens :D .

Sean - I agree with the Mikes (Feudo and Wolfplace) regarding the compression. IMHO, 10.5 - 12.5 is no man's land... why waste race fuel (although I am well aware of the difference in cost between VP-Red and VP-C25).

But, I would also be careful about my expectations regarding percentage power gains with compression increases. If the compression is less than the cam and heads want, then increasing it may give you a decent power increase. But a shyt motor with two points additional compression is still a shyt motor.

Who said I was building sh!t motor? That's pretty ugly, and really uncalled for. :(

Originally posted by SS_Sean:
Who said I was building sh!t motor? That's pretty ugly, and really uncalled for. :( i dont think thats what Roger meant. seems to me he was making a general statement that a 2 point increase in compression isnt going to make a noticable difference.

like he was saying a 2 point jump in comp isnt going to wake up an already poor combo. (not saying your combo is poor).

Whoooaa there Sean. You have grossly mis-interpreted my comment. I wasn't referring to your motor.

Brandon hit it on the head. Compression isn't the cure all if the rest of the combination doesn't match.

I've been particularly careful to ensure I have a matching combo from the rear end all the way to the headlights. I've picked each and every part very carefully, not just throwing away money...Are you seeing a problem here I don't?

I'm not adding 12.7:1 compression by choice, however. As I said, I'd be perfectly happy with 11-11.5:1, but don't have a choice in the matter.

I am going to check with my builder and see if I can have the pistons milled down a little to get some cc's off the dome. This was suggested to me by a friend of mine.

oh...just as a side note, I called the comp cams techline and asked for a recommendation, based on my combination. They suggested:

275/284 (@.05), .745/.746, 108 LSA solid. :eek:

i doubt my opinion is worth much, but why build a combo that requires race fuel when it isnt needed to achieve your goals?

i would do anything i could to get the comp lower, that way you can run pump gas.

about the pistons, some piston domes are hollow (lighter) and cant be milled. if you do cut them make sure they are solid dome pistons.

Sean - No, as I said, I wasn't referring to your motor in any way. My intent was just to keep anyone who happened to read this thread from thinking that they could increase the power in their motor (regardless of how good or bad the combo) by 50-75 hp just by increasing the compression 3 or 4 points.

BTW, given the rest of your combo and the 12.7 cr, Comp Cams recommendation is about what I would expect from them ( I think it's a touch big, but not too bad).

Roger that. I'd say that cams a touch to big. I'm running a stock GM forged bottom end, and that lift is pretty ugly. A .6xx lift is fine, but .7xx just isn't needed at my level, even though these heads would flow it.

just run good gas, sounds like a nasty engine. What rpm are you shooting for peak power at? I bought SRP pistons for my 454 after looking at what was available, there really wasn't much to pick from in streetable compression ratios for me either.

Well, I hate to say it, but I ran the numbers through Desktop Dyno, and here's what I've got:

Engine
RPM Power Torque
2000 178 468
2500 233 489
3000 292 510
3500 360 541
4000 430 564
4500 494 576
5000 545 572
5500 577 550
6000 584 511
6500 579 468
7000 548 411
7500 510 357

HP drops off pretty rapidly from there. Peak HP built 6000-6500, which is good, since I should be running through the traps at 6500 using a TH400 and 4.30 rear gears I have for my 9", with my 28" tall M/T's.

The stall converter I have my eye on is a B&M 3800 stall to get me into peak torque. As we know, they aren't stalling at what they claim. If it was stalling at 3500 or slightly lower I would still be introducing roughly 500lb's to the rear out of the hole, and could ease into it a little more.

I know, I know, you folks are going to say, 'don't buy a crappy converter,' but I wanted to get a cheaper converter to start with, figure out what the combination is really going to do, instead of bench racing, and then get the EXACT converter I need later. Probably something like a ATI 8".

Anyway I should be able to get high ten's, low eleven's with a 3400lb car, if I can get it to hook.