Hey guys, I dropped my block off this morning, getting tanked and magna fluxed. I told him Id probably go 30 over when/if the block checks out. He said he needs the pistons because not all pistons are the same and may be off a hair. So I need to order some pistons right away! Probably 30 over, I dont remember the differences between flat top, and domed, all that stuff. This is a street engine, 454 Id like 500HP out of, we have 93 for high octane here in CA...

My heads I just bought are all machined and surfaced, new valves, springs, tanked, very nice looking large oval closed chamber heads that were for 396/427 I beleive. Heres some stats the guy wrote down; Valves I- 2.065" E- 1.720" Dia. Umbrella style seals, single springs, Force at 1.900=110lb and force at 1.350= 270lb
Not sure what kind of cam either, something real thumpy, my last cam was so mild I didnt like it at all, it was a small block with a 268 comp cam, no fun at all....

Well basically I need help! Pistons, need to order today graemlins/beers.gif Thanks guys...

I am no expert by no means but you would probably be well off getting some advice from the machinist doing the block work. After he cleans it he will be able to measure and find out if 30 over will work. Quite possibly with him doing the work he can offer parts at a reasonable price also

Also try not to get into too much of a rush and really think this thing out. That way you don't end up buying parts that you can't use and you end up exactly with what you initially wanted

..wait until your machinist bores the block.
I didn't order my pistons until my block was bored as well.
What size combustion chamber/and or what is the casting number off the cylinder heads?
..that will determine what pistons to get as far as large dome,small dome.
Put it this way,if you have closed chamber heads(101 cc's)a flat top will give about 8.9 to 9 to 1
a .100 dome will give at least 9.5 to 1
..you really don't anything bigger than a .100 dome w/small chamber heads
If you have open chamber heads (119 cc's)
a flat top will give you about 8.0 to 1
.100 dome at least 8.5 to 1
.270 dome will get you 10 to 1 or so

Hope this helps..

Don't order the pistons until after the block has been bored. Never can tell when he'll come across something unusual in a bore or 2 and need to go bigger. You'll also need to know either the casting number or chamber size or both. I haven't seen enough difference in skirt sizes with any of the JE, Wiseco, SRP, Ross or Arias pistons I've used myself or seen used by my friends in the last few years.

These are my heads, they are 100cc:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7938324469&ssPageName=STRK:MEWN:IT

Well it makes sence to wait until its bored to get my pistons, but it also makes sence to buy pistons then bore. Pistons arent always exactly the size they are noted as are they? Say I end up .60 over, will a .60 over piston definately fit. He said there not always the same and coule be like a hair off.

Phil

im no machinist but he should be able to bore the block and finish hone to the proper size when the pistons arrive.

you need to get an idea of what camshaft and rpm range you are looking for. this will help decide what compression ratio to shoot for, which will allow you to choose pistons. it kinda sucks being stuck with a set of pistons and having to choose a cam around a set compression ratio.

also, depending on the cam you choose the valve springs that are on the heads may or may not work. so you my end up having the springs changed.

like i said in one of your previous posts, i think you should mimic Chris's combo as close as possible.

he uses closed chamber heads, .100 dome pistons (H426cp i believe) and a 280/288 lunati hydraulic cam(one of udharold's).

assuming a standard deck height, 100 cc heads, .030 over, stock head gaskets (.038-.041 i think) and .100 dome pistons, you should be 9.5 to 9.8:1 comp. which would be perfect with the 280/288 cam and 93 octane. you could install steel shim head gaskets (.022 thickness i think) and get about 10 to 10.25:1 comp. which is what Chris is running i believe, also with premium.

the H426cp pistons are $226.00 at www.flatlanderracing.com (http://www.flatlanderracing.com) .

My machinist did the same thing, pistons first-then bore. The machine shop I used has a reputation for building high end engines so I trusted him. Worked out well for me. My machinist said if he bores first he will not warranty his work as he wasn't given the proper measurements to work off of. I do believe, if I remember right,Keith Black was the piston that is generally found the furthest off for him, but I am no machinist so I just go by what he tells me. Good Luck with your new engine, Jeff

I think your right Brandon, its a nice sounding combo. Im going to go back to that post and find it. I wonder how that cam sounds smile.gif Im just affraid of a mild sounding cam again, I hated the 268comp on my small block, didnt sound anything like I wanted. I really dont want to change my springs, those pistons look like they'd work perfectly. Is that part number for .30 over?

The L2399 TRW is the forged equivalent of the H426 - .095 dome compared to .100 dome. Once the machine shop checks the block decks, they may recommend resurfacing the deck. depending on the amount of cut, you may be able to use anywhere from a .022 head gasket or may need something in the .039 to .041 think. Either way, you will not want anything over .100 dome with those closed chamber heads. Either of the above pistons will get you to about 10.0/1 - 10.25/1 CR. which is more than enough to support most of the cams you will want to look at.

Thanks GRN, I read a little about the L2399's Alot of guys here at work told me to get forged pistons, which I guess is good for running NOS, even though im not and wont, they still said its a good idea and will take a better beating if given. I know the forged are more expensive though, if I can get away with the H426CP I will probably go with those.

I know a guy here on the list (hint) who has a set of the 2399's in .060 over that I used to own that were for sale?
:)
Ron

Isnt that compression ratio a little high for stock heads and pump gas? Maybe some flat top pistons? Or what if I went with this piston we're talking about H426CP which has a .100 dome right? At .30 over thats making Chris 10.5, if I use that same piston and go 60 over does that drop the compression? Id feel better at 9.5 on stock heads, no?

Haha, yeah Ron, Chris emailed me smile.gif Its in concideration

Originally posted by pnutkemist:
This is a street engine, 454 Id like 500HP out of, we have 93 for high octane here in CA...

....highest I ever see around here is 91. Been that way for a few years now. 93 is long gone, bud. Where are you getting 93 at?

I got it out my A$$... typo smile.gif Sorry

Good news! The block checked out fine and it's clean. Score, now I can sleep well. He said .30 over would be fine. Thats my choice unless someone convinces me otherwise. I was looking through some books of compression ratios and I came up with these:

TRW/ Speedpro H109CP (30 over)
with my heads they say 9.80 Compression
1 relief & a .90 dome
These are hyperuetectic

You'll need the pistons before he bores and hones the block, The set of SRP pistons I bought measured perfect/all the same, but another set the supplier had for a smallblock measured to within .003 of each other which he was returning. My Son's 327 speed pro pistons measured identical/ all the same, but years back I also had a set of speed pro's that were different =or- .002. So buy your pistons and have the machinist size the block for the set you get. Hopefully you'll end up with a matched set with all pistons measuring the same making it easier. Bob

You might find this link to be useful 540 horse pump gas rat (http://superchevy-web.com/tech/0307sc_490rat/) graemlins/thumbsup.gif

pnutkemist,those small domed pistons and closed chamber heads are a nice combo.Anywhere from .090 to .100 domes are fine with your heads.
My compression is higher in my motor,as my block is decked and my pistons are about .008 down in the bore.

I've got a set of 7/16 inch dot rods for sale if your interested. Brand new.

Mmm, that 540 kit is nice. I didnt see any pricing though. I ordered the 30 over pistons H426CP. I want to keep things kind of simple here, everyone says stay with old fashioned parts, manual fuel pump, things like that. Which I think is a good idea, for now... Not all old fashioned, but just easy to manage parts. I think Im going to use my stock rods. 6.135?

Your stock 6.135 rods are all you'll ever need..just use ARP rod bolts.
Good move on the pistons too graemlins/thumbsup.gif

The pistons you select will give you a compression ratio based on the combustion chamber size of the heads you have. If you do infact have closed chamber heads you MUST use a piston suitable for closed chamber heads. If your heads are aluminum you can probably go as high as 11 or 11.5 to 1 and still run pump gas, if your heads are cast iron then I'd try to stay around 9 to 1 or lower. Otherwise you may be looking for detonation problems.

Keep in mind on your cam selection that a lumpy idle will cost you low end performance and wold require a higher stall speed converter on an auto car. If you have a stick then no problem.

You should be able to get close to your 500 HP goal with aluminum heads, a comp ratio of 10 to 1, a cam in the 600-650 lift/230 to 240 duration range, a decent aluminum Performer RPM dual plane, or Victor single plane intake, and an Holley 4150 or Speed Demon 850 cfm carb. Good luck.

The pistons you select will give you a compression ratio based on the combustion chamber size of the heads you have. If you do infact have closed chamber heads you MUST use a piston suitable for closed chamber heads. If your heads are aluminum you can probably go as high as 11 or 11.5 to 1 and still run pump gas, if your heads are cast iron then I'd try to stay around 9 to 1 or lower. Otherwise you may be looking for detonation problems.

Keep in mind on your cam selection that a lumpy idle will cost you low end performance and wold require a higher stall speed converter on an auto car. If you have a stick then no problem.

You should be able to get close to your 500 HP goal with aluminum heads, a comp ratio of 10 to 1, a cam in the 600-650 lift/230 to 240 duration range, a decent aluminum Performer RPM dual plane, or Victor single plane intake, and an Holley 4150 or Speed Demon 850 cfm carb. Good luck.

This is great info, but I think Phil's motor has been running for at least a few months now. ;)

Guy's,

The link to his ebay heads didn't work so what heads are they??

E-brock, 100 cc aluminum "rovals" or just old style stock, say, maybe -215 type closed chamber ones??

pdq67

215-type

Phil, there's a local member that has a beautiful balanced rotator for sale with the L2399 + .060 pistons, GM steel crank, Eagle rods complete with balancer and flexplate. It's so awesome looking, it should be in the Smithsonian! I passed on it because I have open chamber heads.

Guys, Phil's motor is up and running already. Been running for months from what I recall.

"71-454" broght the post out of the dead. Look at the date of the last post before "71-454".

Im not expert, but when my block was done my machinist as well wanted the pistons. For final bore and torque plate honing each slug was to be mic'd for slight differences. I looked in TRW catalog, and using the heads I have, and knowing their CC's (you have to know the cc volume of your head before picking a piston; and should know cam lift to make sure piston you have has correct valve relief depth if you are gonna go with a high lift, high duration cam) you can determine which piston you need and they give a real close estimation of compression ratio's. (For example: my 781 head which is approx 119cc will yeild 9.68:1 with a TRW 2449 forged stock bore piston). My recomendation would be to order the pistons through the machine shop...that way if he finds he needs to go more than .030 over after you already bought .030 over pistons... you bought them from him, and since he "HAD" to have them before boring... now he "HAS'" to get you a new set and reurn the old ones no questions asked. This is what I did anyway. Good luck in your quest.

Thanks Slow for the come-back!

pdq67

My machinist did the same thing, pistons first-then bore. The machine shop I used has a reputation for building high end engines so I trusted him. Worked out well for me. My machinist said if he bores first he will not warranty his work as he wasn't given the proper measurements to work off of. I do believe, if I remember right,Keith Black was the piston that is generally found the furthest off for him, but I am no machinist so I just go by what he tells me. Good Luck with your new engine, Jeff

I think you guys are confusing boring and honing. No way does a machinist need the pistons to bore the block. If it will make a .030, they bore it about .025, then hone it to size based on the piston measurement. If they tell you they need the pistons to bore it, I believe they just don't want to wait before they hone it. In other words, they want to get it done all at once so they can get it out of their shop and get paid for it. JMHO