piston dome size need help

[1968BM]

Im building a 454 with a set of 049 open chamber heads. I currently have flat top pistons in it. I have a forged cross drilled crank in it now. I want to put in a high lift cam. But the pistons are my hang up i want to go at least with some sort of dome piston, but i dont have a clue on how to figure it out. Thank you. Oh by the way the heads have been done i was told they will handle a .700 lift cam but i need a good piston. Thanks

[Z15 SS 454]

Ok, Loaded question here and i will try to answer it with a few questions

1-You need to decide on compression ratio that you want (cc volume of head chamber,head gasket thickness and choose dome volume of piston )

2-You need to choose a cam and mock up short block to check valve to piston clearance.

3-There is no set up that you can buy that will guarantee no valve to piston interference due to the following inconsistencies,Deck of block machined to "zero",Cylinder heads machined many times for straightness,cam shaft timing (580" lift cams can have enough overlap to crash pistons),head gasket thickness and a few other things to consider.

Keep in mind that if the pistons say they are 11to1 the true engine compression is not 11to1 due to above stated variables.

Sorry for long post but hope it helps.

[VintageMusclecar]

Do you know the chamber c.c's? You'll need to know so you can calculate how much dome volume you'll need to achieve your desired compression ratio.

[markjohnson]

I've had very good luck with Speed Pro 7060P or TRW 2399F pistons when used with #781 or #049 oval port cylinder heads. Pump gas friendly and I've ran .650 street rollers with plenty of piston/valve clearance. It's a very popular piston for your particular cylinder heads.

[the427king]

Make sure you get rid of those small valves.

[1968BM]

Thanks, guys i want to be able to run on pump gas. The head cc is 113 factory, dont know about the head gasket thicknes and the piston volume. Whatever piston i can get to fit. lol

[Stefano]

You are going about your quest Bass Ackwards.

You need to first determine what you expect to get out of your engine, which is based on many factors such as how you plan to use it and get out of it? RPM range? HP and TQ level? etc?

The only working parameter which you provided is "pump gas".

Once you have determined the above you can decide on a combination that will best achieve your objective.

[Salvatore]

Wiseco makes a pretty good piston also.

[GreenLS6]

Used to build alot of "781-049" big oval port Large valve 454 and 489 ci Motors for people, 15-20 years ago. Used the TRW Ls6 replacement piston (or speedpro equiv ), 3/8 truck rods ARP rod bolts, cast or forged crank ( Cast 8lbs lighter plenty strong and cheap) with felpro Blue .041 head gasket. end up true comp. 9.8-10.1 range. You do have to releive the edge of the chamber about .030-.040 thou.. Hits very edge of dome on some heads due to core shift( always check!!!)

The 489-496 motors I would mill about .085-.100 off the deck face of the piston(not dome) to acheive a postive +.005 out of the hole, then run the same .041 head gasket for optimum quench of .035 thou. then run the Comp cam 288AR solid roller .623 lift. Super torque and almost 600hp. <span style="font-weight: bold">CHEAP!!!!!</span> Street monsters

[VintageMusclecar]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Stefano</div><div class="ubbcode-body">You are going about your quest Bass Ackwards.

You need to first determine what you expect to get out of your engine, which is based on many factors such as how you plan to use it and get out of it? RPM range? HP and TQ level? etc?

The only working parameter which you provided is &quot;pump gas&quot;.

Once you have determined the above you can decide on a combination that will best achieve your objective. </div></div>

This.

[GreenLS6]

Sorry forgot cc's trw 2349 LS6 piston was 30cc if i remember, the speedpro 2365 was like 26ish.

For those wondering 1/4 inch more stroke how doesn't it hit?? 1/2 of 1/4 inch more stroke is .125.... mill deck face .085-.100 depending on pistin in hole DECK height. leave .005+ out of hole so you can run Cheap but good head gasket for optimum quench(Free 5hp)

Lots of good pistons out there now that are great ,cheap open chamber designs. Didn't have them back then.

[1968BM]

Now this is sounding more like what i need to know. Right now i have a 454 stndard bore with a forged crank and flat top pistons, and 049 heads. I have to get cylinder 4 sleeved and put back to standard bore. I dont think i can get enough compression out of the flat tops to be where i wanna be without out nitrous or supercharging. That is why i want to go with a forged dome piston. Now my question is this what sized dome can i put under the 049 heads? My other option would be to build a 427 out of it.

[69 Post Sedan]

If you build a 427, you HAVE to use 427 pistons as the location of the wrist pin is different than a 454 piston......along with using a 3.76 crank vs. a 4.00.

Kurt

[1968BM]

Thanks, yes i knew that for the 427, ran into a guy that has all that, hes lookin to sell me for around 600 cash, just not sure yet which way i want to go.

[ssl78]

I would check into building a 496 stroker motor, sometimes its cheaper to go that way the kits are fairly reasonable.