Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
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Finally found your piston specs in the Federal catalouge!
However, I can't copy the link or copy the saved web page.
They do show your 4 valve relief forging with a 6.1cc valve relief volume.
Thanks skinny but i think im gonna have to get different pistons with a 10cc volume in the four reliefs this would bring my SCR and DCR and i came up with 9.8:1 SCR and 7.9 DCR and thats with a .015 gasket and a .025 deck height
If you do not have heads yet, I would say go AFR if you have plenty to spend, but if you are like me and on a budget, I had good luck with the patriot performance heads, they flowed well and the quality seemed good, but most any aftermarket head will be of high quality, and if you asked 100 people which was best, you would get 100 answers.(well, probably at least 50 people would say AFR).Some good names are Canfield, RHS, Dart,Brodix, and many others, the only one I would NOT reccomend is edelbrock, just let them stick to making intake manifolds.
It would be awesome to use aluminum heads but the price is way to high to for me it would be cheaper for me to return those pistons i have and get the ones that were in that linkn i posted. They would give me 9.8:1 SCR and 7.9 DCR and thats with a .015 gasket and a .025 deck height
If you can't get your money back on the pistons, consider this.
XE274 274/286 adv duration. 110 LCA. 106 ICL.
64cc chamber
4.04 cylinder bore x 3.48 stroke
.025" x 4.100" gasket (.050" quench )
.025" piston below deck
6.1cc piston valve relief volume
10.05:1 SCR
8.13:1 DCR
Again you may at the point where you have to precisely measure to ensure accuracy. Unfortunately that's something you can't do without assembling the pistons and rods and mocking up the engine.
Thank you that and is that quench alright to run? if so that could be very helpful if i cant get my money back but thankyou very much again i will consider that
Take a sand drum to the chambers to polish them, grind a little more aggressively around the exhaust valves, and open them up to 68cc's. You'll lower your compression, save your quench, and improve exhaust flow a bit. Polished chambers also help lower the propensity for detonation.
Take a sand drum to the chambers to polish them, grind a little more aggressively around the exhaust valves, and open them up to 68cc's. You'll lower your compression, save your quench, and improve exhaust flow a bit. Polished chambers also help lower the propensity for detonation.
That is probably a good idea, I have heard of polishing chambers to quell detonation, but I never considered how it might increase the size of the chamber, sounds like killing two birds with one stone.
Probably not, which is why I said to grind a little more aggressively around the exhaust valve. As in, deshroud them (see Standard Abrasives' do-it-yourself porting guidelines).
I simply polished the chambers on my Worlds, after getting done they cc'd at 64. I have no idea what they were before polishing, but they're supposed to be 58cc. I didn't deshroud the exhaust valves or anything.
Your heads may very well have larger than 64 cc chambers now, I have had 3 different sets of heads measured at different times, none of them were accurate, most were off at least 3ccs, so you may need to do less work than you think, but deshrouding the exhaust valve is a good idea, be sure to stick an old valve in the valve seat to protect it.
The edge of the valve comes close to the edge of the combustion chamber. By carefully grinding away some of the edge of the combustion chamber, you "unshroud" the valve.
I am not sure if a dremel will have enough power, I am sure it will work but will probably take longer, but that is probably a good thing with you being new to porting.
You should be able to find some porting guides online, and they should cover chamber polishing and valve deshrouding.
Yeah thats what you get when a engine stils will coolant in the cylinders from a bad head gasket and no there not pittd the machine shop just said it stained the cylinder wall and it will not affect anything
So ive ran into an expensive problem, the machine shop said that the rods have to be balance when i put these forged pistons on. Will i have to get the rods balanced if so its 270 just to get them balanced so is there any other way around not getting them balanced
Unfortunately, no.
Some pistons, such as a stock cast replacement are close enough to the original weight that balancing is considered unneccesary in non performance application. Forged pistons tend to be heavier so there's no way around it.
Unfortunately, no.
Some pistons, such as a stock cast replacement are close enough to the original weight that balancing is considered unneccesary in non performance application. Forged pistons tend to be heavier so there's no way around it.
Well heres the thing
When i weight my forged pistons compared to my stock ones
THe stock ones WITH rings and carbon build up came in at 32 grams heavier then my forged ones and they did not have rings, so i think the new forged pistons will be close to the originals if i was to add the rings to the new pistons
Last edited by 19transamtpi86; 03-25-2009 at 03:59 PM.
When i weight my forged pistons compared to my stock ones
THe stock ones WITH rings and carbon build up came in at 32 grams heavier then my forged ones and they did not have rings, so i think the new forged pistons will be close to the originals if i was to add the rings to the new pistons
That's a valid point to bring up with your machine shop.
If there is any doubt though, balancing is relatively cheap insurance. Certainly less expensive that having to have a engine rebalanced after it's installed.
I'm trying to find the weight specs in the Sealed Power catalouge to confirm my comment about forgings vs. cast/hypereutectic. I know they CAN make a casting lighter than a forging. It may not always be the case.
That's a valid point to bring up with your machine shop.
If there is any doubt though, balancing is relatively cheap insurance. Certainly less expensive that having to have a engine rebalanced after it's installed.
I'm trying to find the weight specs in the Sealed Power catalouge to confirm my comment about forgings vs. cast/hypereutectic. I know they CAN make a casting lighter than a forging. It may not always be the case.
Yeah thats what im gonna bring up with the machine shop tomarrow when i measure the pistons again this time the stock ones cleaned up a lil bit and with out rings. But in theory if they fall with in 5 grams to 10 grams would that much really be that much for me to have to get them balanced.
Yeah thats what im gonna bring up with the machine shop tomarrow when i measure the pistons again this time the stock ones cleaned up a lil bit and with out rings. But in theory if they fall with in 5 grams to 10 grams would that much really be that much for me to have to get them balanced.
There is an excellent explanation of what the tolerances are in David Vizards Max Performance Small Block Chevy book. The total balance can be in the range of 50 grams for the piston assembly and connecting rod however the method for determining the overall weight ( because part of it is reciprocating ) is not so straight forward. You would have to read it.
It's also stated that an out of balance engine (within reason) is no less likely to fail than a balanced one. It's just not a smooth as we like.
On a personal experience note, my 86 had very annoying driveline vibration. The engine was fresh with new pistons/resized rods and stock crank. It was never balanced when it was first assembled. In fact the topic never even came up at the machine shop. When this vibration didn't go away after all the driveline line fixes, I went back to the machine shop and had the engine balanced to see if that would help. It didn't make any difference whatsoever. Even the machinist commented that 9 times out of 10 a piston swap as I had done dosen't result in an out of balance condition.
You may have to rely on your machinist's opinion.
so i reweighed my pistons today and the old OEM piston with out the rings and carbon build up are 14grams exactly less then the new forged piston. will this 14 gram difference realy make a difference if i dont balance the rods???
anybody kno if that extra 14 grams (which is 5 pennies) would throw my whole motor out of blance if i dont balance the rods?
Can't say for sure as I'm not an automotive machinist or engine builder. ( engine assembler, yes )
What I can find on the internet is that a small difference between the new and the old won't be an issue and balancing shouldn't be required. The margin that's used seems to be the 50 gram mark. The OEM typically balances to within 50 grams more or less. There appears to be more attention paid to keeping all the assembly weights the same. All the big ends of the rods are more or less equal and likewise with the rod small ends and pistons.
I'm an automotive machinist. I've seen stock engines that far out of balance, mostly late '70s Mopar, but they're fine for grandma, who never ever sees the high side of 3000 rpm.
Within 5 grams is fine for a "performance" build, that mostly lives below 5000 rpm, except maybe at the top of first gear.
But the effects of centrifugal force multiplies those few grams into hundreds of pounds. I don't have the exact figures on hand, but I'm strongly advising you to not insist on trying this.
I would not think that it would need balanced, but if I trust a shop to machine all the parts of my motor, I would also trust there advice on this one, they do this for a living.
Alrighty well the engine has to be balanced unless the pistons are within 5 grams of each other, so i sold my piston cause there was no point to having the forged for what i am doing. so i was wondering if any body could point me in the direction of cheaper stock replacement pistons that would be close in weight?? ive tried looing a couple times but ive come up short
When I built my latest 350 ( a NEW 1979 truck long block found in a shop teachers garage 5 years ago) I took it to Beatty and Woods machine shop to have new pistons installed along with resized rods and ARP bolts. At the time it was never considered having the engine rebalanced and all seemed fine.
To make the story a little more interesting, the drive train had a terrible vibration. I tried everything to solve the problem. It documented in the following link. http://www.thirdgen.org/techboard/tr...vibration.html (drivetrain vibration)
To make a long story short, having the engine rebalanced made NO noticable difference with respect to the vibration.
In summary, in my application, having Speed Pro H345NCP pistons as a replacement did not require balancing as evidenced by before and after.
I not saying that's what you can count on in your situation, however it's a little info for you.
I would however have my next engine balanced just for the piece of mind ( like ARP bolts)
Well finaly found a deal getting my rotationg assembly balanced for 250 bucks so thats the good deal now the next thing on the pl8 is the heads and the cam. I have in mind the COMP cam EX 274 from you guys but just wondering i there is anything else out there that is beter. And as of now im still sticking to the Vortec heads but also if there is anything better heads out there below 600 bucks let me now.
Well finaly found a deal getting my rotationg assembly balanced for 250 bucks so thats the good deal now the next thing on the pl8 is the heads and the cam. I have in mind the COMP cam EX 274 from you guys but just wondering i there is anything else out there that is beter. And as of now im still sticking to the Vortec heads but also if there is anything better heads out there below 600 bucks let me now.
I'm sure you already know that's it's important to match the heads and cam. There are many other factors to consider as well: vehicle weight, transmission type, rear end gearing, etc.
Check the Comp Cams web site and try their cam selector. That will give you an indication of what you can expect.
For the record, my Vortecs love the XR276HR cam. This is a (high) 12 sec car and 26 mpg (Can)/23 mpg (US) hiway setup.
