[Eldi Z]

Information on the stock weight of the LT4 pistons as optional replacement of the stock LT1s.
Is the bob weight similar, so that a direct drop-in replacement can take place?

Obviously, the CR with the LT4 slugs is going to be lower and probably close to 10:1 - if the head gaskets of the LT1 and LT4 are the same thickness?

[SSUNDVL]

According to the chev media page the rods have the same balance mass. But since the cranks are made of different material idk about bob weight of full assembly.

Also lt1 and lt4 use different head gaskets, lt4 is thicker and what I used when I did my cam install to lower comp slightly.

https://media.chevrolet.com/media/us...owerhouse.html

[Eldi Z]

Originally Posted by SSUNDVL

According to the chev media page the rods have the same balance mass. But since the cranks are made of different material idk about bob weight of full assembly.

Also lt1 and lt4 use different head gaskets, lt4 is thicker and what I used when I did my cam install to lower comp slightly.

https://media.chevrolet.com/media/us...owerhouse.html

Yeah, add to it the issue of forged material in the LT4 slugs Vs. the cast of the LT1... but again, it could be that some areas of the piston of one type of engine, have less/more material than the piston of the other type of engine.
Bottom line: Someone who actually put each type of piston on the scales could provide a legit input regarding the weights.
Basically, this is the information I am after....

If by chance (I guess very slim chance) both types of pistons have the same weight, then it would be possible to simply swap out the OEM LT1 pistons in favor of LT4 OEM pistons, as another good alternative to the aftermarket - so called - "drop in" sets (I.E. Wiseco, Diamond)

[EDFHOBBIES]

I have some Lt4 pistons I can weigh. I think its best just to have the asm balanced the setup I'm going with I'm still going to have it balanced and its supposed to be good to go since its all Lt4 parts.

I'm searching for 2 Left and 2 right Lt4 rods and pistons. My friend gave me his LT4 block the number #8 rod let go and took out 4 rods and pistons and the block. The last crank journal has a little damage but it can be filled and reground. Hard to believe the crank is 1000 bucks but the lt1 is forged as well but half the price.

I plan on building a budget LT4 for the wife's SS. She's been making 615 to the wheels for 5 years now and at 75k miles so just planning ahead so the bill will not be so high at 1x.

Going with..

19431901 new block $2250
12669751 New rods $89.00 4x 6.098 length unless I can get used
12669436 New Piston Left side $108 2x unless I can get used
12669437 New Piston Right side 108 2x unless I can get used
12674746 Probably repair or pick up a LT1

Other option is..

Used block $2250 from Mast 4.070
Off the self pistons for around 1000
Summit racing Hbeam rods mad by K1 Technology but way cheaper for 500 6.125 length

One thing I noticed is that when you switch to a 6.125 rod a lot more piston options are available especially now with shortages.


Either way its expensive trying to have a motor ready to go vs waiting for your motor to die and reusing block and crank.. then paying labor to have the block's cam bearings replaced, line honed, bored with tq plate.

I think its best to use a new block on used pistons even though the pistons are low milage I was worried a used block might make a to loose fit and have some clatter.

seems like a wash to use custom pistons in my situation that works with a 6.098 rod. the pistons would cost the difference over a new block vs a used block if I were to go to 4.070 bore.

If you go into the motor just make sure you fix the issue of the center crank bearing with the 2 piece thrust style to bearing. The replacement set is a Clevite MS2339A or H depending one application H is for racing

[Tim M]

EDFHOBBIES: Can you please tell us more on the bearing?

[EDFHOBBIES]

On higher hp engines the 2 piece designed bearings can't handle the loads I don't know if the shims fall off under load or If the thrust from the trans always pushing on them is to great and they wear off the tabs and then just fall off leaving to much end play that results in engine failure. Remember the crank is always wanting to walk forward so that thrust bearing or shim is constantly wearing.

The pic shows the upgraded all 1 piece designed half by clevite the shims are not removalable like the gm one.

I can only think that GM has a few different thickness of shims and uses the correct size for end play vs on like a clevite you test the end play and grind on the bearing if need be. Why else would they use this design?

[Eldi Z]

Very interesting and informative indeed EDFHOBBIES
Would be interested to know how close the weight of the LT4 pistons is to the stock LT1s
BtW:
Is it correct that your Wife's SS has an Edelbrock blower on?
What kind of fuel is run to bring about 615 R-WHP? What is the boost level?
and is this a stock LT1 engine?
What about fuel parts? All LT4 Low-to-High I presume...
Front seal LS3 or stock?
Catch can?

[EDFHOBBIES]

Lt4 injectors and pump
Dax low side
Trunk tank reservoir
Front seal ls3
Headers
Rotofab
Might mouse can
I can't remember boost level I have guages but need to install a sender to read on guage
615rwhp 666 tq

I plan to lower here compression, port the blower, and add a cam shooting for 800 on 93 Maybe dsx flex kit she keeps bothering me about adding E to hers.

[Eldi Z]

Originally Posted by EDFHOBBIES

Lt4 injectors and pump
Dax low side
Trunk tank reservoir
Front seal ls3
Headers
Rotofab
Might mouse can
I can't remember boost level I have guages but need to install a sender to read on guage
615rwhp 666 tq

I plan to lower here compression, port the blower, and add a cam shooting for 800 on 93 Maybe dsx flex kit she keeps bothering me about adding E to hers.

Who tuned it?
615 RWHP is a nice number indeed and is holding up well after so many miles. Is she driving it hard, or mild?
Why would she wish to add "E" - More power, or safety / cooling?
Are stock CATs still in place?

[EDFHOBBIES]

Originally Posted by Eldi Z

Who tuned it?
615 RWHP is a nice number indeed and is holding up well after so many miles. Is she driving it hard, or mild?
Why would she wish to add "E" - More power, or safety / cooling?
Are stock CATs still in place?

Sorian tune

She drives it pretty damn hard. E will squeeze out more power with high compression you need the octane.

no cats

[Eldi Z]

Originally Posted by EDFHOBBIES

Sorian tune

She drives it pretty damn hard. E will squeeze out more power with high compression you need the octane.

no cats

Very nice indeed! So the idea of adding E in her case is to get more power.
Got it...
Question about the non-CATed situation:
Any smell of gas fumes? Or did you leave the primaries on and just removed the secondary?
Is there such a difference with Vs. without CATs?
I thought that the difference is negligible

[Kerry]

Man it would be supper if someone would weigh the lt4 piston with rings and pin.
Pretty please!

[Joshinator99]

Friendly reminder that the drop-in piston kits like the one from GPI are already matched to the LT1 weights, so you get a very robust piston and rod assembly that is stronger than OEM LT4 stuff and does not need balancing. Plus you can drop the compression a point or so at the same. Win-win deal.

[Kerry]

Thanks but I put a set of wiscos in with the stock rod instead of the car being down for a few months waiting on rods. So if the piston is the same weight maybe I could do the lt4 rod. I probly never do over the 750 or less.