bp m1009

iTrader: (2)

I need some opinions because I cant make up my mind. Im doing a cheap little build for my 72 C20.

Ive got an 02 LM7 5.3. Im going to be running gen 4 rods and flat top pistons, 98 LS1 Cam and backed by th-350 w/ 2500 stall.

Now, what heads should I run!?
Stock 862's that came off the engine. Or I also have a pair of 243's that have been sitting on the shelf. Will their really be any noticeable advantages with one head over the other?

keep in mind this is a budget build, mostly using parts I have around the shop.

G Atsma

No brainer; 243's will flow WAY better than the 862's, though you might want to mill them a bit to get some compression back because of the bigger chamber.

qweedqwag

Yep ported 243 or even stock will be a good runner.

bp m1009

iTrader: (2)

I have a problem. I just started to re-assemble the engine with the gen 4 rods and pistons and it appears the rods are longer then the old gen3 rods. Has anyone ever heard of this?? The top comp. ring on the piston shows itself at tdc????

07NBSChevy

iTrader: (1)

What are the rods from, they should be 6.098". If they are 6.125" you will need to use a crank designed for 6.125" rods.

Also, they are stock pistons as well right?

bp m1009

iTrader: (2)

Im an idiot. I dont know how I over looked this, but I never knew 4.8's had longer rods. It obviously all makes sense now but I just over looked it I guess. So that seems to be whats going on. I have gen 4 4.8 rods and pistons that are too long. Damn it

bp m1009

iTrader: (2)

I would like to mill them a bit, but then I would most likely need longer pushrods. And if I beefed up the pushrods I would wanna put springs in it. And all of that starts adding up, when Im trying to keep this as cheap as possible.

99 Black Bird T/A

iTrader: (4)

With your goals in mind, I would replace the 98 LS1 cam with an LS6 cam or similar LS2 cam or a used GT2-3 cam. All of the alternative Cams will work pretty well with stock manifolds if headers aren't in the budget. Next I would sell the 243's and use the cash toward getting the 5.3 heads CNC'd by TEA or a similar shop. A properly ported 5.3 head can make very good cost effective power.

G Atsma

Milling the heads needs SHORTER pushrods, not longer. IF you put a cam in it, THEN you would need springs. Do the pushrods if you mill, do springs if you re-cam. You have to figure what you want out of this engine. If your only concern is doing it cheaply, you might not be satisfied with the result. The 243's are overall the superior head, and milling is not expensive. Pushrods aren't either.
OK, 99Black Bird T/A posted while I was writing this post. His ideas are good too. You have some choices to make. Just be sure to not take shortcuts and use quality parts.

LLLosingit

iTrader: (4)

You would need shorter pushrods, Milling would put the rockers closer to the cam centerline. You can use your old springs, Milling the heads won't make a difference there. You can always pick up new take off LS3 springs cheap, I gave $50 for new take off springs retainers and seals. If the heads are used it would be a good idea to mill them so you know they will seal and new springs and seals would be cheap insurance.

bp m1009

iTrader: (2)

Yes shorter pushrods, brain fart on that one. I think my problem is more so that i am impatient and dont want to wait to find deals on used parts. I know i can get push rods and springs cheap if i wait for some to come up for sale. But I am an impatient mother F****r.

I just found out I cannot use the flat top pistons I have because I wasnt thinking and just bought 4.8 rods and pistons assuming I would just slap them in.

So now wanting to just get this thing together I am debating just reassembling it back to stock and running it as is. Lifes too short to wait for parts!!

G Atsma

Why did you order 4.8 rods and pistons when you have an LM7 5.3? The pistons will fit, all you need is the shorter rods. Using the 4.8 pistons will give you more compression; that is how the L33 came about. If you can exchange the 4.8 rods for the correct ones and you will be set.

07NBSChevy

iTrader: (1)

I have seen a lot of people do that without knowing the difference in length.

He will need 6.098" rods from a Gen4 5.3 or Gen3 L33 which are the same.

A.R. Shale Targa

iTrader: (2)

for under a hundred bucks (usually $80) a decent machine shop can press off your dished 5.3 pistons and put the flat 4.8 ones back on the shorter 6.098" rods....you can one by one swap the rings over to put each ring pack back into the same cylinder of the block
Do a slight clean-up mill on the 243s, hand lap all the valves in and pop some good LS3(blue) springs w/new seals on them
The GT2-3 cam would be my choice, they are usually only $200 bucks used, work with the blue springs and stock push rods....good little 10:1 combo IMO

bp m1009

iTrader: (2)

What happened was I came across a set of gen 4 4.8 rods and pistons, and I without thinking thought I could just use the whole rod and piston assembly, not realizing the 4.8 rods were longer. I can't simply put the flat top gen 4 pistons onto my gen 3 5.3 rods, thats where I am at.

pantera_efi

iTrader: (1)

Hi BP, review the Gen-IV, Internal Thread "What head has best Discharge C/D"

The is a Chevy Magazine article with the requested heads tested in the thread.
The Speedmaster heads (ProComp Electronics) WON, my opinion.

My case : A drifter, young, little extra cash, 240SX.
I purchased the "Cathedral' ($700.00) heads for his requirement with included C&C porting , machined, my valves, springs, etc.
The cost of a C&C Job, and a V.J. with your heads could be greater.

I could provide these ?

Lance

Darth_V8r

iTrader: (4)

Another alternative, if your budget allows, grab a set of used AFR 205. Many of them are set up with 59-60cc chambers and would be bolt on and go for you - with the added expense of pushrods.

Also, if the heads are off, consider replacing the lifters for a few hundred dollars. Cheap insurance.

G Atsma

The 205's will fit a 5.3L bore? I'd always read/heard that AFR heads wouldn't go on anything under the 5.7 bore. Unless they are/were playing it REAL safe...

KCS

iTrader: (20)

I wouldn't put too much money into the top end of a small motor like a 5.3L.

If there's nothing wrong with the 862 heads (ie non-castech heads), I would just refresh them with a valvejob for 2" intake valves and mill them to 57cc chambers (~.025") which would give you a solid 11:1 compression ratio with flat top pistons. Sell off the 243 heads and you might actually come away with a little extra money in your pocket.

bp m1009

iTrader: (2)

If I were to go through all the trouble and expense of adding 2" intake valve to 862 heads wouldnt I be better off just milling the 243's??