Hey everyone I been away for a great while well I’m jumping on the band wagon and getting into the modern world with Chevy gen 3 blocks. I picked up a 4.8 for practically free. 75,000 miles on it and heard it run before pulled. I tore the top end off and damn this thing is clean still has hash marks on the cylinder walls. Not even broken in lol. I want to make some nice numbers with this I know they are already around 285-300 from factory. This is going into a street car 88 gta digi dash car. I have a t56 for it as well. My question is what cam can I put to make at least in the 300 numbers for hp and tq now I know it’s going to be a high revving motor which is no problem with me lol. I’m using the stock 706 heads as well since I saw something that they are on flowing heads and aren’t prone to cracking. I as well did a shaved truck intake manifold as well and going to be getting a f body oil pan, pick up tube and dipstick for soon. Speed engineering headers are on order as well I want to get the motor in for spring time at least I’ll figure out wiring harness and all that a later time. So let’s hear some cam part numbers that would be for a power range of 1500-6500 I would say is pretty good to me.

 

BTR truck cams either stage 2 or 3.

 

An LS6 cam would give you 400ish hp with good drivability and fuel economy. Those 706 heads have small combustion chambers, 61cc I think. That would give you some high compression. Are your pistons dished or flat top ?

 

Do any of you guys know part numbers to the LS6 cam or this BTR truck cam In the stage 2 looking to keep it a street car and don’t want that lumpy idle. Like a nice smooth idle from my cars. The pistons on this are flat top pistons will it be ok to run these 706 heads with those and that came set up. I was thinking about doing the rocker upgrade since it’s something that can get done since the heads are off will this be a good idea or no.

 

https://www.briantooleyracing.com/bt...218-111-0.html

stock rockers are fine and prefered.

 

What heads are on the engine that you have ? Ls6 cam part # NAL-12565308 out of summit. I did the C.H.E. trunion upgrade and that has been good to me for 13,000 miles so far. Avoid the comp cams trunions. Ws6store also sells trunions with a different bearing design. These are a for stock rockers.

 

If your 4.8 has the 706 heads it is an early Gen 3 motor which means it does have dished pistons. They look like flat tops at first glance but aren't. You could mill your heads a touch and pick up some compression. Compression is free power (well, sans the machine cost). You want a cam with negative or zero overlap (use a cam calculator) for it to idle and drive like stock. Smaller the better for it sounds like you want. Plus being a 4.8 a mild cam for a 5.7 would be more rowdy in the 4.8. Trunion upgrades for the rockers is fine, I recommend the straub kit. You will want to keep the cam under .600 lift so you don't side load the valves. A small cam and a set of beehive springs will go a long way with that engine. Unless you are on a strict budget I would go aftermarket for the cam. A stock LS6 cam is fine and cheap, but an aftermarket grind with nearly the same specs will likely carry more power up top. When you say 300hp, do you mean at the crank or wheels? It's likely already there now at the crank. A small cam and headers should add a solid 30 to 60 more. Time to start reading up on LS1tech as well as watching videos of 4.8 trucks with cams to see how they idle, run, etc. Not totally an apples to apples due to exhaust differences, but will give you an idea.

https://straubtechnologies.com/ls-bu...trunnion-kits/

 

I mean if I can be in the 400’s for numbers I’ll take that too lol. You are right I looked the pistons over once again and they are dished I thought they were flat sure seemed it at first glance. What would i mil the heads down to machine shop told me they cc chamber now is at that 61cc like you said. I was thinking going to a 54cc chamber like the old gen 1 small block 113 heads don’t know if that will cause piston to valve clearance. I do believe the LS motors are already up there in compression running in the 10:1 at least. Would be in the 11.0:1 be to much. I was thinking on going with the btr cam the specs seem real decent for a nice smooth idle I mean even a little lump isn’t to bad.

 

Are you sure it's a 4.8 ? I thought 4.8 had flat top pistons and the 5.3 had the dished and flat tops for the 5.3 H.O. What is the stroke 3 1/4 or 3 5/8 ?

 

If it's a 4.8, IT HAS FLAT TOPS.

My gen III 4.8 has flat tops.

Even the Gen IV 4.8s have flat tops; trust me, I've changed the heads on a 2011 Chevy Express van, IN THE CAB, and it's not fun.

GM did that because the 4.8 and 5.3 have the same bore size and cylinder heads, but different strokes, and they wanted to keep the same compression ratio.

Milling the heads or going to domed pistons is your only way to go to get more compression.

Also, you say that you have 706 heads; those ARE prone to cracking, if they are the "Castech" heads. They can be identified by a casting mark that looks like a AA battery under the rocker arm guide.

862 heads are the ones that don't crack (unless you really screw up).

 

This is correct. I retract my previous statement. The Gen 4 5.3's came with flat tops. The only Gen 3 5.3 with flat tops was the L33, IIRC.