Instead of putting the 862 heads on the 4.8 and dropping it in the car this weekend... I picked up a set of 799's for $100. One head was left in some sort of parts wash over night and it ate it up pretty bad. Spend the weekend doing a Harbor Freight quickie port job (3 hrs a head or so) and I'm dropping them off at the machine shop monday. Hoping this head deck cleans up at .024-.030 and I can use it. If not I ordered another 799 for $200 as a spare.

One head is perfect. The one in parts cleaner looks like this...



Set of China alum rota bits off Ebay was $30
HF router speed control - $19
HF Sanding tootsie rolls - $23
HF rota tool $10



Took down the valve guides a bit, smoothed out the valve seat to pocket and gave it all a good clean up. Figured I'd do more harm than good if I went crazy on them. Polished up the exhaust ports and left the intakes kinda rough 80 grit finish on most of it, left some areas that were hard to reach alone.

 

That looks like someone soaked them in Super Clean or something similar. It really should be in an FAQ somewhere. I know several people (including myself) that have used it and damaged aluminum engine parts. It's much more aggressive than what you'd expect to find in a parts store spray bottle.

 

Yea it’s bad… the machine shop said its junk. It ate away at the oil passages and head bolt holes so it will never seal. Wish I would have thought of that before porting it!

Means I only paid $100 for 1 good 799 head though, so not a horrible deal. I grabbed another single head off ebay.

 

I was concerned about my oil bypass in the F-body pan. I found some metal debris in a few turbo bearings now. One setup being mine and 2 others now. All on LS setups fed form the filter housing port. So the turbo *should* be seeing filtered oil only. Figure I’d plug the bypass just for kicks. They do make billet plugs for this, but at $25.50 for the plug, I decided to find another way.

Pulled the oil filter threaded insert. Then used an easy out for the bypass plug.

Picked up a new OEM bypass for under $3 shipped on ebay. Then filled the spring “cage” with JB Weld. It’s done in a way that the epoxy won’t have a way to escape. (at least I hope). The little cage for the spring should hold the epoxy plug in. Shouldn’t be able to bypass the filter now assuming the filter I run doesn’t have a bypass either.

 

Figure I have something like 24 hours in the heads. (not including the time it took to port the junk head) I’m sure my porting isn’t worth enough power wise to justify the time. Unless you have A LOT more time than money, I wouldn’t’ bother porting and LS head for SBE turbo builds.

I picked up another 799 head off E-bay for $200 shipped. Ended up having 3 bent valves. (that wasn’t mentioned in the Ebay AD!) Luckily I could use the valves from the head that I scrapped. Spent another 5-6 hours porting the new head. Then dropped them off to be milled .025.



Spent 5 hours porting and lapping all the valves in. Used valve compound and a drill, probably not the best method, but they turned out OK. Then installed the BTR .660 dual spring kit.




Went with the felpro .041 MLS gaskets this time. No idea how well these will work but I liked the extra bump in compression. I’m trying to spool a T6 S480 with a super tight converter. Figure I need all the help I can get. Should be around 10:1 I’m guessing.




With all the luck Denmah seems to have on the OEM head bolts… I decided to do away with the ARP studs to save a little $. I couldn’t convince myself to run the OEM head bolts though. So I picked up a set of new ARP head bolts for $102.

Cut some channels in an old OEM head bolt to make a tap, and cleaned up the block threads good. Torqued them down to 78ftlb. Hope these hold!


Cam was ½* retarded to the card with the original timing set (this engine only had 12k so I didn’t see the need for a new timing set).



Installed the fancy summit 1.8 roller rockers. About .030 clearance on the end rockers and the head/VC perimeter. May go back and clearance that a bit. Also need to measure for push rods. Guessing the OEM length is close with the smaller base circle cam and .025 milled heads and .010 thinner HG. Lifters were all pumped down so it was hard to tell.



My balancer went with the old motor, so I picked up another pro-comp deal. Hope to drop it in next weekend and fire it.

 

Dropped the 4.8 in the car this weekend, it fired right up. Cruised around a little and all seems well. Can’t get these 160lb injectors to idle below 950, so the cam has no noticeable lope. Sounds the same as it always has. On initial start when it’s at lower RPM briefly it has a nice lope to it. Need to find a trick to get the idle down on these huge injectors.

Underpowered out of boost now compared to what it was, but that was expected. Makes boost easy on the brake just needs more RPM to do it. Raised the 2 step to 4800 from 3400. It makes 12lbs quick, even with the tight 14 stator PTC converter. Was raining all weekend so I didn’t get much testing in. Should run pretty well.

 

What do you think of 862s vs 799s?

 

Hard to say don’t have any sort of a direct comparison. I was surprised it came into boost faster than the old 4.8 with the JFR triple 12 cam and T4 S476 and 706’s (ls9 HG). But I had a 2.5” hot side on that setup. I’m guessing the 2” hot side (1.87” ID) is the reason for the improved spool, but some of it could be the heads.

With the .041 HG and .025 milled heads, I should be right around 10:1. We’ll see how it does trap wise at the track. Haven’t checked cranking compression yet either. I was expecting it to sound raspy and mean, but it doesn’t.

Also haven’t checked the pushrod length yet. With the heads .025" and the .010” thinner gasket it would take a .035" shorter pushrod. But if my cam centerline to lobe heal is .025” smaller, it should basically cancel out. Need to check it either way and order a decent push rod. Running the stockers now.

 

862s have smaller valves?

 

Yes, the 862/706 have the 1.89” intake valve VS the 2” on the 799’s. All have the same 1.55” exh valve.

 

Missed the TNT night but got a little street tuning done. Seeing about 22psi of back pressure at 20 intake. Engine really wakes up around 17lbs, below that it's s dog. Also doesn't do much till 5k or so. Only seeing 155-160 cold cranking compression. Which seems off for a 10:1 engine. Think I'd really benefit advancing the cam 3-5*, but we'll see how it does at the track before tearing into it again. Last 4.8 went low 9's at 19lbs. This feels slower.

 

This thread is one of my favourite things on the internet. Thanks very much for taking the time to document all of this.

 

Sounds like really low compression, same in all cylinders? What is the rated stock compression of that engine?

 

Thanks!

Yup, within 5psi or so on all. The last 4.8 I had with the triple 12 cam spit out about the same numbers with the small chamber heads... So I guess it might not be to far off. I'll see if I can borrow another gauge. That was also a cold engine with the same Harbor freight gauge I've had for 10 years or so.

 

Well I'm guessing you can throw some timing at it then eh. Boost too. Where do you typically shift with the various 4.8 combos you've had?

 

Photobucket isn't showing your pics. This makes me sad lol.

 

Never really had enough gear to take advantage of the 4.8. Below 6k thru the traps and shifting around 6500-6800. Need to gear this sucker up!



I wrote a note to those *******! Photobucket really sold out, horrible site now. No idea why all my pics disappeared. I'll get it fixed shortly but they are gone from the site as well.

 

Finally got the car out. Not so great results...

The S480 Easily made boost, so much so that I had to keep pulling boost by speed to get it to hook. Fought traction all night but slowly ramping in boost over 4 seconds or so I was able to run some 9.70's @ 150. @ 24 stink'n lbs and 13*. Dog slow for the amount of boost in the thing. Saw a few small coolant drops on my hood after about 6 passes. Couldn't figure out where they came from. Last run of the night I blew a HG (I think). Puffing smoke like crazy stunk like coolant. Logs looked great. 12-13* in it, 10.8 AFR and plugs look fine. No idea why it pushed coolant. I will say I used the MLS felpro HG's this time around instead of the usual LS9 gaskets. Also went with ARP bolts instead of studs. If we've proven the factory head bolts can hold 1200whp or so I think we can rule out the ARP bolts.

 

And how did the Felpros look compared to the GM gaskets ?

And maybe the OEM headbolts being a stretch item, are more forgiving or resilient than people give them credit for ?

Whereas ARP's are usually not stretch ?

I know in the UK, lots of guys running the old Sierra Cosworth engine either go the whole hog and long stud the block, or just use factory head bolts. Regular direct fit ARP stuff is frowned upon because so many have had problems with them.

 

Went with the .041 MLS felpro to try and get a little more compression.

So far it looks like it was the #4 only going by the coolant on that plug alone. The rest looked good, even the #4 plug looked good heat wise. Just into the first thread and 3/4 down the strap. Not seeing any coolant in the pan. May have been an issue with E85 goo on that cylinders injector. I flush all the inj with gas when I remove them, but I did not clean/flow them. I'll do that as well. I'd think the plug would show signs of getting hot if that was the case though.

Spose I'll pull it and see what I'm working with. The trans also was acting goofy. If I launched off the brake the rpm just hung and the car didn't move when I released it for a good second, then the RPM dropped down to like 2200 from 4500ish and it took off like a mini van. So the rest of the night I was playing off the foot brake. Something may be goofy with the trans as well, so the power level may have been there. Slippage looks on par though thru the traps on the 150 runs.

I think the ARP will stretch like any fastener really. I don't see how an OEM head bolt could provide anymore clamping force than an arp bolt. Torqued to 75ftlbs. If the OEM bolt held the ARP should hold. More flex or stretch isn't going to provide any benefit that I can think of?