My 4.6 V8 Rebuild Thread

[Davo]

Yeah lots of work vs gain and it really needs to be part of a bigger upgrade path if induction. Such as inlet, larger MAF (or elimination), cams, valves, exhaust.

The V8's they ran in the grp A 3500's had little if any actual valve work. I know they are smaller but as a comparison the Toyota 1UZ (4.0) runs same set up in that, the 4.7 and larger. I went to the maximum lift and duration that could be done within the scope of machining the original heads for lobe clearance and spring capacity (added about 6-7mm to the tip of the lobe in weld) and still used the stock valves and they weren't the restrictive area of the intake.

Yeah, wot 'e said. Since you're not building a high-rev engine then a lot of the above won't make a huge difference anyway. Very often the performance work people get into is great for racing but pretty useless for a low-revving torquey engine that you need for a 101.

[clubagreenie]

I have read a lot of papers on theories of plenum volumes and dimensions/tapers etc and influences on pulse reversion and such.

These days you really just need to look at a few of the major performance designs of engines (Ferrari/McLaren etc) at their plenum designs and go from there. They all seem to base their's on a bridged design, with dual intakes. MAF-less and tuned trumpets and optimised volume vs taper to satisfy inlet tract pulse reversions.

Keep it simple, longer stroke, strengthen it (even consider a girdle for the block) and make sure cooling system is up to the job. Consider a new heavier flywheel, keeping the energy of the engine available and rotating longer. It'll rev up slower but be better for moving the mass of a 101. If you start building a torque monster you have all sorts of other issues.

[101RRS]

I mounted the block on my engine stand and test fitted the old head bolts and noted that on the hole that was repaired seemed a bit loose around the treads. On checking closer I could not detect any helicoil which they were supposed to install - wasn't on the bill either. They had just retapped the hole and unfortunately the treads in the middle 2/3 had previously been stripped so the block is back getting the helicoil put in.

After discussion with the workshop I will stay with standard heads and valves and they will just clean up the heads and check them right over.

I have yet to speak with Crow Cams about a torque cam but will do shortly.

I will look at ordering bearings, rings and gaskets tomorrow from local sources - is there anything you do not get in a gasket kit that I should be ordering.

Oh - head gaskets - with the block being lightly shaved (decked) and possibly the heads skimmed and the piston compression ratio at about 9.2:1 should I be getting composite or tin head gaskets. I will be using ARP head studs not bolts so a three stage torquing up process will be used and not the degree process.

Thanks

Garry

[bee utey]

Composite gaskets are standard for all later engines with TTY bolts so I would stick with them. I'm not keen on the tin ones, too little room between the head and piston edge for any carbon to fall into safely.

[clubagreenie]

As long as you follow the ARP torque procedures to the letter and don't worry about buying their assy lube, but don't use oil. Get a good moly assy lube, I know Crane Cams have one and most people will market something under their name, just use liberally on bearings and lifters/rockers, everywhere that won't have oil until you prime the system for the first time, not sure of the procedure for the 4.6 w/out dizzy hole?

[bee utey]

As long as you follow the ARP torque procedures to the letter and don't worry about buying their assy lube, but don't use oil. Get a good moly assy lube, I know Crane Cams have one and most people will market something under their name, just use liberally on bearings and lifters/rockers, everywhere that won't have oil until you prime the system for the first time, not sure of the procedure for the 4.6 w/out dizzy hole?

For oil priming remove the oil pressure switch and slowly hand pump a litre or three of oil in that way. Works on any engine.

[101RRS]

I got the block back today with the helicoil in and the thread is now all nice and tight.

Priced the bearings, gaskets and other bits and pieces from a local supplier and all seem good so will order early next week after clarifying a couple of things.

Contacted Crows Cams and got a price of $310. I am looking at getting the Highway Cam



Logic being that the 101 manages 4000rpm at 100kph so that I need torque a bit higher up the rev range. At the lower end the increase from 3.5 to 4.6 litres should be enough to cover the small gap from idle (900 rpm) to 1250 rpm. I just need advice from Crow whether different valve springs are needed. I am staying with the standard 4.0 heads. (I believe they are the same as the 4.6s.

So it is slowly coming together - the next issue is whether to go with rejetted CD carbs which I have, run a Gems injection system (from a 3.9 which I have) run by something like MegaSquirt or put a Thor manifold and injectors on (which I don't have but can get) and also run by something like Megasquirt. Standard maps for both systems are available saving a lot of cost and time on a dyno.

One thing I can assure everyone is that even doing a relatively base rebuild sure does run up the bills - hence why this is a slow build.

Garry

[clubagreenie]

Ask about springs they recommend and also check what the nose pressures will be. To soft will have the valves floating due to the loss of control of the valve, and is the common cause of valve bounce. It can also have the faces of the lifters fracturing due to the resonance of the system bouncing the lifter on the cam. I wouldn't recommend on a standard cam as they are soft enough to wear out at the increased load, but an aftermarket cam should handle it.

You think a std build runs up the bills, I spent $1600- on valve springs alone for a build. $4000- on pistons, $8000 on cams. For the first engine. Total budget exceeded $50-K

[101RRS]

Ordered all the bits to rebuild the engine - while most bits were of similar price I found the cost of rings were over a wide range. Those who only sell rings for individual pistons were around $50 per piston - where they are in an engine set the cost was a lot less - down to $200. So I guess you pays your money and takes your chances.

Also found an interesting thing re differences between 4.6 piston gudgeons and 4.0 gudgeons - while the outside dia is the same on both - the wall of the 4.6 gudgeons are much thicker than the 4.0s I guess reflecting the greater downforce in the 4.6 combustion process. However without knowing this it would have been easy to leave the 4.0 gudgeons on the 4.0 pistons when I put them into the 4.6 - a spot for possible failure in a hard working engine of the future.

Crow Cams have come back to me and recommended the cam I was looking at in my previous post so I have ordered it. Standard springs will handle the extra lift and as has been highlighted here - running in is important as is machining the lifters.

Induction Question Time

For ease of the build I was going to make the engine with carbies and sort whether I should change in injection later - however when discussing this with my local independent this morning he indicated that GEMs injection would be just as simple with the loom and ECU as it only has basic inputs. I have the manifold, plenum, and injectors and would just need to source a loom MAF and ECU from a wrecker.

I asked about a Thor system and he was less sure but thought it would work OK as most of the sensors are in the induction system but he was not sure.

So - comments - suggestions - pros - cons?

I can do a GEMS and Carbies real easy - is a Thor system going to give me any real advantage over Gems.

Thanks - and thanks for all your ongoing comments and input. This was always going to be a slow build but it is slowly happening.

Also thanks to the comments over on Chiefs Engine Assembly Thread http://www.aulro.com/afvb/technical-...echniques.html this has reinforced that the way I was going to put the engine together is generally the correct way - indeed as I have done on a few rebuilds in the past.

[Pedro_The_Swift]

but pretty useless for a low-revving torquey engine that you need for a 101.

I
Logic being that the 101 manages 4000rpm at 100kph so that I need torque a bit higher up the rev range.

Garry

hmmm,,,