New member/preload/compression/head gasket.38D,suffix A?

[twinpipes]

Hiya,to all you v8 fans.I have a 38D suffix A 3.9 in a classic range rover,I bought the vehicle some years ago with the head gasket gone between pots 1 & 3.upon stripping the engine it had composite gaskets with a chunk missing between the two pots.I had the heads pressure tested & skimmed & also opted for the standard tin gaskets has I run LPG most of the time.Myself being a qualified toolmaker,did a bit of porting which I have done on various other engines in the past/A series,B series & ford pinto.This done I rebuilt the engine using the standard cam & followers,these were like new,this being my first v8 I used the standard torque setting in the haynes manual,to find the head bolt between pots 1&2 stripped hence the blowing head gasket,this I helicoilled & repaired,no problem,I did not know anything of setting the pre-load as it is not mentioned in the haynes manual.I am now setting the pre-load and thinking of shortening the pushrods to achieve this,what do you think & what would you recommend setting the pre-load at.What do you think my compression ratio will be,the head dimensions are now, 63.2 & 63.3mm.Any help appreciated,many thanks Mark/twinpipes!!!!.P.S. it was low compression 8.13-1 before/it is now running headman headers & twin pipes right through,with the lambdas in the headers,although I am running a 3.9/4.2 non cat fuel map in the 14 cux,by the tune resistor,Thanks again Mark/twinpipes!!!!Back again its an auto box!!!

[mgbv8]

You dont shorten the push rods to get pre load. You shim the rocker pedestals. If you have fitted tin gaskets in place of comp head gaskets I guess you are worried about the heads now being lower, and hence the push rods now being effectively longer than they were before?

So you buy a shim kit and put shims under the rocker pedestals to move the rocker assembly up a bit

[twinpipes]

hiya,thanks for the advice,it seems as though there is conflicting ideas with regard to the pedestal shims because it makes the angle that the rocker pushes upon the valve stem even worse.What size pre-load should I set them to,these also come under conflicting ideas with regard to dimensions.I have emptied all the oil from each follower and re-torqued the rocker assemblies,all of my pre-loads are on the big side of an approx 125 thou,one 1/8".Any advice greatly appreciated many thanks Mark/twinpipes!!!

[DEVONMAN]

hiya,thanks for the advice,it seems as though there is conflicting ideas with regard to the pedestal shims because it makes the angle that the rocker pushes upon the valve stem even worse.What size pre-load should I set them to,these also come under conflicting ideas with regard to dimensions.I have emptied all the oil from each follower and re-torqued the rocker assemblies,all of my pre-loads are on the big side of an approx 125 thou,one 1/8".Any advice greatly appreciated many thanks Mark/twinpipes!!!

As you are using a standard lift cam then you should be ok using shims but as you say it is not the best way. Other ways will cost you far more dosh. Even if you but adjustable push rods, depending on the supplier, you may need to shorten them.
The preload should be between 20-60 thou.
So with your current value of 125 thou, I reckon you will need 50 thou shims allowing for the 1.6 rocker ratio.

Regards Denis

[twinpipes]

Thanks for the reply devonman,I thought that the 20 thou mark would be fine also.Me myself being a toolmaker thought about shortening my own pushrods,obviously keeping the correct radius on the ends & sharing the excess between the two ends,whats do you think?Thanks Mark/twinpipes!! P.S. love the A40 just had a peep on photobucket.I am thinking of later going the twin turbo route or maybe I am just dreaming,although I can probably make most of the metalware myself.What turbos do you use and what boost do she run/I presume you are using mapable fuel & ignition on the car.Many thanks again Mark/twinpipes!!!

[softdash3.9]

I have the same engine spec 38D in my Range Rover Classic, I fitted steel gaskets to up the compression, I just checked the dry follower clearance and it was acceptable.

Ran no problem.

Later I rebuilt the engine with 9.35 pistons

[DEVONMAN]

I don't know much about the way push rods are heat treated, so can't really comment on your shortening proposals.

The turbos on the A40 are T3 4x4 sierra units with .63 exhaust housings.
No noticeable lag with the 5.0 engine.
I currently run 10 lb boost with 9.5 CR but did previously run 15 lb boost when the CR was 8.5. The car is more drivable now but the top end has suffered slightly.
The Holley fueling is mappable and the ignition is megajolt.

Great fun but still waiting for the TVR crank to go bang.

Regards Denis