Shaving heads Vs added filler

[Tweety]

There will come a day when I'll want to complete the SPFI install by increasing the compression of the ea81 to 9.5:1 up from 8.7:1.

A friend told me that its just as easy to get someone to weld filler in the head to increase compression. Can anyone confirm this proceedure occurs and any problems with it?

[Subydoug]

Yes welding will work, but as long as its smoothed out afterwards as I feel a lumpy bead may effect flame propagation and be a prime spot for deposits of carbon to cause pre-ignition. The guy doing it will need some means of accurately measuring each heads volume like a pipette tube.
Major benifit is that the rocker assemble, push rod lengths and whatnot all stay the same.

Advantages with machining, or shaving the heads is that if you spend the time to get the head level in the machine, the volumes will come out all but identical.

My opinion on the SPFI build would be to get the heads shaved and regrind the cam which will keep the pushrod lengths the right length and also throw a bit more pepper into the mix .

That being said, my car with its heads shaved and standard cam works just fine, but I have closed up the tappet clearances a bit to quieten it down.

Regards

Doug

[Tweety]

mm, think after you explaination shaving the ehads 40 tou is the easier way to go.

I have two early small valve heads Doug. If I get those heads shaved 40 thou it should bring the compression up to 9.5. Can I fit larger valves and is it worth it.

So many questions, so little time....oh yeh, am retired now!

[Subydoug]

I do believe shaving the heads is a better solution, or chasing down some pistons that increase the static compression. Welding into the heads could potentially be harder but that being said I haven't done it before so maybe getting them the same is less work then it seems.

I think that as long as you get a 3 angle cut done you should be in pretty good shape with the smaller valves, though if you can get a set of heads in good shape with larger valves then it can't hurt.

A cam regrind will be where you will gain more berries. Steptoe seems to be the goto guy about that though.

Regards

Doug

[Bantum]

Yeah I'd agree with shaved heads - welding then milling the result sounds like a lot of work for not much gain ...

... oh yeh, am retired now ! ...

Congrats ! - Although it means less money coming in, it should give you more time to work on stuff ...

Cheers, Bantum ...

[Brumby Kid]

Shaved heads, then get the new specs sent off to the cam grinder for the perfect cam grind

Cheers Cam

[TOONGA]

See if you can get thin headgaskets (subaru originals?) as well every little bit helps.

TOONGA

[El_Freddo]

Everyone's suggesting a cam grind. With the EA81 you need to split the block to get the cam shaft out. While you've got the block split you might as well rebuild it with high compression pistons or what ever you need to raise the compression

The welding idea sounds great, but I think it would be difficult to do with the valves etc, then the smoothing of the welds would be pretty important too and I'd imagine hard to get all cylinders the same.

Cheers

Bennie

[Tweety]

thanks for your replies. think all things considered, as the bottom end appears in good nick, when the time comes a head shave and possible original head gaskets are the go. Yeh retirement, less cash but thankfully am on the tail end of all Tweety's mods. A Detour motorcycle camper trailer is on order. These are light tare 175kgms with brakes, queen size bed etc. I have a set of spare heads. Next year I'll take the next step. Much touring coming up after the very hot weather has gone.

Just a mention. VW trikes have a definite weight tow limit. 250 kgms no brakes, 300 with brakes. the detour camper trailer allows 125 kgms for- toolbox poly at 12 kgms) porta potti, fridge 17 kgms, 28 AH dry cell battery, chairs, cooking, water. yeh close to max. We sold the Guppy van. it weighed 460 tare, 580 gross. Too heavy for the frame and illegal. Too big an investment to risk.

Detour http://www.detourcampers.com/motorcycle.htm was chosen as it has a lift up bed for storage access, rear tailgate magnetic brakes and strong triple framed drawbar, For you guys looking for a light camper for your 4WDing its a good choice however its small wheels might be its only set back.