Noahs944

Dropped off my original 1988 n/a 8 valve head to an engine rebuilder facility, so he can assess & quote.

I told him:

"I'm considering 2 paths.

1) fit & machine 47mm intake valves & open up the exhaust ports. Plus the basic rebuild guides/seals/valve lap

2) shave .030" off the bottom to increase the CR. Stick with the factory valves. Open the exhaust ports, perform the basic rebuild.

In either scenario Turbo valve springs will be installed."

I'm leaning towards option 2 because the larger valves might require fly cutting the piston which might be opening a can of worms I might regret, plus that adds quite a bit of parts expense.

(And the little voice in my head is telling me I can get around the same performance gain by shaving the head).

So, if I were to do option 2, should I go further? Is there a lot more I could do? Or all things considered (budget is a concern), is option 2 the way to go?

Am planning on keeping the factory hyd lifters, factory 1.1mm head gasket, and am considering going back to the camshaft I had before with .474 lift. Or if the valves don't hit the pistons, maybe stick with the .502 lift cam I have been running.

Thinking the .030" shave would still allow for pump gas to be used. The exhaust port REALLY has a lot of metal preventing the flow as one can see clearly when a gasket is mounted.

Thoughts or suggestions? Thanks.

odurandina

all this for 9~13 hp?

get an Evo. this kind of stuff just isn't necessary for an 8v '80s classic.

I know I sound like the biggest ***

sorry. but I think people sometimes go a little haywire without seeing the big picture....

enjoy your nice resto for what it is - and not get all hurt with occult ****.

V2Rocket

unless you are running high RPM, bigger displacement or a bigger cam you will be OK with just a standard head rebuild and standard valves.
your 1988 engine is already the highest-CR 2.5 engine offered in north america, upping CR the amount you'd gain with that kind of shave wouldn't really net you much power.

the 1987 944 had 9.5:1 CR and the 1988 had 10,2. going up 0.7 CR (all in the piston) got 5 HP but required higher-octane gas to get there.

you might get 1-2 more by shaving the head more than is necessary for a clean-up. the head as standard will support you just fine, a hot cam is what you should try.

Noahs944

I already run one of the hottest cams bro.

thomasmryan

the early 70's 2.4 mfi motors came in three flavors; T, E and S. The intake runners and throttle butterflies (28-30-32) where sized to match the different cams with a huge disparity in HP numbers and drivability.

I would port match and shoot for 10:1 with your 'big stick'))

it is a dark science....100hp/liter is magical but it comes at an expense. ask any S2000 owner.

odonnell

What about porting and polishing the head? I bet you could DIY and save a lot of money. V2 is right about the CR being less relevant.

Arominus

don't shave the head, 10.2 is enough with the head design for pump gas. I like the port/polish/port match ideas here. I'd go there.

Van

Do your research... while a DIY port/polish job will save you money, it won't really give you much power gain (if any). There is a real science to that... and experience pays off.

Paulyy

bigger valves, ported head. get bigger exhaust valves also since there's no ceramic like the turbo heads.
4-1 tuned headers, probably a short runner intake.
47mm intake
42mm exhaust

Then you should see some results.

wildcat077

That is a lot of cam ... you definitely would need larger intake valves and some professional porting if you want it done right !
I would question the experts like Michael Mount or Jon Milledge regarding all the work you plan on doing as you might just be throwing your money away if not done properly.
Obviously you would need to tune everything on a proper dyno with an adjustable fuel pressure regulator and AFR gauge ...

Just sayin ...

Cheers
Phil

Paulyy

You can have a lot of lift, but if you have low duration, wont do to much more.

reno808

LOL

Brah if you already running one of the hottest cams then why upgrade your head even more if it had to be upgraded. Your already running one of the hottest cam bro.

If I'm incorrect bro, can you please define "hottest cams"

reno808

not much, specially if thats the only mod. and depending on what your looking for 4-1 "tuned" headers may hurt you. At least by the looks of the OP

Noahs944

My mistake for the short answer. I just wanted to focus on the head & not the cam. If I could re-word what I said: "One of of the hottest cams that I know of, without needing to machine the head, and still have something thats street-able for a DD".

I've posted this information before. The cam I have been running lately: Milledge 8sr-14: http://jonmilledgeengineering.com/product/8sr-14/

Big THANKS to everyone for the insights & ideas.

V2Rocket

save your money on valve work/porting. even with that cam you just aren't moving enough air to overwhelm the stock head. while the shape could be improved the ports are pretty darn big already and flow very well as standard.

unless money is no object for this car, then go nuts.