rodj

Wondering what people have done when installing LT4 /ZZ4 springs on L98 heads?
Did you use the LT4 spring seats supplied or keep the original ones?
My inlet seals are fine but will have to replace if I swap the seats.
Did you reuse the original splash shield under the retainer?I'm of the opinion that anything that keeps the excess oil off the stem is worth keeping , it worked fine stock but appears to have been deleted when they went to umbrella seals on all valves

rodj

ttt

65Z01

When I did the 1.6:1 ProMagnums, though I used CC 981 springs I tossed the oil shedders and installed Ti retainers with 10deg locks to lighten up the valve train and raise the safe rev limit. BTW I also instlled all new upper & lower OEM oil seals on the valve train; that was nearly 5yrs ago and no oil leakage.

CentralCoaster

Any difference on spring fitment on the iron heads vs 113s?

rodj

" I also installed all new upper & lower OEM oil seals "

So you installed umbrella seals on the exhausts where there were only umbrellas on the intakes and the "O" ringunder the retainer on all?

What seals did you use GM or aftermarket?
Are installing the lightweight LT4 retainers that are part off the hot cam kit.
Just looking at saving some money by not destroying the intake seals to replace the seats if not needed as no smoke problem at present.

Grace91

I did the LT4 valve springs, seats and light weight retainers on my L98 113 heads last winter. I also used the keepers designed for the LT4 retainers. You can’t use the old spring seats or retainers, the LT4 springs won’t fit on them.

The L98 seats are much thicker than the new LT4 seats so you will need to be prepared with a ton of shims. I think I used somewhere between .100 and .090 worth of shims per spring to get the correct installed height.

I pitched the oil shedders that sit below the L98 retainers. I have zero oil control problems. I also put in new intake and exhaust oil seals along with the little rubber o-ring that goes in the retainer while I was in there.

HTH,

rodj

"You can’t use the old spring seats or retainers, the LT4 springs won’t fit on them."

Maybe the sizes changed through the years.On the '89 engine I am using the zz4 / LT4 spring fits perfect on the L98 seat.That is why I queried if anyone was using them.
Have run 2 meetings with no problems except smoke at hot idle because I was in a hurry to go racing and forgot to buy the "O" rings which had gone brittle.
Have time now to go back and do it properly.

AGENT 86

I put them in my 86 2 years ago. LT4 seat/shim and cap are required. I also installed 16 felpro viton intake seals and all 16 "O" rings. On my 86 heads i had to shim the exhaust side as i got rid of the oil shreaders and rotators. I don't think your year had the rotators so your shim should be quite thin.

nel

Hmm...I installed the LT-4 springs, retainers and keeps on my '87 but don't believe I installed any shims. What problems should I expect (car is not currently operating)?

Grace91

I’m afraid that if you didn’t install the LT4 seat under the spring you will probably have two problems.

The first will be a spring that is not installed to the prescribed spring height. This will leave you with sub-optimal valve seat pressure which will subject the valves to “float” at high RPMs which is a bad thing. You probably also need to add some shims to this equation to achieve optimal spring height.

Secondly, with no steel between the spring and the aluminum head, the spring will eat away at the head over time, putting aluminum shavings in your oil and ultimately ruining a good pair of 113s and maybe a perfectly good L98.

rodj

" don't believe I installed any shims"

Is that you installed the LT4 seat with no "shims"
or you did not install the seat at all in which case you will get the result mentioned above.
Using the stock L98 seats and a zz4 cam I have been reving well past the cam 's peak with no problems

AGENT 86

You "NEED" the LT4 seats on all springs !!
You "NEED" to check installed height and add shims if needed.
Only if you want things to last

65Z01

rodj, by OEM I meant GM lower seals and upper O-rings.

So it sounds like the LT4 springs are larger dia at the bottom than the stock late L98 spring seats??
Are the LT4 springs the "bee hives"?

When installing valve springs you should always:
-check installed heigt vs mfg spec
-check for coil bind
-check for valve seat clearance
-shim as required to meet these

Comp Cams has a nice "variety shim pack" that can be ordered directly from them.

shotchkiss

Here's what I used on an '89 with the 113 heads, we didn't use any additional shims other then what came with it and the installed height seemed to come out fine:

LT4 springs #12551483 (kit #12495494)
LT4 caps #10212808 (kit #12495492)
LT4 shims #10212809
Lock kit #12495503

johnnyevans

They aren't beehive, they are the same od as the 113s +- couple thousandths. Do use the LT4 spring seats and the retainers and keepers. The older L98s used a rotator on the exhaust valve, The iron head ones I saw at least. Do use the vitons, I don't normally use the o-rings and I don't have oil control problems.
Hi performance springs tend to chew on the spring seat of au heads.

tequilaboy

Sorry for the late response, I was on a cruise last week.

Here's what I did to go with my comp XR276HR12 cam:

I used the LT4 seats, springs and retainers, and re-used my original keepers. Installed height looked good with a steel rule. 1.78 or 1 25/32" I think.

Note: L98 installed heights are more like 1 23/32" or 1 21/32" if rotators are present. This is due to the thick L98 seats and retainers

I replaced the 8 rubber intake valve seals and 16 O-rings. You're right these must come off to get the seats off. Use pliers on the seat stem to pull the seats and seals off at the same time.

I also installed 1.45" comp cams oil shields on the exhaust valve springs, under the retainer, since I didn't have enough retainer to seal clearance to run the plastic umbrella type or rubber intake type seals on the exhaust. They are larger diameter than the springs which are 1.32" but I don't see any problems going this route if your rockers can clear the shields. No problem with my crane gold 1.5s.

If you use the original spring seats then you will reduce the installed height, since they are thicker than the LT4 seats. This will put you closer to coil bind, raise seat pressure etc, but I think it could work depending upon the cam etc.

Davemc1963-87conv

nel, If you have the stock 87 '128' heads, your exhaust valve installed height will be way too tall. The 128 heads have different spring seat depths to cater for the exhaust rotator that is about 0.125" thick.
You may be able to get nearer by shimming up a little, but the easiest way to loose height is with crane "short installed height" valve locks (keepers/collets or whatever people wish to call them). On my 87, albeit with probably a different combo and Manly pro flo's, I have gone with a short installed height lock on the exhausts and a long installed height lock on the intakes. This gives me a 1.822" installed height on all my valves. But like I have mentioned, I have different valves and springs to you, so you may end up with different heights. But like someone else has mentioned, if you have not shimmed up the exhausts, you could have serious trouble. Valve float usually means pistons and valves can get very cosy with each other! As an example, I am using NON stock 1.1/4" OD springs and I am shooting for about 115lbs seat pressure at this height. With a loss of only 0.050" compresssion height, I would loose 20lbs seat pressure. ( I don't have figures for my springs outside this range, although they tend to be linear within the springs operating range) You are loosing more than double that and I suspect my springs have a higher rate than the ones you have. If you are using a stock L98 cam, you might get away with it, but I wouldn't bet on it. Please check them out.

nel

Davemc and others, thanks for all the helpful advice. I have to tear back into the car because of a leaking waterpump back plate, so I'll definitely look at the installed height of the valve springs. I'm fairly certain I made some mistakes, but hopefully any damage will be minor because I really haven't had the chance to drive the car this year.