Rich92 RS

iTrader: (16)

My 86 Iroc has been running like crap lately. It is hard to start up, sluggish, and can barely hold an idle. For a while now it has been puffing smoke on start up too. Today I took out the number 1 spark plug and it was coated with oil. So I’m thinking it has to either be my oil rings or the valve seals/guides. I will be doing a dry/wet compression test to see if it’s my oil rings, but I’m leaning toward the valve seals/guides as the culprit.

Instead of rebuilding my current heads, I was thinking of maybe buying a set of L98 heads or something else that I can put on there. Will L98 heads work on my LB9? Do I have to do anything to make them fit? I’m still high school so I have to keep a budget in mind.

Thanks

3rdgenZ

iTrader: (1)

as long as you get some L98 heads from a 85 or 86 vette.
or you could go with these > http://store.summitracing.com/partde...5&autoview=sku <

bonz

Sounds like valve guides to me. Mine did the same thing. Once I put on new heads no more problems. It would more than likely smoke under load if it were rings.
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Mods. GMPP Vortec heads, Comp Cams XR269HR, Crane Gold Rockers, Hooker headers, SDPC intake manifold, free flow exhaust, Air Foil, De-screened MAF, TB Bypass, K&N filter. Future mods, TPIS Runners, AFPR.

anthony64ss

iTrader: (1)

The L98 heads will totally screw up your compression. Going from little 58cc chambers to 64cc cambers is not good. If you have to get l98 heads, shoot for the aluminum vette/zz4 heads.

It just sounds like valve seals. Totally easy to replace. Takes about 3 hours and less than 50 bucks. It can be done with the heads on the car. Search and there are tons of threads on how to do this.

Rich92 RS

iTrader: (16)

The main reason I thought about putting L98 heads on is because they weren’t too expensive, and I could find a pair fairly cheap.

I know the valve seals will be easy to replace, but I thought why not just get a new set/used set (rebuild them if I have to) and maybe get a few extra hp. To me I think that would be easier.

I was doing some searching and I found this thread. I haven't read the whole thing yet, but it looks like 1MeanZ put a set of L98 heads on his 86 LB9 without any modification. Here's the link https://www.thirdgen.org/forums/tpi/...ight=58cc+64cc

Brisk

iTrader: (25)

The difference there is he put on aluminum L98 heads from a Corvette. These heads are 58cc, and not 64cc like the iron L98 heads found on F-bodys.

Rich92 RS

iTrader: (16)

Ok, so as long as they are aluminum L98 heads off a Corvette, I should be fine. Do they have to be a certain year like 3rdgenZ said?

Thanks for the help, now I just need to find a set.

3rdgenZ

iTrader: (1)

the reason they need to be 85 or 86 is because of the intake bolts. on our heads (85-86) they used a diagnoled bolt pattern where as the 87 to present use a straight down bolt patern. the combustion chamber is bigger but thats nothing some milling cant fix. i belive that they didnt make the aluminum heads until 87.

1MeanZ

iTrader: (9)

There is TONS of BS in this thread!! Man this is crap. You guys need to get your facts straight before you post please!! Brisk is the only guy on here so far that has not spewed complete garbage here. This kind of misinformation will only discredit this site.

86 corvette heads are aluminum and have 58cc chambers just like 305 heads. The early heads dont have the improved exhaust ports. I cant remember off the top of my head the casting number for these, If you need to know it do a search. I think Zepher is runnign a set of these early heads, but I could be wrong.

87-91 Corvette heads are aluminum as well and have 58cc chambers just like 305 heads and they have the good D port exhaust ports. The last 3 digits in the casting numbers for these is 113. These heads are basically the same as the ones used on the ZZ4 crate motor, although later 113 heads have had minor improvements. I bolted a set of these heads (from 91 vette) on my 305 and had no issues.

On ALL of the aluminum L98 heads I have seen, the intake bolt pattern is the old style, all of the intake bolts are the same angle. The center bolt iron heads (exc. vortecs) have the revised intake bolt angle on the center 4 intake bolts.

To sum this up, any aluminum L98 head will bolt right onto a 305 and work nicely, they should have been installed from the factory in my opinion. I ran these heads on my 305 with a mild flat tappet cam, headers, and ported intake ran 13.70s @100.5mph with my 5speed. That was with a terrible 2.1 60ft. with a good launch the car would have went mid 13s at least. This combination also got 28mpg on the highway with 3.23 gears. Many people say that these heads dont flow that much better than iron 305 heads, and if you port your iron heads you can outflow these. That may be true, but for the money I just bought a set of these used, did a valve job, and slapped them on. No porting, no hassle, great power and reliability. Do a search for my screen name for more info.

Brisk

iTrader: (25)

well said 1MeanZ, now thats one guy who knows his aluminum L98 heads!

3rdgenZ

iTrader: (1)

but why would GM chang the intake bolts for the iron head and not the aluminum head? in 87 and up

and i was refering to the iron heads

ajk511

oh crap. i was gonna go buy some aluminum l98 heads out of a 91 vette at a junkyard tomarrow. will it kill my 91 L98 TPI to go from 64cc to 58cc heads? or will i be fine. im also putting in the lt4 hotcam package from summit.

3rdgenZ

iTrader: (1)

no it will help make more power. but the intake bolts are different from what 1meanZ says. the springs in that kit wont fit in the stock L98 seat. but that may be different too in the aluminum heads???

rocluvr0013

Aluminum heads help with cooling so the increased compression will not be that big of a deal.

1MeanZ

iTrader: (9)

if you had an aluminum head and an identical iron head, they say you should raise your compression one full point to get the aluminum heads to make the same power as the iron heads due to heat loss of the aluminum. I have not done the math to figure out what your compression would be if you swithched to 58cc chambers from 64cc, but given the fact that the heads are aluminum, you may be OK. Just do your own homework on that, I can not give you a recommendation in good confidence because I just dont know.

As far as the intake bolts go that is not a big deal. Lots of guys will just hog out the bolt holes in their intake manifold so the bolts fit. I have heard of no one having a problem doing this, so the intake bolt angles should not scare you off.

I also can not answer the LT4 valve spring question. However I can say that the stock 'vette L98 springs are double springs. Do some checking, but you might be able to just use the 'vette springs with the LT4 cam as long as the coils don't bind up. It is also possible that the LT4 springs will fit the 'vette heads anyway.

Brisk

iTrader: (25)

The springs from the Hot Cam kit work perfectly fine and are the correct size for the aluminum L98 '113' casting heads, I know this for a fact because I'm currently using them with my setup.

As for the inatke holes, 1MeanZ is correct, they are in the same location just at a different angle. With 30 seconds and a die grinder, I elongated the holes on my intake for a perfect fit.