Fast355

iTrader: (2)

I know, but I have seen ALOT of flat-tappet truck L03/L05 engines transplanted into these cars.

neagan

iTrader: (7)

I must say; that Gilbert Chevrolet site was extra-extra helpful and I'll bring along print outs to my next meeting with the engine builder.

It looks like I just need to focus on a few areas for finding cheaper parts off our classified board:

~ The Valvetrain: The World S/R Torquer heads arrived today and they look great; even came with a new set of Edelbrock valve covers! It appears to have a 76cc chamber, valves: 2.02x1.600" 11/32 with a max lift of .560". We'll be porting the hell out of these and upgrading to heavy double springs. How do I choose my roller lifters? What's the highest lift I should shoot for? The advertisers in Summit/Jegs claim 15-40 friction free horsepower and pricing is all over the place, including Crane Cams $800 set of lightweight high-performance rocker arms. Then there's mention of rocker designs that 'change' the geometry of where the lifter opens to the relationship of the cam lobe.... huh???

~Double roller timing gear set: Do I need a billet true roller with infinitely adjustable timing? Is a two piece cover neccesary?

~ oil pan and pump: I understand that one can put to much of a high volume pump in the pan? Does it really matter what shape of pan I use or is it important for longevity (my goal) to use a higher quart capacity unit?

~ Lastly, the Water Pump:What is appropriate for hot california summer, stuck in traffic for hours???

This is going to be fun! I'm glad I chose not to just freshen up my 150k mile engine. There's nothing like a forced crash coarse learning curve

Is there anything else I should know before sitting down and ironing out the parts list next week? This engine is going to sound so sweet that I just may need to delete my radio!!!
Nitro

Kevin91Z

iTrader: (1)

With those 76cc heads you're going to need pistons with one hell of a dome on them to get the compression up to the mid 9's like you'd want. Your engine builder should know this. A lot of roller cams have lift around .500" with 1.5 rockers. You can go with 1.6 rockers for more lift, if you want. You dont need the $800 set. A $300 set of Harland Sharps or Crane Golds should be fine. Just make sure they are for centerbolt valve covers if thats what you have. Most are only for perimeter bolt valve covers.

Only if you want to spend more money. The two-piece cover is if you want to change the cam later. Keep in mind, they are notorious for leaking oil.

Yes the shape of the pan is very important. I've seen many aftermarket pans designed for 82-92 Camaros really dont fit with the y-pipe. I havent found a good one yet, perhaps someone else here has. You dont need a high volume oil pump unless you have a blower or turbo that needs oil. Your engine can only push so much oil thru it, and if you're trying to push more you're just wasting power turning the pump. Most of us have had lots of success with the Melling M55A oil pump.

A stock pump will work, with a 160 degree thermostat and a clean radiator. If you want to spend money, see Stewart (first choice) or Edelbrock.

Good luck with this! You're up in NorCal, right? Check out the guys on the West Coast board here. I'm sure they'll be happy to help you get it fired up.

Damon

Guys, the compression on the L-98 was officially rated at 9.3:1 for all years of production except the first (1986 when it was 9.5:1). I won't argue about 90-92 pistons being flattops, becuase I can't remember the last time I ripped into an original L-98 of that vintage (if I ever did). Just be aware that to hit 9.3:1 with flattops either the factory would have needed to use a significantly thicker head gasket, changed the combustion chamber volume of the heads (they didn't), or they just flat-out fudged the stated compression ratio numbers where the motor actually had more compression than they said it did.

bluegrassz

iTrader: (3)

With all things equal: combustion chamber, deck height, head gasket.
A L98 with a dish piston could not have the same compression as a flattop as said the 9.3 to 1. I have ran across the 9.8 to 1 numbers in either my chilton or haynes manual. When I tore down my 91-92 L98 motor this winter, it did indeed have factory flattop pistons. I even have a pic of someone elses motor with the same pistons. I beleive the stock head gasket from GM was part #10105117 which is .028 thick. When we measured the deck height, it was either .020 or .025 in the hole.

Im not trying to argue, just post some first hand info and some I have dug up.

Here is a pic of the stock L98 flattops.https://www.thirdgen.org/forums/atta...r-pistons2.jpg

Dished Stock L98 Piston pic>https://www.thirdgen.org/forums/atta...jr-piston3.jpg

Fast355

iTrader: (2)

Keep in mind that the 9C1 Caprice came with the same shortblock/cam as the F-cars back then. In 1990-1991-1992-1993 the Caprice 9C1 came with flattop pistons and an advertised 9.8:1 compression. Even the tame civilian version was 9.6:1.

Damon

I think we can safely say that GM fudged the compression ratio on the later motors, given your experience with them (thank you for noting the head gasket!). With that later combo using flattops you're right at 9.8:1.

Looks like GM just carried the published specs forward from the old days of dished pistons even though they actually made a change to flattops in the production motors.

Wouldn't be the first time we've found that things were different in production TPI motors than what the specs said they should have been. The lively discussion about the infamous "peanut cam" in later 90-92 305 TPIs with automatic transmissions comes immediately to mind. They were supposed to have them, but they didn't.

bluegrassz

iTrader: (3)

Your welcome!

I was pleased to find I had the flattops and not the dished. I ended up going with the same head gasket, stock piston, stock deck, but had my AFR 190's milled to 60cc's. I should be somewere between 10.3 and 10.8 to 1 compression.

Damon

Assuming a 30-overbore on the motor I calculate you at just shy of 10.4:1.

bluegrassz

iTrader: (3)

Nope stock bore. I just did a head/cam/intake swap on the L98 bottom end. I did a compression check and every cylinder was within 5 of each other.
It ended up being a strong motor. Its strong out of the hole and pulls hard on the big end. I really give props to Edels RPM airgap intake.

Of course we worked the heads and intake, so they are not exactly out of the box pieces.

bluegrassz

iTrader: (3)

Oh yeah, here is my sig with my complete combo and track times.

ReEntry Racer

I bought a new GM ZZ4 partial engine last year to refresh my road race TA.
I refreshed the (very) used GM alum. heads with a good valve grind (no porting) and installed the used stock ZZ4 roller cam with the used stock lifters. I thought I'd replace the single roller cam chain set with the Edelbrock double one... big mistake! I thought it was a fluke that the cam spocket rubbed on the block, so I tried another one...it did too! I got out the dial gage and found a .009" wobble in both spockets, right out of the box. I bought the GM parts from the GMPP catalog and have been running this engine very hard for about 30 hours of road racing, with no issues at all.
I do use the Edelbrock Air Gap intake and a 750 Holley, and it has corrected dyno numbers that are disappointing, 280RWHP, 300LBFT. I know it would make more HP with a bigger cam, as I got just over 300RWHP on the previous block with Crane's best hyd. roller cam, with all the same parts. I've elected to run with less power to conserve the rest of the car (tires/brakes/diff/trans) for this year. Its even better on fuel consumption!
One more note: the timing chain cover is plastic, and is supposed to be a single use item, and it actually is. Don't reuse it, and don't try to put an older style metal one on, as it will really leak! Good luck with your car!
Larry in BC

Damon

10.25:1 with a stock bore, in that case.

five7kid

iTrader: (14)

I'll try putting my oar into this CR water here:

'82-'86, the "higher" compression engines (LU5, L69, LB9, and '85-'86 LG4) had flattops with 4 valve reliefs (something like 6cc piston crown volume) for 9.5:1 CR. In '87, they all (LO3, LB9, L98) went to slight dish with 4 valve reliefs (something like 12-13cc piston crown volume) to produce 9.3:1 CR. In all cases, the 305's had 58cc head chambers, and 350's had 64cc head chambers. All used a steel shim head gasket.

I don't know about the '86 L98 (or '84, or '85), as those were Vette engines (and a very, very few '86 f-bodies). They don't exist in the "real" world, don't ya know. . .

The ZZ4 comes with 4-relief flat-tops, which is why it's higher with 64cc heads than the production L98's. Gee, you can get those pistons from Pace for only $90.78/each!

anesthes

iTrader: (12)

The vette L98 had flat tops too, or at least my '87, and my friends '89 did.

I pulled apart a L05 from a police caprice and that had flat tops too.

I don't know why the early L98 f cars got the dish pistons.

-- Joe

Damon

Almost all 350s from the early-mid 70s on up to (apparently) about 1990 used very similar dished pistons. I'm sure the factory just kept on using them when they started putting FI on the motors, like the early TPI motors. You're jsut lucky that the TPI motors got smaller 64cc heads unlike the really dark days of smog emissions when they were almost all 76cc heads and compression was in the low 8s!

Tight quench and high compression used to be the enemy of passing factory emissions testing for the manufacturers. Full-face dished pistons were a common trick to help them out so it's not surprising they would keep using them for a while, even with fuel injection.

You can beleive it or not, back in the mid 80s a factory motor with 9.5:1 compression was like "pinch me, I must be dreaming!" It was a big deal back then. Today it's a snoozer, but back then we had all been dealing with factory motors in the low 8s for almost 15 years. It was like we could all finally see the light at the end of the tunnel. Then all we had to do was figure out how to use this new-fangled electronic fuel injection stuff vs. the carbs we had all grown up with! But that's a story for another day.

87cmroiroc305ho

iTrader: (2)

does anyone know if a l98 water pump will work on the 305 sbc, p m me yea or no please, thanks in ahead