When I was young, dumb and full of ... well you know... I had some chopshop engine and tranny exchange place take out my 305 ho and put a rebuilt back in. My question is what are the physical difference's between a 305 and 305 ho? the only thing I'm positive of is the cam... but are there any others? Do the heads have a smaller comb. chamber? different pistons? Also a side question.. I thought I read somewhere that chevrolet put a DOVH cam 32v v8 in a corvette sometime in the 90's... Is that true?? I got called on it and now ( of course ) i can't remember where I read that.. Thanks alot

 

Early LG4's had dished pistons resulting in lower compression the L69's too. Later ones were the same.

The Corvette you're thinking of was the ZR1 with the LT5 aluminum DOHC engine available from 1990 until 1995. The 90-92 TPI LT5 had 375 hp @ 6000 and 370 lb ft @ 4800, and from 93-95 it had MPFI making 405 hp @ 5800 and 385 lb ft @ 4800.

[This message has been edited by Apeiron (edited August 24, 2001).]

 

Right... differences between L69 and LG4 changed over the years. In my year, 83, the heads, intake, crank and block were the same. The L69 came with X rods, flat-top pistons, a MUCH better cam, better carb calibration, dual-snorkel cold-air breather (in the Z28 anyway), electric fan, MUCH bigger exhaust all the way from heads to street (2¼" manifold outlets vs. 2", 2¾" I-pipe vs. 2¼", 2¼" tailpipes vs. 2"), 3.73 gears, and different timing curve. The LG4 had 145 HP that year, the L69 was rated at 190 but seems to have had a bit more than that. In later years (maybe 85 or 86 up) they added the knock sensor to the LG4, improved its timing curve, and put flat-top pistons in it; and IIRC it even got the eoectric fan. It still got the "peanut" cam and the 4-cyl-sized exhaust.

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"So many Mustangs, so little time..."
ICON Motorsports

 

I guess I should have stated that I have an 84 Z-28. SO... The quickest way to tell if I got shafted would by to pull off one of the heads and see if I had flat top pistons or dished. If I've got dished pistons then it is safe to assume that this place put a straight 305 in and I'm on my way to small claims court.. Did the heads vary?? Thanks a lot for the help

 

84 L69 and LG4 motors continued much the same as 83.

Heads are the same in both motors: 416 casting. AFAIK all other 305 castings that would interchange directly (perimeter bolt VCs, etc.) are inferior to those.

You should be able to look into one of the spark plug holes and see about the pistons. Most likely they're dished; very few 305s had flat-tops.

So what are we really doing here? Does the new engine not run as good as the old one, or what?

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"So many Mustangs, so little time..."
ICON Motorsports

 

I didn't see it mentioned so... the early 305 HO (carb'd) motors had larger intake valves, and starting in 1985 the '85 IROC carbureted HO had a 1.92 intake as opposed to the early non-HO standard 1.76 intake (that is soooo small), and later the 1.84 305 heads.

Had a buddy who found out the hard way about his 305 HO heads and toooooo much cam (lift). "What is that tapping noise ?" he asked after installing the new cam... as the motor destroyed itself. He didn't do his home-work in high school either.

Two f-bodies back I had an '88 Formula with 1.84 intake valve and installed a .505/.525 lift cam (1.6 rockers) and it worked great and made a ton of rpms -- till I spun the bearings. Well, I am definitely meandering here.

My point is, the 305 HO sometimes had bigger valves as in 1.92. If you have one then WARNING, watch out for the lift on your cam -- there is not alot of room for the 1.92 to move about in a 305 combustion chamber.

have a nice day eh ?

 

So....

I'm a little confused. Do the L69's have flat top piston or are they dished?? One reply said yes then they said later very few 305 had flap top pistons.. or did they mean regular 305's... also if the L69's had a considerable larger intake valve then wouldn't they require a different head or is there sufficient clearance in the comb chamber?? Just trying to tell if the 305 in my z is an L69 or not.. I know what it is suppose to be... it has the dual air snorkel, but that doesn't mean anything..

 

L69s all had flat-top pistons. LG4s had dished until 86 or 87. You can look in one of the spark plug holes and determine what you have.

Heads were identical between the LG4 and L69 in all years that they both existed, all had 1.84 valves, all were 416 castings, until 87 LG4 (no L69 in F cars that year, only in Monte Carlo SS) when they went to centerbolt valve covers and the other intake bolt angle. I don't know what number those were. The 87 MC SS L69 had 081 castings IIRC like the LB9 but for all I know the LG4 in that last year could have gotten the swirl-port ones they put on the L03 in later years.

I've known an awful lot of these cars and engines; I've never heard of any of the stuff the guy mentioned in that other post, except for what happens when you put a big cam under stock valve springs, he hit that one on the head. The only valve size I've ever seen in 305s besides 1.84" came in late 70s and early 80s ones with a 2-barrel, and those were 1.72" IIRC like some of the old 283 heads. I've never heard of a stock 1.92" Chevy valve, nor seen any such listing in a book even; there are lots of 1.94" ones, but not on 305s.

As far as how to tell if a replacement engine is at least close to a L69, look at the head castings, they should be 416s. Look at the pistons, they should be flat-tops. It's going to be hard to tell about the cam, but I'd almost bet money it has something pitiful in it. And yes, very few 305s had flat-top pistons; about the only ones were the last year or 2 of LG4s, all the L69s, and all the LB9s. All those together are barely a drop in the bucket of total 305 production, probably less than 5%.

Did you get your original carb back? electric fan? original distributor? if you did, and you have flat-tops and 416 heads, and you're willing to swap the cam, you can make it back into a L69 easily.

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"So many Mustangs, so little time..."
ICON Motorsports

 

While on the topic of 305 HO's..
I got mine at the shop right now and they told me my exhaust is pretty much crap from the cat back. Needs replacing.
Now they told me that there is an odd size comming off the cat, or rather a piece welded to the cat that isnt a standard size. The exhaust would have to be specially made for me to fit it.

Is this something to do with HO's? Were they funky sized with their exhaust? If so, is a special exhaust gonna run me up more than a regular flowmaster exhaust and new cat for example?

He told me the cat is pretty new so theres a chance something stupid is in there, how can I tell if its a stock replacement or not?

 

The cat is the same as the one that came on Vettes in about the same years; it's huge, has oval (2½" x 3½") inlet and outlet, and has a large (4"x 7") 4-bolt flange at both ends. The I-pipe is about 2¾".

If an exhaust part, any exhaust part at all (with the exception of the AIR check valves), lists as being for "305 all", it won't fit the L69. Most likely somebody sodomized it fairly brutally, by looking it up in the book; then pulled a "305 all" cat off the shelf; and graunched a little weenie LG4 cat into your L69 system somehow, thereby fornicating one of the best single exhasuts GM has ever made.

I believe you can still get L69-specific cats from Catco and a cat-back from any number of places, including at least Edelbrock and Dynomax that I know of. I'm sure there are others.

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"So many Mustangs, so little time..."
ICON Motorsports

 

RB83L69, so I need to go check if i still have that vette style type of cat on my car first, then I can order something through edlebrock?

If it is the same cat and if the exhaust comes off willingly any suggestions what I should replace the exhaust with? I have a fair bit of money for it, but I max around 500.

THanks again

 

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There's a few to get you started

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"So many Mustangs, so little time..."
ICON Motorsports

[This message has been edited by RB83L69 (edited August 28, 2001).]

 

OK.... I pulled the head off this weekend... Now forgive my ignorance.. But stock dished psitons have four little semi-circles on the top of the piston right??? I would assume that flat-top pistons have nothing on the top of them , right? Mine has the semi-circles on them... so I got screwed... Probably next step would be to switch Message boards and gather some info on dropping in a 88 iroc 350....

 

Also I forgot to mention I looked over the head and could not find the number "416" anywhere... Help... what heads do I have..

 

Also I forgot to mention I looked over the head and could not find the number "416" anywhere... Help... what heads do I have..

 

Here's what you're looking for... sorry the image is so huge

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"So many Mustangs, so little time..."
ICON Motorsports

 

Sounds like flat-tops. The little semi-circles are valve reliefs to make sure the valves don't contact those flat tops.

Dished pistons have a big scoop out of them and no semi-circles. I thought I had a stock LB9, turned out to be a .040 over rebuild with dished pistons when I pulled the heads - wish I'd found what you found.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" cat-back, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

RB83L69..... I looked at that number ( and for the life of me I don't know why I didn't write it down ) but I'm positive it did not have the #'s 416 in any part of it. I'm not sure what it had but I know it wasn't 416. I'm gonna call the old man tonite and have him take a look and I'll update this when I know what those #'s are? Thanks alot for your help... Also now that I know I have flat top's I'm assuming that the #30 stamped on the top of the piston means it's been bored out .030 over???

 

Hey the casting # is 14022801... I also have the casting # for the intake.. 14057053 I'll post that on the carb BB... SO... what are these heads for????

 

Regular ol' 305.

Put some World S/R Torquer 305's on it. Better than the 416's anyway.

 

Yup, you got boned, they downgraded your heads... there's not alot of sense in spending money to put the original ones back IMHO, the 305 Torquers would be the way to go if you're going to buy something.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Well.... My target HP was at least 300 and after considering what all I have to buy to get it to make that.. I think I'll try to find an 88-92 350 roller cam block and put a set of vortec heads on it with 1 3/4 SLP headers and a few other things and I'll be at or a little over my 300 hp target and I think I'll still come out ahead money wise with a lot of room to go upgrade the HP down the road... Thank you for all your help with my dumb 305.....

 

Not to burst your bubble, but you aren't going to save money by going Vortecs vs. World S/R Torquers or Sportsman II's. Here's why:

1) You need a Vortec-specific intake manifold. About $175.
2) Vortec heads need self-aligning rockers. Okay, you can combine #'s 1) & 2) from SD for about $350.
3) The Vortecs have press-in rocker studs and weird valve springs. Not good for over .470 lift, and expensive to fix. Figure a couple hundred buck to get that machining done and new parts.
4) Despite their reputation, the Vortec exhaust ports need some help. $100-200, unless you do it yourself.

Okay, you've got almost a grand in these heads, and they don't flow any better than bolt-on World's (~$630-$800). And, if it matters to you, your EGR valve won't work unless you plumb some exhaust up to your intake manifold - The World's don't have that problem.

I'd strongly recommend going with World heads as a less expensive and better-running combo over Vortecs.