Hi all,

I've been absent from the forum for a while due to life (along with a bad experience with Hawks Motorsports) keeping me from playing with my third gen for a while. I finally have things settled down and am about to dig into my car. Due to some back and knee issues, I converted the car to a 700r4 from the t56 (queue long story with Hawks) but the transmission didn't last after having it "built" twice. So while that is out getting rebuilt by a different shop, I also plan to do the following:

new gears in the rear end (3.42 or 3.73)
body work and paint job
convert the car from TBI to carb (650cfm FST with vacuum secondaries and electric choke)
swap heads on the 305 (hopefully obtaining a set of L98 aluminum heads this weekend)

which leads me to my question... looking for a cam to slap in this thing. Now, before it gets mentioned, yes I know that this 305 is not the best motor to sink money into. Honestly, I'd like to build a 350 at some point, but I'm not there yet. I'm sinking a good bit into everything else on the car, and I know the bottom end of this 305 is solid as it only has 5-600 miles on it since a tear down with new bearings, seals, rings, etc. The goal is to get the car as good as can be, then build another motor at some point in the future. I'm not looking for a race car, just a nice cruiser that I can have a little fun with.

The L98 heads I'm supposed to be getting have been worked some. Comp .550 lift springs, locks, and retainers, multi-angle valve job, ARP screw in studs, new valve seals, 1.94 int/ 1.60 exh valves, and stock 58cc combustion chambers. Supposedly the guys selling them has paperwork to show all of this on invoices. With that being the case, what kind of cam specs should I be looking at? Not looking at anything radical with a lot of lope, and not looking to make crazy power. Honestly, the aluminum heads, better gears, fresh transmission, and getting a better flowing intake will probably wake this thing up a lot, I'm just looking for something a bit better than the stock peanut cam this L03 has in it.

Any and all advice is appreciated.

Thank you,
E

 

I don't have a cam recommendation for you, but you will need to select head gaskets sized for the largest bore - in this case your heads. If you use 305 gaskets, they would most likely hang into the combustion chamber, causing potential problems. Try to fit the gaskets as close as you can to avoid a large crevasse between the head and block. Try to keep the quench distance close to .040". Good luck.

 

Most definitely. I’ve always preferred Felpro gaskets so I’ll likely use a standard Felpro gasket for a 350 in order to make sure the bore is right. I’ve been looking and the L98 aluminum Corvette heads seem to be a common recommended upgrade for fools like me that want to spend money on these 305s.

 

If this is the original engine for the car, i.e. roller cam, I'd suggest the Comp 08-408-8 or 08-412-8. The 408 if your gears are still stock, the 412 if they're 3.42 or better. I HIGHLY recommend that you upgrade them to 3.42 or 3.73. And of course, EXHAUST; EVERY SINGLE PIECE from the heads to the street, but NOT for a 305. Headers, high-flow cat, & cat-back; for a TPI 350.

Gasket brand is largely irrelevant as long as it's a composition one of some kind. FelPro is fine, Victor-Reinz, GM themselves, there are others as well. I'd avoid steel-shim of ANY kind.

People love to accuse people like me of "hating on" the 305. That's true to some extent. But they fail to read the fine print. What I hate on is, TOUCHING the 305 short block. As long as you leave that alone, and don't choose some sort of 305-specific parts around it, it's OK to try to make it better. Cam, heads, exhaust, etc. are all good. But DO NOT TOUCH the short block. Once you do that, it's INTO THE TRASH, and get a 350 short block to touch instead. Butt as long as all you're doing is bolting stuff onto your existing short block, it's not stoooopid.

The aluminum L98 heads are actually a DOWNGRADE for some 305s. Probably not so much for yours, since you're getting rid of the 187s. Butt, they will give you only about the same compression you have now, and because aluminum conducts heat out of the combustion chamber so much more than iron (i.e. leak, i.e. energy loss, i.e. inefficiency), the compression typically needs to be raised somewhere between a half and a full point, to keep performance (energy extraction from the fuel that is burnt) EQUAL to otherwise equal cast-iron. Of course you'll pick up A BUNCH of flow by getting rid of those POS swirlies you have now, but ALL ELSE BEING EQUAL, you will lose bottom end and other properties because the compression is effectively lowered by the greater heat losses through the aluminum casting. Not saying you shouldn't do this; only, be aware going into it, that's it's not all roses and happiness. Mostly you will notice that it's not as "sharp" at low RPMs like right off idle.

The 305 gaskets won't have a problem with the 113 chambers. Not an issue. Don't worry about it.

The advice about .040" "quench" is good as far as it goes, except, you have a stock short block. You have almost no control over that since you're NOT touching the short block. It is what it is, PERIOD. The pistons are ALREADY so far "down in the hole" at TDC that that's a pipe dream. It's not something you are in a position to optimize. Don't worry about it. As far as I'm concerned the best thing you could do is to use yerbasic HS-8510PTxx whatever PT number they're up to nowadays. Don't work yourself up over things you can't control, or even influence. Instead, direct your attention to things you CAN control. Like, making sure the gaskets SEAL. For all time.

 

Thank you for the advice. The car already has good hedman headers with 1 3/4 primaries, 3” collectors, hedman y-pipe, and 2.5” cat-back with the cat deleted.

Rear gears and a posi carrier are a part of this go around. Thinking 3.42 or 3.73 gears.

I’ll take a look at those cams you suggested here shortly to check specs. You have a point about the short block, but I was on a very tight budget a while back, so I went through and did a stock rebuild on the motor when I swapped the transmission out. Mainly looking to just bolt some “decent” upgrades on the top end to give it a bit more power than stock so I can enjoy the car until I get around to putting something else together to drop in. Not wanting to go farther than I have to. Honestly if the 187 swirl port heads didn’t suck so much, I’d probably just drop a cam in and get on with my carb swap and the other needs.

 

Stock L98 cam would be a nice upgrade. GM Performance also sells one around $100 that's a touch more. 214-220 dur maybe? Think the number ends with 9446? Basicly the old 2032 comp cam.

 

I learned a lot reading this thread. Thanks everyone.

 

GM 94666492

 

2032 was a Crane cam, not Comp. Regardless, a reasonable choice; very similar specs to the Comp 412 grind I referred you to up there.

 

Alright guys, so I may be a little crazy.

Just picked up my 128 casting heads that have been mildly ported, 3 angle valve job, polished surface, retainers, screw in rocker studs, seals, and new springs. The guy I bought them from still had, in the box, the cam he had the heads worked to pair with. I bought it off him for a couple extra dollars. A bit more aggressive than I was planning on, and I'll need a higher stall converter, but I think it'll give decent top end, even if I do lose a little torque.

COMP Cam link:
https://www.compcams.com/xtreme-ener...all-block.html

 

That's not a little bigger...…………… IT'S A LOT BIGGER!

 

Yeah, I’ve gathered that the more I’ve looked. Thankfully the plan for the car is a fun weekend cruiser. Definitely not a daily driver. Exactly how radical of a cam do I have here?

 

Flat tappet too.

3300 stall converter recommended! 2800 to 7000 rpm power band!

 

Yeah, that seems pretty insane. I do have a stall converter picked out already. Figured I'll add that to my shopping list when I make the road trip to Summit and slap it in while I have the transmission out to redo the lockup kit and cooling setup. I still need a rocker arm set for the new heads and lifters. I'm not a master engine builder, so to play it safe I'll probably get the kit from COMP that includes the rocker arms, push rods, and lifters. Any ideas what I'd be looking at for power numbers out of this thing once I get it all put together. Thinking with that cam, I'll be better off with 3.42 gears and a posi carrier in the rear than I would be with 3.73s to tame it down a touch. Any thoughts?

 

Use this chart to see how far you are out of the ballpark:

 

I'll let someone with more racing experience help with the ratio, but I would "guess" that cam would like the 3.73s better. That power band is going to want a very good breathing set of heads (think aftermarket aluminum) and a large single plane intake I would think.

Your duration at .050" lift puts that cam in the Stage 5 class looks like to me. Look at the desired compression ratio in that table above. Way more than you are likely to have.

All those things make that cam a mis-match for a warmed over street 305. I'd see if the guy will buy it back, and get one of the ones recommended above.

 

So, assuming this is definitely too much cam for what I'm looking to do? Could always offload it or use it on a different project. Highly doubt the guy is going to buy it back from me.

 

Maybe I'm reading something wrong, but the link you provided in post 10 goes to a cam with these specs...





...which puts you in the Stage 5 group as I read it.

 

No, I edited my response as I wasn't thinking right when I was replying. You are correct, that would put it in the Stage 5 group as far as that chart goes. Wouldn't be the first time that I "wasted" some cash on an impulse buy. I'm definitely looking to be more in the Stage 3 group at the most. Little lope with some good power would be one thing, full on race cam is definitely not what I'm looking for. I remember even telling the guy that I think it's a bit bigger than I was planning on for this car....

But you know what they say, no two things are easier to separate than a fool and his money.

 

That cam is bigger than I would dream of running in my street 383, let alone a 305....flat tappet to boot. Sell it, although I don't see to many buyers for that cam.

 

Listen, counting my stock pieces, I have 3 intakes, and still not the one I need....four sets of heads, only one of which I will use. Two sets of headers, 3 pairs of valve covers, three cam shafts, 4 complete axles.

Now except for one of those cams, these were all purchased used, some for mere pennies, a couple were even free. But still, I've put the cart ahead of the horse more than once with my planned 305 build.

 

I definitely know how that goes. I've jumped the gun before too, and it just is what it is. I'll see if I'm able to sell it, but if not, it was a relatively inexpensive mistake. If you add in the heads, all in all I didn't get hurt too badly. I'll be re-evaluating options and pick out a cam kit that will put me where I'd rather be.

 

Yeah, I should have trusted my gut on it being too big initially rather than overthinking it and buying it. But, live and learn. On the bright side, I know where you can get a cheap race cam if you decide to overhaul that 383 for a drag car

 

That cam in that engine would be a mistake. Sure, it'll have a mean lopey idle that "sounds" powerful, but it'll run like a slug.
3.42 is NOT enough gear, and tht 305 is not likely built to run up to 7000 RPM. And flat-tappet is like going backwards.
I would sell it and go with one of the suggestions from Sofakingdom...

 

Yeah, that's definitely the plan at this point. This thing will get listed locally in the morning and I'll be ordering something that fits my goals much better.