15 hours ago in Articles
The physics behind load transfer are crucial to performance driving.
Some machine shops purchase reground stock cams so make sure you're getting a brand new cam and not the regrind.
Good point, Jerry. I've not seen that happen very much recently. With the proliferation of inexpensive cast roller blanks it doesn't seem to be cost effective anymore to do the regrinds.
while you are out grabbing the lifters, dogbones, and spider- don't forget to grab the pushrods since they are shorter than the flat tappet ones are..
you have a roller block and vortec heads.. i'm going to make a suggestion that i have actual real world experience with in my 71 Nova: get the GM HOT cam kit.. it's spendy, yeah, but oh, man, is it ever worth it.. the GM part number is 12480002 (yeah, i remember that part number 11 years after i ordered it...)..
anyways, what you get is the cam, 1.6 roller rockers, LT4 springs, retainers, and keepers, and a few other odds and ends. put screw in studs in your heads, open up the pushrod slots a bit for the 1.6 rockers, and put it all together with thin head gaskets and as close to 10:1 compression as you can get.. you will have right around 400hp with a smooth 800rpm idle that will pull better than a stock 350 from idle to 3500 or so, then the power kicks in and it pulls hard until 7000rpm or so.. my Nova had 3.70 gears, a T10 4 speed, and 245/50/16 tires and it would average 17mpg. my next change to the car was going to be a Tremac TKO 500 trans to see what kind of mileage i could squeeze out of it, but i traded the car off before doing that..
when i first built the engine, the car still had the TH350 trans and 2.56 gears and other than being able to go damn near 90mph in first gear it didn't seem like it was struggling even in such a mismatched car... and after the trans and rear end swap, i could start the car in 3rd gear without it lugging too bad.. oh, and i ran 89 octane in it without any audible detonation, too.. that car was a blast, and that engine was pure heaven..
no, you won't fit this into the challenge budget without getting really, really creative- just the cam kit and the head mods to make it all fit together will put you near $1000 if you don't have a dealer parts counter connection- but over the long term it would be so very worth it..
Unfortunately it will be Saturday before I could get back out to strip more off the engine the heads came from- hopefully the parts I want will still be there!
Fortunately though the reason I can't get free until then is all of the people I have coming over to buy the parts I'm selling off.
Another question- is it worth hanging on to the gear drive that came with my first engine, or should I sell it and just use a normal (or upgraded) timing chain setup?
depends.. if you are going roller- and you should definitely go roller- then you need a different cam gear anyways. the factory GM single roller timing chain that they started using in the mid 90's is plenty good enough for a factory roller cam setup, and it's decently priced for a factory part.
So, I finally got out to one of the machine shops- one that is explicitly advertised (right in its name) as being a cylinder head shop, and that came very highly recommended by an auto shop owner I know (runs the local shop that specializes in rotaries...). I chatted with him for a while about what I was working on and prices on work on the heads.
I mentioned novaderrik's suggestion of the GM HOT cam, and he pretty much said the exact same thing- that if I could even begin to make it work in my budget that it was WELL worth it. He also said that if I was using self-aligning rockers (and it sounded like he thought the HOT kit came with those...) that I wouldn't need to do any slotting of the Vortec heads- so in essence, if the heads are good, I wouldn't need to have any work done on them at all. If I did want to though, a 3-angle valve job would be $150 for both heads, milling them down a bit to up compression would be $40 apiece, and a hot bath and pressure test on them would be $40 apiece.
The ridiculous thing is, if my sell-offs continue to go remotely as well as they have been, and I get a bit more creative with the rear end, I may well actually HAVE the budget for the GM cam...
the HOT cam kit comes with self guiding 1.6 ratio roller rockers.. they gain the ratio over the stock 1.5 rockers by moving the pushrod hole in closer to the fulcrum. this causes a problem on -most- vortec heads because the slots where the pushrods come up from the lifter valley aren't always long enough for the 1.6 rockers.. 10 seconds with a die grinder on each slot opens them up enough to clear, and it isn't always necessary.. it's one of those things that doesn't hurt to do anyways.
the guides will need to be cut down a hair for the .525 valve lift if you use the included LT4 springs and retainers, but man, is it ever worth it...
a little backgound on this cam kit: it was designed for factory installation in the 96 LT4 powered Corvettes, but apparently they thought that 400hp was too much- or maybe they couldn't get it to pass emissions or something- but they dialed back the specs on the stock cam and kept this one as an over the counter upgrade for LT4 powered Corvettes in some road racing classes that require factory parts.. they put it in the limited edition ZZ430 crate motor that was rated at 430horses/430torques. the reason for the higher ratio on the rocker arms was to be able to get .525 lift without poking the lifters too far out of the holes and dislodging the dogbones that hold the roller lifters straight..
i was probably one of the first people to match that cam up with the vortec heads, but about 6 months after building my engine Chevy High Performance built an engine exactly like mine except for single plane intake and Holley 3310 carb where i used a Peformer and Quadrajet and they made 410 horses and it ran low 12's in the quarter in a 67 Chevelle with a TH350 trans. my Nova ran 8.80's in the 1/8 mile at 88mph with the tires smoking thru first and most of second gear and going thru the traps right at the top of 2nd..
Interesting history on it. I'm hoping it will work out to use it, it sounds like a perfect fit for both the Challenge races and beyond, assuming I can take the budget hit.
Assuming my sell-offs go extraordinarily well and I have way more free budget than expected, how would this cam and my setup handle a modest nitrous shot?
the pistons will dictate how it takes nitrous..
Well, it looks like being able to use (or rather, afford) that cam may be a bit more of a trick than I had hoped. When I got in to looking over the heads more closely, I notice that one of the valves wasn't seating properly. So while I'd hoped to not have to take the budget hit, I dropped both of them off at the machine shop to be hot tanked, pressure tested, and generally gone over to make sure there wasn't anything else wrong with them and to hopefully get that valve issue resolved.
Since I should be able to use a roller cam, what are some more Challenge-budget friendly roller options I could consider? Roller cams are more reusable IIRC, are there any cars in particular whose stock cams would work well?
Nothing wrong with using a used roller cam. Damage would be obvious. It can be a bit of a crap shoot if the engine has been changed at all.
Problem is, there were no traditional SBCs with good roller cams. Even the LT1s were pretty mild. Factory spec on my LT1 iron-head engine was 181/186 with a 113 LSA. The factory didn't get into decent cams until well after the LS1 years, especially because most SBCs were in trucks and large cars during the early years of OBD smog compliance.
Best cam I can think of was in the F-body or Y-body LT1, but its not a bolt-in. The snout and distributor drive are different, and it has no fuel pump eccentric. The other problem with factory GM roller cams is that they are designed with fuel efficiency and EFI programming in mind. For that reason they have very wide LSAs that (IMO) are nowhere near optimal for a performance build. Some of the LT1 cams are 117 LSA.
LT4 hot is a very nice cam. Worth the money, but not necessarily challenge money. You can get cams that are close for much less cash. I'll do some more poking around and see what I find.
I'm not too worried about the fuel pump drive- I'll be using an electric pump for both the carb and the TBI setup when (if) I switch back to it.
search teh internets for ZZ4 takeout cams. a lot of people get them and upgrade to the HOT cam, and they sell them dirt cheap.
regarding fuel pump lobes on factory roller cams: the TBI 350 out of my 92 Caprice didn't have the lobe, but the cam i pulled out of my 94 Caprice LT1 did have one.. i don't know what their logic is in which cams get it and which ones don't, but it might just depend on which cores the cam grinder had in stock at any given time.
any LT1 cam works in a regular roller small block, with maybe a few hammer taps to the dowel pin on the front to push it in and keep it from gouging a hole in the timing cover.
another thing to look for if you want some "free" compression: take the whole rotating assembly out of an LT1 and put it in the regular block. this gets you flat top hypereutectic pistons, powdered metal rods, and a crank that is made out of better material- and it all slides right in as long as your block doesn't need to be bored..
I hate threads like this.. They make me go shopping...
So, that plot thickens a bit. I've got a buyer lined up for the nearly-fresh TBI heads (yes... seriously... stop laughing...) that wants them on Saturday, so I decided I should get to pulling them off. I only had time to pull one, but was surprised when I pulled the head off to see the numbers '030' stamped on top. Specifically '423NP 030', which makes them Sealed Power 30-over pistons- and means that I've actually got a 355 instead of a 350. Hey, every little bit of displacement helps, right?
Now more than ever I want to talk to the guy who rebuilt this engine and find out what ELSE may have been changed on it when it was rebuilt. The guy I bought it from said a relative of his rebuilt the engine, so hopefully he doesn't mind connecting him up with me so I can get the run-down of what exactly was done to it.
I'll keep an eye out for LT1s to pull a cam from when I'm out in the yard tomorrow afternoon. The $20 it would set me back would make for at least another option.
Something else- If I can track down one of the GM HOT cams on its own, it would still be a solid improvement, just not as much as with the 1.6 rocker arms, right? (I'd still need new springs though I imagine...)
HOT cam just flat out works and does everything well..
yes, it can be run with 1.5 rockers, but you'd be giving up some lift and duration- down from .525 lift to .492 lift, which is still a decent amount of lift for a street small block cam.. probably still gonna need roller rockers, tho, due to the slots in the stock rockers being too short for that much lift- so might as well just go for 1.6 rockers for the same price..
So, I had hoped for today to be a pretty good day- since work was really slow, I took the afternoon off and headed to the salvage yard to retrieve the rest of the hardware from the truck I pulled the heads from. I actually came away from the yard a lot better than I expected. The Haul:
2 full engine sets of roller hardware (lifters, pushrods, spider, and dogbones) 1 LT1 camshaft (GMPT BC-13-600) from a 94 Buick Roadmaster
Total bill before taxes: $48.84 (they didn't charge me for better than half of the lifters and pushrods, and ignored the spiders and dogbones completely).
The LT1 camshaft may not end up being useful, but It was there and I had the time to pull it.
Unfortunately, after I got done there and checked my voicemail, I had bad news that far outweighed the good: the cylinder head shop had called, and BOTH of the 062 Vortec heads are cracked. So I'm back to the drawing board as far as heads go.
The Chevy Circle track 602 crate motor cam would work well. Should have no PTV clearance issues and was made to make good low and mid range torque from 3000-6000.
In these 9 to 1 compression circle track motors this makes almost 400 lbs ft torque and is easy on the valve train. Only about .460 lift
In reply to Ashyukun:
You and I may have just become friends, I work in Lexington. Small world, huh? If you need a wrench gimmie a holler, I might be able to help.
I know a guy in Shepherdsville that is always buying and trading chevy stuff, here'sa CL search with some of his stuff.
In reply to BoostedBrandon:
Sure, we should definitely meet up sometime! I don't have any other gearheads here in LEX that I know very well, so knowing there is at least one more GRMer around is comforting. :)
That's kind of funny about your friend- I was actually -THIS- close to calling him up today about one of the cams he has.
where are the heads cracked?
The LT1 cam you have should spec out to 191/196 duration, 111 LSA, and .418/.430 lift at the valve (with stock 1.5 rockers). In the LT1 it made 260 hp and 330 lb-ft with 10.25:1 compression.... made possible with 87 octane because of EFI, knock sensors, and reverse flow cooling.
No commentary, just thought you could use the data.
In reply to Ashyukun:
I don't actually live in Lexington, I just work there. I drive about 90 minutes so I'm not available at the drop of a hat, actually I probably won't be able to much at all but we'll see.
I bought a motor off of him about 3 years ago, I wound up not doing anything with it and selling it about a year later. He's a really nice guy.
In reply to novaderrik:
They're apparently cracked from the centermost exhaust ports. I actually had noticed what looked like a white line one one of them when I was looking them over, but my first instinct was to try rubbing it, and the grease from my gloves made it disappear.
The shop is closed over the weekend and I didn't get back into town early enough before they closed yesterday, so I'll be going by on Monday to look them over and talk with him.
In reply to curtis73:
I'm an engineer: more data is pretty much always a good thing.
I don't expect I'll really be able to use it, but I figured that at worst it could be used for trading for parts I actually CAN use.
3 days ago in News
The Goodwood Festival of Speed delivers again. A Nissan Juke is taken up the infamous hillclimb on two wheels.
Also get your instant access to the digital edition of Grassroots Motorsports Magazine!Learn More