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Discussion Starter #1
Hey guys,

I am currently in the process of doing a mild top end upgrade on my stock block and had a couple of questions. I am looking to upgrade to gmpp vortec heads out of the jegs catalog that have 64cc combustion chambers and 170cc intake ports with a max lift of .475 for the cam. I just purchased a lunati 268 cam that has a .050 duration and lift of .457. I am of course going to be getting a vortec intake probably from weiand or edelbrock and will just be rebuilding my quadrajet as I have heard that it is a great carb once it is dialed in just right. I was curious what kind of power I should be looking at (I was thinking of around 350 flywheel), if the cam that I just bought is a good deal (I bought it brand new off of ebay for $50 still in original box), and if I will have to pull the engine to swap the cam. Please let me know anything that I might expect to encounter and be easy as this is my first project of this magnatude. As far as exhaust goes I will be getting some 1 5/8 headers, I have no cats, 2.5 inch true duals and flows in the back. Thanks!
 

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you never said what size engine you have- that will have a big effect on power output and parts selection.

no matter what engine, you can pull the came with the engine in the car, but imo it is easier with it out- plus then you can paint it and such at the same time and give everything a good cleaning.
 

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I would be concerned with piston to valve clearance with a cam & head swap. As this could get ya into trouble real quick!
Not too hard to do. Another 'while I'm in there'.
All could be done in the car, but I think much easier if engine is out.
:cheers:
 

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sounds very simular to the cam i also got off ebay. The lift you mention is about max for stock heads before you get valve spring coil bind. you will have to use new lifters to match cam(mech/hyd)dont use s/hand lifters! MUST and i found out the hard way use a cam breakin lube in oil with a old school oil (high zinc content)! breakin as per instructions start,straight to 1500rpm for 15 mins(time it). The one i got came in a plain white box with no tag or markings on it at all?(box or cam). I was running a big holley that i sold after a while to fit a q/jet back on to try and gain back some economy that i lost with the cam install. so in summary fuel:down:fun factor:thumbsup: I did it in car,would i do it again dont know as i got a **** paying mechanics job at the moment that i hope to change i the future for more cash:D
Oh my car is a 79 vet L48/200r4 3.55 gears(max cam for an o/drive trans with carby)no histall fitted. I MISS THE LUMPY IDLE,SO COOL.:D
 

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Hey guys,

I am currently in the process of doing a mild top end upgrade on my stock block and had a couple of questions. I am looking to upgrade to gmpp vortec heads out of the jegs catalog that have 64cc combustion chambers and 170cc intake ports with a max lift of .475 for the cam. I just purchased a lunati 268 cam that has a .050 duration and lift of .457. I am of course going to be getting a vortec intake probably from weiand or edelbrock and will just be rebuilding my quadrajet as I have heard that it is a great carb once it is dialed in just right. I was curious what kind of power I should be looking at (I was thinking of around 350 flywheel), if the cam that I just bought is a good deal (I bought it brand new off of ebay for $50 still in original box), and if I will have to pull the engine to swap the cam. Please let me know anything that I might expect to encounter and be easy as this is my first project of this magnatude. As far as exhaust goes I will be getting some 1 5/8 headers, I have no cats, 2.5 inch true duals and flows in the back. Thanks!
HI,

Am I missing something? A 0.050" duration of...what?
 

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Discussion Starter #10
Fred- I was just posting what the advertised specs were. Like I said I have never really looked into a cam/ head swap so at the risk of sounding really stupid I don't know what you mean... Were you wanting to know int/exh? Please elaborate thanks!
 

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Fred- I was just posting what the advertised specs were. Like I said I have never really looked into a cam/ head swap so at the risk of sounding really stupid I don't know what you mean... Were you wanting to know int/exh? Please elaborate thanks!
Hello there. Don't worry about sounding stupid. That's my job. :laughing: I'm not a small block cam expert, but I'm interested in knowing more than I do. I went to Lunati's website and found what I think is your hydraulic flat tappet cam (part no. 06108). It has an advertised duration of 268 and a lift of 0.457" for both the intake and exhaust. (I think the original lift is 0.390"/0.410".) I'm not looking at the cam card (that shows all of the details for the new cam), but the advertized duration is probably at 0.006" lift at the tappet. It's hard to compare cams from different cam companies, because their advertized durations aren't always at the same tappet lift. The duration at 0.050" tappet lift is an standard that all the manufacturer's use now, so you can compare cams from one company to another.

You also can get an idea of the aggressiveness of a cam if compare the advertized duration to the 0.050" lift duration. The duration at 0.050" for this cam is 218/218 versus the advertized of 268. So from the point at which the lifter is at 0.006 until the lifter reaches 0.050" lift is (268-218)/2 = 25 degrees. If you look at another cam and do the same math, you'll get a number that is either higher, the same or smaller. If the number is smaller, that means the lift gets to 0.050" faster (more aggressive). Higher number means less aggressive.

What's aggressive and what's mild for your engine, I can't tell you definitively. The need for more duration varies with stroke length. In my signature, you can see that I'm running a big block (stroke 3.76" vs. 350ci at 3.48") with a 0.050" intake duration of 230. Right off the bat, if your duration was higher than the 230 on mine, you could see that your cam was on the larger, more agressive end of the scale. But the 218 says to me that the cam isn't too big for sure, at least not with the smaller combustion chamber on the heads you mentioned. If you're starting with an 8.5:1 compression, then you'll be at 10:1 if everything else is the same. That's starting with an original chamber volume of 75.47cc. I assumed a starting point of 8.5:1, but that may not be correct.

Did you notice that Lunati recommends a gear ratio higher than 3.40? Do you have the right gears to go with the cam?
 

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A cam with 268 advertised duration is pretty mellow, probably has a duration in the mid/upper 210s when measured at industry standard 050 lift. I'd classify it as an agressive RV or truck cam and it should work well with your complete vehicle package.

If powertuned to the nth degree on a dyno you might be sitting on 350hp flywheel, but that's a hard number to reach without 10.5:1 compression. A safer guess is 290-320 with a very useable torque curve. It's probably going to stop breathing around 6200.

450 lift is not a concern with flat top pistons. With oem dished pistons it is double not a concern.

Qjets don't like those adapters to square bore intakes, they're power killers. A couple of the popular vortec offerings are square bore only.

You have to loosen the oil pan enough to get the timing cover off, which usually results in an oil pan leak soon after reassembly. It's not alot of money to just pull the starter & pan, clean everything up, install a new high volume pump to help the old loose bearings, and then cap off with a one piece pan gasket and a new rear main seal. Time well spent, plus you'll have it so far apart that respraying the block in the engine bay is a viable option.

I generally don't reinstall stock oil pans, as the local circle track shop sells a generic replacement with stronger rails and an additional quart capacity for $30. The quart is gained thru a smidge extra width and a smoother taper on the front, so no added depth, great street car pan. They're all over the market, look for the plain steel pans with a 1" drain plug nut. Exact same as most aftermarket chrome pans without the problematic chrome.

good luck with the project
 

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Discussion Starter #13
thanks for all of the great information, I am starting to understand all of this a little better. The factory gears for a 77, from what I understand, has a final drive ratio of 3.55 so it should be fine. I was really hoping for nothing too radical but enough to have fun in. Of course quarter mile calcs arent exact but at 350 hp and 3595 weight it should run a mid 13sec and I might even look into upgrading to a higher stall converter. I am toying with the idea of just buying a crate from gm and swapping the vortec heads and cam onto that. That way I know that everything is new and I dont have to worry about blowing the engine. Do yall think 350 is a conservative guess? I know that some magazines have done this build with a gm hot cam and end up pushing out a little over 400hp with the same heads, intake, exhaust and a 650 cfm carb. Do yall think I should go with buying the crate or just rebuilding the original engine? If I buy a crate I can always store the orig. engine and restore later if I want to put it back to stock.
 

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If you want to add pep and make it run like a modern era LT1, stay on the current path.

If you want 350hp flywheel, forget 350s entirely, move up to a 383 or 400. You have a heavy car and a mild gear, in order to have street fun you need more torque than a 350/350 is going to produce. Even a cast crank 400 is good for 6200 rpm and with the same parts you're gonna put on the 350 (but more cam) will lay the smack down as a 13 flat, well mannered street car that might even drink 89 octane.

Once you talk about taking the engine out of the car, the cheapest power per dollar in a street SBC is displacement. Go big, go mild, then try to go easy on the back tires.

The 400s reputation as a non-revver comes from the fact GM never made a 400 specific head runner and they're heavily choked. Put some real heads and a healthy cam in em and they will rev just as hard as similar street 350s.

good luck
 

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Are you looking at the 12558060 Vortec cast iron head? I think that's the one you're talking about from the description.

For what it is worth, the GMPP catalog description for these heads says "Take your small-block to the 350 horsepower level".

With the cam you ordered, Desktop Dyno says 367 HP @ 5000 rpm and 432 ft-lbs @ 3500 rpm. Give or take how much...nobody knows.
 

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Discussion Starter #16
Fred, those are the exact heads that I am looking at. After considering budget and all I think I have decided on a compromise... I can get the 260 hp crate gm motor for around $1500 from summit or jegs. GM has a few motors that I have seen on the two websites one of which has 260 hp another 290 hp another 340. The cam that I have seems to be really similar to what they have in the 290 hp motor so I am thinking with a decent intake I will be right around 300hp for around $1700 total (intake and cam off of ebay). Then when I can save a little more I can purchase the vortec heads for $640 which is what jegs has on their $3000 motor and it pushes 341 hp and 358tq. I should have the engine installed in April, thanks for all of the help!
 

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Does your car run currently?

Here's my advice after hearing the decision.....stab that cam in your current engine, put hedders on it, then keep saving.

For the $3000 you're gonna end up spending just buy the correct crate motor up front. You can get a much better engine for 3k, yours wouldn't even have forged pistons. It'll have head gasket surfaces cleaned off in the car. Your car will have the extra nicks and scratches of the added 8 hours over the fender, etc. There are just compromises & risks when you top end an installed engine.

Cam is the heart of an engine. You do not spend $3000 around a $50 cam just cause it was a good deal. Treat it like a $50 disposable object and stuff it in the L48 while you save. If you won't install it, sell it or just throw it out the window. It's forcing bad decisions with thousand dollar consequence. For 3k you can buy a mild ROLLER cam engine and eliminate the chevy's achilles heel, flat cam syndrome.

No more $50 cam tunnel vision. Please. Not trying to be a jerk, it's the same thing I'd say to a real world friend.

good luck with the project.
 

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Discussion Starter #18
The original plan was to actually get the 383 from blueprint in jegs or summit that puts out 450hp for $3200. After doing a little research on that company I found that there were a lot of negative reviews of them. Thus I started looking to more budget friendly alternatives because any other engine maker that put out a high performance engine was somewhere around 6k for the engine. I came to this option because the cam that I just purchased, albeit for $50, seems to have better specs than what is in the 290 hp engine from GM. So my line of thinking is why would I spend an extra 500 bucks on an engine when I can just swap the cam. Also the heads on the 341 hp engine are just regular vortec heads. So really you can replicate the exact same 341 hp engine for around $2200 rather than spending $3000. If I thought that the blueprint engine was worth anything I would just be doing that instead.
 

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By the earlier math it ended up at 2340 but I guess that included intake too?

Pace sell the vortec headed GMPP 330 hp 350 HO for something like 2850. I still think you're gonna end up with a couple hundy of unseen cost with the head swap plan, that's just how those jobs seem to go. Major props for carefully researching the budget route but that particular blend of crate engine and home building just doesn't make a lot of sense. Here's why......

With the effort/risk you're putting forth rebuilding the crate to your ultimate specs, you could just build your own shortblock at a local machine shop and save even more. Check northernauto.com for the cheapest rebuilds around with forged flat top TRW pistons.

So really, either just save the extra couple hundy and get a turnkey package, or build the darn thing yourself. Anyone capable of the head swap is capable of assembling a shortblock. If you want more power on a budget, 400hp $2000 small block chevies are absolutely real. They involve a 400ci core, cheap performance heads, more cam than you've got, and the local machine shop.

Just a few thoughts from a guy that always has a $1500-2500 performance small block going together on a stand. Build it and they will come also applies to engineless chevy muscle :)

Good luck with your project. It's a fun one and am sure you'll make it turn out great.
 

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Lot of good ideas. That Lunati cam is almost a copy of the good old Comp 268 High Energy cam, 218-218 dur. at .050, .454 lift, 110 LSA. If it were me I would just put the cam in, install a set of Comp. 1.5 stamped steel replacement rocker arms(your stock GM rocker arms are probably only 1.4 ratio by now) and let it go at that. If you save another $500 or so you can upgrade to a set of AFR aluminum 180 heads to bump up your compression ratio. Hot Rod did a test on a 9.7 c.r. 350 with those heads and the Comp 268 cam and made 380 hp with a holley 750, Edelbrock intake and headers. Of course with your stock heads and low compression you will not get close to 350 hp but you will pick up around 30 hp with that cam and it will be much quicker than your current 929 cam is. My buddy put that 268 cam in his 81 4 speed, 3.73, 4 speed C3 and it made a huge difference. Later we put in 260 crate motor(he wound his original 350 too high and too many times and blew a rod) and put in a Crane 274H06 cam which has the same specs as the 268 cam except it is on a 106 LSA which makes the idle sound like a radical cam but still has tons of low and mid range punch because of the short duration. Sounds bad a** out of his hooker side pipes! It is actually a cirlce track cam for .450 lift rules! You can buy a set of cheap Z28 valve springs if you think your spirngs are not up to the job but we left the stock springs on both 350s and he could rev up to 5500 with no valve float. Bottom line is that your Lunati cam will work fine in your combo and I would keep your stock intake and just rejet your quadrajet if needed. Good luck.
 
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