mongoose87

Hi Everyone,
I'm like most, looking to put more power into my corvette.
I have a 1972 sbc L48 engine. I know this engine isn't the best for performance, but it is matching numbers to the car, so I'd like to keep it for resale value.
I've been reading a lot about people putting vortec heads on their engines, but from what I'm reading, most of the vortec heads made by GM don't have a heat riser for my quadrajet carb with divorced choke (since the vortec came out after cars were either fuel injection or electric choke). I'd like to keep the q-jet, and I saw these on ebay:

http://www.ebay.com/itm/NEW-EQ-GM-CH...NS9AX8&vxp=mtr

These look to reduce the combustion chamber size to 64cc (I'm hoping the increase in compression will help some), and also has a heat riser.
What do you think of these, will they allow me to keep my carb?

Since I will be taking some of the engine apart, it seems like a good opportunity to convert it to a roller cam. I've seen several sets of hydraulic roller lifters for less than $200, so it seems logical. I know I will need a cam end play button, new pushrods (although I'd need those anyway with the new heads) and likely a new timing cover, but this seems trivial to the improvement and potential with roller cams. Just finding the required ZDDP oil at 10w 30 for the flat tappet cam is challenge, and I'd like to avoid that in the future.

Most of the articles I've read talking about cylinder head upgrades and cam upgrades seem to be moving the power band to the higher rpm ranges, at a sacrifice to low end power. I don't really want that, as I am mainly using it to cruise around town. It's also an automatic, and I'd like to avoid changing the converter stall.
I'm hoping converting the engine to a roller cam will allow me to have some higher cam lift ramps, so I can improve the low end power as well as the upper rpm range power.
I think the heads above with the 176cc intake runners will be good for the low end and high end power, right?

Any suggestions on cam selection after I convert the engine to a roller?

Of course this goes without saying, the intake and exhaust would be upgraded at the same time.

I'm planning on keeping the engine in the car for this cylinder head installation because getting the engine out and lined back up with the transmission sounds like a bit too much work.
All of this I have never done before, so any other pointers would be greatly appreciated.

Thanks,
Adam

63mako

I used the assembled version on a build. Was very happy with them and the springs were perfect for a mild hydraulic roller. Nice head for a 350-400+ HP street build and ports work with factory components. Assembled price was $820 or so.

mongoose87

one more thing:
If I get these new heads, it seems like a good idea to give them a good porting before i install them. What I've read about porting the intake side of the head leads me to think fuel atomization, especially at low rpms, will be reduced by the porting. With the engine being carbureted, it seems it would be best to keep them rough, apart from getting rid of any large flash marks.
BUT, is there any disadvantage to porting and polishing the exhaust side of the heads?
Will i see much gain from doing just the exhuast side of the heads?

mongoose87

That is very good to know!
I'd imagine you changed your cam at the same time. Do you know what specs the cam had?
Did you aim the cam profile toward high rpm power?

These say they are a vortec hybrid; did you have to get the edlebrock vortec intake?
(I know the vortec type is considerably more expensive)

What kind of exhaust did you put on yours after making this improvement?

63mako

If you have the typical 3.08 gears and 400 Turbo it has a factory 2000 stall convertor. Use the Felpro 1094 head gaskets and this cam with those heads: https://www.summitracing.com/parts/h...make/chevrolet
You will be a happy camper!

Kacyc3

Pull the engine and put it on a stand in the corner somewhere. Go buy a newer roller cam vortec crate engine and drop it in. This gets you an engine with a warranty, has better lower end internal parts than stock engine, uses hyd. roller cam.

HeadsU.P.

Not that great a deal because they are bare. Still need valves, retainers, springs, keepers, seals, and someone has to lap-in the valves. $660 pr. turns into big bucks.
Plus; may need special headgaskets, longer pushrods and may not be able to use your former headbolts. I wouldn't want anything related to a boat on my Vette, but that's just me. Cam selection should be done by a 1-800 call to a pro tech, not someone guessing on a forum.

63mako

That 1800 call to a tech line will likely get you a high school kid with an after school job and a cam book to look up your question. Will they ask your trans, gearing, car weight, intended use, maybe maybe not. As far as "boat" heads if it is small block chevy it is small block chevy.. Who is guessing? Some of us actually know. That may not apply to you and that is fine.

HeadsU.P.

Because marine engines are cooled through the exhaust system using lake water, there is the possibility that there are extra water passages to the block. Otherwise, why would they be labeled "marine"? And JFYI the marine Qjets are different too as I recall. Some SBC marine engines run in reverse rotation when twin engines / props are involved.

OldCarBum

The bare heads and blocks are the same for marine or street applications. The bottom end of a marine motor is built to slightly looser tolerances to allow for the rapid heating and cooling changes within the block. The water passages in the exhaust manifolds on a marine engine are fed through external hoses and are separate from any internal water jackets in the block and heads. The water passing through the exhaust manifolds on a marine engine is for keeping the manifolds cool and; in over the transom exhaust systems water is injected into the exhaust tube to assist in deadening the noise. The carburetors, ignitions systems, starters, fuel pumps, thermostat housings, water pumps, alternators, air filters (called flame arrestors in marine use) and other bolt on accessories are rated for marine use and are different than those for street use. All marine components can be used for a street application however the components designed for street applications should never be used on a marine motor. Marine ignition systems, starters and alternators are designed and sealed to prevent spark from igniting fuel fumes that can collect in the bilge. The carburetors and fuel pumps are designed so fuel fumes or fuels are pulled into the carburetor or put back into the fuel system and not allowed to contaminate the bilge. Flame arrestors are made with steel mesh and not paper or foam elements.
Reverse rotation marine engines simply run in reverse with no other modifications. The reason for this is simply to have counter rotating props.

BlackC3vette

Lake water? Do you mean fresh water? Where I am, it's salt water, one of mother natures most powerful corrosives. When I was involved in the marine repair industry back before the turn of the century, marine blocks were not special castings. They just had brass freeze out plugs and brass oil gallery plugs, etc.. The marine qjet had a upside down J vent to return fuel to the carb in case of an overflow. There were no extral passages, these engines were not difficult to keep running at a correct temp. The term "Marine" really only adds addition cost to the price. Many boats ran with fresh water cooling which was a closed system, not much different than cars with radiators. Actually, I can't remember which engine, but some marine cams were used by hot rodders due to their aggressive performance .

HeadsU.P.

Yes I mean lake water. My lakes are 150-300 miles across. We run cuddy-cabins with SBCs but we're getting off the subject here. I was stating that for $660 a pr for bare heads, plus parts & labor for boat heads may not be a good choice IMHO.
For a little over $8 bills you can get alum, 64 chamber, 185 runners, .575 max lift springs, completley assembled, ready to bolt-on w/ acc bolt holes, ProMaxx heads.

BlackC3vette

And some people refer to the Atlantic as a pond.

Anyway, regarding the ProMaxx, I have seen some very good pricing, do you have these heads?

'75

Those heads don't seem like a good value bare. Also you may have a hard time finding a vortec manifold with the heat riser passage.

63mako

http://www.ebay.com/itm/Chevrolet-35...hUkH4f&vxp=mtr
These are the ones I used. They are ON SALE WITH FREE SHIPPING! Says nothing about Marine. Direct from manufacturer. Might need to swap springs with an aggressive cam but the cam I linked earlier will be fine with them as it has relatively mild ramps and lift for a roller cam. The springs are stronger than the LT4 hot cam springs which is similar hydraulic intensity Spring rate is #352 = mild hydraulic roller. Perimeter bolt valve covers. Early intake bolt pattern, heat riser ports, good flow numbers, thick decks, vortec chamber. If your looking for a 350-400 hp build they are tough to beat @$743 shipped.

'75

Those should solve the manifold issue also, looks like they will take the original intake.

HeadsU.P.

Yes I do, Mr Black C3. A certain performance company that first letter starts with a "J" runs those ProMaxx on sale in the winter. I then called the other company that starts with an "S" for a price match and ordered. I know-I know, thats tacky, but I have my favorites.
But all this was after a month of research on reviews and some YouTube videos about the quality of those heads. I was terrified of some thin, poor alloy junk from overseas that caused preignition issues, overheating and poor performance, let alone warpage issues / blown headgaskets. But I was rest assured that those ProMaxx were A-1 heads for a smidge over $8 bills.

I couldn't see, nor do I still see the need for $1200-$2000 for a pair of heads to run around on the streets with. There are better bangs for that much buck.

mongoose87

Thanks so much!
This helps a lot.
With the higher flow rate of these heads, its seems like a better intake is in order, even if the stock one would fit. What did you use on yours?
I hear the edlebrock performer is best for fitting under the stock hood.
I see some performer intakes that don't have the divorced choke heat riser port for the carb. Can you confirm you used the intake designed for the stock heads, and possible which edition you used?
It looks like the performer 2101 has the divorced choke opening, but cant tell for sure.

Also, what kind of exhaust did you put on yours after completing the upgrade?
Again, I'm looking for low-mid range power.
I was seeing things saying 1 5/8 primary headers with 2.5 in pipes going back. Not sure if the shorty headers would be better for my goals and clearance.

mongoose87

One more thing:
When you got these heads did you do any porting and polishing before installation?
Any advice on fuel atomization after porting the intake side of the heads?
Has anyone ever left the intake side of the heads relatively rough, but port and polish the exhaust side?

63mako

I used a performer knockoff. Used 1 5/8 LONGTUBES. Was a budget build. I would upgrade intake and exhaust with LONGTUBES, 2 1/2" free flowing dual exhaust. I would just clean up any casting flash and run them as is. Mine were really nice as is, I didn't torch the ports, valve to guide clearance and machining were impressive. Everything checked out.