Roarinbear

My 75 coupe has 78,000 original miles, numbers matching L48.(runs good, but weak) After doing my homework on top end upgrades, I'm leaning towards a 290 hp crate engine. (any opinions welcomed) If I decide on a new engine, is it advised to change out the cam, or is the stock cam that comes in the 350-290 hp. engine satisfying. I know there will be warranty issues, but aside from that, I want to be happy with a good running dependable engine.

G dad

The 290 crate is great for a fun cruiser & is a good bang for the buck! Reliable old school engine

Reggie Dunlop

The GMPP 290 horse motor is basically the L82. Same cam, same compression ratio, similar heads. The difference in horsepower is the rating method. The GMPP is rated with open headers at the flywheel vs the L82 rated as "installed". The 290 engine actually makes less torque than the L48. In town, stop light to stop light, they'll run an even race. In the 1/4 mile the 290 will be ahead by a car length or so. The bad thing about the 290 motor is the 222 @ .050 cam matched with the 8.5:1 compression - it'is just too much cam to make good low RPM power, which is what makes a car fun to drive on the street. If you have gears that are 3.55 or numerically higher, or if you spent a lot of time above 3,500 RPM the 290 is a better performer. If you want something that is a blast to drive and that will produce 1/4 mile times better than the 290, replace your L48 cam with something in 204/214/110 range. And yes, the warranty will be voided if you change the cam or rocker arms or just about anything on the GMPP engines. For whatever it's worth, the Goodwrench 260 hp / 350 trq motor is basically the L48 - again rated with open headers at the flywheel.
If I were to buy the 290 and change something it would be the heads to get the compression up to at least 9.5:1, but then I'd be close to the price of 350 HO - which is a pretty darn good deal in itself.

Roughrider

The 350HO, which is an excellent engine, is a premium fuel engine. The 290 is a regular fuel engine. Consider that when making your decision based on what kind of use you plan on giving the car.

Roarinbear

Thanks for the reply. Currently my set up is all original, show condition. Air pump & cat. delete. Tru duals 2 1/2" W/ Magnaflow's. Do you suggest just replacing the cam? Will a new cam (204/214/110) give a noticeable differance, with everything else stock?

Reggie Dunlop

Yes, the improvement will be noticable across the RPM range. To get the complete bennefit of the slightly larger cam, you should also recalibrate the secondary side of your carb (q-jet, right?) - use secondary rods in the .052 range, adjust the spring that controls the opening rate, and probably even replace the vacuum dashpot that controls the timimg of the opening with a faster one. Do this along with setting the ignition timing curve to 36 to 38 total (intial & mechanical), all in by 2,600 RPM or so and you will be very pleased.

Kellys~hotrods

I installed a 350/290 GM crate engine in my truck and it runs strong. I have an edelbrock intake, edelbrock carb, k&n 4" tall round filter, dynomax headers, and MSD ignition system. On a side note, it doesn't like anything less that premium fuel (pings with lower grades). It was a great choice for the price, and 4 bolt mains included!

Kelly

Roarinbear

Great info. Thanks everyone. I can't find cam combinations with 110 lobe seperation is there much difference with a 204/214/112? I don't have much experience with cams, sorry.

tgcattle

I installed the 350/290 hp in my 79. I have a 350 auto tranny. I installed a edelbrock performer intake, 750 edelbrock carb, headers and a summit cd ignition and dist. I likes above 2500rpm's. Needs a cam upgrade. The cam it has causes low vac. I plan to install new alum. high flow heads. Haven't decided which ones yet and a cam,leaning towards a thumper or ****** thumper. Also an overdrive tranny. Sigh............don't hurt to dream huh? I enjoy driving thr 290 hp.but it definately needs at least a bigger cam

vetteguy75

I have a 75 Vert that was originally an L-48 (165hp).... about 2 years ago I put in the GMPP 290ph crate engine and have been loving it ever since!!

If your's is an automatic, you will have to change your torque converter for a higher stall speed ..from 1600 to 2400. The engine was running rough at idle in drive....tried everything to correct that and finally changed the stall converter and it smoothed out tremendously.

Good luck!!

ZLX

The Production Line L-31 Vortec 350 with 4 bolt main is a hell of a buy
... $2100 with free shipping at Pace Performance.

It's a one piece rear main seal vs. your 2 piece.. it also does not
have a mechanical fuel pump provision..

If you can negotiate those differences and drop in an Lt-4 cam or
Lt-1 (93-96 vintage) before you put the motor in the car...

You'll have a very nice budget powerplant.

Nothing wrong with the 290hp.. just playing devils advocate.


here's the link:

http://paceperformance.com/index.asp...&ProdID=225981

ED69ray

IMO, if you are gonna buy a crate motor - go with a roller cam design.

otherwise, I would just build what you already have.

good luck, Ed

Roarinbear

I guess I will start with a new camshaft. I really have not much to loose.
I would like advice on what I have found for cams, and also any additional opinions.

GM (Crane) #12353917 Dura. 204/214/112 lift .420/.442 $160.00

Lunati #10000LK (Bare-Bones) 204/214/112 .420/.443 $135.00


CompCams #12-305-2 203/212/110 .429/.438 $176.00

CompCams #12-230-2 (XE250H) 206/212/110 .432/.444 $176.00

Edelbrock #2102 204/214/112 .420/.442 $128.00

Reggie Dunlop

Copy and paste to view these.
Both are very good articles doing progressive builds from a stock motor.
I recomended the 110 LSA because of the low compression of your stock motor and not knowing the rear gear ratio. The 110 will make more power in a narrower RPM range - usually off idle to about 4,800 RPM in a 350. The 112 LSA spreads the power out a little more so you'll gain some RPM on the top end. I have used the Summit brand 204/214/112 cam several times in low compression motors in cars and pick ups - it works great. Idles good and works well with a stock converter, pulls 20" vac at idle so your stock carb won't need any mods to the idle circuit. And the great part is you can get the cam, lifters, and gaskets sent to you for about 125 bucks!

http://www.superchevy.com/technical/...ons/index.html

http://www.corvettefaq.com/c3/goodwr...20part%201.htm

TedH

I went with the Crane Energizer cam with 216/216 duration @ .050 and .454" lift. It is very torquey and really woke up the engine. The nice thing about this cam is you get the lift of the L82 cam but with a shorter duration that builds torque and is usable at much lower rpms.

Add a recurve of your distributor to that carb re-jet and you will find 40hp+ improvement easily with that camshaft.

I recall Lars can rebuild/refresh the q-jet to suit any power setup you have. He did mine in my '80 L48 as well as the carb/distributor in the '69 L46 I had until spring 2008. Both performed great!

Roarinbear

Thanks guy's, great reading Reggie. Oh yes, I have a Q-jet, and the stock rear end gears.(308's) Now I really have questions. But I'd like to keep it simple . So if I just went with a cam, I'm better off find a cam with a 110 degree lobe sep.? If I decide to go the Vortec heads, with Edel. intake, and CompCam XE262, will I have hood clearance problems?

jackson

those 3 are aka RV cams ... get same cam with lifters from summit sum-k1102 for under $100.



the 290 is more like an L48 with too much cam than it is like an L82 ... 290 has dished pistons & 76cc heads ... same as L48.

hotrodrik

Be careful of these crate engines , as they are made in mexico.,most people have had good luck with them, some people have had problems . I installed one of these 290hp crate motors in my street rod 2 years ago . It did not even get 5 miles on it. The first one had a huge oil leak coming out the rear main area,took it to the dealer,they tried to replace rear main seal,turned out to be the main bearing cap was machined wrong. They gave me a replacement under warranty but i was still out time and materials to switch engines. The second engine has 2500 miles on it and it is smoking out the left pipe, took it to dealer , they said valve seals were bad .Warranty up, my problem they said! So be careful !!!Just my 2 cents!!!

Reggie Dunlop

As long as you don't go bigger than the 204 / 214 @.050 numbers (and there is no reason you should) you can use either the 110 or the 112. Niether one will idle rough, just a nice heavy note to the exhaust. The Super Chevy article used the Comp 203/212/110 cam and it made very good power in an engine with compression similar to yours. I really don't think you'd see much difference between the two LSAs with a 3.08 gear. Just about everyone who grinds cams offers a version of the 204/214 cam with the differences being a thousandth or so of lift, and then the 110 vs 112 thing. Like I said, I have used the Summit version several times over the last couple of decades and it works good in a low compression 350. My son had a '72 Vega with a 350 running the Summit cam, stock heads, stock cast iron intake, AFB carb, auto trans, 3.08 gears and manifolds with dual exhaust. It was a kick to drive. There was no low speed traction with this car. You stab the gas pedal from a slow roll and it would just spin the tires. We also put one in a '72 Chevy 4x4 with an auto trans, headers, Performer RPM and 600 Holley and it pulled extremely well - quite satisfying to drive - gas mileage was putrid @ 9 mpg. If it was me, I'd do just the cam (lifters & timing gears), perform the mods to the carb and timing and just have fun driving it for a while.

One more article using the Comp stick. Just shows what kind of power a motor with small but precise mods can make.

http://www.popularhotrodding.com/eng...ine/index.html

ZLX

Option 2:
Buy the 290/hp Shortblock from GM.. then add new Vortec heads...
should be under $2000

Option 3: Buy the 290hp Shortblock from GM and use the
Iron Bowtie Phase 3 heads... also under $2000

either of those 2 options will give you a solid bottom end with
better flowing heads than the 290hp crate..
The Bowtie Phase 3 heads will allow you to run a 1st Generation
intake.. perhaps even your stock intake if that's what you wish.