R66

I have a 300hp/327 mouse that I am considering changing to a 350hp clone in appearance only - Intake and Valve Covers.
I have the 350hp aluminum manifold but I think it takes a different thermostat housing and possibly upper radiator hose correct?
I understand the 300hp has 1.94 Intake valves and 1.50 exhaust valves and 10:1 compression where the 350hp has 2.0 Intake and 1.60 exhaust valves along with 11:1 compression.
So, if I just change the Intake manifold, and not the heads and pistons, will there be any negative effects on performance?

Thanks,
Ron

Nowhere Man

R66

I know of the bypass hose and have the correct configuration water pump, but I am currently running the aluminum intake on our 68RS 350ci and have the bypass plugged on the intake. I have never noticed any cooling problems with the bypass hose plugged. I may swap them out also, still contemplating that.
Thanks for the reminder.
Ron

Nowhere Man

you said appearance I look for that and the always over looked ballancer when people clone L79.

Powershift

Ron:

You will be just fine. Aluminum intake may provide a small bit of HP increase. For 1966, the standard 327 engine had 10.5 advertised compression ratio, so difference in CR is not as great as you expected. Thermostat housing and upper hose are different from base.

Might just as well install the cam as well.

Larry

LouieM

FWIW, when I was shopping for my 327/350 '67 in 2002 I ran across several dealer cars that looked like L79s, and the dealers all claimed they were, but the tachs were the lower redline 300HP versions. So, if you want your car to look like a "real" L79 you might want to change the tach face too. That would fake out even most of the cognoscenti.

Grmvettes

Nowhere Man

the carb is the same for 300 and 350. the 300 intake is a very common part used on a bunch if Imapals, Chevelles, and Chevy II and maybe trucks. so should be easy to find

SI67

You will also want to get the the 350 HP choke rod and fuel pump to carb fuel line.

R66

Sorry, I am not selling the cast intake and carb. I may have another CI intake in the shed, but they are very common and cheap - shipping would kill you.I'll put the intake and valve covers on the shelf in case I decide to sell the car. I am not trying to fool anyone or rip anyone off. I don't plan on having the original engine restamped.

I have the correct Winters snow flake aluminum intake on our 68RS and I like the looks of it along with the aluminum valve covers. I think the 350 hp also had a chrome filler tube and dip stick tube as well as the tack, harmonic balancer, bypass hose, etc. I assume the harmonic balancer on the 350 hp is an 8" which involves changing the timing cover also. I have a couple, but don't know how the harmonic balancer change would effect the mouse engine without the piston and cam change.

Considered changing the cam, but with the original M20 and 3.36:1 gears it might be a little tough on the 10.5 in clutch around town. I ran a M21 with 3.08 gears and the 350 with the 350 hp cam in the Camaro and it is not a good combination around town. Of course it weighs about 3400 lbs.

Was concerned with possible port mismatch on the intake to 300 hp heads. Don't really want to port match the intake as it probably would effect the value should I pull it back off. Sometimes wish I were a little more dishonest as Hagerty lists the L79 at about $10k more than the mouse. I like to sleep at night.

Thanks to all. Think I'll go ahead with the intake and valve covers first, get some ow and ahh at the cars and coffee. Of course it won't have the rump rump.

Ron

SWCDuke

Why not just install the Corvette valve covers and paint the CI manifold silver. Most guys won't know the difference. This was a common practice back in the day.

The '66 and '67 L-79 standard axle ratio with the wide ratio trans was 3.36, same as the base engine. The 2.54 first gear WR trans with a 3.36 axle has the same overall 1-3 multiplication as the 2.20 first gear CR with a 3.70 axle. A CR with a 3.08 is twenty percent taller. It's like a five-speed with no first.

If you change the cam use a L-46/82 cam and install it four degrees advanced to bring the as-ground 114 deg. ATC inlet POML back to 110, same as the L-79 cam.

If you want to simulate L-79 idle behavior, raise idle speed to 750 then lean-out the idle mixture until it roughens up a bit.

Duke

White Monster

Factoid

farmone

I read the intake discuss in the string and have a question. Did GM use any Edelbrock aluminum intakes as a factory install on small blocks?

449er

"Mouse" engines are small block & "rat" engines are big blocks, it has nothing to do with the hp ratings

Nowhere Man

nope

emdoller

R66

Mouse owner corrected, not that I didn't know it. Let's say non L engine or base engine?

Anyway, I am pulling the heads to do the valve guides. Should I find something in the cylinder walls I don't like, you know where it goes from there. Also if I check the cam and find a worn lobe, I may decide to go with the L79 or a similar cam. I don't want to choke out the cam with the small valves, and don't want to put on another set of heads even though I have them but 69 era. I'll have to see once I get into it. I have the intake, so why not. All I need to buy is the thermostat housing and valve covers unless I need a cam, lifters, pistons and rod bearings.
If I make it a real L79, I have a M21 or a DNE 5 speed I could put behind it, with an 11" clutch and etc.. Might as well resto mod it then.

I do agree with the appeal of a L79 to most, but I am happy with the performance as it is. 15 years ago, it would have had it all, but age and health factor in now. I have to set my limits.

I don't think any of this would get close to adding $10K to the value or even returning the investment, as it needs a complete frame off restoration. I like driving it too much to park it for 2 years. I'm not interested in selling anyway.

Thanks for the input.

Ron