C2 65 Fuel Injection Cam

[Rich G.]

Is the cam for the 365 HP and 375 HP Fuelie in 1965 the same?

Thanks

Rich Giannotti

[Duke W.]

Re: C2 65 Fuel Injection Cam

Yes, and it's a real torque killer. I recommend that the '70 LT-1 cam be used to replace the "30-30 cam" used on 64-65 SHP/FI engines. It will considerably improve low end torque with only a slight loss of power at 6000-6500, and if you pocket port the heads there is essentially no loss of top end power.

Duke

[Tom D.]

Please define "pocket port" Thanks *NM*

[Michael H.]

Re: C2 65 Fuel Injection Cam

Rich,

Yes, the 365 and 375 HP cam, the 3849346, is the same and if you have your original, I suggest you use it if it's still in good condition. It's a wonderful cam and is the "sound" of Corvette!

If it's worn, there are a number of cam manufacturers that make excellent blue print cams to the original 346 specifications. I don't understand all the ranting about the later 178 LT1 cam. It's definitely not one of my favorites and it doesn't have the typical sound of an older FI Corvette. It is possible that the LT1 may make a tick more torque at 3000 RPM but no one that I know is racing a 65 Corvette today.

Michael

[Duke W.]

Re: Please define "pocket port" Thanks

It means blending the valve pocket area, which is the area from the valve seat to about an inch upstream.

In particular there is a ridge above the valve where the rough forming of the valve pocket was cut with a conical tool. This ridge should be cut down to blend smoothly into the as cast area of the port.

Also, matching the port opening in the head to the manifolds is useful as is a multi-angle valve job. The interior of the port does NOT need to be opened up, but pocket porting, port matching, and a three angle valve job with .040" inlet seats and .060" exhaust seats will improve top end power by up to ten percent with essentially no loss of low end torque or valve seat longevity.

Instructions on how to do this work have been around for over thirty years in books like "How to Hotrod your SB (or BB) Chevy", and The Chevrolet Power Manual.

Head work even on a medium performance engine will pay dividends. All Chevy engines are limited by head flow, and pocket porting along with a three angle valve job will improve the average flow coefficient by improving flow, particularly at low lifts, where the valve spends most of its time during the open event. Because the heads are the limiting factor, "more cam" than the SHP cams produce only marginal improvements in top end power at considerable expense to low end torque.

The best way to improve power is to massage the heads, and it can be done by the amateur restorer if you obtain the above references and follow the instructions for the valve pocket area, valve seating, and port matching to the manifolds.

Duke

[Duke W.]

Re: C2 65 Fuel Injection Cam

The LT-1 cam has a more aggressive exhaust opening, which effectively phases the exhaust event earlier. With the same exhaust system the LT-1 cam will have a sharper exhaust note.

If you compare the life-crank angle diagrams along with velocity, acceleration and jerk, it's clear that the LT-1 cam was designed with greater insight into valvetrain dynamics and head flow than was known at the time the 30-30 cam was designed.

The result is a cam that produces greater torque bandwidth. With proper head work and a good exhaust system peak power with either the LT-1 or 30-30 cam is about the same, but the LT-1 cam's greater mid range and low end torque give it a clear advantage.

Duke

[Michael H.]

Re: C2 65 Fuel Injection Cam

Duke,

I respect your knowledge/opinion and agree that their might be a slight power gain in the low/mid RPM range with the later 178 cam but that's not my point. I'm sure there are cams today that make a lot more power than either of the GM cams but that's just not what we're after. A big part of the love affair with old Corvettes was the sound and that sound isn't there with the LT1 cam. I would be willing to bet 98% of the 64-65 owners would never feel the difference and I really don't think they care about six more HP at 3000 RPM. I think the idea here is to try to assist owners in restoring their cars back to factory condition. There's hundreds of improvements that can be made to and old Corvette but I don't agree with any that take away from the original image of the car. If we're talking about using modern piston rings or better bearings than we had available in the 50's, I have absolutely no problem with that but please don't take away that wonderful sound of pure Corvette from the mid 60's.

Michael

[Duke W.]

Re: C2 65 Fuel Injection Cam

Like I said, the more aggressive/earlier phased exhaust valve opening of the LT-1 cam will yield a SHARPER exhaust note!

There is NO aftermarket cam that will produce as much peak power as the LT-1 cam without a substantial loss of low end torque, and this also applies to the 30-30 cam, which is down nearly 20 percent at 2000 revs - way more than "slight" and definitely noticeable.

Duke

[Clem Z.]

Re: Please define "pocket port" Thanks

using a "tapered valve bowl reamer" the diameter of the valve bowl should be 81% of the valve OD,a 2.020 intake valve should have a valve bowl diameter of 1.636 or 1 5/8" is close enought. setting up the exhaust port with a "venturi shape" will make a difference in the flow. the orignal BBC aluminum heads had this venturi build into the exhaust valve insert. we added these venturies to cast iron heads with a shrunk in hot rolled steel insert.

[Rich G.]

Thanks for all the info guys *NM*

[Michael H.]

Re: C2 65 Fuel Injection Cam

I surrender. I think you've missed the point of all this.

[Duke W.]

Re: C2 65 Fuel Injection Cam

I think you missed the point.

Duke

[Michael H.]

Re: OH YEA! I'LL GET YOU AT RECESS..

When the teachers not lookin! Ok, I'll probably loose this deal because I know you have a lot of followers on this forum but.. All those in favor of replacing their original 64-65 346 cam and giving up that original Corvette sound for a new LT1 cam, please raise your hand. (or post on this forum)

[Brian Monticello]

Re: OH YEA! I'LL GET YOU AT RECESS..

My fresh 327/365 stock rebuild will receive the LT-1 cam next week. Please don't say that your dad will be up Duke's dad.

If you really want to prove your point and if it means that much to you you can record the exhaust note/lump on stock engine with the 30-30 cam and on a stock engine with an LT-1 cam. Then you have data that you can use to influence opinion and gather support. If you want to start a poll you might want to consider trying another forum.

Brian

[Dave McDufford]

Vote for the LT-1

I am a diehard Duke convert and am installing the LT-1 cam in my original block numbers matching L-79 (I know it could cost me points). I like the sound and based on Duke's, John Hinkley's and other comments, I view the LT-1 cam as the final GM derivation of the original 1956 Duntov solid cam. It represents the final and best of the small block solid cams that GM could create before the clean air regulations took the heart out of the muscle car. It was evolutionary not revolutionary. (Do I sound brainwashed?)

Dave