327 Rebuild

[Bill B.]

65 327/300 Coupe, manual trans.

After the first of the year I'm planning on removing the engine for a rebuild. It is a 327/300 matching numbers. Last rebuild was 1987 so it's due plus I want to change the clutch assembly while it's out. I have a reliable machne shop in the area that I trust so they will do the work. My question is, I'm thinking of putting a L79 cam (350hp) on for a bit more horse power but I've been reading in various articles that I won't gain much particularly at low end. My other concern is I want to keep the engine appearance as a 300hp and I would like to know if the Carter AFB will work on a 350hp. I would appreciate any input. Thanks in advance and Merry Christmas.

[Joe L.]

Re: 327 Rebuild

65 327/300 Coupe, manual trans.

After the first of the year I'm planning on removing the engine for a rebuild. It is a 327/300 matching numbers. Last rebuild was 1987 so it's due plus I want to change the clutch assembly while it's out. I have a reliable machne shop in the area that I trust so they will do the work. My question is, I'm thinking of putting a L79 cam (350hp) on for a bit more horse power but I've been reading in various articles that I won't gain much particularly at low end. My other concern is I want to keep the engine appearance as a 300hp and I would like to know if the Carter AFB will work on a 350hp. I would appreciate any input. Thanks in advance and Merry Christmas.

Bill------


First of all, the AFB will work fine with an L-79. In fact, 1963 L-76 actually used an AFB carb.

Notwithstanding the above, I would not install an L-79 cam. The 300 HP cam is one of the best street, flat tappet cams ever installed. In my opinion, installing am L-79 cam in your engine would cause you to lose more than you gain.

Beyond that, if it were me, I would not install a flat tappet cam, at all. I'd convert to a moderate performance retrofit hydraulic roller cam. I don't think I'd ever install a flat tappet again. To underscore that, I've got 4 NOS L-36/LS-5 hydraulic cams , the best big block, flat tappet street cam ever devised [none for sale]. However, I'd never use one.

[Bill B.]

Re: 327 Rebuild

Thank you for the input Joe, As always I appreciate your responses. I haven't looked into a hydralic roller cam but will do some research and give it some serious thought. Once again, thanks and Merry Christmas.

[Richard G.]

Re: 327 Rebuild

Joe;
"-79 cam in your engine would cause you to lose more than you gain"

Could you expand on the comment? I know you would loose torque.
But a proper wound up small block 327 it a thrill.
Rick

[Duke W.]

Re: 327 Rebuild

Installing a L-79 cam in a 300 HP engine has been common modification over the years. It gains top end power, but loses some low end torque/power.

So, how about maintaining absolute OE appearance, the smooth 500 RPM idle, stump pulling low end torque, but with L-79 top end power, and useable revs to 6500+?

Your NCRS number indicates that you should have received The Corvette Restorer from 2008 that included an article about the development of this "Special 300 Horsepower" configuration along with results of two that were tested. A few others have been built over the years. One of the two original prototypes discussed in the article received a Duntov award.

The article is also on the Web... easy search: a tale of two camshafts

Duke

[Mark E.]

Re: 327 Rebuild

Before taking the original engine to a machine shop, heed this tale of woe from a fellow member:
https://www.forums.ncrs.org/showthre...uild-in-Dallas

I recall reading years ago about a home made bracket that bolts to the block and covers the stamp pad. Either that or make it clear to not deck the block. It's too easy to grind off several thousand $ of value.

[Joe L.]

Re: 327 Rebuild

Joe;
"-79 cam in your engine would cause you to lose more than you gain"

Could you expand on the comment? I know you would loose torque.
But a proper wound up small block 327 it a thrill.
Rick

Rick-------


It's as simple as this: the 300 HP is a 5,000 RPM engine. The L-79 is a 6,000 RPM engine. The RPM range between 5,000 and 6,000 will rarely be used with the L-79. But, in order to have it, one gives up power and torque in the 1,000 to 3,000 RPM range. That's the range that the vast majority of street driving is done at. So, one gives up that which is most used for something little used. That's a bad trade-off in my opinion.

[Duke W.]

Re: 327 Rebuild

The 327/300 max gross torque rating is 360 lb-ft @ 3200 and the 327/350 max gross rating is also 360, but at 3600. So the torque curves cross at about 3400 where both make the same power. Below 3400 the 300 HP engine makes more power at any RPM, and above this engine speed the 350 HP version makes more along with a about 1000 more useable revs.

The Special 300 HP configuration has the 300 HP torque/power curve below about 3500 and the 350 HP torque/power curb above 3500 along with 1000-1500 more useable revs, but idles exactly like an OE 300 HP engine, butter smooth, 500 in neutral with a manual trans @ 18-19" Hg or 450 in Drive with Powerglide at slightly lower vacuum.

The L-79 cam is responsible for the 350 HP engine's idle behavior, which is about 750 @ 14-15" Hg with a slight lope due to the significantly higher overlap than the 300 HP cam, and there is no way to disguise this. Back in the day most guys actually preferred the slight idle lope, but it won't pass judging, especially a PV!


Duke

[Timothy B.]

Re: 327 Rebuild

65 327/300 Coupe, manual trans.

After the first of the year I'm planning on removing the engine for a rebuild. It is a 327/300 matching numbers. Last rebuild was 1987 so it's due plus I want to change the clutch assembly while it's out. I have a reliable machne shop in the area that I trust so they will do the work. My question is, I'm thinking of putting a L79 cam (350hp) on for a bit more horse power but I've been reading in various articles that I won't gain much particularly at low end. My other concern is I want to keep the engine appearance as a 300hp and I would like to know if the Carter AFB will work on a 350hp. I would appreciate any input. Thanks in advance and Merry Christmas.

Bill,

You will get a different opinion from many people here and they are all good so here's mine. Rebuild it only if it needs to overhauled and keep it a completely stock 300hp engine, flat tappet original replacement cam etc., along with the stock compression, oil pump etc.

Maybe it only needs a valve job with attention to the guides and seals. These engines are pretty tough, a clutch and flywheel truing is not a hard job compared to removing a engine.

[Joe R.]

Re: 327 Rebuild

Bill,

You will get a different opinion from many people here and they are all good so here's mine. Rebuild it only if it needs to overhauled and keep it a completely stock 300hp engine, flat tappet original replacement cam etc., along with the stock compression, oil pump etc.

Maybe it only needs a valve job with attention to the guides and seals. These engines are pretty tough, a clutch and flywheel truing is not a hard job compared to removing a engine.

I agree with this. Do not rebuild an engine "just because." It's an expensive proposition and there is always the possibility of something going wrong, such as the machinist decking the block and wrecking the factory pad stampings, or a failed flat-tappet cam break-in that forces a complete tear-down and cleaning. As the saying goes, "If it works, don't fix it."

Duke's comments on how the 327/300 cam compares to the 327/350 cam are correct. Only change to the 327/350 cam (or a roller cam equivalent) if the power above 5000 rpm is important to you.

If you want to jazz up the performance with the biggest bang-for-the-buck, I suggest that you simply install a set of the Trick Flow DHC heads on your existing short block. Externally, these heads look just like the original '461 heads you have, but they will give you a slight bump in compression and they flow far better than even a set of ported '461 heads. And, they will "fix" any deficiencies in your possibly-worn/aged 461 heads. Most small blocks that are starting to show signs of wear have problems with the heads, not the short block.

[Bill B.]

Re: 327 Rebuild

Thank you for that input, Joe. I haven't heard of Trick Flow heads before but I've been reading up on them. An interesting option if in fact the heads are my problem.

[Joe R.]

Re: 327 Rebuild

Thank you for that input, Joe. I haven't heard of Trick Flow heads before but I've been reading up on them. An interesting option if in fact the heads are my problem.

Can you tell us more about the problem you are trying to fix? Based on the symptoms and some careful diagnostic tests, it is usually possible to determine whether a given problem is with the heads or the short block.

[Bill B.]

Re: 327 Rebuild

The engine is using oil. I put the engine together about 25 years ago and it was the first one I had assembled and I believe I did a lot of things wrong through my ignorance of rebuilding. For instance, I didn't pre-oil the valve train before firing it up and it seemed to take forever before oil got to the lifters and I know that couldn't of been good. The engine has used oil from day one, like about a quart every 3 or 4 hundred miles. Due to my occupation I was out of the states for long periods of time (years) so I never really addressed the problem until now. There is no oil on the garage floor so I assume it's in the heads and going out the tail pipe but I don't really know for sure. The car definitely needs a new clutch assembly so my plan is to pull the motor and take it to a good machine shop in my area and just have the engine and heads gone thru. The manager of the machine shop says it may well be bad valve guide or seals but he obviously need to trouble shoot. He did excellent work on a 396 a few years ago for me so I trust him. I did a compression check 2 nights ago and it was difficult getting the tester in some of the spark holes with the engine installed but the reading I got were all between 140-155 psi. Anyway, that's my problem so any advice from members would be appreciated. I'm 73 and although I'm in good health I don't get around like I used to so just wnat to get the issue resolved and enjoy my Vette.

[Joe R.]

Re: 327 Rebuild

Hi Bill:

Three quick questions come to mind:

1) Does the engine smoke on startup?

2) What work was done to the heads in the 1987 rebuild?

3) Did you assemble the heads yourself?


There are others here who will likely have some helpful suggestions for how to determine whether the oil consumption is through the heads or the rings.

If your mind is already made up that you are going to have the entire engine rebuilt, there's probably no point in trying to diagnose the cause of the oil consumption. However, if you would simply replace/rebuild the heads if you were convinced they are the likely cause, it may be worth doing a little detective work before you decide how to proceed.

[Joe L.]

Re: 327 Rebuild

The engine is using oil. I put the engine together about 25 years ago and it was the first one I had assembled and I believe I did a lot of things wrong through my ignorance of rebuilding. For instance, I didn't pre-oil the valve train before firing it up and it seemed to take forever before oil got to the lifters and I know that couldn't of been good. The engine has used oil from day one, like about a quart every 3 or 4 hundred miles. Due to my occupation I was out of the states for long periods of time (years) so I never really addressed the problem until now. There is no oil on the garage floor so I assume it's in the heads and going out the tail pipe but I don't really know for sure. The car definitely needs a new clutch assembly so my plan is to pull the motor and take it to a good machine shop in my area and just have the engine and heads gone thru. The manager of the machine shop says it may well be bad valve guide or seals but he obviously need to trouble shoot. He did excellent work on a 396 a few years ago for me so I trust him. I did a compression check 2 nights ago and it was difficult getting the tester in some of the spark holes with the engine installed but the reading I got were all between 140-155 psi. Anyway, that's my problem so any advice from members would be appreciated. I'm 73 and although I'm in good health I don't get around like I used to so just wnat to get the issue resolved and enjoy my Vette.

Bill------


With the intake manifold removed, make note of whether the intake ports are wet with oil. If they are, then your problem relates to a PCV issue or leakage at the lower side of the intake manifold gaskets drawing oil from the valley into the ports.