augiedoggy

If I drove my corvette in the cold winter months or a lot of cold mornings I would consider keeping the crossover. It does serve a functional purpose for the applications it was designed for and these cars were designed for daily driving in many climates when new.
I had NO issues with my car running poorly when cold UNTIL I went with a bigger cam which now resulted it the car wanting to stall once I put it in gear when its cold out unless I let it warm up for a few minutes after the cold start. I do think some of that also may be the fact that the converter in the trans is a little small for the cam. All this will soon be remedied with my new trans, converter and 406.

When I was doing some work installing electric rad fans and such years back I removed the hood just to make it easier in my garage at the time. I decided to take the car for a spin without the hood it was a fairly cool spring day and it was then and there after feeling how much stronger the car ran that I would build a CAI myself and it was no longer open for debate for me either..

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Read this link from Cliff Riggles website...https://cliffshighperformance.com/si...p?topic=4554.0. Cliff Riggles knows carburetion and fuel atomization.....his entire business and life has been about it. Guess who I am going to believe.

However, as I previously stated, its a matter of how hot or cold.....and the consequences of too cold matter on a street car, driven alot.......not a race car. I may block the exhaust crossover,....althought its a much smaller passage than the factory passage, and therefore would flow much less heat. As Jeremy at AFR told me,....its irrelevant one way or the other, BUT, my decision to go with a NON-Air Gap intake manifold is based on the facts about fuel atomization on startup, and the unknown and uneducated consequences of it,. Folks need to consider what is actually going on when a car runs bad at startup due to an excessively rich, fuel droplet / laden mixture. Its more than just an "inconvenience". That excess fuel is going into the cylinders, washing away oil, and doing what all excessive fuel mixtures do.

But heh.....do whatever you want, just like I will.

By the way......confusing cold air density, and its theoretical benefit with this subject is just that......its not about that. The cold air induction arguement is scientifically accurate,.....but the real life practical benefit on the street, in my car,...the way I drive it, is absolutely irrelevant. Does the car perform better when the right seat is empty....or when the gas tank is half full? How about atmospheric pressure, altitude changes and humidity.......more scientific facts that mean nothing in reality to me. On a race track....it could mean the difference between winning and losing.....otherwise....trivial stuff for guys to argue about on a forum. Blah blah blah.

augiedoggy

I have yet to see any evidence that an air gap manifold has any benefit vs an rpm on a fully warmed up street engine once an open spacer or diver cutout is used/made to the rpm. They do have advantages on the strip though for the right person.

That said I just bought one to try on my 406 build to see first hand if there is in fact any appreciable gains. If I dont care for it I'll bolt my old intake back on.

As far as how my car runs cold at startup, Yes its a real annoyance and it was pretty surprising how just a cam change could make such a difference in this regard to the characteristics of the the engine.. In other regards the performance improved so for me it was something I consider useful knowledge first hand experience.. I dont expect this cam to behave the same way in my 406 with a 2200+ rpm converter.

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Couple comments of clarification for anyone interested:

- Felpro head gaskets do NOT have perfectly round cylinder bore openings. If you buy a Felpro head gasket the exact size of the head bore, you are likely to have gasket material INSIDE the bore. CNC Motorsports recommends the head gasket bore be a minimum of 0.020 larger than cylinder bore to prevent this. And remember, there are not Felpro gaskets manfuactured in ever single 0.0001 increments in every gasket thickness. Incidentally, the instructions on AFR website call out 4.200 inch bore head gaskets for 400 SBC engines...but maybe they have no common sense?. I contacted CNC Motorsports, and they use and recommend a Felpro 1003 head gasket for all their NA 400 SBC engines. That bore diameter on that gasket is 4.166. That is what I will use, and as you will see when I place them on the heads, the difference between the bore of the gasket and bore of the cylinder is very small. Its not an issue, not uncommon, and I believe will work just fine. Chris says they never apply any additional sealant or coating to these gaskets, and never have a problem with it, in an application like mine, especially with the superior surface finish they surface the deck block to. I told him I would gladly buy more expensive Cometic or Felpro MLS gaskets if they would guarentee a better seal....and he said its absolutely unnecessary. On boosted high compressions applications, they may be worth it

- In my multi-car forum research, thin 0.015 inch metal shim style head gaskets have a reputation for not sealing water as well as gaskets such as Felpro 0.039 and 0.041 composition head gaskets. I have no desire to have water or combustion leakage, nor is it worth the risk to use something that has less chance of success. And these Felpro composition gaskets have been around a long time, and have a very long history of successful and proper sealing. And that speaks for itself. I chose this Felpro 0.041 inch composition gasket for that reason. Mark Jones used these on his build, and I had no combustion or water leakage on the head gasket....and that was with a 4.155 inch cylinder bore,.... much less seal material between bores than my 4.125 inch cylinder bore. I have every reason to believe this will work just fine. Or I could sell this short block and order another one with less deck surface removed and use these thinner leak prone shim style gaskets?

- A 9.0 inch zero decked block, with the large number of pistons and gaskets made just for this, is propably the most common configuration in existence. A parts outlet search will prove this to be true. With a Dart SHP block starting with a 9.025 deck, followed by the minimum surface finishing required, the difference between a 9.00 inch deck and lets say 9.020 is 0.020 OR LESS. Reality check...that is a third of 1/16 inch. With that setup, either custom pistons would be required, or steel shim style head gaskets required....to get my target squish / quench. I chose to zero deck the block. Could I have chosen to have CNC Motorsports deck less (and I actually did talk to them about it when ordering the short block)? Yes. And I just explained why I did what I did. But then again....I have no common sense. Or I could sell this short block and order another one with less deck surface removed and use expensive custom pistons or thinner steel shim style gaskets?

- AFR does NOT advertise on their website any option to buy a 195 STREET cylinder head WITHOUT the exhaust crossover port drilled. It is 3/8 inch in diameter hole, much smaller than much larger Chevrolet stock passage. IF AFR would sell you this exact head without an exhaust crossover,.....its not listed as an option on their order forms. I did not call and ask them if they would do it, just as I did not ask if I could get the heads anodized in blue and red dots. In fact, I may use the crossover, but if not, blocking it is a very simple thing if I should decide to do so. As I have already discussed above.....an exhaust crossover has a purpose on a street car, and why Chevrolet went to the trouble and cost of engineeing and producing it

- An Edelbrock RPM NON-AIR GAP intake manifold is one of the most popular performance intake manifolds ever made,.....and it has an exhaust crossover machined into the casting. But then again....I don't drive my C3 Corvette at 170 mph. What do I know about the term "performance"?

- CNC Motorsports balanced my Scat crank to better than the minimum they advertise. I listed the balance specs above. The drilled balance holes are located in BOTH the front and rear counterweights. And I ordered the 350 main journals because they are more than adequate for my application and have no downside for my application. And actually, I am not sure they sell the SHP blocks with 400 mains,....and its not worth me looking to see if they do. Or I could sell this short block and order another one with 400 mains?.

- It would seem unnecessary to repeat this, but for some reason, because of basic lack of reading comprehension by some, it seems neccessary. This engine will be in my 77 Corvette, driven from 0-60 mph, never over 4500 RPM, normally shifted at 3000 RPM, never will smoke the tires on purpose, will never race on a track or on the street. Just remember that when "analyzing" and "criticizing" my choices......because MY common sense tells me that I should build the engine to my application.....not others. I already spent over $20,000 to do that TWICE on the previous engine. See how badly that worked out.

- So far, I am very impressed with CNC Motorsports and work they did on this short block. Chris answers every question I ask without hesitation, and if I ask for further explanation, he provides it until I am convinced. And the answers make sense to me. That is far better than the BS I put up with in the past from proclaimed "performance experts" here and those that I paid to build the engine for me. It is also clear from those conversations with CNC Motorsports that they have successfully built and sold lots and lots of engines and they have the process well established to provide a quality product for many years.

I am always reserved about "absolute" statements.....because I am a humble person, so I will reserve some of my confidence until this engine is back in the car, with thousands of miles of success before I proclaim anything. Based on my experience.....there is still lots of opportunity for failure. Only time will tell.

gkull

I've used these for years. Being Cometic Multi Layered Steel nothing protrudes into the cylinder bore with 4.125. They don't have the aluminum squish ring like a felpro and reuseable.

How to start up any car to get it warm and well lubed as possible because of roller wheels. First off run a 192 or 195 thermostat. You fire the motor and bring the idle rpm up to 2500 rpm and hold it steady at that rpm until you see your temp guage exceed 150 degrees. The fuel is well atomized at the higher rpm. I work on older V12 ferraris with 6 two barrels 38 DCN webers and the F1 Cosworth DFV's and it's in the manual for start up proceedure.

I was surprized to hear that airplane motors are allowed up to 20% leak down. Engines I worked on get refreshed at 8 to 10% My vette had guide smoke at less than 3% so I refreshed it.



https://www.summitracing.com/parts/c...make/chevrolet

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Ordered the balance of the parts today to finish the engine.....from CNC Motorsports and Summit.

4-vettes

Well with the last of your bits on the way. Shouldn't be too long before you have it in the car and running.
Years ago when I did my home rebuild, I moved house halfway through the rebuild, only 850K's away. Had to wait for heads to come by ship, etc. etc. Took me a year!
Didn't spend one cent in a machine shop however. 7 years later, still purring along.
Hopefully in 7 years you will be saying this as well.

OMF

Just wondering if you know that that 1003 head gasket has a steel ring in it and may leave a mark on the aluminum heads. That's why I used the Felpro 1010 which has a copper ring and is less likely to leave marks on the heads. FYI

4-vettes

That doesn't matter. This engine is going to run perfectly and he will never, ever need to remove the heads in his lifetime! (Fingers crossed).
So if the heads get a slight indent from the gasket all that will do is help the gasket seal better.

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Thanks for that information. I suppose a .039 squish is not too much on the 1010, but is why I selected 0.041 in the 1003. It's splitting hairs. I read up on the steel fire ring on aluminum heads, and many stated it as a non issue,...and in fact some stated it does do what 4-Vettes says below. I will consider it. CNC Motorsports says they use the 1003 all the time on 400 engines, they know I am installing AFR 195 heads...but I will call them and verify. Thanks.

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I hope you are right. And, what you said about the indent is apparently not a joke. I have have read on forums that it can make for a better seal??? Not sure I fully agree, but it has some merit.

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Interesting......I copied below the Head Gasket instructions directly from the AFR Instructions that come with the Aluminum Heads

HEAD GASKETS: Fel Pro #1003 for all aluminum heads up to 4.100” bore. Fel Pro #1034 should be used for 4.100” or larger bore. Applications requiring steam holes should use Fel Pro #1014. Late Model LT-1 reverse cool applications use GM gaskets or Fel-Pro #1074. AFR has removed the cooling passage between cylinders #1 & #3 and #5 & #7 to increase strength of the casting. Do not drill these areas out in an attempt to find water jacketing.

Two things noteworthy........ONE is that they specifically are instructing you to use the Felpro 1034 head gasket for 4.100 inch bores or larger. My 400 has a 4.125 bore,.....and the Felpro 1034 has a gasket diameter of 4.200!!!. Its also interesting that they are saying NOT to use the 1003 on a bore over 4.125. This certainly goes against the "advice" I was given in Post #165. But what does AFR know? They must lack common sense, like me. So should I believe AFR or a guy on a forum?

Secondly, they ARE recommending the Felpro 1003 gasket, with the steel fire ring, on their own AFR aluminum heads.

I certainly understand the concept that a steel ring could possibly mark, or indent, an aluminum head. My understanding is that despite all the clamping forces, the rates of expansion difference between steel block and aluminum head can allow "movement" at a micro level. I don't like the idea that I could be causing damage to the heads. BUT......this may go on the list of one of those things that are scientifically correct, but in reality, an over-thinking and extreme concern over a non-problem. ?????

I guess for me, the question is.....for my application, where I will run 5000 miles a year on the street, and hopefully never remove the heads again......is this an issue?

It falls into the same category as decking the block to 9.00 inches. Conceptually, I want to build this engine, put it in the car.....and never disassemble it again. So far, that has not been the case, but it is the goal. In reality, even if I do drive the car 5000 miles a year....I am 65 years old. IF.I live to 85, that is 20 years at 5000 miles a year = 100,000 miles. Will that really happen.....I don't know. Only God knows. Its not something I like to think about.

4-vettes

I'll say this about the Fel-Pro head gaskets on Aluminium heads as I do have personal experience.
When I first built my engine I used the standard type .041 thick Fel-Pro head gaskets. After about 2 thousand miles. I felt I just wasn't getting the tune as sharp as I would like it. So I began to question the quench. I even ran a thread on here asking questions.
My block is not decked and my pistons are .022 - .025 in the hole. With the .041 gaskets. I felt perhaps this quench issue was the reason I couldn't get my tune as good as I wanted it.
In the end I do believe it was a part of it.
Back on track. I pulled the heads back off. Replaced with .015 Fel-Pro shim style gaskets to get quench were I felt it needed to be.
Slight indentations were indeed present in my heads from the fire rings in the previous gaskets. Heads were cleaned up with scotch brite but not resurfaced. Very slight indents remained. New shim style gaskets were preped with copper spray a gasket. That's a few years ago now and a fair few miles. And several days on the track where I am not at all nice to her.
No issues with head gaskets in anyway. The fire ring actually seating right into the head slightly can't be a bad thing. And it really is only very slight. Not enough to disturb even my shim style gaskets.
I realise you have no need for shim style gaskets with a zero decked block. I only run them because I had no real need to deck my block.
So if I were in your shoes. I would indeed follow AFR's recommendations.

augiedoggy

As I understand it they are saying to not use the 1003 on a 4.125 bore as well.

I was planning on using steel shim gaskets and coincidently speedmaster just discontinued them for the 400. So .027 cometics are the thinnest I can find (at $100 each) My block is not decked.

I read up on this a bit when I made the choice to use steel .015 1094 felpros on my aluminum heads in the car now. I was told that many like the 1094 are coated and that makes them ok. I also used copper gasket spray as safe measure.
I also read they might develop indentations from the expansion and contractions at different rates. I guess I will see when I pull my heads to install on my 406.

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I will make sure the head gasket fits properly on the block bores and heads, and no part extends into the bore area. Having as much gasket material possible, without extending into the bores, makes sense to me.

As for indenting aluminum heads or block, seems like MLS gaskets would also do this given the raised sealing beads design…just as a steel fire ring would. But….i think it’s a solution looking for a problem issue either way. I am not concerned about it.