Thread: Surprise under the hood

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Years ago I bought a 68 Camaro RS as a rescue. Stuck it in the barn to keep it safe. It's out of the barn! I was told it had a .030 over 350. Turns out it's a 4 bolt 327. It had a set of mis-matched heads and the cylinders were beyond .030 by .004-.008. So now it will be taken out to .040. I'm buying a set of alum heads (64cc combustion chamber, 185 intake runner, 2.02/1.60) and want to go to a roller cam. Also flat top pistons. SO- I'm looking to you who have gone before me for advise on cam selection and pistons. I'm cross-eyed looking at Jegs and Summit part numbers. Obviously I'm just like all of you. I love the sound of a fast rapping thumping Chevy V8. But I want the right combo to get the best performance. It's a street car not a drag racer. BUT I still want to be able to hold my own when the wild hair shows up. FYI I've got a stick 4 speed and 3:08 rear gears. Thank you in advance from a new guy on this site.

OK since I posted this earlier, I've spent some hours reading similar posts from years back. So based on what I am being told by my machine guy, I will be around 10.2:1 on compression with a flat top piston and above mentioned head. I will select a gasket after the pistons are in just to be sure. Should I wait to buy the cam until this stage of the build? As for pistons- forged, cast, hypereutectic????? Got a link that talks about the difference?

Must be an aftermarket set of main bearing caps, Chevrolet never did make a 4 bolt 327...

As for the cam, whatever it ends up being I hope you're going to a hydraulic roller and the retro-fit hydraulic rollers. The flat tappet cams just don't live long these days with our oil not having zinc and the other additives in it that make a flat tappet live!

Assuming you wish to proceed as a 327, I will resist the urge to try to sway you into a 350 or 383, which might be way more fun with a 4-spd.

I'd begin by inspecting the main bearing bores for being round and parallel with each other and correcting as necessary. Then I'd register the block on the main saddle and cut the block decks to 8.996". This will produce a zero piston deck height with the reciprocating assembly stack of parts that I'm going to suggest. The main reason for cutting the decks in this fashion is to prepare the block for aluminum heads. Most all aluminum head manufacturers will spec a ~0.040" compressed thickness composition gasket with pre-flattened fire rings to minimize brinelling of the aluminum head surface, so in order to set the squish at 0.035" to 0.045", we will begin with a zero deck and make it easy, using a Fel-Pro 1003 gasket that compresses to 0.041". With a zero deck, that gasket thickness will describe the squish, 0.041".

Trying to find good parts that will leave your wallet in decent shape, I would choose these pistons.....
http://www.summitracing.com/parts/sl...make/chevrolet

If I were going to change rods (highly recommended), I'd probably use these.....
2570020P - Chevrolet 5.700 I-Beam Connecting Rods

Piston compression height is 1.671", rod length is 5.7" and crank radius is 1.625". Total these up and find 8.996" stack.

Generally speaking, each cut of 0.005" to 0.006" (depending on chamber shape and size) that is taken off the cylinder head surface, chamber volume is reduced by 1cc. I'm suggesting that you cut the heads ~0.025" for a chamber volume of 60cc's. Rig up a burette, some rubbing alcohol and some food coloring and cc the chambers yourself before you go any farther.

Now, let's calculate the static compression ratio. Our target would be 10.0:1 to 10.5:1 SCR for use with aluminum heads.

.7854 x 4.04 x 4.04 x 3.25 x 16.387 = 682.7 cc's.
zero cc's in the piston deck height.
60 cc's in the chambers.
5.4 cc's in the piston crowns.
9.1 cc's in the gasket.

Add all values together and find 757.2 cc's
Subtract one cylinder volume from total volume (757.2 less 682.7) and find 74.5 cc's
Divide total volume by 74.5 and find 10.16:1 static compression ratio with a 0.041" squish.

Use Howards 111145-12 retrofit hydraulic roller cam and Howards 91164N retrofit hydraulic roller lifters....
http://www.summitracing.com/parts/hr...5-12/overview/
http://www.summitracing.com/parts/hrs-91164n/overview/
This cam, installed straight up on the marks, will produce an 8.78:1 dynamic compression ratio and the motor should make good power and operate detonation-free on pump gas.

Top the motor with an Edelbrock #7101 RPM intake
http://www.summitracing.com/parts/edl-7101/overview/

, 700/750 carb, 14" x 4" air filter assembly so the motor can breathe and 1 5/8" long-tube headers. Choose 3/8" minimum flange thickness to minimize curling up and spitting out the gaskets. Resist the urge to use those fosdick shorty headers. In my opinion, you might just as well walk out to the curb and toss your cash into the street. Construct an H pipe or X pipe immediately after the collectors, then use mufflers of your choice through pipes of your choice all the way to the rear bumper. Pipes that are terminated under the car sound Ricky Racer and will get on your nerves after a very short period of time due to reverberation of the exhaust note against the under-car sheet metal, making you not want to drive the car any more.

The intake can also be found used under Holley part number 300-36 and Weiand part number 8016. Other intake manifolds that will work and can be found new are Professional Products #52021 and Weiand #8150. All these manifolds are dual-plane, high-rise designs that were patterned after the factory intakes found on the '68 and '69 Z-28 Camaro 302's. Best idle to 6000 manifold. Period.

With a 4-speed car, you can use a double pumper if you want to, although your wallet might not like it. Vacuum secondaries will be more mileage-friendly.

OK, that's the best I can do. Let's hear alternatives.....

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Richard not to hijack the thread and definitely not to throw stones, but I was wondering what DCR calculator you are using and whether it takes altitude into consideration. One of the things I noticed when running the numbers on the 283 when I was building it was that altitude made a significant difference in the DCR.

In my case I needed to take into consideration not only where I live (4500 ft) but also where I vacation at (200 ft).


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A 1968 327 block would be a block with the same main bearings as the later 350----------so could have been a 4 bolt block------If wanting to build a hyd roller cammed engine I would suggest using on from the roller cam blocks late 80s and up----------if a one piece seal block used there is a n adapter available to use the two piece seal/oil pan---------


Mike--- altitude won't affect the ratio formulas but will affect the amount of pressure --------

Richard, if built following your suggestions, do you expect horsepower to be 350 - 400?
Scrprin56, are you in Aztec, NM?

WOW-I'm watching the Big Bang Theory. Kind of apropos :>) Thanks for doing the math. It wasn't my strong subject.

The machinist mentioned that he thought the 327 was not made as a 4 bolt but when he looked up the numbers, he determined that it was in fact a 327 block. I have no experience with the 327 so I don't know. I asked him if it could be a 350 with a 327 crank. He said the numbers don't show that. Maybe it's just me but the cool factor went up.

Yes- Aztec NM

Hey Richard- How bout that expected HP?

Have you measured the stroke????? 1968 Camaro was available with 350 which would of had 4.000 bore and main bearing bore in block 2.6406/2.6415
1968 327 would also be 4.000 bore and same main size------------

Jerry
I have not measured but the machinist tells me that it is a 327 crank. It is a LJ 4 bolt main. I have read that in 68 and 69 GM built 4 bolt main blocks that were all 4.00 bore that accepted 302, 327, and 350 cranks. I guess if that is true, GM did produce factory 4 bolt 327's. I am past caring about weather they did or didn't. I am building on a budget and want to invest in heads and roller cam. I had planned to use my .030 pistons. Now I need to purchase .040 pistons and although I appreciate all of the expert information and recommendations posted by Tech1, I can't afford $246.00 per each. I will not sacrifice dependability for cheap so if there is not an economical alternative in a flat top piston, then I will wait to do the build. Can anybody recommend an alternative? What is the diff between cast, forged, and hyper?

Hi scrpirn56, You are reading the Summit add wrong. The price is $246 for a set of 8 not each. Does that help? As for strength in pistons, Cast is standard and used in a lot of engines, Hyper is a stage stronger - some higher horsepower stock engines use these now and are considered good street engines, Forged are the strongest of all, used for racing and serious horsepower engines. The difference in strength of the types of pistons is due to the method of manufacture and the resulting grain structure. Following the suggestion of Tech, he is suggesting a strong piston, that will not fail you, at a reasonable price.
Tech Inspector, I have a 327 in the 40 and am highly interested in your estimate of the horsepower following your suggested build. Any guesses? Thanks

I agree with most everything said though not a Chevy man I do have a couple comments on exhaust that for ME made a difference. Please listen to Tech I've learned the hard way.The X pipe is superior to H pipe in my opinion . Long tube headers are great but in my71 Lincoln Mark iii,1976 Cordoba and 69 Ford LTD/Cobra they ALL dragged terribly. over every bump or incline. The shortys aren't as good as long tube headers nobody is debating that but they are better than manifolds to ME and MY CARS. Also I had my exhaust going all the way out the back l6ft out back that is. It was loud if you were out back but inside or on the side of car not the best. So I dumped two of them out the sides in front of rear tires and used side pipes on another. The underneath may not be good idea. I had my exhaust dumped right in back of front tires on my Lincoln and that did get on my nerves real quick. Just my opinion based on my experiences that's all.The breather to me is almost meaningless. I've run every kind of breather known to man on dyno means little to nothing. Proof of that. is when I went to a functional hoodscoop on my 1969 Ford I see no difference whats so ever.
I wouldn't get to caught up in the 4 bolt main debate. That ain't that big a deal anyway
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Can anyone say Brain Cramp? 1=8 Thanks.

Tech Inspector- I can't thank you enough for the advice/recommendation. I will post the results in a month or so.

Tech Inspector 1- OK I think I may want to take your advise on making this engine build a 350. It's the no substitute for cubic inch thing. So I may need a crank if one that I have stashed proves to be un-usable. I actually have 2. One is out of a 84 C-30 truck and the other out of a 94 C-1500 truck. So can I still use the same cam recommended above? 350 piston and wrist pin? How does this change the math?