Thread: Question about 400sbc and cam clearance

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Originally Posted by techinspector1

Ray, I won't get my shorts all bunched up over your comment, because I was likely building motors while you were still crappin' green. You have to understand that it is encumbent upon the writer to protect the OP (original poster) from doing something that may result in disaster. You might grind on 99 sets of rods and be OK, but the 100th set will unwind due to an occlusion in the metal or some other reason and the OP has suffered a multi-thousand dollar loss. I will always err on the side of caution, I'm sorry you don't see it the same way. A reduced base circle cam is a no-cost option when ordering the new cam and the 25700P rods are a ~$270 cost option. Now, if the OP has already reached out into thin air and chosen a cam, that's not my fault. The cam should be the next to last thing chosen for a build, right before the torque converter.

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I didn't even read your post before. I didn't mean my post toward you personally. It doesn't matter. Sorry to have offended you.

I'm no expert but I build 383, 421, and 434 stokers on a daily basis. Grinding the rods is as common as grinding the block. If you don't want that to be an issue, I can do the stroker kit in a raised cam block. Even though the pan rails are widened in that block I may still have to a little grinding for rod to block clearance in some cases.

I learn everyday. When I quit learning I will proclaim to be an expert.

Duece. This is a 4 bolt block. I guess you would call this a low budget build. I have all the parts to build the motor just had an issue with cam and head combo because I cannot identify what kind of heads they are. I know they are crap compared to aluminum heads but they are what i have right now. If i van figure out what heads these are i can get a cam to match.

I have no problem asking questions. Thats why im here. When i was younger i made vad choices hence the poor slselection with the original cam. But i think if i get a decent valve job, match a good cam, 1 3/4 headers, single plane intake and 750DP I can make a solid 420hp. Then over the courecourse of the next several years I can start upgrading and get a set of nice heads.

The first thing you need to do is to cc the heads. Unless they have been in your possession since they were cast at the foundry, you have no idea what the actual volume of the combustion chambers is or what has been done to them by those who owned them before you. Even if you have owned them since new and had been told what the chambers poured, factory tolerances could be 3-4 cc's off. They could also have been angle milled, so you will want to find that out before you go any farther with this project. This angle milling operation changes the angle of reference between the surface of the cylinder head and the valve centerline to aid flow into the cylinder and raise the static compression ratio, it's an old hot rod trick.....here is a small block Chevy example.....
http://image.hotrod.com/f/10203945+w...le_milling.jpg
If the heads have been angle milled, the intake manifold must be angle milled too, to match up and effect a seal. If the angles of the heads and the manifold do not match, the gaskets will not seal up and the motor can pull oily crankcase vapors into the cylinder on the intake stroke. This is what happens sometimes when fellows find oily spark plugs and blame it on valve seals. No amount of spraying a combustible product around the motor will detect a vacuum leak at the manifold/head interface if the gap is on the underside.

Here's a cheapo cc kit that will suffice....if you're careful, you should be able to keep the results of your pour within one cc and that's close enough for our purposes.
Cylinder Head CC Kit for Measuring Combustion Chambers | eBay
If you want to invest in a better tool that is precise down to 0.2 cc's, you can buy a kit like this that will require less refilling during the pours.
http://www.summitracing.com/parts/sum-911581/overview/
Use rubbing alcohol and food coloring from your local grocery so you can see the meniscus of the column, red, green or blue, your choice.....
Meniscus - Wikipedia, the free encyclopedia
http://www.horsepowermonster.com/wp-.../How-to-CC.jpg
https://www.youtube.com/watch?v=V7V40ZWNgCo

Once you have nailed down the volumes of your combustion chambers, you can do your buddy's chambers for 30 bucks for a pair of heads and recoup your investment plus earn a little gas money on the second and subsequent sets that you do for other fellows. Don't just do one chamber, do them all so you can be sure that the heads were not mis-registered when the faces were cut at the factory, resulting in different volumes on the same head.

You can also pour the intake and exhaust runners the same way. For the intake runners, lay the head on its side with the intake ports facing up. Put a little Vaseline on an intake valve stem and valve face where it seats in the head to prevent leaks, grease the intake port and place the plexiglas over the intake port the same way you did for measuring the combustion chambers. When you've done the intakes, turn the head over so that the exhaust ports face up and repeat the process with Vaseline on the exhaust valve face and stem. It won't take a whole lot of Vaseline on the valve stems, just a light coat. You just want to prevent the alcohol from leaking between the valve stem and the valve guide. If you put too much on, the glob that results will skew your results and make the runners smaller by the volume of the glob. If you pour the chambers, intake runners and exhaust runners and record the results, you will be armed with information that will help you to know what to do next. Choosing the proper cam for a street motor requires that you know the actual static compression ratio of the motor and to do that, you need to know the exact volume of the chambers. Hope this makes sense to you.

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Thanks Tech, I ordered the ebay CC kit and will post the results once I get it done. You are a wealth of information and I very much appreciate it. I wish I had access to these forums 15 years ago when I bought this big ass camshaft that I cannot use with this motor. lol

Well I have confirmed that my heads are in fact Dart II sportsman 64cc chambers and 200cc runners with 1.55 valve spring pockets. I will check them with the CC kit but I think these heads are good for 420-450hp. Definitely usable for my application.

Good heads for what you want.

I have a 2 bolt main stockblock, stroke to a 434. If built right, u will have not problems. 5.43et 126mph in a 1/8

Camaro fever, I would love to see your twin turbo 68. That is a dream setup. Are you big block or small block with the turbo's? Are the turbo's a complete custom setup or do they make turbo kits? It's a long way off in the future but I eventually want to go the turbo route on a stroked small block. Turbo's are the way to go. My daily is a tuned 300whp Sonata turbo and I love it.

I think you will be very surprised at how much horsepower you will have with this combination of parts. Your problem will be with durability and this is where the cam is so critical.

Originally Posted by donmcgowen

Camaro fever, I would love to see your twin turbo 68. That is a dream setup. Are you big block or small block with the turbo's? Are the turbo's a complete custom setup or do they make turbo kits? It's a long way off in the future but I eventually want to go the turbo route on a stroked small block. Turbo's are the way to go. My daily is a tuned 300whp Sonata turbo and I love it.

I'm a small block guy. 383", T67's, Dart block, JE pistons. Etc.

My kit is all built. No kit.

check out this link Photo and image hosting, free photo galleries, photo editing

Hi Duece,
I was thinking this would be a decent motor as long as I can get the cam dialed in. I am going to measure the CC of the heads I have, but what would you recommend for a cam? Just because of price, I was thinking of the Comp Cams 280h or 292h magnum. But I really want a nice roller cam. How much difference in performance and durability will a roller provide over a flat tappet cam. Obviously there is a huge price difference, but I've seen plenty of people make good power with flat tappet cams.

Either way I'm of a 232 or 242 duration with a .5-.510" lift for a flat tappet or .54-.56 lift for the roller. I have a nice set of 1.54" dual springs with dampers so they should be fine anything under .6" lift.

IMHO, a roller would be the best way to go since flat tappets are prone to lobe failure unless you're very cautious about the break in procedure and then it's still a crap shoot. If you're going to run a flat tappet use worn out valve springs for break in and a good oil additive with zinc and don't tighten the rockers too tight on start up.
I don't think that the quality of steel is what it in the 50's and 60's and that along with the lack of zinc in today's oil is a death sentence for flat tappet cams. If I was going to go that route I would be looking at Isky, Howards, or someone like those two who have been grinding cams since Christ was a corporal.
I have an Isky 30-30 ground in 64 that has been in a couple of engines that I wouldn't be afraid to use again and probably will.

I will post this tutorial again, for those who don't understand the perils of using a flat tappet camshaft in today's world.......
http://www.crankshaftcoalition.com/w...ips_and_tricks

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