Thread: Question about 400sbc and cam clearance

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I am going to build a 400sbc. I just posted about the cylinder head question. Anyway, I am running a Crane Mechanical Roller .580/600" lift cam and it hits the connecting rods. My question is are there specific cylinders that the rods need to be ground down or is it all of them. Next, how would I go about doing this. Am I just going to grind away some of the rod bolt until it doesn't hit anymore or is there a tried and true method to clearance the rods from hiting the cam on a 400. I know this is a common problem on 400's, but I haven't found specific instructions about how to do this. I may just have a shop assemble the motor and have them do it, I would just really like to know how to do this though.

I would advise not to grind on a highly stressed part like a con rod. Use a reduced circle camshaft or use different rods. Scat makes a nice 5.7" forged steel rod that is clearanced at manufacture, part #25700P.

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Not uncommon to have to grind a rod bolt or two. Generally #2 and #7. I suggest you let a knowledgeable engine shop assemble it if it seems too much.

It's not very hard to do. I use a paint marker to mark where it needs clearanced, pull the rod/piston assembly out and grind just enough to get .050" clearance. I use plastic tie straps as a measuring device since it's hard to get a feeler gauge in that area. You don't normally remove enough metal to throw the balance out of whack.

Right on. Thats exactly yum what i was looking for. Another guy here said not to shave the rods and i should get different rods or a small base circle cam. But i dont want to spends $4-500 for new rods or a cam when i already have the parts. Now would you suggest different rod bolts for extra clearance and strength since i will be shaving them?

Thanks again. Very helpful.

Originally Posted by donmcgowen

Another guy here said not to shave the rods and i should get different rods or a small base circle cam. .

Some people build, some people read and copy/paste.

Originally Posted by camaro_fever68

Some people build, some people read and copy/paste.

Serioiusly? What does this add to this thread? Nothing, IMO.

Originally Posted by camaro_fever68

Some people build, some people read and copy/paste.

And another 40 year old expert is heard from.

Here are the stats. I'm looking for 450whp and low 12's or high 11's at the track

1968 Camaro

Motor:
406
cast crank
5.7" rods w/ ARP bolts
Crane 252@ .590/600"
Not sure about the heads yet
Victor Jr. intake
750DP Demon carb
Hooker 1 3/4" headers
Turbo 350 w/ B&M 3500 stall
4.11 rear

Help identify these heads. I thought they were old Dart II iron heads but I am not sure. Can I build with them or are they garbage? If so, I will have them ported and flow tested. Here are the stats of the heads.
2.02/1.6"
64cc
1.5" dual springs with damp
valve guids
1.5 roller rockers


If anyone can tell me what kind of heads these are I would greatly appreciate it. Not sure if they will work with this motor or if I need to upgrade.

https://www.dropbox.com/s/vv9pgg9cm3...51331.jpg?dl=0

https://www.dropbox.com/s/r5pvplsd4a...51431.jpg?dl=0

Originally Posted by camaro_fever68

Some people build, some people read and copy/paste.

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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Thanks for all the replies, I really take everything you guys say seriously. However, let's just say I'm stuck with these iron heads. Let's say I will buy a different cam for this motor. Based on these heads and mostly stock internals, which cam would you recommend. Again, I originally bought the big roller cam 16 years ago when I was 20. Now I am trying to figure out the proper way to do it. I know everyone advises forged internals and aluminum heads, but I have seen and head of plenty of people getting 450hp out of a motor with a stock bottom end and iron heads.

Does anyone have a guess as to what these heads are? I know that aluminum heads are the way, but I have what I have. And I know that iron heads can still make plenty of power. Maybe not 500hp, but at least 420 or so. And that would be fine for me.

Techinspector, what cam would you recommend using the 400 small block with these iron heads. Do they they make all cams with the smaller base circle or is this a custom cam that is needed?
I'm thinking something like the Comp Cams Magnum 280. I do have a 3500 stall converter and 4.11 gears.

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.

If you are not using special hardened rod bolts (like ARP), then by all means, change out the old ones for new ones.

What rods and rod bolts do you have? If stock rod bolts, then as suggested above ARP is the way to go. Just know that if you change rod bolts the rods will need to be resized.

I've ran into plenty situations where I've still had to grind "stroker" rods while using a small base cam.

FWIW: Forget about those old iron heads and go for aluminum--Profiler or AFR 210's minimum. You will never get close to 450 rwhp without heads that will breathe freely enough to give you 570 hp at the flywheel. And with that much hp, a forged crank and forged pistons would be a necessity. You are reaching your power limit with a stock 400 block.