Thread: Rods hitting cam, Cam gear scrubs block..

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So Im new to this board, browsed around and seems like a really great forum. Did some searching and still havent found my answers. First off, its a 350 .030 over with 3.75 cast steel crank, forged rods, hypeuratic kb pistons, performer rpm intake, 800cfp performer card, xe274 cam, 1.6 roller rockers, scoggin dickey modified vortec heads, 2 bolt block with ARP studs. First issue was the crank, rod bolt clearancing to the block, gave it .060 clearance all around the oil pan, and the bottom of the cylinder walls where it needed it most. Next issue was/is the oil pan, most people say they beat the crap out of it till it fits, kind of caveman-ish, but supposedly it works well, dont have another 200 to lay down for a pan now. The next problem is the cam hitting the rods in two cylinders, was told to grind the rod down to clear it with a clearance of around .060", the whole assembly was already balanced to within 1/4 gram, looks like I threw that out the window now because I cant pay to have it balanced again. Any input on that issue? Next is the timing gears, its a double roller timing set, and the cam gear is grinding/scrubbign on the block, did some research adn the answer is to grind the block down, ive also heard of shimming? Any input here is greatly needed. Also, I have the classic how much power Q. Only reason being it IS a studded 2 bolt block, there is a lot of debate over how much it can take, I will be using on occasion a 125 wet shot if it isnt goign to be an issue. My only concern is that it is a 2-bolt block. I really have no idea how much hp/tq this will make naturally, so I cant compare it to the supposedly 500hp 2 bolt limit. Any help would be greatly appreciated guys.

BTWQ, Ive also noticed the cam gear seems to be in a tiny tiny bit to far, if I use a straight edge it is a hair deeper than the crank gear, and that is with the cam not in all the way. It seems liek there should be a shim or something, as it is a lot of grinding to get it to rotate freely, and it will also be in deeper than the crank gear, which is wihtout a doubt as far as it will go. The cam seems to be in where it is supposed to be, its all boilign down to the cam gear.

the stock rods will hit the cam and the 1/4 of a grams will not do much if the the rods hit they need to be trimed . you will not see it cutting them two rods.the oil roping the crank when running will throw it that far off than that . l like to get them to a 1/4 grams to. but things will happen inside the engine that you have no control over like the oil roping if the rods are on the same journal .you will be ok or try if not you are still ok. a small base circle cam may work if you do not want to nip the rods. if the crank gear is off you are saying the cam gear is in how much .002to.004 ? if so i would not do any thing if more then you will have to do something and find out what is off cam set or crank or crank gear it many be shimed with a thrust washer or try a new chain set and on the oil pan if you take your time and heat it to red were it needs to be hammer and hammer it in the spots it needs to move it works ok. will work better if you have a body hammer and a backer like a dolly or a chuck of thick steel

Those stock 2 bolt chevy blockc can take up to 600 HP no trouble, since you are useing main studs rather than bolts they have a better hold power than the bolts. So you have a good solid foundation there. This 383 your first motor ?

Thanks for all the help, and yes it is my first motor. I was brought up on muscle cars, and watched my dad closely when he built his 468, i got my first car, an 84 firebird, and started with that, now im on to the motor. It is my only car, but to me driving something a lot less than i normally would, is worth it in this situation. I need to handle the tranny and convertor next, gotta get through this first. Its mostly my dad doing all of the critical work, so its not like I'm fumblign through it myself.

Well you gotta start somewhere, you learn sa lot building your first motor. Ask all the questions you want, from us, from your Dad, from the guys at the machine shop.

From what I see with the delema you had with the rods strikeing the cam lobes, you have probably figured out by now that a prefit befor any machine or balance work is mandatory.

Oh yeah I may mention that I am currently building a 383 myself, just that I am using the eagle H beam rods that do not hit the cam because of the way they are made you still have to grind clearances in the block though.

yes there are no D heads on the bolts on the h rods they use a cap screw. crower makes them to in i beam with a shorter bolt s on the stroker rods all this stuff is all and sometimes more work when building stroker engines

Okay here are some images of different rods with a view from different angles They are all small bpock chevy rods

Mine look exactly like the middle ones, same fastners and all. It sohuld be ok to take some material off the bolt too correct?

As you said you havee had the whole assembly balanced is there any way that you can go for a smaller base circle cam so that the rod misses the cam lobe. Because take to much off the rod and you will have an imbalance problem. To be double sure check with your machinist and work from there.

if your rods are like the middle ones, they are an aftermarket Cap screw rod. You shouldn't have to grind on the bolts, its the back side of the rods that will hit the cam. As for grinding on the front of the block for Timing gear clearance, That is normal. the area above the cam gear where the oil plug is hits those Double chains often. I have had to clearance some of those after a balance. I cant tell that they were ever ground on. Didnt seem to upset the balance at all.

Yea thats what I figured, the machine shop guy stopped by and it turned out it was because it was a factory roller block, and I was using a flat tappet setup with a double roller timing chain and gears. He showed me where it needed to be grinded, which was a whole lot, so we opted to get a truck timing chain and gears instead. As far as the rods and cam problem, I have been hearing that 60 thousanths is the recomended clearance between them, Im barely hitting, and only in 2 cyclinders that I know of as of now. I guess we will see how tha goes, I thought about a small base circle cam, and to be honest I am a little unsure of how the exactly are designed. How much more clearance will I get? And will that mean I need a special pushrod? Thanks for all the input, this seems to be a really active forum, prolly the most active I've been on, very helpful, thankyou.

You can go Small base circle and cure the problem. You will need longer push rods to compensate. It really is a quick fix to just grind the back side of those 2 rods. let me take a guess.... #2, and #5 cylinders? Or #2 and #6. I dont run .060 clearnce. .015 is all i do. Never hit one yet. i guess there is always a first time.

Img2006-07-05_0001.JPGhere is where i have had to grind.

you will not see any thing with the little bit you have to take off them rods i have seen rods off 6 grams out of stock stuff so that little bit will not make much differences and you will never see it or feel it like i said go to a small base circle cam if you want