You only need to focus on a valve event or two to see where you are at. Also you don't need the pistons in, just the crank and cam.
If after you degree the cam in and the lobe still hits hard like it is now checking it the same way, get the crank to the point where the rod and cam hit and freeze the crank there. Then remove the timing chain and rotate the cam to the back side of the lobe on the base circle. Now using your feeler gauges measure how far away the base circle is away from the rod and record that dimension. To get the lobe lift dimension, divide the lift by the rocker ratio and that will be your lobe lift. IIRC you have .584" of lift with 1.6:1 rockers? So .584/1.6 = .365" of lobe lift which means that the lobe is that much higher than the base circle to give you your lift. Now what is the feeler gauge measurement to the base circle? If it is still hitting after the cam is degreed then know the base circle clearance will tell us if the cam will need to be re-ground on a smaller base circle or if the rods can be clearanced or both? This is still uncharted territory using a big roller cam with longer than factory rods with the big lobe lift for a sbb. Others that built a stroker have used shorter rods and or flat tappet cams without any cam to rod clearance issues. That is because the bolt to bolt dimension for the take out rods are narrower than the factory rods so even with .140" more stroke that creates .070" less clearance would be a wash because the bolt to bolt IIRC is around 3/16" less than the factory rods so half of that would be .094". Should be .024" more clearance, but if you look at a sbb 350 rod and how short it is in that area its a wonder that the others that did a stroker didn't have any issues, probably because rods are shorter? IIRC the super charged 370 used 6.300" rods that are .085" shorter than factory without any issues with running a flat tappet cam.(see post 427 for rod length explanation) Derek
From the last paragraph of post 427; "Another thing you may want to do is degree the cam in so you know the cam is where you want it to be. You can remove the cam when you find your zero with the #1 piston and rod in to confirm top dead center. Then take the piston and rod out and install the cam and see if the cam is in where you want it to be. JW has mentioned how poorly some of the cams are off, some as far as installing it a tooth off to get it in right! So make sure you don't grind on the rods until the cam is degreed in, this can drastically change how the cam and rods interact with each other." Dam, I wish we were closer to each other! Derek
Degree'd the cam...here is what we have: Piston at TDC, and crank gear installed on the zero degree... 0.050" rise on intake lifter= 4.5* BTDC (Card says it should be 3.5* BTDC) Maximum intake lifter lift= 0.357". (Card says it should be 0.365") 0.050" rise on intake lifter closing= 47* ABDC (Card says it should be 43.5* ABDC) 4.5 + 47 + 180= 231.5* @ 0.050" (Card says it should be 227*) 231.5 / 2= 115.75 - 4.5= 111.25 (Card says it should be 110) Since the total lift was short by 0.008" (0.008" X 1.6= 0.0128" valve lift.) we measured up the exhaust as well. 0.050" rise on exhaust lifter= 45* BBDC (Card says it should be 47.5* BBDC) Maximum exhaust lifter lift= 0.354". (Card says it should be 0.358") 0.050" rise on exhaust closing= 9* ATDC (Card says it should be 7.5* ATDC) 45 + 9 + 180= 234* @ 0.050" (Card says it should be 235*) 234 / 2= 117 - 9= 108* (Card says it should be 110*) Should we change anything? I will post the cam card in a couple minutes.
I have one up & running. Haven't taken it out on the road yet. It seems a little bit louder now though.... perhaps the roller rockers are louder than stick rockers .....
Just to see if changing the cam timing would help us at all, we changed it from straight up, to 8* advanced, and retarded...rod still hits the cam. At least we know I didn't remove too much material from the rod yet...
Thinking about sliding the old flat tappet cam in and checking to see if it hits... Don't want to go with a flat tappet cam...not after waiting for a roller...
I'd have to check it again Derek. Didn't measure it because there was so much clearance...more than my feeler gauges can provide. With the cam on its base circle, and the rod in its most critical spot with the cam, there was over 1/4" gap...so I may have to try a snap gauge if I have one small enough. (Don't think I do) I'll try something tomorrow...
I'm gonna clearance the first rod to the point of clearing the cam, just to see how much has to be removed. Looking for another set of NASCAR takeouts with the same measurements....just in case I go way too far. Any opinions on the actual cam spec's compared to cam card measurements?
You need to have the cam hooked up to crank and spin both together until the cam and rod touches, lock crank in that position. Then remove chain and cam gear and then spin cam to base circle that is where you need to measure base circle clearance.(incase I was unclear in other post?) You can use drill bits to see what the biggest one that will fit without touching then get the feeler gauge in there to go the rest of the way. The feeler gauges I have are around 3/8" with all of them there which would be around .010" more than what the cam card says, how thick is the set you are using? My brain is trying to think this out, its been a while since I messed with this kind of situation so try to bare with me. With the rod close to where it hits move the crank back until a 3/8" drill fits between the rod and base circle and mark on rod there all the way across, now move crank forward to when the 3/8" drill fits in between the base circle and rod again and make another mark all the way across there. Remove piston and rod and connect the 2 marks together on the side of the rod, this should let us know where to grind clearance. If it goes past the centerline in the bolt you may want to have the cam reground on a smaller base circle. Just so we know while you're in there, move the crank so the rod is the closest to the base circle and take a measurement there and record it, you can put a mark there as well as the center mark. Use a rod that you didn't grind on yet so if the base circle needs to be reduced we'll know how much. If you have calipers or mics, you can measure the cam's base circle by measuring the lobe 90* from the lobe's lift. I wouldn't have it ground down anymore than .125" off the current base circle. If you need .060" of clearance this would clear cam without grinding rods. But now in for the cost to regrind if you want more lift this would be the time to have it ground in. Reducing the base circle without cutting the lobe down would make the lobe .0625" taller! That would give you a potential lobe lift of .4275" which would be .684" lift with 1.6:1 rockers. You don't want THAT much more because we need a little clearance there so maybe enough to go to .600" lift which would be a lobe lift of .375" or .625" would be a .390" lobe lift which would be more than plenty while giving you around .030" more clearance. Getting more lobe lift from grinding down the base circle would mean the rods will more than likely need a little attention if .030" of extra clearance at the top of the lobe isn't enough. We'll see when you find the spot on the rod that is the closest to cam's base circle and can go a couple different ways. Another thing to consider is if your pistons have offset wristpin holes you will want to take your measurements on the drivers side IIRC the offset will be towards the passengers side making the rods closer on the drivers side and a bit more clearance on the passengers side. Someone correct me if in I'm wrong and an offset wristpin is drilled the other way. Sorry for the long posts, but there is a lot of info my brain had to remember. If you have questions feel free to ask, or if you still have my number feel free to call, if not feel free to PM me and I'll resend it. Derek
369 CID NASCAR take out rods 6.370 Custom forged pistons from Scott Brown Poston 114 cam Compression 8.7-1 Running one of the 1st mark Burton twin turbo kits Block was square decks to the mains Heads cleaned up & at 57cc now I believe... Just trying to get the bugs worked out now
Ok, I will try another rod assembly in cylinder #1's spot tomorrow. I will mark it as you have asked. So basically, your saying regrind the cam. The rod is hitting the cam lobe really close to the top of the lobe...almost clearing it. How do the numbers of the degreeing look? Stay with straight up? (Zero)
You won't have to regrind cam if the rod can be clearanced without cutting past the center of the bolt. That way you can still use your stretch gauge to tighten your rods, bolt stretch should be .0065" using ARP bolt lube. They look close to the card, I'm not a cam degree expert, I always refer to my notes when I degree a cam in because I don't do enough of them to have it memorized. But going by my CRS memory it looks like it is 2* advanced, is that where you wanted it? Derek
I thought the idea was to be as close to the cam card spec's as possible. It's not one full tooth out, that's for sure, it seems close...I will play with it tomorrow. Everything seems to be tomorrow....
Usually there is a recommendation on the cam card as to where the cam should be installed, on your cam card that area is left blank. On the upper right hand corner where the picture of the 2 cam lobes are. Looks like you need to decide where YOU want to install it. Maybe try 2* retarded and see if cam clearance is better, if not put it back where it is when you're ready to leave it in? Dealers choice. Derek
