Comp Camps Magnum Roller Rocker Question

[namz7791]

I am finishing up my rebuild of my 88 Chevy 350 and am using the stock 65 cc heads with flat tops (CR at 9.3). My cam choice was a Comp cams 270 with .470" lift on intake and exhaust.

 

A buddy of mine has a new set of Comp Cams Magnum roller rockers that he will give me. Only issue is that they are a 1.6 ratio versus the stock 1.5 ratio. The way I figure I will end up with around .501" lift. I bought Comps "K" kit so have their springs and lifters for the 270 cam. I am using my stock pushrods and am wondering if increasing the lift with these roller rockers will cause problems.

 

Does this affect idle quality? Do I need to use guide plates now. Will the holes in the heads where the pushrods go need to be machined? Will this much lift be to much for push in studs?

 

Any insight on whether or not to use these would be greatly appreciated.

 

Thanks to all!

[jt1]

1. The 1.6's make the cam a little "bigger", so you will probably have a little rougher idle, although not much. The motor will also make a little more power if the rest of your combo can support the additional cam.

 

2. Guideplates are usually installed along with screw in rocker studs. I'm not aware of any that can be added with pressed studs.

 

3. Maybe. The only way to tell for sure is to mock it up, or find someone who has used 1.6's on your particular head casting. Most stock heads require some clearancing. Be sure to check, the pushrod rubbing the head is sure disaster.

 

4. Hard to say. They will probably last a while, but all bets are off.

 

Some other important things to consider, any of these will ruin your day: Coil bind, i.e. too much lift for the spring. Retainer to valve guide clearance. Stock length pushrods may not give proper rocker geometry, which will hammer your valve guides quickly. Before adding studs and guideplates, clearancing, etc, are your heads worth it? No point spending money on a set of castings that will never be good performers.

 

Remember you can always get the rockers, and trade them for something else that would fit your needs better.

 

John

[grumpyvette]

lt1 gave you good advise! many stock heads useing a stock valve train and springs, spring bind near .500 lift,and most stock heads don,t flow well over .450 anyway, almost all stock heads are getting close to or already having clearance problems with a .500 lift and 1.6 rocker ratios someware in the valve train. in short youll need to carefully check all clearances before running that cam and rocker ratio, yeah it might work but chances are good its getting close to having MAJOR PROBLEMS ESPECIALLY if YOU DON,T CHECK THE CLEARANCES AND VALVE TRAIN GEOMETRY OUT!

I don,t use stock chevy heads if theres any choice given , theres just to many good aftermarket heads available ,what you pay may be slightly more but the results can be significantly better

 

look over the TRICKFLOW aluminum heads and DART iron eagle heads, both can be a good value, if you can spend alittle more the AFR heads can be a good deal, keep in mind that a $300-$600 set of stock heads that require $600 extra in valve guide, rocker stud,clearance work,guide plates and valve job work plus porting yet still cost more and perform worse than a $970 set of aluminum 195cc TRICKFLOWS or $800 dart iron 200cc-215cc heads, ESPECIALLY IF A FAIRLY LARGE CAM is installed that requires the extra airflow to preform at its best! it makes little sence to install a 275cfm intake and 6500rpm cam on heads that stop flowing at 4500rpm and stall at 200cfm of flow

 

its VERY easy for a good set of aftermarket heads to make 40hp-70hp more than reworked stock heads, keep that in mind when the first sticker shock hits then carefully price the additional work the stock heads require, youll suddenly see the aftermarket heads as at least a reasonable priced option if not an outright deal!

 

http://store.summitracing.com/partdetail.asp?part=TFS%2D30400001

 

Bolt-on aluminum cylinder heads for the price of cast iron!

 

Chevrolet: 327-350-400, 64cc, 1.26 in. diameter valve springs, 23 degree cylinder heads

 

Trick Flow's 23 Degree heads are a direct high performance replacement for stock heads. For about the price of a good cast iron head, the Trick Flow 23 Degree head gives you the weight savings of aluminum--and more power. By simply replacing a set of GM iron 441 castings with a set of Trick Flow's aluminum 23 Degree heads on a 383 Chevy, the guys at Chevy High Performance Magazine picked up 67 more horsepower and 70 more ft.-lbs. of torque at the top end--with no other changes!

 

$970.00

[RPMS]

its VERY easy for a good set of aftermarket heads to make 40hp-70hp more than reworked stock heads, keep that in mind when the first sticker shock hits then carefully price the additional work the stock heads require, youll suddenly see the aftermarket heads as at least a reasonable priced option if not an outright deal!

 

Heya, Grumpy.

 

I agree that what you say is true for carbureted Chevy heads, but does it also hold true for the Vortec heads? $500 a pair assembled is a tough price to beat! Would you consider Vortec heads (especially the new ones which mate up to older intake manifolds) to be a decent price/performance compromise?

 

Thanks,