1.6 roller rockers

[justcruisin]

Could anyone give me some advice on roller rockers, I have ordered a comp xe275hl cam and lifters for my 448. I have also ordered a set of PRW 1.6 roller rockers  in stainless. The lift will be 0.560".Will the hydraulic lifters be able to cope with this fast ramp rate and lift or should I swap them for 1.5"s.

[firefighter3931]

With the Comp HL hyd cam profiles the lobe design is very agressive. I would definately use a 1.5 rocker to keep the valvetrain stable at higher rpms 

What heads ? Valvesprings ?



Ron

[justcruisin]

The heads are edelbrock rpm and I am using the springs that came with em. The heads are new.

[firefighter3931]

The heads are edelbrock rpm and I am using the springs that came with em. The heads are new.

The "stock" RPM springs are a single with a dampner.....spring specs are 120 seat/340 open which is fine for the XEHL series hydraulics with a 1.5 rocker ratio. To run a 1.6 would require a valvespring swap (dual springs) but that just places additional stress on the valvetrain and you risk wiping the cam or suffering lifter collapse from excessive spring pressure. Not worth it, inmo 


Ron

[justcruisin]

OK thanks Ron, I will take your advice and run the 1.5"s. Another thing, I have ordered K1 rods, this type of rod seems much of a muchness compared to others but the main reason I went with the K1"s is the rod width. What difference would it make to oiling in a street engine with the narrower rods, some I have seen are around 1.005".

[justcruisin]

One other thing, the install instructions that came with the heads say Max lift .600" is this not right with the stock springs?

[firefighter3931]

OK thanks Ron, I will take your advice and run the 1.5"s. Another thing, I have ordered K1 rods, this type of rod seems much of a muchness compared to others but the main reason I went with the K1"s is the rod width. What difference would it make to oiling in a street engine with the narrower rods, some I have seen are around 1.005".

The narrower rods have excessive side clearance which will sometimes splash too much oil around. Opinions differ on whether or not this is actually a detriment. 

I prefer to keep close to the factory spec 


Ron

[firefighter3931]

One other thing, the install instructions that came with the heads say Max lift .600" is this not right with the stock springs?

Yes, the stock RPM springs are rated to .600 valve lift, but the cam profile determines the suitability of that spring. 

Agressive lobe profiles require increased pressure to keep the valvetrain stable and avoid spring surge/valve float at upper rpm's. An agressive cam with a high(er) rocker ratio is such an example of too much lift, too fast for that particular spring. 

A slower ramped cam profile would be fine with those springs. You allways need to consider the "rate of lift" on any cam when matching valve springs


Ron

[justcruisin]

Thanks very much Ron for your advice and sharing your knowledge, it eliminates any grey area that I have with my decisions on my build. One other thing I am not sure on before I start assembly, I am planing on 500 - 520hp, should I use main studs or will the original bolts hold up? Also the only oil mod I will be making will be a high volume pump, the engine has the original 6 quart magnum pan, is there something else needed or will this be OK at these power levels. I don't want to go to a 1/2" pick up if it's not necessary
10.15:1
rpm heads and intake OOTB
1 7/8" headers
QF 830SS ms carb
XE275HL
1.5 rollers
93 pump gas

[redmist]

Your build is almost exactly like mine. I am running a comp XS282S Solid though. I will have dyno numbers in a couple weeks.   

I studed the whole damn thing! haha! I want this short block to go a long way, and may spray it a little.

[justcruisin]

Great, like to see your dyno results, hope all goes well