Inliners International Forums General Discussion Engines Rhoads lifters in 250 - anyone?

Couple of questions here: Over the years I've rebuilt my 250 three times. This time its got .040 over, Comp 268H .500" lift I&E, Offy, 390 Holley, Langdon split cast irons, HEI, and a T-5 out the back. Idle vac is 15", and I'm getting 15mpg (up 2 from my last cam), but just not happy with the bottom end torque - really its never been as grunty as I think it should be, even when it was stock with the 3-on the tree long ago. Anyone got any time with Rhoads in this motor? I'm not bothered with the solid lifter sounds Rhoads make; just thinking of going this route vs longtube headers and redoing the exhaust. Also, oil pressure has never been high even with two successive new "stock" Melling pumps - 15-20 psi at idle and no more than 40 at speed. IS that enough pressure for a Rhoads to work proper? Oh yeah, its in a '65 C-10 Short Fleet. Thanks for any input.

What is your cranking compression? You would need good cranking comprssion to have low end grunting power.

With your camshaft you currenly have & if your cranking compression is only 110-120PSI,that's not going to get it (meaning grunt) done.

As just a guess, you probably do not have enough compression in the engine.

What is the compression ratio in the engine?

If it's not that high, you probably need to go one or 2 steps down on your camshaft to get better low end grunt.Depending on compression. Most people on average will overcam an engine.
I've done it.

What are the specs on your last cam?

Timing plays a big role in low end grunt also, so you could possibly play around w/your initial timing & timing curve in your dizzy.

Did you zero your deck?, or is it down the hole .025+ or more down the hole? All those little things done correctly can add up to having a snappy/efficient little 6 cyl

What type & size is your exhaust system? Dual ,single? 2",2.5", 3"? What muffler/s?

Or install a set of 3 DCOES,those will greatly increase torque.


I have used Rhoads lifters in a couple 250 6 cyl's.

They (Rhoads) do work, your oil pressure should be OK, I used a stock Mellings pump as well as High volume Mellings.

The Rhoads are guite noisy, louder than my solids IMO.

Also one thing to consider, running a solid lifter camshaft, you can get away w/approx 10 dgrees more duration as compared to a hyd lifter camshaft.
A solid lifter camshaft will give you more grunt as compared to a hyd camshaft w/same specs, they are typically faster acting camshafts.
After a couple of initial valve adjustments w/solids, the valve lash would stay the same for a long, long time.

Perhaps you need the low end grunt of the 292 engine, w/4.120" stroke, that will give you plenty of low end torque as compared to a 250.
Your truck is no lightweight & you do not have a turbo or blower to make gobs of torque for your 250.

Only real time I thought my 250 made real good torque (naturally aspirated) (the kind that puts a smile on your face) is when I ran a small chamber 194 head milled it a lot, & had 3 DCOE Webers.Ohh, & having 12.0:1 compression helped tremendously.
220-230 PSI cranking compression.
The engine had a positve deck & solid lifter camshaft.

I am not saying for you to run that much compression,just stating what I found it took to make good torque.

I also, made good torque when I blew through my 3 DCOEs w/a Paxton supercharger,but thats another story.

MBHD

Most people on average will overcam an engine.
X2!
This is also what generally happens when you select a cam profile by idle quality ("I wanted it to have a nice lope").
Lope is the opposite of idle quality, and frequently of low-speed power. More lope = engine must turn faster to produce even as much power as stock.

Guys, its just a "working truck", not a street machine. And believe it or not, its my wifes truck, so blown, slammed, tubs, flame paint job - no no, wrong direction. Really tho, it sounds more like this motor (which is the one it came with) probably just is too small for the size truck, and I really just want a little more smirk on my face, not a whole fat grin. I'll keep the 250 - cost nothing to keep, and I like the 6 vs a V8 as it seems everyone has a 350 in their truck, so I like the different path. I do have stock compression pistons, not zero decked (I like my $3.50 87 pump gas - its a trade off I know). I haven't done a compression check, but I'm less than 5000mi on the rebuild. There's no unusual blowby so I don't think I have a compression issue. It is probably overcammed, so rather than pop for yet another cam and lifters, I just thought the Rhoads would salvage the existing situation, get me 2-5 more inches vac, thereby a few more mpg and make the trips to the pump just a little more tolerable. And make pulling up hill in 5th that much better too. BTW, yes, its duals, 2.75" I think, with nothing special for mufflers - they exit LHS & RHS under the cab, and the sound is fine...thoughts on this?

a few Questions how was the cam installed? straight-up deg before or after TDC? sec what is your rear gearing??

Straight up. Simple match the dots. I've degreed cams before, but didn't have a reason to differ with the Comp cams card for this one. Rear end=stock traction-loc, which by the book is 3.73. To complete this, the tranny is a T-5 with 2.95 1.94 1.34 1.00 .85 gears ala this S-10/Camaro switcheroo http://www.inliners.org/Jack/T5tech.html.
With this combination I do most of my driving between 1500 and 2800 rpm, and in 5th, about 2200 at 65mph. Its a very nice combo on a straight and level. Any incline, and I need a pretty heavy foot to keep from having it pull down into 1700's, thus forcing a downshift. The cam is a 1500-6500 rpm cam, so its over cammed for this application (as noted before). My previous cam, was an old Langdon marine cam, which I think had about a.450" lift. It was milder than the 268H, but like I said, no real difference in torque between the two cams. I can go back to the marine cam, but if Rhoads will give me the bottom I'm looking for with the 268H, then why not? Hence the original thread question...

Yes,
Rhoads lifters will give you some more bottom end.,
Actually having a zero deck will help reduce the chance of detonation & will allow you to run more compression & on 87 octane fuel.

If you do indeed have 2.75" dual exhaust,that will usually decrease some bottom end power,,even though some will disagree w/that statement.

Degreeing a cam is done to check & see if everything (cam timing) is as it should be.
But if the timing set is off, improperly machined or marked incorrectly, you will not know if the cam timing is way off.

If you ran it straight up , & going with the thinking everything is as it should be w/your cam timing, I would advance the cam a few degrees & run some Rhoads lifters for now.

One other thing to add is, if you do a stock rebuild,thicker head gasket than stock, pistons are down the hole (which could actually increase the chance of detonation) cly head cc's could be larger than it should be, you will have a lower compression engine that a completely stock original engine, mainly because of thicker head gasket, & now that you added a larger than stock camshaft, your cylinder pressure will be way down,& that will kill your bottom end grunt.
So in the end, your compression ratio will or could be 7.5:1- 8.0:1.
Part of the reason why when you build an engine & check all those areas I talked about. In the end, you will have a snappier engine.

MBHD

Right, that makes sense to me given what I've heard about these. You answered my original concern and that was the oil pump pressure being "good enough" for the Rhoads. I'd only heard of big motors, rats and such, running them. Just wasn't sure if a motor this small would really show any appreciable difference.

Yep,

Like I said, I used Rhoads on a couple engines & a stock oil pump w/about the same oil pressure you have.

They do work, I just did not like the Clifford camshafts I used w/the Rhoads.

MBHD

Well, I'll give it a whirl. $100 is worth a try. Better in the motor than in the stockmarket just now.

Thanks for the info.

You can always add an MSD box & an adjustable timing knob to kick up the timing when cruising on the freeway to increase mileage.
http://www.msdignition.com/products/ignitions/
http://www.msdignition.com/Products/RPM/...ng_Control.aspx

MBHD

look thru the membership for a Joe H, that's Jim Hand's ( long time Pontiac guru ) son, and PM him, he has a '37 pu with a 250 and has used Rhoads lifters in it. He also uses it as a tow vehicle so bottom end is a consideration for him too.