Bill,
I wish I had a book on mods for these. The flow numbers come directly from
the heads we are putting on the engine we are building up. Maximum RPM, I
would think that 5,500 would be about tops for a stock motor. The weak links
are the weight of the valve train assembly (primarily the lifters), the
lifter bores and the factory rocker hold down assembly. The factory hold
down bolts are 5/16-18. On my heads, we switched to SB Chevy studs, 7/16-14
on the bottom and 3/8 on the top. This strengthens the top end of the valve
train. Stiffer springs will control valve float. The lifters, all HP cams
have a smaller base circle so the lifter rides lower in the lifter bores.
This will hopefully stabilize the lifters, there is not much we can do about
the weight. As far as valve train components, I am actually partial to
Crane. The cam that I am running is a Crane. Because of the lift I want to
run, I needed a 1.7/1 rocker. The only company that I know of that has the
1.7's is Crower. Select pieces that give you what you need. The only company
that makes guide plates (last time I checked) was Crower, so that is what I
am using. Again, pick the pieces that accomplish your goals. I am hoping
that the combination that we have selected would be stable up to 6,000. I
could probably raise it a little with stiffer springs, but the cam won't go
much past 6,000, torque peak will be around 4,200. On your engine, at
minimum, switch to a stronger rocker hold down bolt. A rocker stud would be
better yet. The roller rockers are more stable and they do provide for less
wear on the valve tips and guides. If you don't need any additional lift,
then any roller rocker would be better than the factory rocker. Make sure
they have been successfully used on the Magnum. Hopefully they will utilize
a rocker arm stud. Ideally, the studs should have the jam hex as part of the
stud. This actually stabilizes the stud. I hope this info helps...........
> -----Original Message-----
> From: WillTier@aol.com [SMTP:WillTier@aol.com]
> Sent: Saturday, November 06, 1999 5:45 AM
> To: dakota-truck@buffnet.net
> Subject: DML: RE: 318 Hop Up, Heads VS NOS
>
> In a message dated 11/4/99 12:17:56 PM Eastern Standard Time,
> Frank.T.Holloway@KP.ORG writes:
>
> << The factory heads do flow well for a production truck engine. Stock
> form,
> the intakes flow approx. 210 CFM @ .500 lift, exhaust flows approx. 133
> CFM
> from .400 to .600. Porting and larger valves on the intake can push the
> flow
> up to 270 CFM @ .500. Lifts much greater than .550 cause a decrease in
> flow
> and actually decreased to 250 CFM. The exhausts continue to increase in
> flow, even with lifts up to .650 inch. At .550 exhaust lift, flow is
> approx.
> 175 CFM. Because of the difference between intake and exhaust, split
> duration cams are necessary (greater duration on the exhaust).
>
> Frank >>
>
> Frank
>
> You got to have a secret cheat book there don't you ? :-) Your knowledge
> of
> these engines amazes me and I appreciate you sharing it with us. As I skip
>
> through the posts deleting those of little interest I always check the
> author
> and read all of yours. I am a more knowledgable person because of that :-)
>
> Thanks for your contributions..
>
> I do have a couple of questions though. How high can we reliably rev
> these
> engines, for drag racing purposes ? I have read that over 5500 is trouble
> but
> with the new mods I have done the power band seems to have risen and the
> thing is still pulling good and I seem to be getting the most gains in
> performance by running it close to 6000. I believe the MP comp, in 93
> atleast, has the rev limiter set to 6500 ? The second question is to do
> with
> the roller rocker deal again. Still have the stock rockers and have been
> looking at going with the rollers. I know you are a crower fan but I have
> read good about others and recently about Wolverines. They had a couple of
>
> things (according to the article in sport truck) like a set screw to keep
> the
> studs from loosening, precise ratios and the showed where they could be
> used
> with the stock valve covers by drilling holes in the splash shield ? I
> don't
> know cost diferences but the crowers seemed rather steep ?
>
> Your thoughts on these ?
>
> Thanks again for your input..
>
> Bill
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:19:08 EDT