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| PART
III: INSTALLATION |
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After some delays,
the engine is complete and running! We dropped it into Project
11.99 a couple weeks ago, and it fired right up. The solid roller surprisingly
made no fuss, and immediately settled down to a smooth idle. Not having to break
in the cam is reason enough to go roller! Oil pressure was lower than we had expected,
so we ended up replacing the standard volume pump with a high volume. Initially
oil pressure wa about 20-25 psi at hot idle, and 55 psi max at high rpms. With
solid lifters, this isn't a problem, but we wanted more on the order of 10 psi
per 1000 rpm. Since we plan to spin the motor to 7000 rpm, 70 psi above 6000 would
make us comfortable. The high volume (Melling 68HV) did the trick, with 50 psi
hot idle and as much as 80 psi at high rpms.
We
had originally planned to give you the dyno and track numbers in this, the third
part of the article series. However, it looks like we'll be stretching this out
to a fourth article while we try to get our local dyno shop to answer the phone
and schedule us an appointment. If the weather holds up we'll take it to the strip
as well. In the meanwhile we'll go over a few more technicalities and hurdles
we resolved, which undoubtedly will go a long way in getting us to out goal of
400 horsepower. |
Intake Alignment
(above) Milling the heads 0.030" resulted
in alignment problems with the intake. The intake roof was too high, and the walls
didn't quite match up either. | 
Milling the intake
0.020" per side dropped the intake down a total of 0.040". Port matching
the walls and floor results in a smooth and non-turbulent transition.
| Last month we finished up the 302
by putting on the mildly modified World Sr. heads and Edelbrock Victor jr. intake.
However when we took a close look at the intake alignment we noticed the intake
sat about .040" too high in relation to the heads. In other words, if we
looked down the intake runners we could see an uneven transition from the intake
port to head port. What we could see was the some of the upper head mating surface
showing in the intake port. Consequently the floor of the intake port was higher
than the floor of the head port, creating a "cliff". This did not come as a surprise,
considering that we had milled the heads 0.030". Furthermore the intake port openings
on the Victor Jr. intake are slightly smaller than the openings on the World heads.
We rectified the problem by having the intake milled 0.020" per side. We
arrived at this figure by placing the intake on the heads with the intakes gaskets
in place, and torquing the bolts to spec. We did not use any sealer or end rail
gaskets. Then we visually examined the port alignment, and also used a coat hanger,
with a small bend at the tip, to probe into the port and "feel" the drop between
the floor of the ports. Finally we use feeler gauges to measure the gap at the
end rails (distance between manifold and block surface). These steps gave us a
good approximation that the intake needed to be lowered 0.020". This would align
the tops of the ports, with a minor cliff remaining at the floor. We would then
port match the intake manifold and heads to obtain a perfect alignment. To further
confirm 0.020" would suffice, we set the intake on the heads without any
gaskets (Fel Pro "Printoseal 1262 gasket is approximately 0.025" when compressed.)
Without the gaskets the alignment was very close.
We took our manifold
to the PRI show in Sacramento, where DCM had their latest and greatest computer
controlled milling machine on display. This is the same machine used by Rousch
racing for building Winston Cup motors. Eventhough they didn't have the proper
intake mounting pad, the talented engineers took up to the challenge of milling
the intake to our specifications. Once they figured out how to mount the intake
securely, it was simply a matter of setting the parameters in the computer, and
sipping coffee while the mill did it's job. Interestingly we found that the intake
surfaces had nearly 0.003" twist, occurring right near the water passages. The
hot water and thin aluminum casting is most likely the cause. Since were were
taking 0.020" off per side, this would set the surfaces true. |
State-of -the-art, computer controlled,
milling machine by DCM. We're proud to say our intake was milled by the same machine
used for Nascar Champ Dale Jarret's motors! |
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| The
intake was milled 0.020" (per side). The end seal surfaces were not milled.
| | The reason
we went through so much trouble taking measurements is two fold. First and foremost,
we wanted a perfectly smooth transition from intake to the head. There is no point
in porting heads, or even buying a set of decent flowing heads, if you are going
to throw it away on poor alignment. The transition you see in the picture not
only reduces port volume, it creates poor flow and turbulence. Secondly, we wanted
very accurate measurements because we didn't want to screw up milling the intake!
We did quite a bit of research trying to find a "formula" for milling intake manifolds,
and the conclusion is that there is none. It would be nice to say that if you
mill the heads 0.030, you mill the intake 0.015 per side. However because most
intakes and heads aren't perfectly aligned to begin with, this formula would still
leave you with poor alignment. Another thing to consider is that obtaining perfect
alignment is much easier with a single plane manifold because you can actually
see the transition on four of the eight runners. On a dual plane intake this is
impossible, and you must resort to using a coat hanger to feel the transition.
We surmise that most people who have milled heads or decks, or have swapped on
an aftermarket manifold or heads, have an alignment problem. It is worth checking
out and resolving. Continue
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