[wynter919]

ok its been w while since ive been on here but i would be very grateful if anyone/everyone here can let me know what you think of my first combo about to be done....it is as follows:

1981 Trans Am (originally had 301 in it)
now has 1970 400 standard rod / crank /pistons
1970 400 290HP 16(sm valve) 1.96/1.66 listed as 10 c.r.(thou ive been guessing it at about 9.25 as ive heard thats more accurate)
very mild port/cleanup
swirl polished valves/cc polish/clean
comp cam CCA-51-222-4 (XE262H) advertised Duration 262/270, Lift .462/.470 (also have summit 2082 cam in shed but told not so good and also looking at 275DEH?????)
comp cams valve springs CCA-988-16
Lunati Bracket Master II Pushrods LUN-80726
Hedman Hedders 28150 full length 1/34"
full 2.5" exhaust no cat with mufflers
Holly street avenger 780 cfm carb
Holly 80ghp /7.5psi mac fuel pump
Edel Performer rpm Intake
Flow Kooler 1649 ALU water pump
melling high pressure oil pump
mallory 8.2 ignition leads on H.E.I
mach 1 underdrive ALU crank pulley
3.08 gears/standard converter
and in uk we have 97-99 ron petrol

car interior is striped w no air con so expect car to be around 3700-3800lbs i think,is this a good guess????

what does everyone think of this combo??? is a car to be used for fun on weekend and down track
want to see around 350-380hp at fly and 420-460lbs torque roughfly and /or low-mid 13's on the 1/4

am i along the right line ???.i have dyno simed/drag simed/cam quested my life away and ahve been looking at similar setups here on py and think this is good and have been told the XE262H is very strong and torqey...cant convert the sm valve to big so don ask (cant afford)
about 1 month away from ordering the parts so i need to finalise my list
all sugestions welcome. thanks for the help

[prostreet64]

My gut level feeling is that there are some mismatched pieces in the combo. Cam is smallish but if you go up in size to the XE268 or equivalent you will need to do more work on the heads, at least in the case of the XE268 which will require machining of the spring seats to use the 995 springs. You could probably find another cam and spring combo to avoid this extra work to the heads. Then there is the issue of adjustable valve train; you didn't say, so I am assuming that yours is not adjustable which in turn limits your cam choices. Also, if affordable, more gear and converter would help but may not be desirable if primary use is street not track. Everything is a tradeoff.

[wynter919]

i did look at the XE268 and 275DEH but didnt know what needed to be done to make them fit.

what exactly do i need to do to the seats to make them fit???? easy job or hard???

just looked on comp cams website and say (needs adjustable valve train) what exactly do i need to adjust...was hoping to just do a straight swap??????

[Mr. P-Body]

Yup, a few "mis-matches"... The overall concept is pretty good, in that a low-to-mid range engine with most of this will be pretty powerful.

Rather than change ALL the specifics, I would recommend a change to Performer intake instead of RPM. XE262H is a GREAT cam for a milder engine. It makes very good power and a fairly broad range. This is our (CVMS) cam of choice in stockish rebuilds, where GTO "sound" and performance are required. A combo very similar to this put 280 RWHP with an E-carb (ick) and went to just under 300 with one of Cliff's Q-jets.

XE262H does NOT require "adjustable valve train", even though it may say so. We've built many with the "torque to 20 lbs. and go.." method. Valve stem length and pushrod length ARE critical here. For a cam like this one, if your oiginal pushrods aren't rusty or bent, reuse them.

Based on your "Melling high pressure" comment, i suspect you are looking at parts in Summit or Jeg's. They're the ones mislabeling the oil p[umps. The part number of choice is Melling M54D-S. While it's listed as "high pressure", that's inaccurate. It's the"high volume" and "medium" pressure (if there is such a thing). The oil pump thing can get confusing. Trust me on the part number. Be certain to get IS-54A along with it (new oil pump driveshaft).

Good luck, have fun, and ask questions HERE, not from those selling the parts.

Jim

[wynter919]

thanks for the advice.

since been reading up on a few thing...ie...i know mine are pressed in stud and i will now be converting them to screw in studs as its not as big a job as i feared, so allowing me to run a larger cam.

the XE268 or crower 60210 or even XE274H ,sumthing like that or any better sugesstions as i have no direct experiance with any of the cams im looking at.

basically i want to feel the torque pontiacs are know for while being able to have a decent hp range all the way to 5500rpm

p.s whats the deal with this valve seat maching thing...reading sumthing about shims needed for these cams...please help

[prostreet64]

Ditto what Mr. P-Body said. It all comes back to your intended use. For great street manners the XE262 and Performer intake would make things real easy but if you want a little more you could go for the XE268 or equivalent and then back to the RPM intake. I don't think a bigger cam than say, 224/230 @.050 would help any and might actually hurt the overall performance unless you port the heads and increase valve size. As to fitting the Comp 995 springs, which are the ones they recommend for the XE268, you have to machine the valve guides down smaller so that the inner spring will clear. Then depending on valve stem length, you check the installed height of the spring to make sure it is correct. If the i.h. is too high you can shim it to the correct amount; if it is too low you can machine the seat to compensate. Otherwise your open/closed pressures will be off. This is all assuming that you have the correct length valves to start with. Correct length means that the valve stem tip moves across the center of the rocker arm nose as the valve opens and closes. Please ignore all of this if it is old news. Good luck with the build. Pontiac V-8's rule!

[prostreet64]

One correction to the last post; got in a bit of a hurry. The pushrod length is the primary factor in determining correct position of rocker arm nose to valve stem tip. Valve stem length is important in determining correct installed height of spring.

[wynter919]

what if i went for xe268 with CRN-99838-16 springs. inner springon that should clear vlave guides and is virtually same spring otherwise???

or how do you machine the valve guide smaller and is it much work???

[prostreet64]

I am not familiar with those Crane springs but if they spec out the same as the Comp 995 then they should be fine. The 995's require a 1.70 installed height which gives about 115 lbs. pressure on the seat and then 340 lbs. at max. lift of .550. With 1.5 rockers the lift will be .470/480 and with 1.65 rockers it would be .517/.528. That should yield about 280-310 lbs. depending on max lift.

[BVR421]

Some one correct me if Im giving the wrong info here but I think youll need longer valves with those 995 springs wont you? 5.2"? depending on which head early or smog era. I believe crower has a good spring to use with stock length valves and higher lift cams. Cant remember the number. Offset keeper may be an option as well.
Also the 995s may setup at 1.8" in spite of what the catalog specs
I think they they changed the specs on that spring (stiffer) some time ago but failed to change the catalog.