Asking for a cam advice.

Engine:
1992 model L05, 350 small block factory roller, and i have been told, with flat top pistons, because the donor car was a Buick Roadmaster government car.

The swirl port heads will be switched to Vortec heads that plus Edelbrock Aig Gap intake that I have on the shelf. Carburetor is a QFT (Holly based) 670 cfm doblepumper.

Car weight is 2860 lbs,
6-speed T56 trans With 0,5 overdrive in 6th gear.

Rear axle ratio: 4,09:1
Rear Wheels:
295/50-16. Diameter 27,6 inches.

My guess is that the car will probably do best with lots of low end power, but of course, lots of max power is always welcome!

I am aware of the max lift limit on the Vortecs. I'll change to Beehive/LS6 springs.

I will probably change to roller rockers as well.

For my set up, Comp Cams customer service recommends their CS XR270HR-10 over the GM hot cam. They claims that the GM Hot cam is more suited for injection aspirated engines.

Which of these cams do you suggest?
-The GM Hot cam?
-Com Cams XR270HR-10?

Rocker ratio 1,5 or 1,6?

 

The Hotcam is just fine for carbureted applications. What you got is the typical lame Comp "tech line" spiel.

There's not a huge difference between those two cams. If you do use the Hotcam, install it at a 106 or 107 ICL, not the 109 that they typically drop in at. If I got the Hotcam for $100 as you typically can, I'd use it instead of dropping $350 on a new Comp cam. Depending on your hp goal/requirement, you may justify the difference.

However, with your gearing and weight, I'd be considering a bit more duration. Something along the lines of a Comp XR276 with 110 LSA and 106 ICL. Of course you have to verify that you have enough compression ratio for it to run well at low and mid rpms. I seriously doubt that a Roadmaster "government car" came with flattop pistons.
If you have the right springs and retainers to give adequate lift margin, I'd run 1.6 rockers. Never mind the comments about "choking" the Vortec ports above a certain lift. The faster opening to low and mid lift values will pay dividends.
DEFINTELY run 1.6 rockers if you use the Hotcam.
Stock LS6 springs will probably not be enough to control any of these cams.

 

Thank you for your quick reply. Sounds like the GM cam will fit my needs best. But I guess flat top vs dished pistons is important to know before I choose cam?

From what I have read, the L05 engines has flat top pistons in personal cars and dished pistons when it's used in van's and pick up's.

I guess the only way to find out is to physically remove the heads to see...?

 

I had a 180 hp L05 out of a 90 or 91 caddy and it had flat top pistons and the 155' peanut cam.

 

That's what I have found out is in my car, too, after decoding the vin number from the donor car.
Factory roller block as well.

 

OK......if you have flattops, that's a big plus in making any of those cams work well! I guess I shouldn't have doubted that so much since I think the lowly LG4 also had flattops in some years.
I'm assuming you won't rebuild the shortblock, so your deck clearance is stock? If so, I would run .015" steel shim head gaskets to get a good quench clearance and enough compression to run the Hotcam (or any of those above for that matter). Just verify you have good flat surfaces on block and heads. Even if you choose to mill the heads for extra compression, I'd still plan on the thin gaskets and mill for compression accordingly. With the iron heads, I'd target about 10.0:1 CR for either the Hotcam or the XR276 cam, and a few tenths less for the XR270. While the XR276 has more .050" duration, its seat duration is similar to the Hotcam, so it will capture just as much low rpm cylinder pressure.

 

No rebuild of the short block, that's correct.
sounds like the GM Hot cam is best for me.

Not too hard on the valvetrain. I like that.
Does that mean I can use looser springs? Like the GM LS6 beehive springs?
http://www.summitracing.com/dom/parts/nal-12499224

 

I wouldn't run those LS6 springs at their rated seat load of only 80 lbs, even with the Hotcam. You'd be lucky to make it close to 6000 rpm before the valves floated. If you do use them, shim them to 100 lb on the seat, of course making sure you still have the valvelift capability before coil bind. Standard springs need to be about 110 on the seat to utilize the Hotcam; beehives can get away with slightly less.
Here's another option for a spring/retainer kit that will work:
http://www.alexsparts.com/valve-spri...rf-hyd-roller/

 

I have seen this store on Ebay, but wasn't sure of the quality, since he have such low prices.
Do you have good experience with Alex's Parts?

 

I have them in only one engine, at about 9000 miles now.
Naturally, I had the same concerns initially, but with so many people running them now without any failures I'm aware of, I'd trust them every bit as much as the Comp and Crane offerings for mild setups like this. I've broken several Crane springs (the 10309 kit for Vortec or LT1 iron heads) with a milder cam, and Comp beehives do not have a stellar record either.
When you consider Comp and Crane put about a 200% markup on the springs that they get from a VERY limited supply base, I wouldn't call Alex's prices terribly low, more like "about right". You can find plenty of springs for $30-$40 per set, including production GM LT4 springs, but none I know of that will support the Hotcam to 6000 rpm.

 

Recently helped a buddy put a Hotcam in his L31 truck and we set his heads up with the Alex springs/retainers. Went right on, installed new seals runs well. He is stock PCM tune for now, but has the Lextech spreadsheets and scouring the wrecking yards for a cheap 0411.

 

The ls6 springs are right around 105# at 1.75 installed height with stock vortec locks and comp 787-16 retainers.
Manufacturing tolerances vary so measure, measure and measure.

That setup should work fine with the hot cam and 1.5 rockers.

I would rather use that setup over alex parts kit. No reason other than I am hesitant over the "possible" quality issues with generic parts. Broken valve springs can lead to a completely junked engine.

 

It would almost be a shame to give up the intended lift afforded by 1.6 rockers with the Hotcam. The Vortec heads will really benefit from it.
I'm not saying it would run "bad" with 1.5's; it's just easy money left on the table.
If you happen to feel more comfortable with the LS6 springs, then run YOUR numbers from YOUR measurements and see if you can shim to at least 100 lb on the seat and still have enough room to coil bind and retainer-to-seal clearance to run the 1.6's.

 

I am of the opinon that 1.6 full roller rockers would gain a substantial amount over stock stamped 1.6s too. The LT1 hotcam test I saw was nearly 8 hp peak to peak and 5 ft/lbs. The averages from 2,500-6,000 came up nearly 6 hp and 7 ft/lbs. Might not be something you would feel seat of the pants, but you would certainly see it in a time slip. The average power increased nearly 2%.

 

After som initial mailing, I decided to buy from Alex's Parts.

I followed his recommandations and bought a kit with his beehvie owate springs with 110 lbs seat pressure.

The kit is intended for flat tapped cams, but he claimed that it was suitable for a somewhat mild rollercam as the GM Hot cam as well.

Springs intended for roller cams had 130 lbs seat pressure and cost nearly the same. He could sell me that, too, but he said the seat pressure was more than needed for my plans.

I took his advice and ordered the 110lbs kit.

I haven't bought rocker arms yet, but are looking at Speedway Motors stainless steel 1,5/1,6 ratio self aligning rockers for 3/8" rocker studs:
http://www.speedwaymotors.com/SBC-St...ing,45206.html

I have also ordered Mr Gasket 1076 screw in studs as I have heard those are often used when switching from pressed- to screw in studs without machining. It thread the stud holes out to 7/16-14 threads by the help of an big drill press that I have.
http://www.summitracing.com/parts/mrg-1076

At my work I can have the heads milled at a low cost. If the engine has the flat top pistons, how much milling do you recommend?
The Swirl Port heads have 64 cc chambers and the Vortec heads have 63 cc, correct?

If the engine turns out to have dished pistons, I guess the heads should be milled more? How much would that be?