Rokshocka

hey, well this is wat my combos gonna be:

350 small block
10:1 compression
comp cams 262H kit
cloyes dual roller
MSD ignition and 6AL
GM vortec heads
edelbrock performer RPM vortec manifold
road demon 625 cfm carb
700r4 trans
TCI breakaway lockup converter
342 gears

i wanna run 13s possible with this? should i get road demon 625 cfm... or a speed demon 750 or 650 cfm? its all in my 91 RS, and is this a streetable motor? or is the cam too much? power estimates? thanks

MorgRS

April 2001 Chevy High Performance built what they called the "Miserly Mouse"
390Hp @ 6000rpm 426 Ft lbs @ 4000
The only difference is it was made to run 87 octane so the compression was down from yours 8.75 to 1. The cam was a 268 XE. From a quick glance that is the differences between yours and the "Miserly" I'd check out the the artical. 13's should be easly attained. The GM up grade kit has a little less power and runs Mid 13's. GM noted they upgraded the suspenion, I'd get some after market LCA's (min)with your combo.

Rokshocka

thats a coincidence lol pretty cool though, so is the comp cams 262 a streetable cam?

F-BIRD'88

The only thing I would add to your combo
to ensure 13's is a pair of BFG Drag Radials.

[This message has been edited by F-BIRD'88 (edited November 22, 2001).]

Cosmik Debris

With 3.42 gears and a higher stall converter I would be tempted to go up a step in the cam to a 268.

86irocL98

...its torquey....

arthur

The CompCams XE262H has a dur at 0.050" of 218 deg. .462" lift and the RPM range is 1300-5800. I like the XE268H with 224 deg at 0.050", .477" lift (still I think, within the stock vortec abilities, though find out for sure) RPM range 1600-5800. This cam will definetly take advantage of the setup you have proposed. According to CompCams, this cam can still be used with the stock Tq converter. It is also very streetable. The 1970 LT1 350 had a dur of 317 deg, but was 246 at 0.050". It only had .435" lift though. Anyway, this was in the Corvettes as a street car. Then this issue of compression. I was looking into using the vortec heads for a friends engine build up, and found that the one difficulty with these heads is the tight 64cc chamber, which I believe is tighter than advertised as well. To use flat top pistons would yield a 10.2 comp ratio with 7cc valve reliefs. So, to make this combo work without fueling up at the airport, a dished piston is the way to go. I think a 9.5 ratio is a happy medium, not too much, and not too little. The thing about compression is that at wide open throttle, you generally get a 2-4% HP increase per compression number. ie. 8 to 9. However, the beauty of increasing compression is that during throttled conditions, that HP increase can be as much as 25%. That is a big number, so maximize the quench are with a d-shaped dished piston. Keith Black makes a Hyp D-dish piston with a 12cc dish. A good strong ignition wil aid the battle against detonation. MSD knows what they're doing. I would at least check out Jacobs ignition products, this guy really knows what he is doing. The best carb for the combo would have to be the Holley 3310 780 cfm vac sec ( or Demon equiv) This carb was OE on famous engines such as the 302, Z28 350, LT1 350. They are very simple and highly adjustable. Why I believe some people don't like the Holley carbs, they didn't know how to tune them properly. Anyway, the 3310 can be found used, then rebuilt. Or buy one new. In both cases, make sure that the secondary metering block has the removable jets, not the plate system. ie. the secondary block should look just like the primary side. The original 3310 were 780s because of a different more cfm efficient booster. The new ones are only avail at 750cfm. I suggest getting a good HP book on the Holley 4150 style carbs, making sure it has a good tuning section, if you haven't already done so. Don't forget that you can e-mail the tech guys at most perf parts manufact. Good luck...

88IROCs

I'd agree with dropping the compression. You could make 10:1 work with iron heads and pump gas, but you'd have to pay a lot of attention to the cooling system and head prep. For the small amount of added power, it probably wouldn't be worth the added cost and hassles.

You mention "streetable". While this has different meaning to each individual, I'd think smooth response, and maximizing drivability in the rpms you will use the most on the street(i.e.,... <2500) should be your goal. A big cam and the Performer RPM manifold will produce big peak numbers, but at 3500 rpm and below, the motor will have a very off/on feel. I'd suggest a Performer(non-RPM) manifold and the CompCams XE262 cam. This combo will give you very nice response between idle and 5000(possibly peaking around 5500 rpm), with good acceleration all the way to the peak. The XE series have fairly aggressive lobes, which lengthens duration(more important than lift, IMO), while minimizing overlap(good low-end and decent mileage).

The carb you mentioned(Road Demon 625 cfm) sounds about right for this combo. It will give you very good transitional response(something you'd probably lose with a 750 cfm or larger carb) and won't cost you a lot of top-end(you might gain 3-4 hp at peak with a 750 cfm carb).

I'll be helping a friend soon, who is putting together a very similiar motor. It will be going into an '81 Malibu, but he will be using Iron Eagle heads and a 687 cfm Holley. The plan is to make 350 - 360 hp(installed hp vs dyno hp), turn 13.0's and get 20+ mpg. If it works out that way, he'll have what I would consider a very streetable driver.

[This message has been edited by 88IROCs (edited November 23, 2001).]