nitrous with tight lope sep

[tresi]

My friend has an S10 with a 355. 12 to 1 comp, old set of 461 heads, solid flat tappet cam 248/253 @.050 and 102 lobe sep, 750 carb, 3500-4000 stall, 4.56 gears and 10x28 slicks. He's determines to give it a 75hp-100hp nitrous shot. He has a 300 hp fogger that he would put on if he could find all the jets. I'm telling him he needs much wider lobe sep at least 110 preferably 112-114. What problems might he encounter?

[user-3597028]

He'll be giving up some performance because of the increased overlap. backfires could also be a concern. Sneak up on it and he'll probably be ok with the lower HP levels of added power.

We ran a 250 shot on a 106 LSA cammed engine once. It blew a head gasket right away because of the high cylinder pressure. (I did not do the machining on the block or heads, which was too rough). I resurfaced the heads and we installed copper head gaskets. It ran like an animal after that.

[lorax]

You sure the cam is 102 LSA and not 102 IC

[Keith Morganstein]

Really 102 or is that ICL? If its 102 LSA, that's a specialty cam usually for a compression rule restricted circle track engine.

He will still gain power from 75-100 NOS, just not very efficient. I would not recommend the 300 fogger at all (will be destructive).

[tresi]

Yep it's 102 lobe sep and it is a 2 barrel circle track cam

[1967stroker]

that cam prob has about 100 deg of overlap.

[tresi]

that cam prob has about 100 deg of overlap.

I degreed the cam for him. it has a lot of overlap but I don't remember it being quite that much but it's been a year since i did that for him. It does have a nasty idle.

[1967stroker]

the tightest lobe sep i have run with NOS is 106. a 150 shot only made 138 hp.

[Strange Magic]

Way to much cylinder pressure. Even without the nitrous it's to much cylinder pressure.

[steve cowan]

hey tresi,i ran a 355 sbc 20 years ago with 12.8:1,double hump fuelies,i used a crane flat tappet cc 270 i cannt remember lsa(sorry) ran it on c12 with 100 shot,ran 10;8s @125mph srteeter,the problem i had it cracked exhaust seats every run with spray,after repairing several times i bought a set of track 1s and threw the fulies in bin (junk) if i ran fueliies again i would never spray them, i dont think personally a cam change will help you much( i know with later intake closing will blow a bit off)still wont help,maybe 10:1 comp might be better but it is all about the almighty dollar

[Ron Sutton]

The cam in an engine I have is 108° LSA and that makes me concerned with running Nitrous. 102° is asking for problems.

[bigcam406]

it would be cheaper to replace the cam than repair the damage the wrong cam and nitrous would cause.

[tresi]

it would be cheaper to replace the cam than repair the damage the wrong cam and nitrous would cause.

Sure it would. I beat this horse to death with him but in his mind this set up is going to run 10.90's, 7 5/8 rear end with a welded governor lock posi and all. It's a collection of crap he could get for little or nothing.
My guess is more like a mid to low 12 on the throttle and I don't think it's making down the track on the bottle.

[351crules]

curious as the what damage can happen with tight lobe separation cams...my cam is on a 106 and plan on shooting 200 through it

[bigcam406]

tight lobe centers create too much cylinder pressure if nitrous is used.thats why you see blower and nitrous cams spec'd at 112-116 lsa,with distinct valve events ground specifically for boosted applications.