Hi guys honest question here. I have an 91 L98 with some bolt ons. I have vortec HSR sitting around and I am in market for a set of heads and a cam. Can 375 rwhp be had on a 9.5/1 comp 350 with a set of SDPC vortecs and a cam swap? My budget is farely limited, but this is a project and will not nesarilly be a DD it will have 4.10 gear soo a pretty agressive cam is an option. I would prefer a set of edelbrock etecs but I think I would have to pick those up used to justify buying them. The reason I am kinda hung up on 375 is my buddy has a 94 mustang with 347 putting down 360/370 to the wheels, so it would be great to start beating him again any and all information would be great. Thanks, in advance

 

Thru a manual trans and a happy dyno it maybe possible... Thats a good bit of power on a stock vortec casting but it should be doable with the manual trans and some help with parts. Stock LT1 castings have done 360's whp so a vortec head being somewhat similar and abit better intake flow SHOULD beable to get there as well. I would think abit more compression and a huge custom cam will do it. Maybe port the intake to go along with the heads. Wont be that streetable and have nothing below 4500 rpm but it will make huge numbers and really stress that bottom end because you need to rev to 6500 to take advantage of the cam...

A set of AFR 190 vortecs should do it much easier...or a set of bowtie large port vortecs but if you have to buy new heads, could easily get something like a normal head port and a normal intake port. Its up to you.

 

I understand that it is asking ALOT out of a factory casting, but with some port work, I didnt think that serious of a cam would be nessasary! nothing below 4500 thats crazy! The stealth ram likes to rev much more than the TPI but I can imagine having basically a usable 2,000 rpm. I am in no way doubting you but that seems crazy that it would be that high strung. Its a bit of a shocker, I have had 2 ls cars so its a bummer how well those cars respond to mods. Theres a shitload of guys on LS1tech with 400 plus rwhp with bolt ons and a cam that are quite streatable bummer. Thanks for your input and please guys keep this going. Also guys with this paticular setup post your numbers.

 

If you get the right parts cam head intake itll be streetable, your best place is to call comp cams and tell them your build and what u want.

 

Without the HSR I am running a set of vortec heads, dual plane air gap, 9.5:1, and a 224/230 .502"/.510" cam. Through a TH350, stock rear with 4.10s and a 2,200 B&M stall I'm looking to make about 300 RWHP. At the crank I'm making what you want at the wheels... just isn't going to happen nicely.

To get what you want through an automatic trans just isn't going to be practical to drive. As stated, they do get over 400 RWHP out of LT1's (comparable to vortec heads) with 6 speeds but they have a significantly higher compression. With 9.5:1 you won't be able to support a cam big enough.

You can build a less powerful motor than your friend and still walk him with the proper gearing, suspension and tires. Dyno numbers don't mean anything if you can't use the power.

 

Well if you ported the heads you wont need as much cam, thats correct. It will shift the power curve back down into lower rpms. It will be much more streetable that way.

SBC's just dont work like LS1's. The difference is in the head flow. You need a heck of a head on a 23 deg sbc to do what a 15 deg LS head will do, plus more cam for sbc's vs ls. More head less cam or run more cam less head.

Last sbc I worked with thats similar to what you are doing was an old AFR 190 head motor thats somewhat similar to a ported 113 L98 head. Not the best head compared to others out today. He ran a fairly large 230/236 .570's lift cam on a 113. Even with the wide lsa it loped pretty hard in a stock bottom L98 with bored over .060" pistons with stealth ram. It was abit soft down low under 4000 rpm. It had 3600 stall and 3.90 gears but should have had 4500 stall to get best 60 foots. Would have been a 350-360whp car thru an auto and those heads are better than vortecs... Just the way bigger cams work...pushes peak torque above 4000 and softens the power below that, especially with shorter runner intakes like HSR. Stock LS1 is same way even in stock form. My car with stock stall really didnt wake up until 3000-3200 rpm. It wouldnt spin tire from a dig with stock converter and 2.73 gears with a WOT smash. But it break loose at 3000 rpm.

Another guy on this forum over the on the drag racing board has a stock vortec head 350 with a 236/242 cam and ran 11.90's so far in the 1/4. 112-113 mph I think it was?
Car is light tho but it could be 330-340 whp which isnt bad for stock combo. It needs alot of RPM and lots of converter to work tho. He turns 6700+ rpm

 

And how practical is that to turn on a stock bottom end?

 

Its a huge risk for sure. I wouldnt do it for long but its where the car works best. Big cam stock heads to run 11 sec ET. Thats what it takes sometimes

General rules for building street motors. Get as many cubes as you can afford. Spend more money on quality heads to make your hp goals easier and combine them with smaller cams to keep driveability and as much torque as possible. This gives a mild mannered car with a lower rpm power band but plenty of hp and plenty of torque, and all reliable at the same time. Now not all cases needs this. A build 350 turning 6500 rpms is definately fun...just dont expect power to really kick in until 4000+ rpms.

My turbo car is like this. Its got nothing below 3600. I mean absolutely nothing. Will not spin tire without help of 2 step brake boosting. Cant even spool turbos til above 4000 really. Big cam big heads. Its very driveable and will do alot better once it gets more gear but it really needs more converter and gear combined to keep power band starting at 4000-4500. You definately dont want a low stall speed with a high rpm torque curve or your asking for lazy results down low.

With a manual trans you have more control on gearing and rpm to start a wot run....

 

You'll rather need to build your bottom end and valve train to handle high RPMs or save up for a good set of heads and try to make your power at a significantly lower RPM.

If I was going to waste my time doing a bottom end you have to debate the cost of a balanced stroker kit (SCAT makes a descent one for about $900 that I can first hand say was nicely balanced and the crank was true to size and required no additional clearance down low) as opposed to having your crank cut/polished ($60-120), new rods ($300), new pistons ($300+) and about $300 to have it all balanced.

Ultimately, you'd gain torque and generate peak power at a lower RPM (roughly 400-500 RPM sooner) and get away with less of a converter.

 

Thanks for all the input guys, I truly do appreciate it. I no longer run the auto, so the stall isnt an issue. I suppose I will continue to do some more research and shop around for some better heads. I knew it was gonna be more difficult to make around 400hp to the tires but had no idea it would have to be sooo high stung. Its funny when I started talking about using a cast iron head and trying to beat my friends 347 mustang, he strongly suggested saving for better heads to have a chance. I hate when hes right Anyway thanks again to everyone that contributed, and its still open so some of you vortec guys feel free to post.

 

With some port work it can be done. I have seen 580 hp from vortec heads but they had alot of money and time into them and several camshafts to find best overall power. Iron heads can make power its all in the port shape. Its just easier to work with aluminum so most machine aluminum castings for custom port designs.

With better heads you can make 375 whp under 6k rpm. It wont be high strung at all