Sorry if this post seems confusing. Just having trouble figuring out if I can do a two stage build.


I've been itching to dive into the motor and build it up. Reality set in and I am first going to get a nice paint job so I can look good driving around town. At this point I am not sure if I want to keep the car mild stock or go all out with a 383 stroker. Going with a 383 will require lots of money, upgrading transmission and changing rear end. I would like to install some basic parts soon for more power that would not require transmission and rear end upgrades. I am not sure if I can get parts for a mild 350 build that could be used for a future 383. I'm thinking of upgrading intake, heads and cam now for mild 350 build. Here are some questions I have been thinking about.

1) I know stock intake is restrictive and needs to go. I like the FIRST intake since it comes with larger runners, improved manifold and monobody throttle body. It would definelty work on future 383. Would it flow too much air on a mild 350 that it would hurt performance (torque)? Price wise it is comparable to TPIS large tube runner, big mouth base and 52mm throttle body.

2) Could I use stock injectors for mild 350? I think they will work since I'm looking to bump stock 245hp to around 280-300hp. Just will need adjustable fuel pressure regulator.

3) GM bow tie vortec heads flow great for their price. Stock heads have limited lift and $$ would be needed to modify for more lift. It then makes sense to spend a little more for AFR heads with high lift. Do I go with 180cc or 195cc AFR heads? 195's are not much more $$ than 180's but I believe 195's are too much for mild 350 stage.

4) AFR's are aluminum heads that need higher compression. Would I have to get heads milled for lower compression to work on stock 350 bottom end? If so, I wouldn't be able to use these heads for future 383 build. I would then be stuck with cast iron vortecs for mild 350 build.

5) I'm ok buying mild cam for 350 and then upgrading to another cam with 383. I know that reprogramed ECU will be needed for both builds.

Thanks!

 

Super rod did a test of different tpi intakes on a 383 a long time ago. I cant find the actual article but heres a link to the results https://www.thirdgen.org/forums/tpi/...feb-super.html . If you find the actual article, they have dyno graphs and detailed info on all the intakes tested.

Stock injectors may work (for the 350), I dont know for sure, but Im guessing with a prom burn they could work well enough.

Keep in mind any vortec head would require a $400+ base manifold no matter what but to the same end, its a good flowing piece and gmpp has some pretty high flow iron vortec heads, they may even have some aluminum ones. That would be the route I would go, you get vortec heads and you are required to get a new base manifold which is a good idea anyway to flow more.

Depending on your time table, upgrading the intake and heads on the current motor may be enough to hold you over while you upgrade your drivetrain for the 383 and getting a cam for the 350 would be kind of wasteful since you would be better off with a new cam in the 383. Keep in mind roller cams are $300 or so, thats money you could spend towards upgrading your drivetrain for the 383.

Ive never heard that aluminum heads 'require' higher compression, I just always assumed you can get away with higher compression since aluminum transfers heat so much better, not that its required by any means.

 

Thanks for the reply and link. I did see another similar test done by Comp Cams called "ten times the tourqe" http://www.compcams.com/Community/Ar...?ID=1737510521

I would like to stay with TPI since it will keep car close to original intent and will be a good street machine. FIRST makes a version that it is vortec compatable. I would go FIRST since it gives you everything in one package and flows better than other TPI LTR runners. http://www.firstfuelinjection.com/

I believe stock cast iron compression ratio for l98 is around 9.3:1. Since aluminum releases heat better than cast iron, you are supposed to have a higher CR of 10.3:1 to maintain combustion temps inside the head for optimal power. Going aluminum now for 350 with same combustion cc size as stock maybe bad due to heat loss. Also, I think a 383 would benefit from larger combustion cc size than stock 58cc's. Putting larger combustion chamber now on mild 350 would lower CR right?? I thought that is why when people go 383 they increase combustion chamber size and get domed pistons to help get to proper CR.

Another thought is that if I go AFR now, I will need a new cam for the higher lift right? However I could probably get away with stock cam for GM bowtie vortec heads since lift is not to much higher than stock heads. I could always get vortec heads upgraded for higher lift if I go 383. The small port vortecs have 66cc combustion chamber, 185cc intakes and 0.53" lift which would be good match for either build. Maybe I could upgrade to LT1 cam with 350 build to help with higher lift of vortec heads.

Looks like I will have to dive into an engine CR comparison with both heads and builds. It would be nice to do a mild build that doesn't require upgrading bottom end and drivetrain. Might be tricky to get parts that support 383 so I don't feel like i'm wasting money. 383 sounds nice but mild 350 would probably be enough excitement for me.

 

Buy good flowing heaeds now. Then you won't need as aggressive a camshaft to flow enough air to make power. Because of the mild cam, your dynamic compression will be better and you won't need as much static compression. So you don't need to mill the heads down.

 

Think I figured it out.

I ran CR numbers for a stock 350 with no overbore. I came up with 10.37:1 compression ratio for the AFR 180's with 65 cc combustion chamber. I will have to get unsual gasket size around 0.02" to get good quench. This should be good for aluminum heads. 75 cc's drop CR to 9.06:1 and would only be good with cast iron heads. I think AFR 195's might be little too much for a 350. Not sure though since they flow 274/207 cfm at 0.50" lift where 180's are at 260/207 at 0.5" lift. 195's would probably work but push power band higher and result in need for higher stall converter. I would like to keep 3.23 gearing so 180's look like a winner. Plus 180's have better E/I ratio of 79.6% versus 75.5% of 195's. I think 180's would give me better torque. Looks like AFR will upgrade to 0.6" lift. Higher lift with low duration cam would make a good street engine right? Vortec bowties are tempting at $500 cheaper but they lack heat passage. Plus AFR's flow a lot better.

Does higher compression with aluminum vs cast iron hurt the engine and cause more wear/stress? Or not really since aluminum dissapates heat faster so in end percieved engine stress is same? If aluminum heads cause more stress I will go with cast iron vortecs. Thanks for the input.