First time posting here - so please be gentle.

I`m planning an engine upgrade for my car....
It`s a kitcar - 1050 kg (2300lb) incl driver, Tremec TKO transmission, sticky tyres and 3.07 LSD rear.
I like the look of TPI and like the idea of plenty of low/mid torque from the long runners. I also like the idea of smooth cold starting/running and "reasonable" mpg - running with Holley vac sec carb now.

The parts I have and want to use are.....
1 piece rear main seal 350 block (bored 0.030" over)
Vortec heads (SDPC items - for up to 0.550" lift)
Stock complete TPI set up - but will probably upgrade base, runners, throttle body and injectors

I want to run this with Megasquirt fuel and spark with edis ignition
The car is used 95% street - long cruises including 2000miles+ European driving holiday once a year. The other 5% being circuit trackdays (amateur)

I`m looking for bags of torque up to 5000 revs and for the occasional trackday maybe fitting nitrous for extra power at high revs when the TPI will struggle to supply enough air. I prefer a lumpy idle - although not really necessary.
I have a flat hyd cam fitted now, but want to upgrade to a roller hyd - the block is machined for this.

I really need advice on cam choice and static CR.
Also is it worth upgrading to a 383 stroker or will the vortecs choke the engine?

Any suggestions/ideas welcome.

Cheers
Paul

 

Welcome aboard!

Vortec heads and the stock TPI are incompatable. Different intake port location and different number of mounting holes. Vortec heads have raised intake runners and 8 intake bolt holes, versus standard SBC's 12 holes. You'll either need to go with an aftermarket intake, Vortec-specific. Or get aftermarket heads with a standard SBC bolt pattern.

The decision has a lot to do with the budget.

I would look for about 9.5-10:1 compression with a medium spec cam. 220ish duration @ 050" on a wide LSA. The more aggressive the cam (lumpier idle quality), the more aggresive the tune is going to have to be. Though, aftermarket EFI control will make it easier.

Just a thought, on a 383, a stock TPI would choke out the engine, RPM-wise, before a set of Vortecs. If you upgrade the base, runners, TB and injectors, it's not a stock TPI anymore.

If you're debating whether or not to keep it a 350 or go up to a 383, do you have a rotating assembly to work with, or are you going to have to get one anyway. If you have to aquire a rotating assembly, might as well go 383. They cost the same.

 

Really. Then why do i have a tpi with vortec heads????? i might be mistaken but i am pretty sure they are vortec heads. its on a 1992 305 firebird

 

If you have 12 intake bolt holes, you don't have Vortecs. Get a casting number.

 

Stekman
Thanks for your reply.
I knew about the differences in baseplates re vortec heads - but will probably go for an aftermarket base and runners anyway.

The budget won`t stretch as far as, say, a complete aftermarket injection system, but I realise the limitations of the stock TPI system and I want to do it right first time.

I have a rebuilt short block with stock crank and rods bored 0.030 over with 5 cc valve relief pistons. I was considering getting the block decked and wondered about stretching the budget to a stroker set up while I`m at it, mainly to upgrade the bottom end to take a healthy shot of nitrous and to be capable of any future power upgrades.

 

As I understand it stock GM vortec style tpi base is cast number 18483572.

 

http://www.purplesagetradingpost.com...fo/heads1.html is the link for heads and numbers.

and http://www.mortec.com/ is also a very good site.

good luck.