350 bored .30 over (355ci)
stock heads shaved, full port and polish and multi angle valve job
Hedman shorty 3" headers. full 3" exhaust (flowmaster 80)
everything portmatched
ported lower intake
ported upper plenum
edelbrock runners
pcm for less tune
getting fuelpressure regulator
compression ratio 10.25:1
comp 08-503-8 cam.
112 lsa
int .503
ex.510
.050"lift int 224
ex 230
duration int 276
ex 281
what are your opinions ?
want it to be a mean little motor !!!!

 

If you're starting from the point of all stock parts now, then a good quality port job on the stock heads with a performance type valve-job could get you 30 to 40 horsepower depending on the quality of the work, and if valves are upgraded, like the conversion to LSX type 8mm valves.

A complete exhaust upgrade with 1.75" shortie headers, no CAT, and a mandrel bent 3" single exhaust could add 25 to 45 horsepower, depending on how well the heads are ported, and/or the effectiveness of the camshaft used.

It is possible to run 10.25:1 compression with iron heads, but you had better know what you are doing. Hotspots around the combustion chamber, and/or hot sparkplugs will produce detonation and lead to engine damage.

The camshaft and tune are both wildcards. The cam you listed would require some head modification and upgraded springs. It would also require extensive PROM tuning to realize its potential power and allow a drivable vehicle. A mail order tune will not cut it. The end result of what you get could be less power than stock, or a large amount of extra power, all depending on how good the tune is. A lot of hands-on attention from a very experienced tuner will be needed.


You give little or no information about what you have right now, as in year and specifics of your car or ECM type, but If I were you I would run a smaller camshaft that is made to peak power in the same range as the TPI system that you are planning to use.
For a hydraulic roller I would suggest this one:
http://www.lingenfelter.com/mm5/merc...egory_Code=C30

The above cam will still need some head modification and a spring upgrade. The amount of required tuning will be less and streetability will be much better than with the longer duration cam.

I wouldn't bother spending money on aftermarket runners, unless you have enough money to upgrade the base as well. Even so, there is comparatively little power to be gained per dollar by upgrading the LTR TPI parts on a 355.

Porting your plenum and base may help slightly, but bigger gains will be had by lowering the temperature of your intake pieces. The best way is to block the EGR/exhaust crossover passages that feed hot exhaust gas into your intake manifold. I prefer to weld the passages at the exhaust port bowls (before porting), then back-fill with high-temp RTV and epoxy up to the surface that mates to the intake manifold, but there are other methods.

 

thank you for the detailed reply. the engine shop i am using knows what they are doing (i hope lol) the car is an 88 camaro and the engine is a mass air flow, and everything has been done. all new seals, valve seats 1.5 roller rockers, stronger springs, new valves, and mahle flat top hypertauctic pistons. with the vehicle running right how much hp, tq do you think is possible.

 

When I said you had better know what you are doing, I meant you need to thoroughly understand thermal management around the combustion chamber, and take steps to prevent hotspots, as well as upgrade the factory cooling configuration in the engine block and heads. This involves steps like minimizing quench height, improvements to cooling flow and bias around certain areas of the combustion chambers, radiusing the edges of the valves, and polishing the chambers and valves. A non-projected tip sparkplug of a colder than stock heat range is highly recommending.

You will also have to use extensive tuning knowledge to keep detonation from occurring at times when the engine is being loaded. This is done in the tune as in hands-on PROM tuning by a very experienced tuner. Running the ECM in closed-loop mode is unlikely to to avoid detonation without pulling a significant amount of spark advance. A practical solution for this would be to convert to a 730 ECM running in OLSD (open-loop speed-density) mode. An experienced TPI tuner will (should) know how to do this, and the required tuning.

This assumes that you actually do have the mechanical compression that you mentioned in your original post. Most people have less compression than what they think. Measure and calculate carefully.

What you said about head upgrades is confusing. Why would you need "new" valve seats? as in inserts or ?

Normally the factory seat is recut, which is part of a standard valvejob. Just replacing the valves does not imply any performance improvement, nor does just a standard valvejob.

The required head modifications for allowing the use of that camshaft without causing catastrophic parts breakage, would be the machining down of the valve guide boss for extra lift clearance.

For springs, you have to measure the installed height on the head, then subtract the spring's bind height (as measured on a spring tester), then subtract an extra 0.050". The number that is left HAS to be larger than your actual valve lift, or spring bind, and breakage will occur.

Proceed with caution.