1990 c1500 Engine Upgrade Questions?

[JGM350]

ok i see i have a question i heard how restrictive the 90c1500 heads are by chance can i port them to flow better instead of getting all new heads or not worth it at all? because i plan to buy rockers and springs already for new heads but if i can port mine i would save 400+ dollars

 

[PlayingWithTBI]

is there anything you can recommend as far as upgrading the tbi unit then on a 350 ?

1st, get rid of the original ECM by upgrading it to the EBL Flash-II, bore your TB and swap a 20LB spring, depending on what you do with upgrades. Get a WBO2 so you can accurately tune it. The EBL can automatically tune your VE tables with a NBO2 but, it won't do any good with WOT and higher RPMs. As @Scooterwrench mentioned, I bored the Edelbrock 3704 intake manifold to 48mm for the 46mm TB.

i heard how restrictive the 90c1500 heads are by chance can i port them to flow better instead of getting all new heads or not worth it at all? because i plan to buy rockers and springs already for new heads but if i can port mine i would save 400+ dollars

Some guys have played with them but, IMHO, don't bother. Get yourself some decent aluminum heads (mine are made for TBI with the center bolts @72° so, they fit fine). You save weight and won't have any cracks. Plus you'll gain ~5+ HP alone over iron heads. but that's just me.

 

[JGM350]

thank you so much your help is really appreciated ill try posting later this week with a better build list thanks

 

[Scooterwrench]

ok i see i have a question i heard how restrictive the 90c1500 heads are by chance can i port them to flow better instead of getting all new heads or not worth it at all? because i plan to buy rockers and springs already for new heads but if i can port mine i would save 400+ dollars

Yes,and I highly recommend it. The thing to check for is if the rebuilder pinned cracks and check valve guide wear. Many rebuilders will drill cracks and install cast iron pins to repair cracks. It's just a get by and will fail down the road. There are many books and vids on how to port heads. Most of the work is in the bowls under the valves,you actually do very little to the ports themselves,just knock off proud flash and match the openings to your intake and exhaust. The idea is to increase port velocity. I have a 1979 two bolt truck engine with '79 441 Z28 heads that makes about 400hp at 5800 RPM. I ported the heads myself,you can do it too. The RPM rise is so fast it outruns the tach needle in neutral.

 

[Scooterwrench]

For your viewing pleasure.
These are a set of 991's I started to port but gave up. They were 1.72"(valve dia.) intake heads and I got worried the port walls would get too thin by the time I opened them up for 1.94's so I scrounged the 441's and gave them the same treatment.
Bear in mind these heads are not finished so the finish wasn't smoothed. I wanted to show you how to split the air around the guides.

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This pic kind of shows how you can relieve the chamber to allow more air to pass by the head of the valve. It hadn't been done yet but basically you match the radius of the valve head as much as the head gasket will allow.

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Here you can see how restrictive these heads were in the bowls especially the exhaust ports.

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These heads have nice,tight valve guides and no cracks but even after opening them up for the larger intake valves I feel they would have hit a wall at 5000 RPM. Probably should toss them in the scrap iron pile but they would make emergency spares.