Technical Tips > Engines - Carbies - Exhausts - Dissys

Engine upgrade

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TIPPA:
Just a qik addition to the hijacked half of this thread... VO mentioned to white rider the 400ci. From what i've heard i wouldn't go near one. they have a siamese bore, meaning water jackets don't go around all bores, but PAIRS of bores. in big hp engines this uneven cooling leads to bores going oval when hot... and for very little advantage.

Vette Obsessed:
Thats a valid point but the old "cooling issues" opinions on the old 400 castings varies depends on who you ask.

From what I understand if setup properly for your application you shouldn't have any issues.

If I were going for big hp from a 400 block I would personally go for an aftermarket casting - better blocks suited to bigger hp and bigger capacities.

Just my two cents. :22

87Z51:
Meanwhile back at the farm.

Vortec heads.
Best flowing stock cast iron  GM heads made  , outflow Bowtie heads.Based on LT1 Vette heads.
Can upgrade to 2.02 / 1.6 valves but that is all that is recommended as ports are so good stock.
Flow  190@.300
         227@ .400
         239@.500
Stock springs will only go .450 , need to cut valve guide boss down if wanting more  lift and change springs.
Vortec cam won't fit L48 as a bolt in.It is a roller cam and needs mods to fit. Also needs roller lifters (expensive) and new pushrods..
Better to get a  flat tappet cam to suit the flow of new heads and retain all your existing valve gear.
Exhaust  ports are the same as stock , changes are on  the intake side.
Need to check CR with new heads.
Vortecs are 64 cc , from memory smoggy L48 heads are 72cc so compression may become a problem.More than low compression L48 is better up to a point.
Cheap take off centerbolt valve covers can be had on US eBay for $20+.
If you want some expensive polished alloy ones see me.My new TFS heads take old style covers so my shiny new centerbolt covers won't fit

two89w:

--- Quote ---Originally posted by Cameron 77C3

--- Quote ---Originally posted by Brutus
What are the flow figures for the Vortec heads and also the camshaft specs?
You may also find that the 750cfm Holley is a little more than you need for that engine as is.
--- End quote ---


Agree with Brutus.  Unless your beast is doing some serious RPM's a 650 should be fine.
My beast is reving to 6200 rpm, roller rockers, cam, etc with 355ci and the holly 650 double pumper, competition  style, is fine.  Bigger is not always better
--- End quote ---


I agree with the above (I know its a ford engine) but my engine makes power to 6k and I run a 650dp.

From memory you said you have a 330hp crate engine?

My engine makes 337rwhp and only needs a 650dp so would say you would only need a 650 vac sec.

I am not bragging, just trying to help make a point.

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