383 stroker valve size ?

powerplay230 · 10-09-2009, 05:40 PM

Im running vortec heads with 1.94in 1.50ex. Im also running comps 276hr cam which is a little to big for my stock exhaust im getting some reversion at lower rpms so ive got to get alittle smaller cam. Have not decided on what to go with yet. But was wondering if i should have the heads redone with 2.02in 1.60ex valves. Thought i heard or read somewhere that the bigger valves would kill bottom end torque.

Sunshadow · 10-09-2009, 07:56 PM

Get rid of that exhaust get tubes as long as your budget will allow to get that water away from your heads. The 383 will like the bigger valves . The specs on that cam are similar to mine. I'm big fan of dry pipes but I'm able to do my own fabrication.

powerplay230 · 10-10-2009, 07:28 PM

New exhuast would be nice but that type exhuast is pretty salty. I just figured i could run a cam with a little less duration and valve over lap to cure the reversion. I ran comps 270hr before i had the motor stroked and didnt have any reversion problems. But since the motor has to come out to change cams i figured it would be a good time to go with the bigger valves.

Ryan00TJ · 10-10-2009, 10:16 PM

My AFR 190's have 2.02, 1.60 valves and there is no loss of power anywhere in the rpm range. Larger valves will do nothing but help a 383 SBC. Actually if you are pulling the heads and going through the trouble of modifying them, you would be better off going with an aftermarket set rather than sinking more money into the Vortec's. The Vortec's are a good stock head but do not compare to the uplevel aluminum heads like Brodix, AFR, Dart etc.....

Your right about going down in cam size to reduce reversion. The Comp XM270H is about the largest you can go without needing longer risers that mix the water further back.

I am running GLM aluminum manifolds and FastGlass stainless short risers. I had reversion at idle with the short risers. I then welded 22" extensions onto the short risers making a homemade dry setup as water and exhaust does not meet until inside the tip. I believe it to work very well vs expensive headers and manifolds. Boat runs 78-80GPS @ 6000-6200rpms.

yikes · 10-13-2009, 01:49 PM

I have two 260HP small blocks (86 vntage) in my 24 footer. The heads are junk so it's been in the barn for two years. I want to repace the motors with 383s but I don't have the funds. I was looking at Pro Comp heads on ebay with 210 CC and 64CC chambers. Is it worth putting these heads on the stock blocks to get it running and then building a couple of 383 short blocks or tuff it out until I can afford the strokers? I do have two pair of Gill manifolds and risers.

Ryan00TJ · 10-15-2009, 08:12 PM

Quote:

Originally Posted by yikes

I have two 260HP small blocks (86 vntage) in my 24 footer. The heads are junk so it's been in the barn for two years. I want to repace the motors with 383s but I don't have the funds. I was looking at Pro Comp heads on ebay with 210 CC and 64CC chambers. Is it worth putting these heads on the stock blocks to get it running and then building a couple of 383 short blocks or tuff it out until I can afford the strokers? I do have two pair of Gill manifolds and risers.

Procomp heads do not have a very good track record from what I have been hearing. They are a Chinese casting and quality control is not very good at all. Save the $$ for a better head or until you can do the 383's.

yikes · 10-16-2009, 06:34 AM

Thanks I have always been partcial to Dart so I'll continue saving. I just hate to see it sitting sitting on the trailer for another season.

Ryan00TJ · 10-16-2009, 07:11 PM

Quote:

Originally Posted by yikes

Thanks I have always been partcial to Dart so I'll continue saving. I just hate to see it sitting sitting on the trailer for another season.

I understand, but you will thank yourself in the long run. Heads are everything and not something to be skimped on. The Procomp heads can be made to flow but with the addition of alot of $$ from a competent porter. You will then be at or above the price of a proven set of aftermarket aluminum heads like the Dart's. You then throw the QC question of the casting and assembly into play on the Procomp's.

buck30 · 10-16-2009, 10:38 PM

boats love fuel & air. a 2.02 x 1.60 will make good power in any case. much better then stock anyways. the thing to watch with the stock vortec head is the weak valve spring they come with. be sure when you order your new camshaft to order the valve springs also. i dont know where you are located but if it's anywhere near the detroit metro area give me a shout. i work at baldwin performance machine. i can cut your seats and fit them 2.02's in your heads with a 3 angle valve job for around $200 plus parts. we are a engine machine shop with crankshaft service also. i also have a set of world products sportsman 2's i will be selling at a good price. first things first make sure and check that your manifolds will clear your spark plugs on a angle plug head. i have seen alot of them that wont. and most of your performance aftermarket heads are angle plug. be carefull. they say the vortec head has around a 180cc intake runner. but will flow as well as a s/r sportsman with it's 200cc runners. i have never ran a set myself but have heard alot of good things.

GERRYM454 · 10-17-2009, 12:07 PM

64 cc heads limit piston choice to deeply dished pistons if you want to keep the compression 9 to 1 range or lower. Other than custom made pistons there are few choices. Larger CC heads allow for a wide choice of off the shelf pistons. Also the shorter 400 rods give slightly more low end torque than the 5.7 or 6.0 rods and of course bigger valves are good