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2V head, welded exhaust floor

3K views 18 replies 6 participants last post by  buzz 
#1 ·
I'm considering welding up the floor on the exhaust ports of my 2V heads. Has anybody had any experience with this modification?
 
#5 ·
buzz said:
they have poor flow do they? On the 2v,s it is the intake which needs work not the exhaust.The stuff all the magazines talk about in relation to poor exhaust flow only pertains to 4v heads.If you actually knew anything about these heads you would know that the exhaust is very strong in relation to the intake.a properly ported exhaust port will yield over 200 cfm (2v) and a properly ported 4v around 220cfm. ported 4v intakes can flow up to 375 cfm and this is where the imbalance lies due to the intake being so strong and the exhaust is restricted somewhat.Thats why most clevo cams are biased towards the exhaust side giving them more duration and lift to alleviate some of the problem,whereas 2v headed motors do not require the use of a split cam.
 
#8 ·
russxr67 said:
how much do the heads flow in cfm at 28?
I picked these heads up second hand with a bunch of other gear. Have just got them back from being flow tested.


Intake flowed with Funnelweb, long runner.

0.103 65
0.205 136
0.308 194
0.411 216
0.513 218

Exhaust

0.082 47
0.165 83
0.248 112
0.331 132
0.413 147
0.496 167

Intake Valve dia = 2.055"
Exhaust Valve dia = 1.655"
302 Cleveland heads
Pocket ported bowl & short turn radius
Intake Volume = 170cc
Combustion Volume = 64.5cc
 
#9 ·
xbgs351 said:
I picked these heads up second hand with a bunch of other gear. Have just got them back from being flow tested.


Intake flowed with Funnelweb, long runner.

0.103 65
0.205 136
0.308 194
0.411 216
0.513 218

Exhaust

0.082 47
0.165 83
0.248 112
0.331 132
0.413 147
0.496 167

Intake Valve dia = 2.055"
Exhaust Valve dia = 1.655"
302 Cleveland heads
Pocket ported bowl & short turn radius
Intake Volume = 170cc
Combustion Volume = 64.5cc
Unfortunately the closed chamber heads tend to shroud the valves somewhat so some unshrouding may bring you the desired results at the expense of more cc,s.at least the heads have got the 2v sizes still intact.Are the heads going on a street car or are they to be used on the strip?
 
#10 ·
russxr67 said:
Unfortunately the closed chamber heads tend to shroud the valves somewhat so some unshrouding may bring you the desired results at the expense of more cc,s.at least the heads have got the 2v sizes still intact.Are the heads going on a street car or are they to be used on the strip?
Plan on doing some circuit racing whilst still keeping it streetable.

I don't want to open the combustion chamber up any more due to the loss in compression. With a 351 calculated compression will be 10.5 : 1. If I go the 393C route with dished pistons it will drop to 10 : 1.

The heads flowed better with the inlet manifold than with the bellmouthed plasticine on the bare heads.

I'm trying to keep a lid on engine costs so that money can be allocated to the things that will make the car fast being: wheels, rspec tyres, rollcage, seat, harness etc.
 
#11 ·
I can understand that you don,t want to lose any more comp ,but surely ,wouldn,t it be better to lose a tad of comp at the benefit of gaining flow? The cc exhaust valve is highly shrouded and this may be the only way to get the exhaust to move more air.Either way,I think you have got to get into these heads some more by way of porting if you want to circuit race.I,m not sure if the figures that you quoted would cut it.You should be able to get in excess of 240 cfm on the intake with more work.
 
#12 ·
russxr67 said:
I can understand that you don,t want to lose any more comp ,but surely ,wouldn,t it be better to lose a tad of comp at the benefit of gaining flow? The cc exhaust valve is highly shrouded and this may be the only way to get the exhaust to move more air.Either way,I think you have got to get into these heads some more by way of porting if you want to circuit race.I,m not sure if the figures that you quoted would cut it.You should be able to get in excess of 240 cfm on the intake with more work.

After the quote I recieved today it looks like I will be going the 393C route. Flat top pistons will give me far too much compression and the 16 cc dished Probe pistons will put the compression at 10:1. I may have to mill the heads.

The last set of heads I had did have the exhaust unshrouded. Unfortunately a large hole developed, which let the water in!

The circuit racing will only be club level track days and sprints. I will get more gains spending my money on other areas of the car. The biggset gains will probably comef from track time.
 
#13 ·
svo347 said:
why not just use those s/steel port tongues that you can buy nowdays.
Smart idea and they are cheap. About $120 a set. I have 2 different sets but they are for the 4Vs I have. Anyway it is also advised to use plates on the 2Vs because of the angle the exhaust gas exit into the extractors. Not as bad as the 4Vs but still bad. The bottom of the extractor is blocked off but I will get the article from Price Motorsport which states it is better for the Clevo heads this way !!!
 
#14 ·
clevo400 said:
Smart idea and they are cheap. About $120 a set. I have 2 different sets but they are for the 4Vs I have. Anyway it is also advised to use plates on the 2Vs because of the angle the exhaust gas exit into the extractors. Not as bad as the 4Vs but still bad. The bottom of the extractor is blocked off but I will get the article from Price Motorsport which states it is better for the Clevo heads this way !!!
The extractor mismatch should reduce reversion at lower revs. I will probably be using anti reversion cones anyway. Do you know who sells the plates?
 
#18 ·
My intake plates were made by Active Performance and my exhaust plates were custom made by Steve Gaye from Mackay Cylinder Head Developments. Others such as Terry Parker of the Funnel Web in Maryborough makes alloy intake and stainless steel exhaust plates and so do most of the other Aussie clevo manifold makers. Price Engineering in USA still make the exhaust port plate which you actually cut the head and bolt into to make a Ford Yates C3 style head !!!

xbgs351 said:
The extractor mismatch should reduce reversion at lower revs. I will probably be using anti reversion cones anyway. Do you know who sells the plates?
 
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