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The Edelbrock TBI 3704 intake manifold comes with smaller 42mm bores than the O.E. TBI intake 46mm, does not have the crossflow bore between the two bores and has some little details that appear can be improved.
I used this intake with enlarged 47mm bores on a LO3 with LT1 cam + all supporting moods and then on the DIY 360 TBI, it worked well.
Recently I had the engine apart due to an oil pressure issue, I then decided to do some major porting to the 3704 intake manifold before I put it back on.
First of I increased the ID of the bore to around 48mm and made the crossflow hole about 1 in. x 1.4 in. in oval form.
The porting bit measures around 0.47 in. D x 1 in. tall.
The Edelbrock TBI 3704 intake manifold comes with smaller 42mm bores than the O.E. TBI intake 46mm, does not have the crossflow bore between the two bores and has some little details that appear can be improved.
I used this intake with enlarged 47mm bores on a LO3 with LT1 cam + all supporting moods and then on the DIY 360 TBI, it worked to well.
Recently I had the engine apart due to an oil pressure issue, I then decided to do some major porting to the 3704 intake manifold before I put it back on.
First of I increased the ID of the bore to around 48mm and made the crossflow hole about 1 in. x 1.4 in. in oval form.
The porting bit measures around 0.47 in. D x 1 in. tall.
I wish Edelbrock had cast their TBI performer intakes like they did their performer TBI-MPFI conversion intakes. They were small plenum single planes.
Check out this aspect of porting the intakes. I noticed the same thing on my 3704 when I had it. Cleaning up the ports really helped for me.
It looks like you are getting there. I think the reason these manifold runners flow so unevenly is due to the differences in runner shape, location and dimensions. Once they are all cleaned up, it makes a huge difference.
Are your heads setup to run the 1204 or 1205 gaskets? My 081 TPI heads were brought out to the 1204 size and I opened up to a 1205 on my 187s.
Not sure, I used the stock replacement FEL-PRO MS93317 as template, I then put the engine back together and used Victor Reinz MS15401, this time I did not want any blue gaskets on my engine.
One detail I forgot to mention is the bottom of the bores (red arrows), I spent a lot of time to chamfer the edged as much as possible with the tools I had, particularly the deep one.
Last edited by thomas1976; 08-11-2015 at 02:08 PM.
Reason: insert pic
My car is not a race car so this works good enough. Crossflow hole is about 1 in. x 1.4 in. in oval form, it made a noticeable positive difference. I would do it again.
Off course if stock look is not required, there are certainly better intake manifolds out there.
09-01-2013, 01:55 PM
