4bbl 360ci HiPo Question?

[CDN-Sebring]

I bought my car awhile back it does not have the original engine but from whats been done to the car before I bought it seems like the guy was trying to add performance to it. I dont know if there is any work done on the inside of the engine and I dont plan to take it apart. The engine is a Orange 1981 4bbl 360ci with the Edelbrock LD4B intake/Performer 600cfm carb. I did some research from whats on the outside of the engine but came up with nothing besides Chrysler making "HiPo" engines with LD4B intakes and rarely making 360 HiPo with them. I came across this when I was searching the intake which is a "Edelbrock LD4B". My question is what kind of performance (horsepower and torque) would I get from a basic 1981 360ci 4bbl with the Edelbrock LD4B intake and the Edelbrock Performer 600cfm? If it is a HiPo 360ci would that make much of a difference because I read somewhere that they came with a 340 cam?

 

[rumblefish360]

Chrysler Corp. never made a single "Hi-Po" engine with any after market/other manufactuers intake except the Edelbrock 6 pak intake manifold. The LD4B is an over the copunter aftermarket part from Edelbrock. You could purchase it from Direct Connection (MoPar Performance) or through a speed shop.

The LD4B is designed as a stock replacement type of intake with a squar flange. Designed for the 273/318 engines, the port window size is small for the 340/460.

The Edelbrock 600 cfm carb issmaller than a stock AFB/AVS and the TQ. While it may be sized well for general duties, it is small.

The stock as delievered 360 4bbl. was around 255 HP if it was a HP version, and not knowing if you have that HP version, I'll just assume it could be and go on from there. Yes, the 360 cam with the 340 cam shaft, but, suffered a low compresion, (Sometimes less than 8-1) small valve size (1.88 Intake) and emmision equipment to bog it down on power. (Not all of the smog equipment was power robbing.)

Since the HI PO engines were rated ataround that 255 HP area, the loss of the iron 4bbl and TQ carb is hurting it's performance. The Edel. intake and carb are less of a performer than the OE equipment delivered on the engine. I was take an educated guess and say that this engine would make 260 Max HP.

To bolt on a few parts for performance, step up to ethier the LD340 or RPM and a 750 carb, add a 340 or your cam of choice. Add headers and a 2-1/2 exhaust. Grab a performance distributor if your current unit does not have a vaccum advance on it. (AKA Lean burn distributor does not have a vaccum advance on it.)

Milling the heads down for added compresion is a big help. Look to gain 1 point or so in this area. The max you want to go is 9.5-1 with an iron head and pump gas. Installing a 2.02 intake valve is generaly not needed. Any porting done shoul;d consider the level of performance being sought. If only a little performance is desired, AKA daliy driver or street machine, just bowl port the heads.

Power without bowl porting can be expected in the 350 hp area
Bowl porting included can added approx. another 25 - 30 HP on this mellow mill.

 

[Jonnyuma]

Know of any good references for DIY head porting? The only way to learn is by doing, but I'd surely rather the cost of the lesson not be trashing an otherwise serviceable cylinder head. Something with lots of pictures, online or even *gasp* a book.

 

[rumblefish360]

LOL, it is ethier pay the piper for his services or get some tools, video and that "*Gasp! A book!" with a quick trip to the junk yard for a few practice heads.
MoPar may still offer porting templates for certain heads. They are for porting the bowl area, just under the valve. Port matching the heads windows to the intake/exhaust gasket is a "On your own" job that shouldn't be to hard after the bowl work is done.

 

[Meep-Meep]

Just changing from the original high rise iron intake and TQ to the LD4B and 600 Holley you will not see any earth shattering difference in total power output. However drivability may be better/worse depending on carb tuning. What will drive your performance curve to the positive side will be the aforementioned compression increase. Nothing makes power like a compression increase and should be the first step in any modification. Naturally any increase in CR should take into account the available fuel. 9.5:1 iron head and 170-180 PSI should be good on 91 R+M/2.